Effect of the anxiolytic drug buspirone on prolactin and corticosterone secretion in stressed and unstressed rats.

Buspirone is an atypical anxiolytic drug that exerts its action at a receptor site other than the GABA-benzodiazepine-chloride ionophore complex. The present study examined the effect of buspirone on plasma prolactin and corticosterone levels in both control and stressed rats. In unstressed rats, buspirone produced dose-dependent increases in plasma prolactin and corticosterone levels. The minimal doses of buspirone which led to significant elevations in plasma prolactin and corticosterone levels were 1.0 and 2.0 mg/kg (IP), respectively. The effect of buspirone on both hormones was maximal 30 minutes after injection. The plasma levels of prolactin and corticosterone were significantly elevated in rats that were stressed using a conditioned fear paradigm. Buspirone produced a dose-dependent attenuation of the stress-induced increase in prolactin secretion. The stress-induced increase in corticosterone secretion was inhibited by the 0.5 mg/kg (IP) dose but not by the 2.0 mg/kg (IP) dose of buspirone, which increased corticosterone secretion both in stressed and unstressed rats. These data suggest that the effect of buspirone on plasma prolactin and corticosterone levels may be mediated by two different mechanisms of action.