INHIBITORY EFFECT OF ARGININE-VASOPRESSIN ON LH-SECRETION IN THE OVARIECTOMIZED RHESUS-MONKEY

Arginine-vasopressin (AVP) has been previously shown to act in synergism with corticotropin-releasing hormone (CRH) in mediating stress-induced changes in the hypothalamo-pituitary-adrenal (HPA) axis. We have previously shown that both AVP and CRH play a role in mediating IL-1alpha-induced changes in gonadotropin secretion. In this study, we investigate the effects of exogenously administered AVP on luteinizing hormone (LH) secretion in the ovariectomized (OVX) rhesus monkey. Adult OVX rhesus monkeys were given an intracerebroventricular (ICV) infusion of AVP (I 5 mug/h, n = 8; 50 mug/h, n = 5). Control animals received an ICV infusion of physiological saline at a rate 30 mul/h (n = 12). LH concentrations were measured at 15-min intervals during a 3-hour preinfusion morning baseline and 5-hour postinfusion period. Cortisol concentrations were determined at 45-min intervals. Pulsatile LH release remained unchanged after a control saline infusion. After an AVP infusion, however, LH concentrations (ng/ml) significantly decreased (I 5 mug: from 172.9 +/- 6.4 baseline to 129.4 +/- 5.3; 50 mug: from 142.8 +/- 8.3 to 106.7 +/- 6.0, mean +/- SE; p < 0.05). By the fifth hour of the AVP infusion, areas under the LH curve were 64.3 +/- 10.5 and 62.9 +/- 11.0% of morning baseline for 15 and 50 gg hourly infusion rate, respectively. While cortisol concentrations decreased throughout the experimental period in the animals receiving saline (a.m.: 35.4 +/- 2.4 mug/dl vs. p.m.: 27.7 +/- 1.9 mug/dl), they increased after AVP infusion (I 5 mug/h: 42.3 +/- 2.4 vs. 54.6 +/- 2.0 mug/dl; 50 mug/h: 41.9 +/- 6.6 vs. 50.8 +/- 8.5 mug/dl). These results provide compelling evidence for a role of vasopressin not only in the regulation of the hypothalamo-pituitary-adrenal axis, but also of the hypothalamo-pituitary-gonadal axis in the primate.