ROLE OF MONOAMINES IN OVULATION: EVIDENCE FOR A SEROTONINERGIC PATHWAY FOR INHIBITION OF SPONTANEOUS OVULATION

Abstract

SUMMARY The effect of a monoamine oxidase inhibitor (MAOI) (mebanazine) given alone or in combination with 5-hydroxy-dl-tryptophan (5-HTP) or dihydroxyphenylalanine (l-DOPA) on spontaneous ovulation was tested in 4-day cyclic rats. Injections of the MAOI or 5-HTP alone, which cause a selective rise in the hypothalamic serotonin level, blocked spontaneous ovulation in 32% and 0% of rats, respectively, and in 73% of rats when given together. By contrast, a combination of MAOI and l-DOPA, which causes a selective rise in the hypothalamic catecholamines, did not block ovulation. A single injection of α-methyl-p-tyrosine, but not of α-methyl-m-tyrosine, blocked ovulation in 100% of rats. These results provide experimental support for the existence of a serotoninergic component in the control of ovulation.