Facilitation of sexual receptivity in the rat by an ovulation-inhibiting analog of LHRH.
An LHRH analog known to inhibit ovulation in the rat ([N-Ac-Phe1, D-p-Cl-Phe2, D-Trp3,6]-LHRH) was tested for its effects on sexual receptivity. The dose of 500 ng/rat was found in dose-response experiments to be most active and was further investigated for its behavioral effects in rats treated with either estrogen or estrogen plus progesterone. The analog significantly facilitated the behavior of rats in regimens producing low [estradiol benzoate (EB) (2 microgram)] and intermediate [EB (2 microgram) plus progesterone (2.5 mg)] levels of sexual behavior. In rats given regimens producing high behavioral scores [EB (5 microgram) plus progesterone (1 mg)], the peptide did not reduce mating behavior. In the same experiment, rats given EB (5 microgram) but not progesterone showed significantly higher scores after the LHRH analog only if they had been designated "responders" by a previous screening test with 1 microgram LHRH. These results demonstrate that in animals showing low, intermediate, or high levels of sexual behavior, the LHRH analog can affect mating behavior in a direction quite different from that exerted on pituitary reproductive functions.
D000818:Animals; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000031:analogs & derivatives* / Q000494:pharmacology; D010060:Ovulation / Q000187:drug effects*; D011374:Progesterone / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012726:Sexual Behavior, Animal / Q000187:drug effects*
D007987:Gonadotropin-Releasing Hormone; D011374:Progesterone; D004958:Estradiol