Physiology & Behavior, Vol. 50, pp. 869-871. ¢ Pergamon Press plc, 1991. Printed in the U.S.A.
0031-9384191 $3.00 + .00
BRIEF COMMUNICATION
Blood Pressure Responses and Drinking Following Central Angiotensin II in Adult Rats Guanethidine-Sympathectomised at Birth S. N. T H O R N T O N ,
C. L A R U E - A C H A G I O T I S 1 A N D S. N I C O L A I D I S
Laboratoire de Neurobiologie des Rdgulations and Laboratoire de Neurophysiologie Sensorielle et Comportementale Colldge de France, 11 place Marcelin-Berthelot, 75231 Paris Cedex 05, France R e c e i v e d 14 F e b r u a r y 1991 THORNTON, S. N., C. LARUE-ACHAGIOTIS AND S. NICOLA~DIS. Blood pressure responses and drinking following central angiotensin H in adult rats guanethidine-sympathectomised at birth. PHYSIOL BEHAV 50(4) 869-871, 1991.--Rats pups were sympathectomised with daily, for 3 weeks, injections of guanethidine (0.01 ml/g body weight), starting the second day after birth. They were separated from their respective dams at 6 weeks, and when they had reached their adult weight (350 g), the males were used to study the role of the sympathetic nervous system in the blood pressure and drinking responses to central injections of angiotensin II (AII, 250 ng). Littermates injected with 0.15 NaCI served as controls. Mean blood pressure was similar in both experimental and control groups (118_+6 versus 128_+4 mmHg) though the sympathectomised rats had a less stable baseline blood pressure than the controls. AII injected into the third cerebral ventricle produced similar increases in blood pressure and drinking responses in both groups. From these results we conclude that other systems appeared to have compensated for the lack of the sympathetic nervous system in normal blood pressure regulation and in stimulated (AII) blood pressure increases. Guanethidine
Sympathectomy
ICV
Angiotensin II
INTRACEREBROVENTRICULAR (ICV) administration of angiotensin II (AII) produces an increase in blood pressure (5, 9, 16, 21, 24), vasopressin release (8, 13, 16, 20, 24) and drinking (6, 16, 20, 21). Part of the increase in blood pressure is due to an AII-induced increase in sympathetic tone (9, 16, 19, 24). The role of the sympathetic nervous system in the AII-induced blood pressure response has been investigated in adult rats that have been sympathectomised as adults (14), but never in rats sympathectomised from birth. Therefore, we have investigated the role of the sympathetic nervous system in the blood pressure responses to ICV AII in adult male rats that had been sympathectomised at birth with injections of guanethidine.
Drinking
Blood pressure
Rats
of 0.01 ml/g body weight guanethidine (10 mg/ml Ismelin, Ciba Geigy) for three weeks starting the second day after birth. This procedure produces a permanent peripheral sympathectomy (3, 10-12). The littermate controls received a similar volume of physiological saline. At the end of the injections, the rat pups were left with their respective dams for a further 3 weeks before separation, and the males put into individual cages.
Surgery All subsequent surgery was performed on the male rats when they had reached 350-430 g. The guanethidine-treated rats were consequently lighter than their littermate saline-treated controls, but any one litter was operated at the same time, thus the rats were of the same age at the time of the operation. The small weight differences did not have any influence on the subsequent response to ICV AII (unpublished observations). The rats were anaesthetised with Nembutal (0.1 ml/100 g body weight) and a cannula (27 gauge, 15-mm long, with obturator) implanted in one lateral cerebral ventricle and secured in place dental acrylic around three jewelers screws in the skull. When the rats had recovered to their preoperative weight, they were reanaesthetised with Nembutal and polyethylene catheter (Biotrol, 0.58 m m i.d.
METHOD
Animals A total of 20 experimental and 18 control rats (Wistar) were obtained from 5 litters. Each litter was divided approximately in two, with one group serving as the experimental animals and the other as the littermate controls. The experimental group was sympathectomised with daily injections in the back of the neck
1present address: Laboratoire de Neurobiologie de la Nutrition, Universit6 Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 05, France.
869
g70
FHORNTON. LARUE-ACHAGIOTIS ANI) N I('()LAII)IS
770
r
160
? E E
ensure that the animal was calm and the blood pressure recording stable. All (Isoleu 5 Angiotensin 11. Sigma, 250 ng, dissolxed in 0.15 M NaC1) was injected ICV in a volume of 2 Ixl orer 15-30 s. ICV injections of a similar volume of I).15 M NaCI served as the control. The volume of water drunk and the blood pressure changes to both injections were measured over the subsequent 30 min.
1
(8)
(9)
2z
150
!
140
I
2E 5Or
o)
13C
40F
(8)
(8)
4o
Statistics
(8)
o 12C I 110 100 0
s
S All
All
a_ 3 0 F
30
~, 201=_ o) 101-
2o
O
o
0 L
=
o c
FIG. 1. Blood pressure changes (mean_+ SEM) in rats treated soon after birth with 0.15 M NaC1 (open columns) or with guanethidine (shaded columns) following ICV injection of 0.15 M NaC1 (S) or 250 ng angiotensin II (AII). The absolute and percent changes in blood pressure following the ICV injection of AII are also shown. **p
0031-9384191 $3.00 + .00
BRIEF COMMUNICATION
Blood Pressure Responses and Drinking Following Central Angiotensin II in Adult Rats Guanethidine-Sympathectomised at Birth S. N. T H O R N T O N ,
C. L A R U E - A C H A G I O T I S 1 A N D S. N I C O L A I D I S
Laboratoire de Neurobiologie des Rdgulations and Laboratoire de Neurophysiologie Sensorielle et Comportementale Colldge de France, 11 place Marcelin-Berthelot, 75231 Paris Cedex 05, France R e c e i v e d 14 F e b r u a r y 1991 THORNTON, S. N., C. LARUE-ACHAGIOTIS AND S. NICOLA~DIS. Blood pressure responses and drinking following central angiotensin H in adult rats guanethidine-sympathectomised at birth. PHYSIOL BEHAV 50(4) 869-871, 1991.--Rats pups were sympathectomised with daily, for 3 weeks, injections of guanethidine (0.01 ml/g body weight), starting the second day after birth. They were separated from their respective dams at 6 weeks, and when they had reached their adult weight (350 g), the males were used to study the role of the sympathetic nervous system in the blood pressure and drinking responses to central injections of angiotensin II (AII, 250 ng). Littermates injected with 0.15 NaCI served as controls. Mean blood pressure was similar in both experimental and control groups (118_+6 versus 128_+4 mmHg) though the sympathectomised rats had a less stable baseline blood pressure than the controls. AII injected into the third cerebral ventricle produced similar increases in blood pressure and drinking responses in both groups. From these results we conclude that other systems appeared to have compensated for the lack of the sympathetic nervous system in normal blood pressure regulation and in stimulated (AII) blood pressure increases. Guanethidine
Sympathectomy
ICV
Angiotensin II
INTRACEREBROVENTRICULAR (ICV) administration of angiotensin II (AII) produces an increase in blood pressure (5, 9, 16, 21, 24), vasopressin release (8, 13, 16, 20, 24) and drinking (6, 16, 20, 21). Part of the increase in blood pressure is due to an AII-induced increase in sympathetic tone (9, 16, 19, 24). The role of the sympathetic nervous system in the AII-induced blood pressure response has been investigated in adult rats that have been sympathectomised as adults (14), but never in rats sympathectomised from birth. Therefore, we have investigated the role of the sympathetic nervous system in the blood pressure responses to ICV AII in adult male rats that had been sympathectomised at birth with injections of guanethidine.
Drinking
Blood pressure
Rats
of 0.01 ml/g body weight guanethidine (10 mg/ml Ismelin, Ciba Geigy) for three weeks starting the second day after birth. This procedure produces a permanent peripheral sympathectomy (3, 10-12). The littermate controls received a similar volume of physiological saline. At the end of the injections, the rat pups were left with their respective dams for a further 3 weeks before separation, and the males put into individual cages.
Surgery All subsequent surgery was performed on the male rats when they had reached 350-430 g. The guanethidine-treated rats were consequently lighter than their littermate saline-treated controls, but any one litter was operated at the same time, thus the rats were of the same age at the time of the operation. The small weight differences did not have any influence on the subsequent response to ICV AII (unpublished observations). The rats were anaesthetised with Nembutal (0.1 ml/100 g body weight) and a cannula (27 gauge, 15-mm long, with obturator) implanted in one lateral cerebral ventricle and secured in place dental acrylic around three jewelers screws in the skull. When the rats had recovered to their preoperative weight, they were reanaesthetised with Nembutal and polyethylene catheter (Biotrol, 0.58 m m i.d.
METHOD
Animals A total of 20 experimental and 18 control rats (Wistar) were obtained from 5 litters. Each litter was divided approximately in two, with one group serving as the experimental animals and the other as the littermate controls. The experimental group was sympathectomised with daily injections in the back of the neck
1present address: Laboratoire de Neurobiologie de la Nutrition, Universit6 Pierre et Marie Curie, 4 place Jussieu, 75252 Paris Cedex 05, France.
869
g70
FHORNTON. LARUE-ACHAGIOTIS ANI) N I('()LAII)IS
770
r
160
? E E
ensure that the animal was calm and the blood pressure recording stable. All (Isoleu 5 Angiotensin 11. Sigma, 250 ng, dissolxed in 0.15 M NaC1) was injected ICV in a volume of 2 Ixl orer 15-30 s. ICV injections of a similar volume of I).15 M NaCI served as the control. The volume of water drunk and the blood pressure changes to both injections were measured over the subsequent 30 min.
1
(8)
(9)
2z
150
!
140
I
2E 5Or
o)
13C
40F
(8)
(8)
4o
Statistics
(8)
o 12C I 110 100 0
s
S All
All
a_ 3 0 F
30
~, 201=_ o) 101-
2o
O
o
0 L
=
o c
FIG. 1. Blood pressure changes (mean_+ SEM) in rats treated soon after birth with 0.15 M NaC1 (open columns) or with guanethidine (shaded columns) following ICV injection of 0.15 M NaC1 (S) or 250 ng angiotensin II (AII). The absolute and percent changes in blood pressure following the ICV injection of AII are also shown. **p
