European Journal o f Pharmacology, 58 (1979) 203--206 © Elsevier/North-Holland Biomedical Press
203
Short communication RELATION OF THE C E N T R A L L Y EVOKED P R E S S O R E F F E C T OF ANGIOTENSIN II TO CENTRAL N O R A D R E N A L I N E IN THE RABBIT CLAUDE CHEVILLARD, NICOLE DUCHENE, RI~GINE PASQUIER and JEAN-MICHEL ALEXANDRE
Department o f Pharmacology, 1NSERM U. 28, Hospital Broussais 96, rue Didot, 75674 Paris, France Received 26 June 1979, accepted 10 July 1979
C. CHEVILLARD, N. DUCHENE, R. PASQUIER and J.M. ALEXANDRE, Relation o f the centrally evoked pressot effect o f angiotensin H to central noradrenaline in the rabbit, European J. Pharmacol. 58 (1979) 203--206. Experiments were performed in urethane-anaesthetized rabbits using ventriculo-cisternal perfusion. Central infusion of angiotensin II (50 ng/kg/min) induced a rise in blood pressure which was accompanied by an increase in the noradrenaline concentration of the cerebrospinal fluid. Both effects were highly correlated. Conversely, an i.v. infusion of noradrenaline (5 pg/kg/min) which caused a similar increase in arterial pressure did not affect the cerebrospinal fluid catecholamine levels. These results suggest that peripheral cardiovascular effects of centrally administered angiotensin II are related to the activation of noradrenaline structures in the brain. Angiotensln II
Central noradrenaline
1. Introduction Interactions of angiotensin II with the sympathetic nervous system are well established for the periphery especially in postganglionic nerve terminals. At this site, there is good evidence that the peptide facilitates noradrenaline (NA) release (Chevillard et al., 1971; Zimmerman et al., 1972) and synthesis (Boadle et al., 1969; Chevillard et al., 1975). In the central nervous system (CNS), the interactions of angiotensin II with central noradrenergic neurones are n o t so well established. Although it was shown that angiotensin II interferes with the uptake, release and metabolism of central NA (see review from Severs and Daniels-Severs, 1973), most of the data available are from in vitro experiments and consequently do not correlate with alterations of central NA metabolism induced by angiotensin II and the biological effect of the peptide, i.e. the increase in blood pressure. For this reason, we have used a ventriculocisternal infusion of angiotensin II in rabbits, to study simultaneously the effect of the peptide on NA levels in the cerebrospinal fluid
(CSF) and its action on peripheral blood pressure. 2. Materials and methods New Zealand male rabbits (1.8--2 kg) were anaesthetized with urethane {1.25 g/kg, i.p.). The right femoral artery was catheterized for measurements of mean arterial pressure (MAP) and heart rate (HR) via a Sanborn 267 BC pressure transducer connected to a Hewlett-Packard recorder. The left femoral vein was cannulated for administration of drugs. The animals were placed in a stereotaxic apparatus and a hypodermic needle was then stereotaxiC-ally located into the right lateral ventricle through a hole drilled in the skull. The cannula was then secured to the skull with dental cement. The muscles of the neck were incised and retracted to expose the occipito-allantoid membrane. An outflow catheter was advanced into the cisterna magna through a hole pierced in the membrane. Artificial CSF (Merlis, 1940) maintained at 39°C and oxygenated ~(95% O:, 5% CO2) was then continuously infused from the lateral yen-
204
C. C H E V I I , L A R D ET AL.
infused (i.v.t.) for 3 h, and during the 2nd hour, NA (5 pg/kg/min) was i.v. infused (NA group). In all experiments, MAP, HR and catecholamine levels in CSF were measured every 20 min. CSF catecholamine levels were determined according to the method of Gauchy et al. (1976). This method involves the O-methylation of catecholamines in the presence of the radioactive methyl donor, S(3H methyl) adenosyl-methionine (10 Ci/mmol, The Radiochemical Center, Amersham, England). The O-methylated derivatives were then extracted into organic solvents, oxidised and finally assayed b y liquid scintillation counting. Data are reported as means-+ S.E.M. The significance of differences was assessed using Student's t-test.
tricle to the cisterna magna at a rate of 0.1 ml/min using a Gilson Mini-Pull roller pump. Three groups of experiments were performed: (1) after a 45 min stabilisation period, CSF was infused for 3 h through the ventricles (control group); (2) CSF was also infused intraventricularly (i.v.t.) for 3 h, b u t during the 2nd hour of the experiment, angiotensin II (50 ng/kg/min) was added to CSF (angiotensin II group}; (3) artificial CSF was MAp mm
Hl 130
120
II0
I00,
90
HR b/rain 390
T
1.75
31¢) 37o 36o 350
1.50 340
I ?0
I 5O
1.25
/
I 30
&[
,,o
i 1.00
o,o 20
1
z ' , 40
~)i°
i 80
i
1
]
[
1
, ~00
i 120
i 140
i I00
i II0
Time
(:mi n)
Fig. 1. E f f e c t (in u r e t h a n e - a n a e s t h e s i z e d r a b b i t s ) o f p e r f u s i o n t h r o u g h t h e c e r e b r a l v e n t r i c u l e s o f artificial CSF, e i t h e r a l o n e ( c o n t r o l s : ©o n = 6) or cont a i n i n g a n g i o t e n s i n II ( 5 0 n g / k g / m i n ; ~ n = 7) a n d o f i.v. p e r f u s e d n o r a d r e n a l i n e (5~ug/kg/min • ~ n = 6) o n m e a n arterial pressure (MAP, m m Hg) h e a r t rate (HR, b ] m i n ) a n d c a t e c h o l a m i n e levels ( N A n g / m l ) in t h e CSF. * P < 0.05, ** P < 0.01, • ** P < 0 . 0 0 1 .
e J
_ n=9
_
r =0.97
p
203
Short communication RELATION OF THE C E N T R A L L Y EVOKED P R E S S O R E F F E C T OF ANGIOTENSIN II TO CENTRAL N O R A D R E N A L I N E IN THE RABBIT CLAUDE CHEVILLARD, NICOLE DUCHENE, RI~GINE PASQUIER and JEAN-MICHEL ALEXANDRE
Department o f Pharmacology, 1NSERM U. 28, Hospital Broussais 96, rue Didot, 75674 Paris, France Received 26 June 1979, accepted 10 July 1979
C. CHEVILLARD, N. DUCHENE, R. PASQUIER and J.M. ALEXANDRE, Relation o f the centrally evoked pressot effect o f angiotensin H to central noradrenaline in the rabbit, European J. Pharmacol. 58 (1979) 203--206. Experiments were performed in urethane-anaesthetized rabbits using ventriculo-cisternal perfusion. Central infusion of angiotensin II (50 ng/kg/min) induced a rise in blood pressure which was accompanied by an increase in the noradrenaline concentration of the cerebrospinal fluid. Both effects were highly correlated. Conversely, an i.v. infusion of noradrenaline (5 pg/kg/min) which caused a similar increase in arterial pressure did not affect the cerebrospinal fluid catecholamine levels. These results suggest that peripheral cardiovascular effects of centrally administered angiotensin II are related to the activation of noradrenaline structures in the brain. Angiotensln II
Central noradrenaline
1. Introduction Interactions of angiotensin II with the sympathetic nervous system are well established for the periphery especially in postganglionic nerve terminals. At this site, there is good evidence that the peptide facilitates noradrenaline (NA) release (Chevillard et al., 1971; Zimmerman et al., 1972) and synthesis (Boadle et al., 1969; Chevillard et al., 1975). In the central nervous system (CNS), the interactions of angiotensin II with central noradrenergic neurones are n o t so well established. Although it was shown that angiotensin II interferes with the uptake, release and metabolism of central NA (see review from Severs and Daniels-Severs, 1973), most of the data available are from in vitro experiments and consequently do not correlate with alterations of central NA metabolism induced by angiotensin II and the biological effect of the peptide, i.e. the increase in blood pressure. For this reason, we have used a ventriculocisternal infusion of angiotensin II in rabbits, to study simultaneously the effect of the peptide on NA levels in the cerebrospinal fluid
(CSF) and its action on peripheral blood pressure. 2. Materials and methods New Zealand male rabbits (1.8--2 kg) were anaesthetized with urethane {1.25 g/kg, i.p.). The right femoral artery was catheterized for measurements of mean arterial pressure (MAP) and heart rate (HR) via a Sanborn 267 BC pressure transducer connected to a Hewlett-Packard recorder. The left femoral vein was cannulated for administration of drugs. The animals were placed in a stereotaxic apparatus and a hypodermic needle was then stereotaxiC-ally located into the right lateral ventricle through a hole drilled in the skull. The cannula was then secured to the skull with dental cement. The muscles of the neck were incised and retracted to expose the occipito-allantoid membrane. An outflow catheter was advanced into the cisterna magna through a hole pierced in the membrane. Artificial CSF (Merlis, 1940) maintained at 39°C and oxygenated ~(95% O:, 5% CO2) was then continuously infused from the lateral yen-
204
C. C H E V I I , L A R D ET AL.
infused (i.v.t.) for 3 h, and during the 2nd hour, NA (5 pg/kg/min) was i.v. infused (NA group). In all experiments, MAP, HR and catecholamine levels in CSF were measured every 20 min. CSF catecholamine levels were determined according to the method of Gauchy et al. (1976). This method involves the O-methylation of catecholamines in the presence of the radioactive methyl donor, S(3H methyl) adenosyl-methionine (10 Ci/mmol, The Radiochemical Center, Amersham, England). The O-methylated derivatives were then extracted into organic solvents, oxidised and finally assayed b y liquid scintillation counting. Data are reported as means-+ S.E.M. The significance of differences was assessed using Student's t-test.
tricle to the cisterna magna at a rate of 0.1 ml/min using a Gilson Mini-Pull roller pump. Three groups of experiments were performed: (1) after a 45 min stabilisation period, CSF was infused for 3 h through the ventricles (control group); (2) CSF was also infused intraventricularly (i.v.t.) for 3 h, b u t during the 2nd hour of the experiment, angiotensin II (50 ng/kg/min) was added to CSF (angiotensin II group}; (3) artificial CSF was MAp mm
Hl 130
120
II0
I00,
90
HR b/rain 390
T
1.75
31¢) 37o 36o 350
1.50 340
I ?0
I 5O
1.25
/
I 30
&[
,,o
i 1.00
o,o 20
1
z ' , 40
~)i°
i 80
i
1
]
[
1
, ~00
i 120
i 140
i I00
i II0
Time
(:mi n)
Fig. 1. E f f e c t (in u r e t h a n e - a n a e s t h e s i z e d r a b b i t s ) o f p e r f u s i o n t h r o u g h t h e c e r e b r a l v e n t r i c u l e s o f artificial CSF, e i t h e r a l o n e ( c o n t r o l s : ©o n = 6) or cont a i n i n g a n g i o t e n s i n II ( 5 0 n g / k g / m i n ; ~ n = 7) a n d o f i.v. p e r f u s e d n o r a d r e n a l i n e (5~ug/kg/min • ~ n = 6) o n m e a n arterial pressure (MAP, m m Hg) h e a r t rate (HR, b ] m i n ) a n d c a t e c h o l a m i n e levels ( N A n g / m l ) in t h e CSF. * P < 0.05, ** P < 0.01, • ** P < 0 . 0 0 1 .
e J
_ n=9
_
r =0.97
p
