[Central modulation of the baroreflex response to phenylephrine in rats. Lack of interaction between calcium channel modulators and the renin-angiotensin system].
We have previously shown that a calcium channel activator (BAY K 8644) can decrease the baroreflex control of heart rate in SHR when intracerebroventricularly (i.c.v.) administered. In pentobarbital anesthetized SHR, the inhibitory effect of BAY (3 micrograms/kg i.c.v.) on baroreflex sensitivity (BRS; ramp method: phenylephrine 2 micrograms i.v.; BAY: 0.14 +/- 0.05 vs control: 0.39 +/- 0.08 msec/mmHg; p less than 0.01) was fully suppressed after pretreatment with the muscarinic antagonist atropine methylnitrate (80 micrograms/kg i.c.v.) suggesting the involvement of cholinergic pathways in the inhibitory effect. Since A II was reported to centrally increase arterial pressure through an enhanced release of acetylcholine and to depress BRS, we tested whether the effect of BAY on BRS could involve central A II systems. The A II antagonist [Sar 1Ile8] A II (30 micrograms/kg/min i.c.v.) suppressed the inhibitory effect of A II on BRS (control: 0.32 +/- 0.09; A II: 0.10 +/- 0.02; Sar1 Ile8 + A II: 0.39 +/- 0.08 msec/mmHg) but not the inhibitory effect of BAY (3 mu g/kg i.c.v.) on BRS. These results suggest that the central inhibition of BRS by BAY unlikely involves central A II systems.
Lacolley
P
P
Inserm U 228, centre de diagnostic, hôpital Broussais, Paris.
Laurent
S
S
Tsoucaris
D
D
Brisac
A M
AM
Schmitt
H
H
Safar
M
M
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000804:Angiotensin II / Q000502:physiology*; D000818:Animals; D010656:Phenylephrine / Q000494:pharmacology; D011311:Pressoreceptors / Q000187:drug effects / Q000502:physiology*; D051381:Rats; D011918:Rats, Inbred SHR; D012084:Renin-Angiotensin System
D000804:Angiotensin II; D010656:Phenylephrine; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester
Modulation centrale de la résponse baroréflexe à la phényléphrine chez le rat. Absence d'interaction entre modulateurs des canaux calciques et système rénine-angiotensine.