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

Arginine-vasopressin (AVP) has been previously shown to act in synergi sm with corticotropin-releasing hormone (CRH) in mediating stress-indu ced changes in the hypothalamo-pituitary-adrenal (HPA) axis. We have p reviously shown that both AVP and CRH play a role in mediating IL-1alp ha-induced changes in gonadotropin secretion. In this study, we invest igate the effects of exogenously administered AVP on luteinizing hormo ne (LH) secretion in the ovariectomized (OVX) rhesus monkey. Adult OVX rhesus monkeys were given an intracerebroventricular (ICV) infusion o f 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 prein fusion morning baseline and 5-hour postinfusion period. Cortisol conce ntrations were determined at 45-min intervals. Pulsatile LH release re mained unchanged after a control saline infusion. After an AVP infusio n, 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 th e 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, re spectively. While cortisol concentrations decreased throughout the exp erimental period in the animals receiving saline (a.m.: 35.4 +/- 2.4 m ug/dl vs. p.m.: 27.7 +/- 1.9 mug/dl), they increased after AVP infusio n (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 eviden ce for a role of vasopressin not only in the regulation of the hypotha lamo-pituitary-adrenal axis, but also of the hypothalamo-pituitary-gon adal axis in the primate.