Effects of bromocryptine on hepatic blood volume responses to hepatic nerve stimulation in cats.

Arterial pressures, portal pressures, and hepatic blood volumes were recorded after hepatic denervation in cats anesthetized with pentobarbital. Bromocryptine (50 micrograms/kg) lowered arterial pressure but did not significantly change portal pressure or hepatic blood volume. However, both portal pressure and hepatic blood volume responses to hepatic nerve stimulation were significantly depressed after bromocryptine especially at low frequencies of stimulation. Responses to intraportal infusions of norepinephrine were significantly impaired only at the highest dose. The inhibitory effect of bromocryptine on the neural responses may, therefore, involve a presynaptic inhibition of norepinephrine release, but the mechanism requires further study. These data provide further support for the hypothesis that drugs which impair hepatic venous responses to sympathetic stimuli cause significant impairment of postural reflexes and orthostatic hypotension during clinical use.