EFFECT OF DELTA-OPIOID RECEPTOR AGONIST DELTORPHIN ON CIRCULATING CONCENTRATIONS OF LUTEINIZING-HORMONE AND FOLLICLE-STIMULATING-HORMONE INHEALTHY FERTILE WOMEN

There is evidence that endogenous opioid peptides exert an inhibitory effect on pituitary luteinizing hormone (LH) secretion both in animals and in humans, by interacting with mu-opioid receptors, However, a ro le for delta-opioid receptors in the regulation of gonadotrophin relea sing hormone (GnRH) secretion has recently been suggested. In the pres ent study, we evaluated the effect of the highly selective delta-opioi d receptor agonist deltorphin on the LH and follicle stimulating hormo ne (FSH) responses to naloxone in six healthy fertile women during the luteal phase of the menstrual cycle. Deltorphin infusion alone (7 mu g/kg/min for 60 min) did not significantly change the basal serum conc entrations of LH in this group of women, The intravenous (i.v.) bolus administration of naloxone (15 mg) induced a significant (P < 0.001) i ncrease in serum LH concentrations (from a mean basal value of 4.24 +/ - 1.10 IU/l to a peak of 13.27 +/- 1.8 IU/l), The LH response to nalox one was significantly (P < 0.001) blunted by preinfusion of deltorphin (13.27 +/- 1.80 IU/l versus 4.80 +/- 1.18 IU/l), No significant chang es in FSH concentrations were observed during deltorphin, naloxone or deltorphin plus naloxone administration, These data indicate that acti vation of delta-opioid receptors can reduce naloxone-induced LH releas e, suggesting a possible role of delta receptors in opioidergic modula tion of LH secretion in women.