Differential effects of prostaglandin on lordosis behavior in female guinea pigs and rats

Abstract

The facilitatory and inhibitory effects of prostaglandins PGE2 and PGF(2α) on lordosis behavior were compared in guinea pigs and rats. In the first part of experiment 1, PGE2 or PGF(2α) (500 μg) failed to facilitate significantly lordosis behavior in ovariectomized, estradiol benzoate (EB)-primed guinea pigs. However, in the second part of experiment 1, in guinea pigs treated with EB followed 44 hr later by progesterone (P), PGE2 and PGF(2α) (500μg) significantly inhibited lordosis responses when given at the same time as P, 5 hr after P (at the onset of heat) or 8 hr after P (at the time of maximal lordosis responding). Doses of 20 μg or 100 μg PGE2 or PGF(2α) also inhibited lordosis responding when given 5 hr after P to EB-primed guinea pigs. Oxytocin treatment (100 mU or 500 mU) given 5 hr after P to EB-primed guinea pigs had no effect on subsequent lordosis responding. In experiment 2, PGE2 (100 μg) significantly facilitated lordosis in EB-primed rats but, in contrast to guinea pigs, 500 μg PGE2 or PGF(2α) had no inhibitory effect on lordosis behavior when given 4 or 8 hr after P treatment to EB-primed rats. Inhibitory effects of prostaglandins on lordosis behavior in guinea pigs and facilitatory effects of prostaglandins on lordosis behavior in rats may be indicative of differential neurochemical mechanisms for the regulation of lordosis behavior in guinea pigs and rats.