CARDIOVASCULAR EFFECTS OF ETHANOL IN RATS SELECTIVELY BRED FOR HIGH OR LOW-SENSITIVITY TO THE HYPNOTIC EFFECTS OF ETHANOL

The cardiovascular effects of acute ethanol administration were studie d in rats selectively bred for high (HAS) or low sensitivity (LAS) to the acute hypnotic effect of ethanol. In chronically cannulated, consc ious animals, the intravenous administration of 1 g/kg of ethanol caus ed moderate hypotension and tachycardia in both HAS and LAS rats. The phenylephrine-induced reflex bradycardia and the baroreflex slope were significantly reduced by ethanol only in HAS and not in LAS rats. In urethane-anesthetized HAS rats, the baroreflex inhibitory action of et hanol was present under control conditions, but it was absent after de pletion of endogenous GABA by treatment of the rats with 100 mg/kg of 3-mercaptopropionate. These findings confirm the role of endogenous GA BA in the baroreflex inhibitory action of ethanol, and are compatible with the documented differential sensitivity of the GABA(A) receptor c omplex to ethanol in HAS and LAS rats.