Vascular responses to vasoactive agents in dietary alcohol-treated rats

1. Young male Sprague-Dawley rats were fed on either solid regular rat chow, control liquid diet or liquid diet containing alcohol for 26 weeks. 2. Phenylephrine (0.5, 1, 2 or 4 micrograms/kg) was injected to monitor the reflexogenic bradycardia and nitroprusside (2, 4, 8 or 16 micrograms/kg) was also used to establish the relationship between drug-induced hypotension and baroreceptor-mediated tachycardia. 3. Multiunit renal nerve activity was determined under pentobarbitone anaesthesia as an index of sympathetic nerve activity during the treatment with phenylephrine or nitroprusside. 4. Alcohol-fed rats showed greater nerve responses to phenylephrine without corresponding decrease in heart rate, which suggests alcohol directly affects arterial wall compliance. This study does not support the contention that dietary alcohol increases blood pressure and it impairs significantly the baroreceptor function.