The effect of repeated treatment with antidepressant drugs or electroconvulsive shock on the phenylephrine-induced elevation of the plasma corticosterone concentration in rats.

The selective alpha 1-adrenoceptor agonist phenylephrine, administered intracerebroventricularly in doses of 20-80 micrograms/10 microliters, increased the plasma corticosterone level in rats in a dose-dependent manner. Repeated treatment with amitriptyline (10 mg/kg po, twice daily for 14 consecutive days) or electroconvulsive shock (ECS) (once daily for 10 consecutive days) neither modified the basal corticosterone concentration nor affected the increase in the hormone level induced by phenylephrine (40 micrograms/10 microliters) injected 24 h after the last treatment with amitriptyline or ECS. Repeated treatment with imipramine (10 mg/kg po, twice daily for 14 consecutive days) did not affect the basal corticosterone concentration, but enhanced the corticosterone response to phenylephrine. These results indicate that repeated treatment with imipramine, but not with amitriptyline or ECS, increases responsiveness of the alpha 1-adrenoceptors involved in the hormonal response.