Effects of clorgyline and deprenil on corticosterone levels in rats.

Adrenal and plasma corticosterone levels were measured in adult female rats after i.p. administration of specific MAO inhibitors: clorgyline (IMAO-A) and deprenil (IMAO-B). Brain and adrenal MAO activity was also determined. The IMAO effect was found to depend on 3 interrelated factors: (a) dose of drug, (b) time after injection, (c) specificity in MAO inhibition. One hour after injection, clorgyline (1 and 2.5 mg/kg) but not deprenil (20 mg/kg), appeared to inhibit the adrenocortical stress response to i.p. injection. At higher doses, MAO-B inhibition by deprenil (40 mg/kg) induced a moderate but sustained increase in corticosterone levels, while MAO-A inhibition by clorgyline (5, 10, 20 mg/kg) resulted in a large and sharp rise. This effect of clorgyline was potentiated with alpha-methyl-p-tyrosine and blocked with p-chlorophenylalanine. On this basis, the involvement of serotonergic mechanisms could be considered to explain the stimulatory effect of clorgyline on adrenal cortical function.