Effect of chronic ethanol administration on arterial baroreceptor function and pressor and depressor responsiveness in rats.

The effect of chronic ethanol administration on arterial baroreflexes was investigated in rats. Comparison of the results with those obtained from rats kept on an isocaloric control diet revealed that chronic ethanol had a differential action on baroreflex sensitivity (BS). The BS after evoked graded rises in arterial pressure was inhibited significantly whereas that tested after an evoked fall in arterial pressure was augmented significantly in chronic ethanol rats. These changes in BS were not secondary to changes in blood pressure as resting arterial pressure was similar in both groups. However, the heart rate was slightly, but significantly lower in the ethanol group. Challenging isocaloric control and chronic ethanol rats with an acute dose of 0.5 g/kg of ethanol produced nonsignificant changes in BS when evoked changes in blood pressure were both pressor and depressor. A dose of 3 g/kg of ethanol decreased the BS tested after phenylephrine-evoked rises in pressure in both groups; however, the percentage of inhibition of BS was greater in the isocaloric control group. The pressor responsiveness to phenylephrine was reduced slightly in chronic ethanol-treated rats, in contrast to that evoked by angiotensin II which was augmented slightly as compared to the control group. There was no significant difference in the depressor responsiveness to nitroprusside. After injection of acute doses of 0.5 and 3 g/kg of ethanol, the dose-response curves to phenylephrine were shifted to the right in a dose-related fashion in both groups, whereas the angiotensin II and nitroprusside dose-response curve remained unchanged after 0.5 g/kg of ethanol in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)