Upper airway cooling and Z-menthol reduce ventilation in the guinea pig G. P. ORANI,
J. W. ANDERSON,
G. SANT’AMBROGIO,
AND F. B. SANT’AMBROGIO
Department of Physiology and Biophysics, The University of Texas Medical Branch at Galveston, Galveston, Texas 77550 ORANI, G. P., J. W. ANDERSON,G. SANT'AMBROGIO,AND F. B. SANT'AMBROGIO.Upper airway cooling and Z-menthol reduce ventilation in the guinea pig. J. Appl. Physiol. 70(5): 20802086,1991.-Cooling of the upper airway, which stimulates specific cold receptors and inhibits laryngeal mechanoreceptors, reduces respiratory activity in unanesthetized humans and anesthetized animals. This study shows that laryngeal cooling affects the pattern of breathing in the guinea pig and assesses the potential role of cold receptors in this response by using a specific stimulant of cold receptors (Z-menthol). The response to airflows (30 ml/s, 10-s duration) through the isolated upper airway was studied in 23 anesthetized (urethan, 1 g/kg ip) guinea pigs breathing through a tracheostomy. Respiratory airflow, tidal volume, laryngeal temperature, and esophageal pressure were recorded before the challenges (control), during cold airflows (25°C 55% relative humidity), and during warm airflows (37°C saturated) with or without the addition of Zmenthol. Whereas warm air trials had no effect, cold air trials, which lowered laryngeal but not nasal temperature, reduced ventilation (VE) to 85% of control, mainly by prolonging expiratory time (TE, 145% of control), an effect abolished by laryngeal anesthesia. Addition of Z-menthol to the warm airflow caused a greater reduction in VE (41% of control) by prolonging TE (1,028% of control). Nasal anesthesia markedly reduced the apneogenic effect of Z-menthol but did not affect the response to cold air trials. In conclusion, both cooling of the larynx and Z-menthol in the laryngeal lumen reduce ventilation. Exposure of the nasal cavity to Z-menthol markedly enhances this ventilatory inhibition; considering the stimulatory effect of Z-menthol on cold receptors, theseresults suggest a predominant role of nasal cold receptors in this response.
cats has been found to increase total pulmonary resistance, an effect abolished by laryngeal denervation (12). The presence of specific cold receptors in both the larynx (17,19,20) and the nasal cavity (9,11,24) suggests a potential afferent pathway for these reflex responses. However, because laryngeal cooling not only stimulates specific cold receptors but also inhibits mechanoreceptors (21), the reflex effects of cooling may be attributed to one or both of these receptor types. l-Menthol, a specific stimulant of cold receptors (10, l&22), should provide a useful tool to establish the potential role of cold receptors, independent of other upper airway receptors (18). This study evaluates the reflex effects of upper airway cooling and l-menthol on the pattern of breathing in guinea pigs and assesses the potential role of laryngeal and nasal cold receptors in these responses. METHODS
Twenty-three guinea pigs (300-900 g body wt) were anesthetized with urethan (1 g/kg ip) and placed supine on a hollow brass block while warm water was circulated to maintain normal body temperature. The trachea was cannulated in the lower neck and connected to a Fleisch-type pneumotachograph for measuring airflow (V) and tidal volume (VT). A second cannula was secured in the more cranial portion of the trachea, facing the larynx, to allow the delivery of airflow through the functionally isolated upper airway. A thermocouple microprobe (time constant = 5 ms) was passed cold-induced reflexes; cold receptors; laryngeal anesthesia; nathrough this cannula to measure subglottic temperature sal anesthesia (T,,,) (Fig. 1). Temperature in the nose vestibule was also measured with a digital thermometer in eight guinea pigs. In 17 guinea pigs a saline-filled catheter was inCOOLING OF THE UPPER respiratory tract affects the re- serted in the cervical esophagus and its tip positioned in spiratory system in several ways (15, 26, 27). In 1960, the midthorax to monitor intrathoracic pressure (Pes). Garcia Ramos (8) reported an inhibition of respiratory All variables (V, VT, T,,, , Pes) were recorded on a Gould muscle activity when air at room temperature was passed polygraph for further analysis. through the nasal cavity in tracheostomized cats and rabbits with both glossopharyngeal and vagus nerves cut. Experimental Protocol More recently, Al-Shway and Mortola (2) have described Cold trials were performed by passing a constant aira marked respiratory inhibition when air was passed through the isolated upper airway in newborn dogs and flow (30 ml/s for 10 s) at room temperature (25”C, 55% cats. Al-Shway and Mortola excluded pressure changes relative humidity) through the isolated upper airway in as a factor but did not entirely rule out the possibility of a the caudocranial (expiratory) direction (Fig. 1). Warm trials were performed with an identical flow of air, temperature-related component. A definite role of upper airway cooling in depressing respiratory activity has warmed to 35-37OC and fully saturated. l-Menthol chalbeen demonstrated in humans (5,16) and newborn dogs lenges were performed by placing -100 mg of l-menthol (14). In addition, cooling of the isolated upper airway in in a container (130 ml) placed in series with the system 2080
0161-7567/91
$1.50 Copyright
0 1991 the American
Physiological
Society
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COLD AIRJ-MENTHOL,AND
RESPIRATORY REFLEXES
2081
nerves (H. Tsubone and G. Sant’Ambrogio, unpublished observations). Section of these nerves, in addition to that of superior laryngeal nerves, would have led to laryngeal paralysis and an increase in laryngeal resistance. Data Analysis
For each trial, the following variables were analyzed, breath by breath, in control condition (5 s before the airflow) and during the airflow (10 s): inspiratory time (TI), TE, VT, TLAR, VE, and peak Pes. constant flow The time course of all variables in each trial was normalized by using a weighted average. In each guinea pig FIG. 1. Experimental setup. Guinea pig breathed through lower trathe mean time course was then calculated for each condicheal cannula connected to a pneumotachograph to monitor airflow (V) and tidal volume (VT). During trials, a constant airflow was passed tion (warm, cold, I-menthol) in the three protocols. through upper cannula in expiratory direction. Laryngeal temperature On the basis of this analysis, the values of each vari(TLAR) was measured with a thermocouple microprobe inserted in a able during the last 3 s of the trial (when T,,, had side arm of the latter cannula. reached a steady state in the cold trials) were averaged and compared with controls by using the Wilcoxon delivering the warmed airflow. The concentration of 1- signed-rank test. The difference between control and menthol was measured by gas chromatography following steady-state values in each of the three conditions was extraction with acetone from sampling charcoal tubes then compared using a nonparametric randomized-block exposed to warm airflows of 30 ml/s; the concentration of analysis of variance (Friedman’s test) and a TukeyL-menthol was 390 rig/ml rig/ml. type multiple comparison test. Differences were considThree different protocols were used. ered significant at P < 0.05. Data are presented as Intact upper airway. airway. In 17 guinea pigs warm and cold means -t SE. trials were alternately performed (3-5 sequences). At least 2 min were allowed to elapse between trials. These RESULTS trials were then followed by l-menthol challenges, which Cold trials decreased T,,, from 34.2 t 0.4 to 24.9 t were always performed last to avoid possible interferences caused by long-lasting stimulation of cold recep- 0.4”C; the steady-state temperature was reached 7-10 s following the beginning of the trials. During both warm tors by L-menthol (18). Topical anesthesia of the nasal cavity. In 11 of the 17 and L-menthol trials, there was usually an initial slight of a small guinea pigs used in the previous protocol, the same se- decrease in T,,, because of displacement amount of room air in the connecting tube, followed by a quence of cold, warm, and L-menthol trials was repeated gradual return to control values. However, T,,, did not after instillation of 0.08 ml of a 2% lidocaine solution into each nostril. At the end of the experiment, an equal vol- change >l.Z”C above or below control. Temperature ume of Evans blue dye was instilled into the nose and measured in the nose vestibule did not change signifipostmortem dissection was performed. Evans blue dye cantly during the cold trials (control: 30.4 t 0.3”C; steady state: 30.3 t 0.3”C; n = 8). always failed to stain the oropharynx and the larynx, indicating that topical anesthesia remained confined to Intact Upper Airway the nasal cavity. Topical anesthesia of the larynx. In six other guinea The mean values obtained in 17 guinea pigs during pigs, a similar sequence of cold and warm trials was per- warm, cold, and L-menthol trials are summarized in Taformed before and after anesthesia of the larynx. The ble 1 and Fig. 2. Changes in VT, TI, and Pes were not L-menthol trials were conducted only after all the cold significantly different in any of the trials. and warm trials. Anesthesia was performed by introducing a small cotton pledget soaked with 2% lidocaine into TABLE 1. Effects of cold and warm airflow with the larynx. One minute later, the pledget was removed and without l-menthol on TLAR, I?E, and TE and the anesthetization of the laryngeal mucosa confirmed by the failure of mechanical probing to elicit Warm Cold I-Menthol cough or any change in the pattern of breathing. 9 "C To determine whether the pharyngeal and nasal cavi- TLARControl 34.020.4 34.2-to.4 33.7kO.4 ties could be contaminated by the anesthetic, a pledget A 1.wo.3* -9.5-tO.6*1-0.4kO.3 soaked with Evans blue dye was introduced into the lar- VE, ml/s 2.13iz0.15 Control 2.19k0.17 2.1OkO.17 ynx at the end of the experiment. One minute later, the 0.01+0.04 A -0.35kO.O6*j-1.25&0.21*t$ pledget wa wass removed and a sequence of six to eight airs flow trials was performed. A postmortem dissection of TE,Control 0.59kO.05 0.57-to.05 0.62kO.06 the upper airw airway ‘ay establish establisheded that the nasal cavity had A 0.04+0.01* 0.23-tO.03"t 3.62_+0.9O*"f$ not been reached by the Evans blue dye. A topical anesValues are means + SE of 17 guinea pigs and represent average thesia of the larynx was used rather than nerve section, control values and changes (A) from control at steady state during the because in guinea pigs a significant proportion of the af- trials (last 3 s). * P < 0.05 from control. t P < 0.05 from warm. $ P < ferent supplv travels through the recurrent larvngeal 0.05 from cold. Downloaded from www.physiology.org/journal/jappl by ${individualUser.givenNames} ${individualUser.surname} (163.015.154.053) on November 28, 2018. Copyright © 1991 the American Physiological Society. All rights reserved.
COLD AIR, I-MENTHOL, Laryngeal
\l
AND RESPIRATORY
REFLEXES
Temperature
i -1 0-1
Ven
-6
-
-8
.
110
*
tilotion
m-m-m-m-m. 90 loo:
m-m-m--m--m
80
-
70
*
80
-
k
t\
50 40
A “f-p*
*
30 -
Expiratory 160
FIG. 2. Inhibition of ventilation by upper airway cooling (left) and by addition of L-menthol to warm airflow (right): time course of changes (means -t SE; n = 17) in laryngeal temperature, ventilation, and expiratory time for warm air (u), cold air (0, left), and warm air + L-menthol (A, right). Note greater inhibition of respiration with L-menthol compared with cold air (ordinate on lower right has a logarithmic scale).
?
q-t
Time 2000
'
1000
'
1 5 I 4-J k "
300
)
/
120.
% a?
1 ! - !-!-!-!-I I AHA’ T A’
140.
f ~~~m-m-~m~m
100.
T/
200
-m-m-m-m-m
'
i
100
80
L
50
,
0
1.
2
1
4
Time
-
3
6
_
1
8
-
'
d-m-m-m-m-m-m-m-m-m-m
l
,
L
10
0
(s)
A
2
4
Time
Warm air trials, which slightly increased T,,, at steady state, did not modify the pattern of breathing (Fig. 3, bottom), except for a minimal but significant prolongation of TE (108% of control) in the second part of the trials (Table 1, Fig. 2). Cooling of upper airway had an inhibitory effect on ventilation, which decreased progressively to 85% of control. This inhibition was mainly due to a prolongation of TE that increased to 145% of control. Records of our experiments are depicted in Fig. 3 and the results summarized in Table 1 and Fig. 2, left. Addition of L-menthol to the warm air reduced VE (41% of control) to a greater extent than cold trials (Table 1). This ventilatory depression was mainly due to a marked prolongation of TE that increased to 1,028% of control (Table 1, Fig. 2, right). An example is shown in Fig.
4 (top). Topical Anesthesia of the Nasal Cavity
Nasal anesthesia, performed in 11 of 17 guinea pigs, markedly reduced the ventilatory depression (i.e., the
6
8
10
(s)
prolongation of TE) caused by l-menthol as shown in Fig. 4 and summarized in Table 2 and Fig. 5. This residual effect of L-menthol was similar to that of cold air after nasal anesthesia. Although both stimuli still prolonged expiratory duration (cold = 135%; menthol = 151% of control), they did not result in a decrease in VE, because of a concomitant slight but significant increase in VT (cold = 113 t 4%; menthol = 117 t 4% of control). Topical Anesthesia of the Larynx
In six additional guinea pigs, before anesthesia of the larynx, cold airflow decreased T,, (-8.9 t 0.8”C, P < 0.05), increased TE (148 t 18% of control; P < 0.05), and decreased VE (84 t 4% of control, P < 0.05). After anesthesia of the larynx, the response to cold (change in T,,, = -9.3 t 0.7”C) was abolished (TE = 106 t 2% of control; VE = 99 t 3% of control), but Imenthol, which did not appreciably change T,,, (-0.9 t OB"C), remained effective in prolonging expiration and reducing ventilation (TE = 497 t 277% of control, P < 0.05; TjE = 57 t 11% of control, P < 0.05).
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COLD AIR, Z-MENTHOL,
T
37 lar
(“Cl
2s
37 lar (“Cl
T
25
AND RESPIRATORY
I
I
REFLEXES
2083
FIG. 3. Experimental records of cold and warm air trials: esophageal pressure (Pes), 9 (inspiration upward), VT, and T,,.
1
2 8OC ’
DISCUSSION
Our results indicate th .at cold airflow through the upper airway depresses VE, mainly through a prolongation of the expiratory duration. These effects are abolished by laryngeal anesthesia and are not elicited bY warm airflow. These observati .ons suggest that the mai n effect of cold airflow (i.e., prolongation of TE) is attributable entirely to laryngeal afferents responsive to cooling. A reduction in local temperature has at least two known effects at the level of the larynx. Specific laryngeal cold receptors are stimulated and different types of laryngeal mechanoreceptors are inhibited; presumably nasal receptors have similar characteristics. Therefore the reflex effects of cooling cannot be easily attributed to a single type of receptor. In this study we used l-menthol, a specific stimulant of cold receptors (10,18,22), to stimulate cold receptors without changing local temperature and thus “clamp” the activity level of mechanoreceptors. The addition of L-menthol to warm air passed through the upper airway depresses ventilation to a much greater extent than airway cooling; this effect is substantially reduced by nasal anesthesia. Because L-menthol stimulates cold receptors (10,18,22), these results suggest that upper airway cold receptors are predominantly located within the nasal cavity. An abundance of cold receptors within the nasal cavity has been reported in cats (9) and rats (24). Indeed, in the cat the electroneurographic activity recorded from the ethmoidal nerve, which supplies the nasal mucosa, is mostly related to cooling (9). In the rat 55% of the fibers of the ethmoidal nerve have an activity originating from cold receptors (24). The stimula-
tion of nasal cold receptors, in addition to laryngeal cold endings, would contribute substantially to the ventilatory inhibition. The failure of upper airway cooling to produce respiratory inhibition similar to that obtained with I-menthol could be simply due to an insufficient cooling of the nasal mucosa; cold air passing through the upper airway in the expiratory direction should become warmer and saturated toward the nasal cavity. Indeed, temperature measurements in the nasal vestibule failed to detect any change during the cold air trials. However, L-menthol transported by the airflow should reach the nasal cavity as well as the larynx and, by stimulating cold receptors in both places, should result in greater reflex responses. This is substantiated by the fact that when the nasal mucosa was anesthetized the prolongation of TE elicited by Z-menthol was very similar to that of cold trials, suggesting a stimulation of laryngeal cold receptors comparable to that obtained with the cold airflow. Although there is no direct evidence, the existence of cold receptors in the upper airway of the guinea pig can be inferred on the basis of what is known of other mammalian species; cold receptors have been demonstrated in the nasal cavity of rats (24), cats (9), and rabbits (11) and in the larynx of dogs (19, 20) and rabbits (17). Furthermore the reflex effects of Z-menthol described here can also be used as supportive evidence for the presence of cold receptors in both larynx and nasal cavity. Although the specificity of I-menthol as a stimulant of laryngeal cold endings (compared with laryngeal mechanoreceptors) has been demonstrated (18), the same is not necessarily true for nasal receptors, because I-menthol
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2084
COLD AIR, L-MENTHOL, WARM
AND RESPIRATORY
REFLEXES
AIR + I -MENTHOL
0 R8
(kPa) -1
WARM
T ler (“Cl
37 25
AIR + l -MENTHOL
I
AFTER
FIG. 4. Experimental records of warm air + Z-menthol trials before and after topical anesthesia of nasal mucosa. Traces as in Fig. 3.
LIDOCAINE
\
t
2 8OC 1
should also stimulate olfactory endings. Indeed, the concentration of L-menthol used in this study was 187 times the olfactory recognition threshold of humans (25). Therefore we cannot exclude a possible role of olfaction in the apneogenic effect of l-menthol. This possibility is not without merit, and it has been explored in previous studies. Olfaction has either been minimized (3,13) or recognized (1) as a contributing factor in the respiratory reflex responses to upper airway stimuli. In the case of I-menthol-induced reflex respiratory responses from the nose, this possibility requires further investigation. A similar problem was encountered by Eccles et al. (7), TABLE
2. Effects of nasal anesthesia on TLAR, ‘CiE, and cold and warm airflow + l-menthol
TE during
Cold Intact
T LAR9 “C Control A \;7E, ml/s Control A TE, s Control A
I-Menthol Anesthesia
Intact
Anesthesia
34.420.5 -9.6+0.6*?
33.6kO.7 -9.2kOA"t
33.7t0.6 -0.420.3
33.OkO.7 0.3kO.3
2.14-+0.18 -0.44+0.07*t
1.93kO.22 -0.13_+0.10-f
1.96-t0.19 -1.39-+0.20*
1.86kO.21 -0.20+0.11t
0.57-tO.06 0.2f3+0.02*t
0.62kO.07 0.13+0.04*t
0.64t0.07 3.72-tO.91*
0.61t0.07 0.25+0.08*t
Values are means + SE of guinea pigs and represent average control values and changes (A) from control at steady state (last 3 s of the trials) and after nasal anesthesia. * P < 0.05 from control. t P < 0.05 from Z-menthol in intact condition.
who, while studying the nasal sensations of airflow, tried to dissociate the effects of l-menthol on cold receptors from that of olfaction. They used two isomers (d-isomenthol and d-neomenthol) similar in chemical structure and odor to l-menthol. Because these isomers were found to be ineffective in enhancing the sensation of airflow, they were assumed to be unable to stimulate nasal cold receptors. In previous experiments (18), we found that d-isomenthol and d-neomenthol do stimulate laryngeal cold receptors and therefore cannot be used to separate the possible role of olfaction from that of cold receptor stimulation. Two further aspects of the present results are not readily explainable. I) After nasal anesthesia, the prolongation of TE elicited by both cold and l-menthol trials, although not different from that obtained with cold trials before anesthesia (Table 2, Fig. 5), is not accompanied by a decrease in VE because of a concomitant slight increase in VT. This could be due to the removal of inhibitory influence on inspiratory activity originating from the nose. 2) The inhibitory effect of l-menthol after laryngeal anesthesia is not as large as expected on the basis of the results after nasal anesthesia (Fig. 5, bottom). Because the relative contribution of laryngeal afferents to the prolongation of TE seems to be only a small fraction of that due to nasal afferents, one should have expected only a marginal effect of laryngeal anesthesia on the response to l-menthol. Instead, after laryngeal anesthesia, the l-menthol-induced prolongation of TE was reduced by one-half (intact airway = 1,028 t 394% of control, n = 17; after anesthesia = 497 $- 277% of control, n = 6; P < 0.05, Mann-Whitney test). Although this reduced re-
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COLD Laryngeal
AIR,
L-MENTHOL,
AND
, o?+a c 0 u
&-A--*=&X$&A-A--a--A
\
-2. -4
-+---~-&--~
\
T
-
E f -6Yi% -8 c0 -10 6 -12 Ventilation 120
-
100
-
2085
REFLEXES
tentiation of the apneogenic tendency with sleep and anesthesia that is presumed to depend on the depression of the arousal system under these conditions. However, cooling of the upper airway has been found to cause significant inhibition of respiratory activity in conscious adult humans (5, 16). In conclusion, cooling of the larynx reduces ventilation in adult guinea pigs. The results obtained with Z-menthol strongly suggest that this inhibition is mediated by cold receptors. This inhibition is markedly enhanced by Imenthol in the nasal cavity, which suggests that nasal cold receptors are more numerous and/or have stronger inhibitory influences than laryngeal cold receptors. Because the nasal cavity is more readily cooled than the larynx in most physiological conditions, the stronger reflex influence of nasal cold receptors seems to be appropriate for eliciting responses related to the thermal homeostasis of the airways.
Temperature
2-
RESPIRATORY
72
+ E 0
80~
z
60-
The authors thank Drs. Norman M. Trieff and Sadagopa V. M. Ramanujam for the gas chromatographic estimates of Z-menthol. They also gratefully acknowledge the secretarial help of Lynette Durant. This work was supported by National Heart, Lung, and Blood Institute Grant HL-20122. Address reprint requests to G. P. Orani, % G. Sant’Ambrogio.
x 40
-
Received
20 L
Expiratory
z! *
-
1000
-
2. 500
).
6 u %
3. 200
a? 100
4.
-
5.
50 L
0
-1
-
2
1
4
-
’
6
-
’
0
_
1
10
6.
Time
1990; accepted
in final
form
27 December
1990.
REFERENCES
Time
1.
2000
14 May
(s)
FIG. 5. Effect of upper airway cooling (circles) and warm air + Zmenthol (triangles) before (open symbols) and after (filled symbols) topical anesthesia of nasal mucosa: time course of changes (means & SE; n = 11) in laryngeal temperature, ventilation, and expiratory time.
sponse to L-menthol could be attributed to some contamination of the nasal cavity with the lidocaine used to anesthetize the laryngeal mucosa, our observations with Evans’ blue dye do not support this possibility. As an alternative, we may speculate that laryngeal cold receptors, besides exerting a small direct influence on the ventilatory inhibition due to L-menthol, have an additional facilitatory influence on the input from nasal cold receptors (i.e., when the 2 populations of cold receptors are recruited concurrently, the resulting reflex response is greater than the sum of the 2 separate responses). The reflex effects of laryngeal afferents, whether naturally or artificially stimulated, are dependent on anesthesia (6), on the wakefulness-sleep state (23), and on the developmental stage (2, 4, 14). In general, there is a po-
7.
8.
9.
10. 11.
12.
13. 14.
ALLEN, W. F. Effect
on respiration, blood pressure and carotid pulse of various inhaled and insufflated vapors when stimulating one cranial nerve and various combinations of cranial nerves. Am. J. Physiol. 88: 117-129, 1929. AL-SHWAY, S. F., AND J. P. MORTOLA. Respiratory effects of airflow through the upper airways in newborn kittens and puppies. J. Appl. Physiol. 53: 805-814, 1982. ANDERSEN, P. Inhibitory influences elicited from the trigeminal and olfactory nerves in rabbits. Acta Physiol. Scud. 30: 137-148, 1953. BOGGS, D. F., AND D. BARTLETT, JR. Chemical specificity of a laryngeal apneic reflex in puppies. J. Appl. Physiol. 53: 455-462, 1982. BURGESS, K. R., AND W. A. WHITELAW. Reducing ventilatory response to carbon dioxide by breathing cold air. Am. Reu. Respir. Dis. 129: 687-690, 1984. DONNELLY, D. F., AND G. G. HADDAD. Effects of graded anesthesia on laryngeal-induced central apnea. Respir. Physiol. 66: 235-245, 1986. ECCLES, R., D. H. GRIFFITHS, C. G. NEWTON, AND N. S. TOLLEY. The effects of menthol isomers on nasal sensation of airflow. Clin. Otolaryngol. Oxf. 13: 25-29, 1988. GARCIA RAMOS, J. On the integration of respiratory movements. III. The fifth nerve afferents. Acta Physiol. Latinoam. 10: 104-113, 1960. GLEBOVSKY, V. D., AND A. V. BAYEV. Stimulation of nasal cavity mucosal trigeminal receptors with respiratory airflows [in Russian]. Sechenov. Physiol. J. USSR 70: 1534-1541, 1984. HENSEL, H., AND Y. ZOTTERMAN. The effect of menthol on the thermoreceptors. Acta Physiol. Stand. 24: 27-34, 1951. HOSHINO, T. In vitro electrophysiologic studies on nasal airway receptors of the rabbit. Ann. Otol. Rhinol. Laryngol. 97: 294-297, 1988. JAMMES, Y., P. BARTHELEMY, AND S. DELPIERRE. Respiratory effects of cold air breathing in anesthetized cats. Respir. Physiol. 54: 41-54, 1983. KRATSCHMER, F. uber Reflexe von der Nasenschleimhaut auf Athmung und Kreislauf. Sitz. Akad. Wiss. Wien 62: 147-170, 1870. MATHEW, 0. P., J. W. ANDERSON, G. P. ORANI, F. B. SANT'AMBROGIO, AND G. SANT’AMBROGIO. Cooling mediates the ventilatory depression associated with airflow through the larynx. Respir. Physiol. 82: 359-368, 1990.
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COLD AIR, l-MENTHOL,
2086 15. MATHEW, 0. In: Respiratory
AND RESPIRATORY
P., AND F. B. SANT’AMBROGIO.
REFLEXES
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21. SANT’AMBROGIO,
1981. 17. MORTOLA,
Waking and ventilatory responses to laryngeal stimulation in sleeping dogs. J. Appl. Physiol. 45: 681-689, 1978. 24. TS~BONE, H. Nasal “flow” receptors of the rat. Respir. Physiol. 75:
1985. 18. SANT’AMBROGIO,
51-64, 1989. 25. VERSCHXJEREN, K. Handbook of Environmental Data on Organic Chemicals. New York: Van Nostrand Reinhold, 1983, p. 809. 26. WIDDICOMBE, J. G. Reflexes from the upper respiratory tract. In: Handbook of Physiology. The Respiratory System. Control of Breathing. Bethesda, MD: Am. Physiol. Sot., 1986, sect. 3, vol. II, p. 363-
Function
of the
Upper
Airway,
J. P., G. CITTERIO, AND E. AGOSTONI. Sulphur dioxide block of laryngeal receptors in rabbits. Respir. Physiol. 62: 195-202, F. B., J. W. ANDERSON, AND G. SANT’AMBROGIO. Effect of I-menthol on laryngeal receptors. J. Appl. Physiot. 70:
788-793, 1991. 19. SANT’AMBROGIO, SANT’AMBROGIO.
G., 0. P. MATHEW, J. T, FISHER, AND F. B. Laryngeal receptors responding to transmural pressure, airflow and local muscle activity. Respir. Physiol. 54: 317-
330,1983. 20. SANT’AMBROGIO,
Characteristics 287-298,1988.
G., F. B. SANT’AMBROGIO, AND 0. P. MATHEW. Effect of cold air on laryngeal mechanoreceptors in the dog. Respir.
Physiol. 64: 45-56, 1986. 22. SCHAFER, K., H. A. BRAUN, AND C. ISENBERG. Effect of menthol cold receptor activity. J. Gen. Physiol. 88: 757-776, 1986. 23. SULLIVAN, C. E., E. MURPHY, L. F. KOZAR, AND E. A. PHILLIPSON.
on
394. J. G., G. SANT’AMBROGIO, AND 0. P. MATHEW. Nerve receptors of the upper airway. In: Respiratory Function of the Upper Airway, edited by 0. P. Mathew and G. Sant’Ambrogio. New York: Dekker, 1988, p. 193-231. (Lung Biol. Health Dis. Ser.)
27. WIDDICOMBE,
G., 0. P. MATHEW, AND F. B. SANT’AMBROGIO. of laryngeal cold receptors. Respir. Physiol. 71:
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J. W. ANDERSON,
G. SANT’AMBROGIO,
AND F. B. SANT’AMBROGIO
Department of Physiology and Biophysics, The University of Texas Medical Branch at Galveston, Galveston, Texas 77550 ORANI, G. P., J. W. ANDERSON,G. SANT'AMBROGIO,AND F. B. SANT'AMBROGIO.Upper airway cooling and Z-menthol reduce ventilation in the guinea pig. J. Appl. Physiol. 70(5): 20802086,1991.-Cooling of the upper airway, which stimulates specific cold receptors and inhibits laryngeal mechanoreceptors, reduces respiratory activity in unanesthetized humans and anesthetized animals. This study shows that laryngeal cooling affects the pattern of breathing in the guinea pig and assesses the potential role of cold receptors in this response by using a specific stimulant of cold receptors (Z-menthol). The response to airflows (30 ml/s, 10-s duration) through the isolated upper airway was studied in 23 anesthetized (urethan, 1 g/kg ip) guinea pigs breathing through a tracheostomy. Respiratory airflow, tidal volume, laryngeal temperature, and esophageal pressure were recorded before the challenges (control), during cold airflows (25°C 55% relative humidity), and during warm airflows (37°C saturated) with or without the addition of Zmenthol. Whereas warm air trials had no effect, cold air trials, which lowered laryngeal but not nasal temperature, reduced ventilation (VE) to 85% of control, mainly by prolonging expiratory time (TE, 145% of control), an effect abolished by laryngeal anesthesia. Addition of Z-menthol to the warm airflow caused a greater reduction in VE (41% of control) by prolonging TE (1,028% of control). Nasal anesthesia markedly reduced the apneogenic effect of Z-menthol but did not affect the response to cold air trials. In conclusion, both cooling of the larynx and Z-menthol in the laryngeal lumen reduce ventilation. Exposure of the nasal cavity to Z-menthol markedly enhances this ventilatory inhibition; considering the stimulatory effect of Z-menthol on cold receptors, theseresults suggest a predominant role of nasal cold receptors in this response.
cats has been found to increase total pulmonary resistance, an effect abolished by laryngeal denervation (12). The presence of specific cold receptors in both the larynx (17,19,20) and the nasal cavity (9,11,24) suggests a potential afferent pathway for these reflex responses. However, because laryngeal cooling not only stimulates specific cold receptors but also inhibits mechanoreceptors (21), the reflex effects of cooling may be attributed to one or both of these receptor types. l-Menthol, a specific stimulant of cold receptors (10, l&22), should provide a useful tool to establish the potential role of cold receptors, independent of other upper airway receptors (18). This study evaluates the reflex effects of upper airway cooling and l-menthol on the pattern of breathing in guinea pigs and assesses the potential role of laryngeal and nasal cold receptors in these responses. METHODS
Twenty-three guinea pigs (300-900 g body wt) were anesthetized with urethan (1 g/kg ip) and placed supine on a hollow brass block while warm water was circulated to maintain normal body temperature. The trachea was cannulated in the lower neck and connected to a Fleisch-type pneumotachograph for measuring airflow (V) and tidal volume (VT). A second cannula was secured in the more cranial portion of the trachea, facing the larynx, to allow the delivery of airflow through the functionally isolated upper airway. A thermocouple microprobe (time constant = 5 ms) was passed cold-induced reflexes; cold receptors; laryngeal anesthesia; nathrough this cannula to measure subglottic temperature sal anesthesia (T,,,) (Fig. 1). Temperature in the nose vestibule was also measured with a digital thermometer in eight guinea pigs. In 17 guinea pigs a saline-filled catheter was inCOOLING OF THE UPPER respiratory tract affects the re- serted in the cervical esophagus and its tip positioned in spiratory system in several ways (15, 26, 27). In 1960, the midthorax to monitor intrathoracic pressure (Pes). Garcia Ramos (8) reported an inhibition of respiratory All variables (V, VT, T,,, , Pes) were recorded on a Gould muscle activity when air at room temperature was passed polygraph for further analysis. through the nasal cavity in tracheostomized cats and rabbits with both glossopharyngeal and vagus nerves cut. Experimental Protocol More recently, Al-Shway and Mortola (2) have described Cold trials were performed by passing a constant aira marked respiratory inhibition when air was passed through the isolated upper airway in newborn dogs and flow (30 ml/s for 10 s) at room temperature (25”C, 55% cats. Al-Shway and Mortola excluded pressure changes relative humidity) through the isolated upper airway in as a factor but did not entirely rule out the possibility of a the caudocranial (expiratory) direction (Fig. 1). Warm trials were performed with an identical flow of air, temperature-related component. A definite role of upper airway cooling in depressing respiratory activity has warmed to 35-37OC and fully saturated. l-Menthol chalbeen demonstrated in humans (5,16) and newborn dogs lenges were performed by placing -100 mg of l-menthol (14). In addition, cooling of the isolated upper airway in in a container (130 ml) placed in series with the system 2080
0161-7567/91
$1.50 Copyright
0 1991 the American
Physiological
Society
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COLD AIRJ-MENTHOL,AND
RESPIRATORY REFLEXES
2081
nerves (H. Tsubone and G. Sant’Ambrogio, unpublished observations). Section of these nerves, in addition to that of superior laryngeal nerves, would have led to laryngeal paralysis and an increase in laryngeal resistance. Data Analysis
For each trial, the following variables were analyzed, breath by breath, in control condition (5 s before the airflow) and during the airflow (10 s): inspiratory time (TI), TE, VT, TLAR, VE, and peak Pes. constant flow The time course of all variables in each trial was normalized by using a weighted average. In each guinea pig FIG. 1. Experimental setup. Guinea pig breathed through lower trathe mean time course was then calculated for each condicheal cannula connected to a pneumotachograph to monitor airflow (V) and tidal volume (VT). During trials, a constant airflow was passed tion (warm, cold, I-menthol) in the three protocols. through upper cannula in expiratory direction. Laryngeal temperature On the basis of this analysis, the values of each vari(TLAR) was measured with a thermocouple microprobe inserted in a able during the last 3 s of the trial (when T,,, had side arm of the latter cannula. reached a steady state in the cold trials) were averaged and compared with controls by using the Wilcoxon delivering the warmed airflow. The concentration of 1- signed-rank test. The difference between control and menthol was measured by gas chromatography following steady-state values in each of the three conditions was extraction with acetone from sampling charcoal tubes then compared using a nonparametric randomized-block exposed to warm airflows of 30 ml/s; the concentration of analysis of variance (Friedman’s test) and a TukeyL-menthol was 390 rig/ml rig/ml. type multiple comparison test. Differences were considThree different protocols were used. ered significant at P < 0.05. Data are presented as Intact upper airway. airway. In 17 guinea pigs warm and cold means -t SE. trials were alternately performed (3-5 sequences). At least 2 min were allowed to elapse between trials. These RESULTS trials were then followed by l-menthol challenges, which Cold trials decreased T,,, from 34.2 t 0.4 to 24.9 t were always performed last to avoid possible interferences caused by long-lasting stimulation of cold recep- 0.4”C; the steady-state temperature was reached 7-10 s following the beginning of the trials. During both warm tors by L-menthol (18). Topical anesthesia of the nasal cavity. In 11 of the 17 and L-menthol trials, there was usually an initial slight of a small guinea pigs used in the previous protocol, the same se- decrease in T,,, because of displacement amount of room air in the connecting tube, followed by a quence of cold, warm, and L-menthol trials was repeated gradual return to control values. However, T,,, did not after instillation of 0.08 ml of a 2% lidocaine solution into each nostril. At the end of the experiment, an equal vol- change >l.Z”C above or below control. Temperature ume of Evans blue dye was instilled into the nose and measured in the nose vestibule did not change signifipostmortem dissection was performed. Evans blue dye cantly during the cold trials (control: 30.4 t 0.3”C; steady state: 30.3 t 0.3”C; n = 8). always failed to stain the oropharynx and the larynx, indicating that topical anesthesia remained confined to Intact Upper Airway the nasal cavity. Topical anesthesia of the larynx. In six other guinea The mean values obtained in 17 guinea pigs during pigs, a similar sequence of cold and warm trials was per- warm, cold, and L-menthol trials are summarized in Taformed before and after anesthesia of the larynx. The ble 1 and Fig. 2. Changes in VT, TI, and Pes were not L-menthol trials were conducted only after all the cold significantly different in any of the trials. and warm trials. Anesthesia was performed by introducing a small cotton pledget soaked with 2% lidocaine into TABLE 1. Effects of cold and warm airflow with the larynx. One minute later, the pledget was removed and without l-menthol on TLAR, I?E, and TE and the anesthetization of the laryngeal mucosa confirmed by the failure of mechanical probing to elicit Warm Cold I-Menthol cough or any change in the pattern of breathing. 9 "C To determine whether the pharyngeal and nasal cavi- TLARControl 34.020.4 34.2-to.4 33.7kO.4 ties could be contaminated by the anesthetic, a pledget A 1.wo.3* -9.5-tO.6*1-0.4kO.3 soaked with Evans blue dye was introduced into the lar- VE, ml/s 2.13iz0.15 Control 2.19k0.17 2.1OkO.17 ynx at the end of the experiment. One minute later, the 0.01+0.04 A -0.35kO.O6*j-1.25&0.21*t$ pledget wa wass removed and a sequence of six to eight airs flow trials was performed. A postmortem dissection of TE,Control 0.59kO.05 0.57-to.05 0.62kO.06 the upper airw airway ‘ay establish establisheded that the nasal cavity had A 0.04+0.01* 0.23-tO.03"t 3.62_+0.9O*"f$ not been reached by the Evans blue dye. A topical anesValues are means + SE of 17 guinea pigs and represent average thesia of the larynx was used rather than nerve section, control values and changes (A) from control at steady state during the because in guinea pigs a significant proportion of the af- trials (last 3 s). * P < 0.05 from control. t P < 0.05 from warm. $ P < ferent supplv travels through the recurrent larvngeal 0.05 from cold. Downloaded from www.physiology.org/journal/jappl by ${individualUser.givenNames} ${individualUser.surname} (163.015.154.053) on November 28, 2018. Copyright © 1991 the American Physiological Society. All rights reserved.
COLD AIR, I-MENTHOL, Laryngeal
\l
AND RESPIRATORY
REFLEXES
Temperature
i -1 0-1
Ven
-6
-
-8
.
110
*
tilotion
m-m-m-m-m. 90 loo:
m-m-m--m--m
80
-
70
*
80
-
k
t\
50 40
A “f-p*
*
30 -
Expiratory 160
FIG. 2. Inhibition of ventilation by upper airway cooling (left) and by addition of L-menthol to warm airflow (right): time course of changes (means -t SE; n = 17) in laryngeal temperature, ventilation, and expiratory time for warm air (u), cold air (0, left), and warm air + L-menthol (A, right). Note greater inhibition of respiration with L-menthol compared with cold air (ordinate on lower right has a logarithmic scale).
?
q-t
Time 2000
'
1000
'
1 5 I 4-J k "
300
)
/
120.
% a?
1 ! - !-!-!-!-I I AHA’ T A’
140.
f ~~~m-m-~m~m
100.
T/
200
-m-m-m-m-m
'
i
100
80
L
50
,
0
1.
2
1
4
Time
-
3
6
_
1
8
-
'
d-m-m-m-m-m-m-m-m-m-m
l
,
L
10
0
(s)
A
2
4
Time
Warm air trials, which slightly increased T,,, at steady state, did not modify the pattern of breathing (Fig. 3, bottom), except for a minimal but significant prolongation of TE (108% of control) in the second part of the trials (Table 1, Fig. 2). Cooling of upper airway had an inhibitory effect on ventilation, which decreased progressively to 85% of control. This inhibition was mainly due to a prolongation of TE that increased to 145% of control. Records of our experiments are depicted in Fig. 3 and the results summarized in Table 1 and Fig. 2, left. Addition of L-menthol to the warm air reduced VE (41% of control) to a greater extent than cold trials (Table 1). This ventilatory depression was mainly due to a marked prolongation of TE that increased to 1,028% of control (Table 1, Fig. 2, right). An example is shown in Fig.
4 (top). Topical Anesthesia of the Nasal Cavity
Nasal anesthesia, performed in 11 of 17 guinea pigs, markedly reduced the ventilatory depression (i.e., the
6
8
10
(s)
prolongation of TE) caused by l-menthol as shown in Fig. 4 and summarized in Table 2 and Fig. 5. This residual effect of L-menthol was similar to that of cold air after nasal anesthesia. Although both stimuli still prolonged expiratory duration (cold = 135%; menthol = 151% of control), they did not result in a decrease in VE, because of a concomitant slight but significant increase in VT (cold = 113 t 4%; menthol = 117 t 4% of control). Topical Anesthesia of the Larynx
In six additional guinea pigs, before anesthesia of the larynx, cold airflow decreased T,, (-8.9 t 0.8”C, P < 0.05), increased TE (148 t 18% of control; P < 0.05), and decreased VE (84 t 4% of control, P < 0.05). After anesthesia of the larynx, the response to cold (change in T,,, = -9.3 t 0.7”C) was abolished (TE = 106 t 2% of control; VE = 99 t 3% of control), but Imenthol, which did not appreciably change T,,, (-0.9 t OB"C), remained effective in prolonging expiration and reducing ventilation (TE = 497 t 277% of control, P < 0.05; TjE = 57 t 11% of control, P < 0.05).
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COLD AIR, Z-MENTHOL,
T
37 lar
(“Cl
2s
37 lar (“Cl
T
25
AND RESPIRATORY
I
I
REFLEXES
2083
FIG. 3. Experimental records of cold and warm air trials: esophageal pressure (Pes), 9 (inspiration upward), VT, and T,,.
1
2 8OC ’
DISCUSSION
Our results indicate th .at cold airflow through the upper airway depresses VE, mainly through a prolongation of the expiratory duration. These effects are abolished by laryngeal anesthesia and are not elicited bY warm airflow. These observati .ons suggest that the mai n effect of cold airflow (i.e., prolongation of TE) is attributable entirely to laryngeal afferents responsive to cooling. A reduction in local temperature has at least two known effects at the level of the larynx. Specific laryngeal cold receptors are stimulated and different types of laryngeal mechanoreceptors are inhibited; presumably nasal receptors have similar characteristics. Therefore the reflex effects of cooling cannot be easily attributed to a single type of receptor. In this study we used l-menthol, a specific stimulant of cold receptors (10,18,22), to stimulate cold receptors without changing local temperature and thus “clamp” the activity level of mechanoreceptors. The addition of L-menthol to warm air passed through the upper airway depresses ventilation to a much greater extent than airway cooling; this effect is substantially reduced by nasal anesthesia. Because L-menthol stimulates cold receptors (10,18,22), these results suggest that upper airway cold receptors are predominantly located within the nasal cavity. An abundance of cold receptors within the nasal cavity has been reported in cats (9) and rats (24). Indeed, in the cat the electroneurographic activity recorded from the ethmoidal nerve, which supplies the nasal mucosa, is mostly related to cooling (9). In the rat 55% of the fibers of the ethmoidal nerve have an activity originating from cold receptors (24). The stimula-
tion of nasal cold receptors, in addition to laryngeal cold endings, would contribute substantially to the ventilatory inhibition. The failure of upper airway cooling to produce respiratory inhibition similar to that obtained with I-menthol could be simply due to an insufficient cooling of the nasal mucosa; cold air passing through the upper airway in the expiratory direction should become warmer and saturated toward the nasal cavity. Indeed, temperature measurements in the nasal vestibule failed to detect any change during the cold air trials. However, L-menthol transported by the airflow should reach the nasal cavity as well as the larynx and, by stimulating cold receptors in both places, should result in greater reflex responses. This is substantiated by the fact that when the nasal mucosa was anesthetized the prolongation of TE elicited by Z-menthol was very similar to that of cold trials, suggesting a stimulation of laryngeal cold receptors comparable to that obtained with the cold airflow. Although there is no direct evidence, the existence of cold receptors in the upper airway of the guinea pig can be inferred on the basis of what is known of other mammalian species; cold receptors have been demonstrated in the nasal cavity of rats (24), cats (9), and rabbits (11) and in the larynx of dogs (19, 20) and rabbits (17). Furthermore the reflex effects of Z-menthol described here can also be used as supportive evidence for the presence of cold receptors in both larynx and nasal cavity. Although the specificity of I-menthol as a stimulant of laryngeal cold endings (compared with laryngeal mechanoreceptors) has been demonstrated (18), the same is not necessarily true for nasal receptors, because I-menthol
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2084
COLD AIR, L-MENTHOL, WARM
AND RESPIRATORY
REFLEXES
AIR + I -MENTHOL
0 R8
(kPa) -1
WARM
T ler (“Cl
37 25
AIR + l -MENTHOL
I
AFTER
FIG. 4. Experimental records of warm air + Z-menthol trials before and after topical anesthesia of nasal mucosa. Traces as in Fig. 3.
LIDOCAINE
\
t
2 8OC 1
should also stimulate olfactory endings. Indeed, the concentration of L-menthol used in this study was 187 times the olfactory recognition threshold of humans (25). Therefore we cannot exclude a possible role of olfaction in the apneogenic effect of l-menthol. This possibility is not without merit, and it has been explored in previous studies. Olfaction has either been minimized (3,13) or recognized (1) as a contributing factor in the respiratory reflex responses to upper airway stimuli. In the case of I-menthol-induced reflex respiratory responses from the nose, this possibility requires further investigation. A similar problem was encountered by Eccles et al. (7), TABLE
2. Effects of nasal anesthesia on TLAR, ‘CiE, and cold and warm airflow + l-menthol
TE during
Cold Intact
T LAR9 “C Control A \;7E, ml/s Control A TE, s Control A
I-Menthol Anesthesia
Intact
Anesthesia
34.420.5 -9.6+0.6*?
33.6kO.7 -9.2kOA"t
33.7t0.6 -0.420.3
33.OkO.7 0.3kO.3
2.14-+0.18 -0.44+0.07*t
1.93kO.22 -0.13_+0.10-f
1.96-t0.19 -1.39-+0.20*
1.86kO.21 -0.20+0.11t
0.57-tO.06 0.2f3+0.02*t
0.62kO.07 0.13+0.04*t
0.64t0.07 3.72-tO.91*
0.61t0.07 0.25+0.08*t
Values are means + SE of guinea pigs and represent average control values and changes (A) from control at steady state (last 3 s of the trials) and after nasal anesthesia. * P < 0.05 from control. t P < 0.05 from Z-menthol in intact condition.
who, while studying the nasal sensations of airflow, tried to dissociate the effects of l-menthol on cold receptors from that of olfaction. They used two isomers (d-isomenthol and d-neomenthol) similar in chemical structure and odor to l-menthol. Because these isomers were found to be ineffective in enhancing the sensation of airflow, they were assumed to be unable to stimulate nasal cold receptors. In previous experiments (18), we found that d-isomenthol and d-neomenthol do stimulate laryngeal cold receptors and therefore cannot be used to separate the possible role of olfaction from that of cold receptor stimulation. Two further aspects of the present results are not readily explainable. I) After nasal anesthesia, the prolongation of TE elicited by both cold and l-menthol trials, although not different from that obtained with cold trials before anesthesia (Table 2, Fig. 5), is not accompanied by a decrease in VE because of a concomitant slight increase in VT. This could be due to the removal of inhibitory influence on inspiratory activity originating from the nose. 2) The inhibitory effect of l-menthol after laryngeal anesthesia is not as large as expected on the basis of the results after nasal anesthesia (Fig. 5, bottom). Because the relative contribution of laryngeal afferents to the prolongation of TE seems to be only a small fraction of that due to nasal afferents, one should have expected only a marginal effect of laryngeal anesthesia on the response to l-menthol. Instead, after laryngeal anesthesia, the l-menthol-induced prolongation of TE was reduced by one-half (intact airway = 1,028 t 394% of control, n = 17; after anesthesia = 497 $- 277% of control, n = 6; P < 0.05, Mann-Whitney test). Although this reduced re-
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COLD Laryngeal
AIR,
L-MENTHOL,
AND
, o?+a c 0 u
&-A--*=&X$&A-A--a--A
\
-2. -4
-+---~-&--~
\
T
-
E f -6Yi% -8 c0 -10 6 -12 Ventilation 120
-
100
-
2085
REFLEXES
tentiation of the apneogenic tendency with sleep and anesthesia that is presumed to depend on the depression of the arousal system under these conditions. However, cooling of the upper airway has been found to cause significant inhibition of respiratory activity in conscious adult humans (5, 16). In conclusion, cooling of the larynx reduces ventilation in adult guinea pigs. The results obtained with Z-menthol strongly suggest that this inhibition is mediated by cold receptors. This inhibition is markedly enhanced by Imenthol in the nasal cavity, which suggests that nasal cold receptors are more numerous and/or have stronger inhibitory influences than laryngeal cold receptors. Because the nasal cavity is more readily cooled than the larynx in most physiological conditions, the stronger reflex influence of nasal cold receptors seems to be appropriate for eliciting responses related to the thermal homeostasis of the airways.
Temperature
2-
RESPIRATORY
72
+ E 0
80~
z
60-
The authors thank Drs. Norman M. Trieff and Sadagopa V. M. Ramanujam for the gas chromatographic estimates of Z-menthol. They also gratefully acknowledge the secretarial help of Lynette Durant. This work was supported by National Heart, Lung, and Blood Institute Grant HL-20122. Address reprint requests to G. P. Orani, % G. Sant’Ambrogio.
x 40
-
Received
20 L
Expiratory
z! *
-
1000
-
2. 500
).
6 u %
3. 200
a? 100
4.
-
5.
50 L
0
-1
-
2
1
4
-
’
6
-
’
0
_
1
10
6.
Time
1990; accepted
in final
form
27 December
1990.
REFERENCES
Time
1.
2000
14 May
(s)
FIG. 5. Effect of upper airway cooling (circles) and warm air + Zmenthol (triangles) before (open symbols) and after (filled symbols) topical anesthesia of nasal mucosa: time course of changes (means & SE; n = 11) in laryngeal temperature, ventilation, and expiratory time.
sponse to L-menthol could be attributed to some contamination of the nasal cavity with the lidocaine used to anesthetize the laryngeal mucosa, our observations with Evans’ blue dye do not support this possibility. As an alternative, we may speculate that laryngeal cold receptors, besides exerting a small direct influence on the ventilatory inhibition due to L-menthol, have an additional facilitatory influence on the input from nasal cold receptors (i.e., when the 2 populations of cold receptors are recruited concurrently, the resulting reflex response is greater than the sum of the 2 separate responses). The reflex effects of laryngeal afferents, whether naturally or artificially stimulated, are dependent on anesthesia (6), on the wakefulness-sleep state (23), and on the developmental stage (2, 4, 14). In general, there is a po-
7.
8.
9.
10. 11.
12.
13. 14.
ALLEN, W. F. Effect
on respiration, blood pressure and carotid pulse of various inhaled and insufflated vapors when stimulating one cranial nerve and various combinations of cranial nerves. Am. J. Physiol. 88: 117-129, 1929. AL-SHWAY, S. F., AND J. P. MORTOLA. Respiratory effects of airflow through the upper airways in newborn kittens and puppies. J. Appl. Physiol. 53: 805-814, 1982. ANDERSEN, P. Inhibitory influences elicited from the trigeminal and olfactory nerves in rabbits. Acta Physiol. Scud. 30: 137-148, 1953. BOGGS, D. F., AND D. BARTLETT, JR. Chemical specificity of a laryngeal apneic reflex in puppies. J. Appl. Physiol. 53: 455-462, 1982. BURGESS, K. R., AND W. A. WHITELAW. Reducing ventilatory response to carbon dioxide by breathing cold air. Am. Reu. Respir. Dis. 129: 687-690, 1984. DONNELLY, D. F., AND G. G. HADDAD. Effects of graded anesthesia on laryngeal-induced central apnea. Respir. Physiol. 66: 235-245, 1986. ECCLES, R., D. H. GRIFFITHS, C. G. NEWTON, AND N. S. TOLLEY. The effects of menthol isomers on nasal sensation of airflow. Clin. Otolaryngol. Oxf. 13: 25-29, 1988. GARCIA RAMOS, J. On the integration of respiratory movements. III. The fifth nerve afferents. Acta Physiol. Latinoam. 10: 104-113, 1960. GLEBOVSKY, V. D., AND A. V. BAYEV. Stimulation of nasal cavity mucosal trigeminal receptors with respiratory airflows [in Russian]. Sechenov. Physiol. J. USSR 70: 1534-1541, 1984. HENSEL, H., AND Y. ZOTTERMAN. The effect of menthol on the thermoreceptors. Acta Physiol. Stand. 24: 27-34, 1951. HOSHINO, T. In vitro electrophysiologic studies on nasal airway receptors of the rabbit. Ann. Otol. Rhinol. Laryngol. 97: 294-297, 1988. JAMMES, Y., P. BARTHELEMY, AND S. DELPIERRE. Respiratory effects of cold air breathing in anesthetized cats. Respir. Physiol. 54: 41-54, 1983. KRATSCHMER, F. uber Reflexe von der Nasenschleimhaut auf Athmung und Kreislauf. Sitz. Akad. Wiss. Wien 62: 147-170, 1870. MATHEW, 0. P., J. W. ANDERSON, G. P. ORANI, F. B. SANT'AMBROGIO, AND G. SANT’AMBROGIO. Cooling mediates the ventilatory depression associated with airflow through the larynx. Respir. Physiol. 82: 359-368, 1990.
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COLD AIR, l-MENTHOL,
2086 15. MATHEW, 0. In: Respiratory
AND RESPIRATORY
P., AND F. B. SANT’AMBROGIO.
REFLEXES
Laryngeal reflexes. edited by 0. P. Mathew and G. Sant’Ambrogio. New York: Dekker, 1988, p. 259302. (Lung Biol. Health Dis. Ser.) 16. MCBRIDE, B., AND W. A. WHITELAW. A physiological stimulus to upper airway receptors in humans. J. Appl. Physiol. 51: 1189-1197,
21. SANT’AMBROGIO,
1981. 17. MORTOLA,
Waking and ventilatory responses to laryngeal stimulation in sleeping dogs. J. Appl. Physiol. 45: 681-689, 1978. 24. TS~BONE, H. Nasal “flow” receptors of the rat. Respir. Physiol. 75:
1985. 18. SANT’AMBROGIO,
51-64, 1989. 25. VERSCHXJEREN, K. Handbook of Environmental Data on Organic Chemicals. New York: Van Nostrand Reinhold, 1983, p. 809. 26. WIDDICOMBE, J. G. Reflexes from the upper respiratory tract. In: Handbook of Physiology. The Respiratory System. Control of Breathing. Bethesda, MD: Am. Physiol. Sot., 1986, sect. 3, vol. II, p. 363-
Function
of the
Upper
Airway,
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