NEUROMODULATORY REGULATION OF GONADOTROPIN-RELEASING-HORMONE PULSATILE DISCHARGE IN WOMEN

The pulsatile release of gonadotropin-releasing hormone and the consequent secretion of gonadotropins are regulated by a complex interplay of steroids, neuropeptides, catecholamines, and environmental factors. Estrogen and progesterone influence the amplitude and frequency of luteinizing hormone pulsatile secretion. These effects lead to both a diurnal variation in pulse frequency, with a lower frequency at night, and variation during the menstrual cycle, with a lower frequency and increased amplitude during the luteal phase. Opioid peptides inhibit the pulsatile discharge of gonadotropin-releasing hormone and luteinizing hormone. The opioid antagonist, naloxone, causes an increase in luteinizing hormone secretion, particularly during the luteal phase. The administration of opioid receptor agonists, such as β-endorphin, results in a decline in serum luteinizing hormone during the early follicular phase. Corticotropin-releasing factor, which is increased during stress, inhibits pulsatile luteinizing hormone secretion, and this effect can be blocked by the simultaneous administration of naloxone. These observations suggest that corticotropin-releasing factor exerts its effects on luteinizing hormone through an opioidergic intermediary. Endogenous catecholamines such as dopamine inhibit pulsatile luteinizing hormone release; however, the mechanism involved is not clear. © 1990.