Brain Research, 111 (1976) 181-184
181
© Elsevier ScientificPublishing Company, Amsterdam - Printed in The Netherlands
Vago-ao,rtic nerves stimulation and REM sleep: evidence for a REMtriggering and a REM-maintenance factor
J. J. PUIZILLOUT and A. S. FOUTZ Unitd de Recherches Neurobiologiques, U6 de I'INSERM, et Groupe de Recherches 25 du CNRS, 280, Bd. de Sainte Marguerite, 13009 Marseille (France)
(Accepted April 5th, 1976)
Vago-aortic nerves stimulation (VA St.) can induce sleep in enc6phale isol6 (El) preparation 1-s. Some characteristics of this artificially induced sleep have been previously described 6,7. It has been shown that it is possible to impose an artificially regular cycle much shorter than the normal one 6 (Fig. 1). The present study attempted to determine: (a) if the number and the duration of REM episodes or the total amount of REM sleep are really increased during periods with VA St. as compared with periods including spontaneous sleep and (b) if the REM episodes durations could be modified by VA St. independently of their triggering effect. Increase in the frequency o f R E M episodes: existence o f a REM-triggering factor. Twelve cats were used of which 6 were REM-deprived for 3 days before the experiment. Each animal was recorded for 6-12 h. The recording time was divided into alternating 1-h control periods and 1-h VA St. periods. Stimulations were applied regularly every 7.5 min. Thus 8 stimulations were given in each 1 h stimulating period (see Fig. 1). In these conditions, when VA St. is applied every 7.5 min the number of REM episodes is increased, the duration of the episodes is significantly decreased and, finally, the total amount of REM sleep is not significantly different in the VA St. as compared to controls (Table I). When each cat is analyzed individually, it appears that the total REM sleep induced by VA St. is inversely dependent upon the amount of REM sleep occurring spontaneously during the control periods. There is a significant negative correlation between the quantity of REM sleep occurring during the control periods and the increase ( ~o stim/control) of REM sleep observed during the periods of stimulation (Table II). VA St. seems to increase REM sleep only in animals which present a low spontaneous REM sleep percentage. Increase in the duration o f R E M episodes: existence o f a R E M maintenance factor. In order to test the ability of stimulation to increase the duration of REM sleep independently of the REM-triggering factor, VA St. was introduced after spontaneous REM sleep was well established, i.e. 30 sec after its onset. Stimulation was applied to 50 Yo of the episodes. It was continued as long as the REM went on, and then was stopped 30 sec after the end of the REM episode. REM episodes occurring spontaneously, without VA St., served as a control. No more than 3 successive
182
E. I$OLE RIDM
VAGO-AORT.
REM
STIM
W
SWS
P~
REM
REM
iii
..~.,~.~=. _ : : L
St--,.,..,...,.,_.,.,...,..,.,..,.,..._.,.. 2
3
4
3d
CONTROL
n : 19 d: 1'26
1
d*pr'iv.
n : 8 cl : 3 ' 5 8
i
.............
,-.,.,.,.,..,.,..,....,.,..,.,..,.,..,.,..,.,.,...,.__
5
6
rain
1
2
3
4
5
6
rain
16 h
St ~ l q l l l l l l l l ~ , r 1
.-~..,r . w - . 7 . . . ~ . ? . . i - . T . ~ . T . . p . I . . r . , . . r . 1 . . r . 2 3 4 5 6 rain
r.~..r.T.r 1
..r .T..e..T._r..T._r.l..r..r ..r ..p.r .l__r.,~..r. ~ 2 3 4 5 6 m~n
18h
St 1
. 4 ,--r..... r-,--,-~--,-~--T..... ~-..... , .... ,~::.--:.;-1
2
3
4
5
6
min
r',','-r...... ~--,-,--r-,'-,'~...... ~...... r..... -r-1
2
3
4
5
6
m~n
Fig. 1. Example of hypnogram with (left) and without (right, control) vago-aortic stimulation. 'Enc6phale isol6' cat, non-paralyzed, vago-aortic and sympathetic cervical trunks bilaterally cut. REM sleep deprivation: 3 days. Abbreviations: W, wakefulness; SWS, slow-wave sleep; PSWS, phasic slow*wave sleep (with PGO discharges); REM, paradoxical sleep; n, number of REM stages; d, REM mean duration.R ight: control hypnogram; 3 periods of 1 h. Left: 3 periods of 1 h with vago-aortic stimulations (8 stimulations/hour). Each VA St. (1.5 V, 30 c/sec, 0.05 msec) lasts 1.5 min and is repeated every 7.5 min after the beginning of the preceding stimulation. Most VA Sts. are rapidly followed by REM sleep phases and are therefore stimulus-bound. In contrast, during the control period, the different phases of sleep are randomly spread. Notice that during the hours with VA St., REM sleep episodes are more frequent (n = 19 instead of n = 8) but much shorter (d : 1.26 min instead of 3.58 min) than during the control hours.
r a n d o m l y determined control or experimental R E M episodes were allowed. This study was carried o u t o n 4 R E M - d e p r i v e d E1 cats. Table III d e a r l y shows that u n d e r these experimental conditions, V A St. largely increased (98.3 ~o) the d u r a t i o n o f R E M episodes as c o m p a r e d with control. However, the i n t e r - R E M intervals which followed these prolonged episodes were longer t h a n those following control. Here, as well as in the preceding case, the total a m o u n t o f R E M sleep ( a b o u t 15 ~ , calculated for each cat) was n o t increased as c o m p a r e d to n o n - s t i m u l a t e d , R E M - d e p r i v e d E1 cats.
183 TABLE I
Characteristics of REM episodes triggererd by vago-aortic stimulation REM episodes induced by vago-aortic stimulations are much shorter than spontaneous ones, both in REM-deprived cats (mean duration 1.94 min against 3.64 min) and non-deprived cats (1.8 rain against 2.93 min). By contrast, the number of induced REM episodes is much greater than the number of spontaneous ones (5.53 episodes/h against 2.35 episodes/h for REM-deprived cats and 3.71 episodes/h against 1.65 episodes/h for non-deprived cats). Finally the total amount of REM sleep is not significantly different in the two conditions (control and VA stimulation).
REM sleep
No./h Duration (min) Percent
REM deprived
Non-deprived
Vago-aort. stim.
Control
Vago-aort. stim.
Control
5.53 -4- 1.11"** 1.94 4- 0.57** 18.2 4- 7.0
2.35 4- 0.44 3.64 4- 1.34 14.9 4- 7.4
3.71 4- 1.10"** 1.80 q- 0.81" 12.4 -4- 5.8
1.65 4- 0.75 2.93 4- 1.74 9.0 4- 7.5
* P < 0.05. ** P < 0.01. *** P < 0.005. Student t-test, one-tailed. TABLE II
Correlation between REM sleep and vago-aortic stimulation Significant negative correlation between the quantity of REM sleep (%) occurring during the control (C) periods and the % increase ((C - - St/C) × 100) of REM sleep observed during the stimulation periods (Spearman rank correlation coefficient, N = 12, rs = 0.749, P < 0.01, one-tailed test). The lower the percentage of spontaneous (control) REM sleep (for example C = 1.8%), the proportionately higher is the percentage of triggered REM sleep (increase of 322%); conversely, the higher the percentage of control REM sleep (for example C = 26 %), the lower the percentage of triggered REM sleep (decrease of 28.8 %).
REM (%)
REMdeprived cats
Non-deprived cats
% increase or decrease
Control
St. VA
16.9 8.5 6 26 12.4 19.7 19.8 7.4 1.8 12.9 3 6.4
15.6 22.1 8.7 18.5 15.3 29.3 22 13.8 7.6 9.4 9.1 8.6
-+ + -÷ + + + + -+ +
7.7 160 45 28.8 23.4 48.7 11.1 86 322 27 203 34.4
I n c o n c l u s i o n , V A St. c a n i n d e p e n d e n t l y i n c r e a s e the n u m b e r o r t h e d u r a t i o n o f REM episodes but does not change the total amount. Thus, VA stimulation-induced sleep is d e p e n d e n t o n a R E M - t r i g g e r i n g f a c t o r as well as o n a R E M - m a i n t e n a n c e factor.
184 TABLE 111 Increase in duration o[ REM sleep episodes by vago-aortic stimulation Four enc6phale isol6 cats (A-D). Control: REM episode, mean durations without vago-aortic stimulation. V. Aort. stimulation: REM episode, mean durations with vago-aortic stimulation. The stimulation was applied 30 sec after the beginning of 5 0 ~ of the REM episodes occurring spontaneously (selected at random) and was stopped 30 sec after the end of each REM episode. Under this stimulation regimen, note the very important REM duration (mean, 98.3 ~ ) in each of the 4 cats studied.
Control (min) V. Aort. St. (min) increase
Cats ............................ A B
C
2.57 i 1.95 1.65 ± 1.03 5.12 ± 1.56"* 3.18 4- 1.97"** 99.2 92.7
2.83 ± 1.8 4.82 i 2.1 5.42 ± 3.17"* 9.85 ± 1.93" 91.5 104.4
D
Mean duration (mitt) 2.97 £ 1.33 5.89 £ 2.82 98.3
* P < 0.002. ** P < 0.001. *** P < 0.00005, Mann-Whitney U-test, one-tailed.
T h i s w o r k was s u p p o r t e d by the D i r e c t i o n des R e c h e r c h e s et M o y e n s d ' E s s a i s ( G r a n t 75-1141) a n d by t h e I n s t i t u t N a t i o n a l de la Sant6 et de la R e c h e r c h e M 6 d i c a l e ( G r a n t 74.5-168-08).
1 Chase, M. H., Nakamura, Y., Clemente, C. D. and Sterman, M. B., Afferent vagat stimulation: neurographic correlates of induced EEG synchronization and desynchronization, Brain Research, 5 (1967) 236-249. 2 Dell, P., Aff6rences baroceptives, phases de synchronisation corticale et sommeil, Arch. ital. BioL, 111 (1973) 553-563. 3 Foutz, A. S., Ternaux, J. P. et Puizillout, J. J., Les stades de sommeil de la pr6paration 'enc6phale isol6'. II. Phases paradoxales. Leur d6clenchement par la stimulation des aff6rences baroceptives, Electroenceph. clin. NeurophysioL, 37 (1974) 577-588. 4 Foutz, A. S., Ternaux, J. P. et Puizillout, J. J., Les stades de sommeil de la pr6paration 'enc6phale isol6'. III. Etude compar6e quantitative des cycles veiUe-sommeil de la pr6paration 'enc6phale isot6 semi-chronique', Eleetroenceph. clin. NeurophysioL, 38 (1975) 579-588. 5 Puizillout, J. J., D6clenchement r6flexe de sommeil paradoxal par la stimulation des troncs vagoaortiques. Faits et hypotheses, Rev. EEG Neurophysiol., 1976, in press. 6 Puizillout, J. J. and Foutz, A. S., Characteristics of the experimental reflex sleep induced by vagoaortic nerves stimulation, Electroenceph. clin. Neurophysiol., submitted for publication. 7 Puizillout, J. J., Ternaux, J. P., Foutz, A. S. et Dell, P., Phases de sommeil ~t ondes lentes avec d6charges phasiques. Leur d6clenchement par la stimulation vago-aortique, Rev. EEG NeurophysioL, 3 (1973) 21-37. 8 Puizillout, J. J., Ternaux, J. P., Foutz, A. S. et Fernandez, G., Les stades de sommeil de la pr6paration 'encAphale isol6'. I. D6clenchement des pointes ponto-geniculo-occipitales et du sommeil phasique b. ondes lentes. ROle des noyaux du raph6, Electroenceph. clin. NeurophysioL, 37 (1974) 561-576.
181
© Elsevier ScientificPublishing Company, Amsterdam - Printed in The Netherlands
Vago-ao,rtic nerves stimulation and REM sleep: evidence for a REMtriggering and a REM-maintenance factor
J. J. PUIZILLOUT and A. S. FOUTZ Unitd de Recherches Neurobiologiques, U6 de I'INSERM, et Groupe de Recherches 25 du CNRS, 280, Bd. de Sainte Marguerite, 13009 Marseille (France)
(Accepted April 5th, 1976)
Vago-aortic nerves stimulation (VA St.) can induce sleep in enc6phale isol6 (El) preparation 1-s. Some characteristics of this artificially induced sleep have been previously described 6,7. It has been shown that it is possible to impose an artificially regular cycle much shorter than the normal one 6 (Fig. 1). The present study attempted to determine: (a) if the number and the duration of REM episodes or the total amount of REM sleep are really increased during periods with VA St. as compared with periods including spontaneous sleep and (b) if the REM episodes durations could be modified by VA St. independently of their triggering effect. Increase in the frequency o f R E M episodes: existence o f a REM-triggering factor. Twelve cats were used of which 6 were REM-deprived for 3 days before the experiment. Each animal was recorded for 6-12 h. The recording time was divided into alternating 1-h control periods and 1-h VA St. periods. Stimulations were applied regularly every 7.5 min. Thus 8 stimulations were given in each 1 h stimulating period (see Fig. 1). In these conditions, when VA St. is applied every 7.5 min the number of REM episodes is increased, the duration of the episodes is significantly decreased and, finally, the total amount of REM sleep is not significantly different in the VA St. as compared to controls (Table I). When each cat is analyzed individually, it appears that the total REM sleep induced by VA St. is inversely dependent upon the amount of REM sleep occurring spontaneously during the control periods. There is a significant negative correlation between the quantity of REM sleep occurring during the control periods and the increase ( ~o stim/control) of REM sleep observed during the periods of stimulation (Table II). VA St. seems to increase REM sleep only in animals which present a low spontaneous REM sleep percentage. Increase in the duration o f R E M episodes: existence o f a R E M maintenance factor. In order to test the ability of stimulation to increase the duration of REM sleep independently of the REM-triggering factor, VA St. was introduced after spontaneous REM sleep was well established, i.e. 30 sec after its onset. Stimulation was applied to 50 Yo of the episodes. It was continued as long as the REM went on, and then was stopped 30 sec after the end of the REM episode. REM episodes occurring spontaneously, without VA St., served as a control. No more than 3 successive
182
E. I$OLE RIDM
VAGO-AORT.
REM
STIM
W
SWS
P~
REM
REM
iii
..~.,~.~=. _ : : L
St--,.,..,...,.,_.,.,...,..,.,..,.,..._.,.. 2
3
4
3d
CONTROL
n : 19 d: 1'26
1
d*pr'iv.
n : 8 cl : 3 ' 5 8
i
.............
,-.,.,.,.,..,.,..,....,.,..,.,..,.,..,.,..,.,.,...,.__
5
6
rain
1
2
3
4
5
6
rain
16 h
St ~ l q l l l l l l l l ~ , r 1
.-~..,r . w - . 7 . . . ~ . ? . . i - . T . ~ . T . . p . I . . r . , . . r . 1 . . r . 2 3 4 5 6 rain
r.~..r.T.r 1
..r .T..e..T._r..T._r.l..r..r ..r ..p.r .l__r.,~..r. ~ 2 3 4 5 6 m~n
18h
St 1
. 4 ,--r..... r-,--,-~--,-~--T..... ~-..... , .... ,~::.--:.;-1
2
3
4
5
6
min
r',','-r...... ~--,-,--r-,'-,'~...... ~...... r..... -r-1
2
3
4
5
6
m~n
Fig. 1. Example of hypnogram with (left) and without (right, control) vago-aortic stimulation. 'Enc6phale isol6' cat, non-paralyzed, vago-aortic and sympathetic cervical trunks bilaterally cut. REM sleep deprivation: 3 days. Abbreviations: W, wakefulness; SWS, slow-wave sleep; PSWS, phasic slow*wave sleep (with PGO discharges); REM, paradoxical sleep; n, number of REM stages; d, REM mean duration.R ight: control hypnogram; 3 periods of 1 h. Left: 3 periods of 1 h with vago-aortic stimulations (8 stimulations/hour). Each VA St. (1.5 V, 30 c/sec, 0.05 msec) lasts 1.5 min and is repeated every 7.5 min after the beginning of the preceding stimulation. Most VA Sts. are rapidly followed by REM sleep phases and are therefore stimulus-bound. In contrast, during the control period, the different phases of sleep are randomly spread. Notice that during the hours with VA St., REM sleep episodes are more frequent (n = 19 instead of n = 8) but much shorter (d : 1.26 min instead of 3.58 min) than during the control hours.
r a n d o m l y determined control or experimental R E M episodes were allowed. This study was carried o u t o n 4 R E M - d e p r i v e d E1 cats. Table III d e a r l y shows that u n d e r these experimental conditions, V A St. largely increased (98.3 ~o) the d u r a t i o n o f R E M episodes as c o m p a r e d with control. However, the i n t e r - R E M intervals which followed these prolonged episodes were longer t h a n those following control. Here, as well as in the preceding case, the total a m o u n t o f R E M sleep ( a b o u t 15 ~ , calculated for each cat) was n o t increased as c o m p a r e d to n o n - s t i m u l a t e d , R E M - d e p r i v e d E1 cats.
183 TABLE I
Characteristics of REM episodes triggererd by vago-aortic stimulation REM episodes induced by vago-aortic stimulations are much shorter than spontaneous ones, both in REM-deprived cats (mean duration 1.94 min against 3.64 min) and non-deprived cats (1.8 rain against 2.93 min). By contrast, the number of induced REM episodes is much greater than the number of spontaneous ones (5.53 episodes/h against 2.35 episodes/h for REM-deprived cats and 3.71 episodes/h against 1.65 episodes/h for non-deprived cats). Finally the total amount of REM sleep is not significantly different in the two conditions (control and VA stimulation).
REM sleep
No./h Duration (min) Percent
REM deprived
Non-deprived
Vago-aort. stim.
Control
Vago-aort. stim.
Control
5.53 -4- 1.11"** 1.94 4- 0.57** 18.2 4- 7.0
2.35 4- 0.44 3.64 4- 1.34 14.9 4- 7.4
3.71 4- 1.10"** 1.80 q- 0.81" 12.4 -4- 5.8
1.65 4- 0.75 2.93 4- 1.74 9.0 4- 7.5
* P < 0.05. ** P < 0.01. *** P < 0.005. Student t-test, one-tailed. TABLE II
Correlation between REM sleep and vago-aortic stimulation Significant negative correlation between the quantity of REM sleep (%) occurring during the control (C) periods and the % increase ((C - - St/C) × 100) of REM sleep observed during the stimulation periods (Spearman rank correlation coefficient, N = 12, rs = 0.749, P < 0.01, one-tailed test). The lower the percentage of spontaneous (control) REM sleep (for example C = 1.8%), the proportionately higher is the percentage of triggered REM sleep (increase of 322%); conversely, the higher the percentage of control REM sleep (for example C = 26 %), the lower the percentage of triggered REM sleep (decrease of 28.8 %).
REM (%)
REMdeprived cats
Non-deprived cats
% increase or decrease
Control
St. VA
16.9 8.5 6 26 12.4 19.7 19.8 7.4 1.8 12.9 3 6.4
15.6 22.1 8.7 18.5 15.3 29.3 22 13.8 7.6 9.4 9.1 8.6
-+ + -÷ + + + + -+ +
7.7 160 45 28.8 23.4 48.7 11.1 86 322 27 203 34.4
I n c o n c l u s i o n , V A St. c a n i n d e p e n d e n t l y i n c r e a s e the n u m b e r o r t h e d u r a t i o n o f REM episodes but does not change the total amount. Thus, VA stimulation-induced sleep is d e p e n d e n t o n a R E M - t r i g g e r i n g f a c t o r as well as o n a R E M - m a i n t e n a n c e factor.
184 TABLE 111 Increase in duration o[ REM sleep episodes by vago-aortic stimulation Four enc6phale isol6 cats (A-D). Control: REM episode, mean durations without vago-aortic stimulation. V. Aort. stimulation: REM episode, mean durations with vago-aortic stimulation. The stimulation was applied 30 sec after the beginning of 5 0 ~ of the REM episodes occurring spontaneously (selected at random) and was stopped 30 sec after the end of each REM episode. Under this stimulation regimen, note the very important REM duration (mean, 98.3 ~ ) in each of the 4 cats studied.
Control (min) V. Aort. St. (min) increase
Cats ............................ A B
C
2.57 i 1.95 1.65 ± 1.03 5.12 ± 1.56"* 3.18 4- 1.97"** 99.2 92.7
2.83 ± 1.8 4.82 i 2.1 5.42 ± 3.17"* 9.85 ± 1.93" 91.5 104.4
D
Mean duration (mitt) 2.97 £ 1.33 5.89 £ 2.82 98.3
* P < 0.002. ** P < 0.001. *** P < 0.00005, Mann-Whitney U-test, one-tailed.
T h i s w o r k was s u p p o r t e d by the D i r e c t i o n des R e c h e r c h e s et M o y e n s d ' E s s a i s ( G r a n t 75-1141) a n d by t h e I n s t i t u t N a t i o n a l de la Sant6 et de la R e c h e r c h e M 6 d i c a l e ( G r a n t 74.5-168-08).
1 Chase, M. H., Nakamura, Y., Clemente, C. D. and Sterman, M. B., Afferent vagat stimulation: neurographic correlates of induced EEG synchronization and desynchronization, Brain Research, 5 (1967) 236-249. 2 Dell, P., Aff6rences baroceptives, phases de synchronisation corticale et sommeil, Arch. ital. BioL, 111 (1973) 553-563. 3 Foutz, A. S., Ternaux, J. P. et Puizillout, J. J., Les stades de sommeil de la pr6paration 'enc6phale isol6'. II. Phases paradoxales. Leur d6clenchement par la stimulation des aff6rences baroceptives, Electroenceph. clin. NeurophysioL, 37 (1974) 577-588. 4 Foutz, A. S., Ternaux, J. P. et Puizillout, J. J., Les stades de sommeil de la pr6paration 'enc6phale isol6'. III. Etude compar6e quantitative des cycles veiUe-sommeil de la pr6paration 'enc6phale isot6 semi-chronique', Eleetroenceph. clin. NeurophysioL, 38 (1975) 579-588. 5 Puizillout, J. J., D6clenchement r6flexe de sommeil paradoxal par la stimulation des troncs vagoaortiques. Faits et hypotheses, Rev. EEG Neurophysiol., 1976, in press. 6 Puizillout, J. J. and Foutz, A. S., Characteristics of the experimental reflex sleep induced by vagoaortic nerves stimulation, Electroenceph. clin. Neurophysiol., submitted for publication. 7 Puizillout, J. J., Ternaux, J. P., Foutz, A. S. et Dell, P., Phases de sommeil ~t ondes lentes avec d6charges phasiques. Leur d6clenchement par la stimulation vago-aortique, Rev. EEG NeurophysioL, 3 (1973) 21-37. 8 Puizillout, J. J., Ternaux, J. P., Foutz, A. S. et Fernandez, G., Les stades de sommeil de la pr6paration 'encAphale isol6'. I. D6clenchement des pointes ponto-geniculo-occipitales et du sommeil phasique b. ondes lentes. ROle des noyaux du raph6, Electroenceph. clin. NeurophysioL, 37 (1974) 561-576.
