The effect of pilocarpine and oxotremorine on hormone-activated copulatory behavior in the ovariectomized hamster.

Abstract

The effect of cholinergic compounds on hormone activated copulatory behavior in the ovariectomized hamster was studied. Pilocarpine and oxotremorine decreased the lordosis response elicited by estrogen plus progesterone at a time which coincided with the time for maximal muscarinic symptoms. This effect was prevented by atropine but not by methyl-atropine pretreatment. Pilocarpine could also activate the copulatory behavior after estrogen treatment only. This effect was obtained after the muscarinic symptoms had disappeared. These data are in general agreement with those previously found in the female rat. However, in contrast to the rat, the inhibitory effect of pilocarpine and oxotremorine on lordosis response in the hamster was not prevented by pretreatment with reserpine or p-chlorophenylalanine and the lordosis activating effect of pilocarpine was counteracted by methyl-atropine pretreatment. In both species, reserpine followed by pilocarpine treatment induced a clearcut tremor, which was not seen after either drug alone. It is suggested that the mechanism of action by which cholinergic drugs exert an inhibitory effect on hormone activated copulatory behavior is partly different in the rat and the hamster.