Endogenous excitatory amino acid regulation of the progesterone-induced LH and FSH surge in estrogen-primed ovariectomized rats

The role of endogenous excitatory amino acid neurotransmission in the regulation of progesterone and triamcinolone acetonide-induced LH and FSH release was examined. Estrogen-primed ovariectomized rats were utilized in this study. Progesterone or triamcinolone acetonide (1 mg/kg body weight) treatment led to a highly significant elevation of serum LH and FSH levels 5 h later. Treatment with the selective noncompetitive NMDA receptor antagonist, MK801, had no effect on serum LH and FSH levels when compared to estrogen controls. However, MK801 administered 1 h prior to progesterone or triamcinolone acetonide administration completely blocked their ability to induce LH and FSH surges. These studies demonstrate for the first time the involvement of endogenous excitatory amino acid neurotransmission in the mediation of progesterone and corticosteroid-induced LH and FSH surges.