Department of Physiology, University of Texas Health Science Center at Dallas, Southwestern Medical School, Dallas, Texas 75235, U.S.A.
(Received 11 August 1976)
Luteinizing hormone releasing hormone (LH-RH) has been implicated in the mediation of sexual receptivity in the female rat (Moss & McCann, 1973, 1975; Pfaff, 1973). Furthermore, prostaglandin E2 (PGE2) has been found to release LH-RH (Ojeda, Wheaton & McCann, 1975). Thus, the possibility that PGE2 might potentiate lordosis behaviour in a similar way to LH-RH has been tested.
Forty-seven ovariectomized Wistar rats were injected s.c. with 0·25 mg oestrone in oil (Theelin, 1 mg/ml) and 45 h later, some received a second s.c. injection of 50 μg PGE2/0·5 ml (n = 10), 50 μg PGE1/0–5 ml (n = 7), or 500 ng LH-RH/0–5 ml (n = 10). Of the remaining 20 animals, ten were injected with 2·5 mg progesterone in oil (Lipo-Lutin; 50 mg/ml) 42 h after oestrogen