Excitatory amino acid regulation of gonadotropin secretion: modulation by steroid hormones

Excitatory amino acids (EAAs) can potently modulate gonadotropin secretion in the male rat and monkey. In the present study we examined of EAAs on luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the female rat under low estrogen (ovariectomized) and high estrogen (proestrus) backgrounds. In ovariectomized immature female rats (NMDA) inhibited LH but not FSH secretion at 30 min post-injection. In contrast, NMDA potently stimulated LH but not FSH secretion when administered on proestrus to adult female rats. Both glutamate and kainate were also found to stimulate LH but not FSH secretion in estrogen-treated ovariectomized immature rats. This study suggests that EAA neurotransmission may be an important component in the expression of gonadotropin surges and that EAA effects appear to be subject to gonadal steroid regulation.