PROGESTERONE-RECEPTOR PARTICIPATES IN THE STIMULATORY EFFECT OF LHRH,PROSTAGLANDIN-E2, AND CYCLIC-AMP ON LORDOSIS AND PROCEPTIVE BEHAVIORSIN RATS

We explored the effect of the antiprogestin RU486 on the estrous behav iour (lordosis and proceptivity) induced in sexually experienced ovari ectomized oestrogen primed rats by: 5 mu g luteinizing hormone-releasi ng hormone (LHRH), 100 mu g prostaglandin E2 (PGE2), or 2 mg dibutyryl cyclic AMP (db cAMP). Pretreatment with 5 mg RU 486 (but not with veh icle) 60 min before the injection of the above-mentioned agents signif icantly decreased both lordosis and preceptive behaviours normally ind uced by such agents. Results suggest that the estrus-inducing action o f LHRH, PGE2 and db cAMP occurs through the activation of the progeste rone receptor.