Antiprogestin RU486 Blunts the Stimulatory Effect of Galanin on LH Secretion from Rat Pituitaries in Vitro in an Estrous Cycle Stage-dependent Manner

Galanin (GAL), a neuroactive peptide detected in the hypothalamus and anterior pituitary, stimulated in a dose (0.1 and 1 microM)-dependent manner luteinizing hormone (LH) secretion from metestrous and proestrous rat pituitaries incubated in culture medium devoid of progesterone (P). GAL had no effect on follicle-stimulating hormone (FSH). Antiprogestin RU486 (10 nM) decreased non-stimulated (basal) secretion of LH and FSH only in pituitaries from proestrous rats and blunted the stimulatory effects of GAL on LH secretion in both metestrous and proestrous pituitaries. These findings are consistent with the hypothesis that GAL-mediated signal transduction interacts with estrogen-dependent P receptor at the pituitary level to stimulate LH secretion.