Stimulus variables influencing conditioned suppression of copulatory behavior in male rats
Male rats received an ip injection of lithium chloride (LiCl, .3 M 20 mg/kg) after each of eight 5-min exposures to an inaccessible estrous female rat (Group E-LiCl). Conditioned suppression of copulatory behaviors was observed when these male rats were subsequently given access to receptive females. Comparable suppression was observed in male rats that received LiCl after each exposure to inaccessible nonestrous female rats (Group NE-LiCl), inaccessible male rats (Group M-LiCl), or contextual cues of the test chambers (Group NR-LiCl). Noncontingent injections of LiCl administered 24 hr after each exposure to an inaccessible estrous female rat did not affect subsequent copulatory behaviors. Copulatory decrements were also observed in male rats during post-conditioning tests with receptive females in the presence of an almond odor that had previously been paired with LiCl. Although comparable levels of suppression of copulatory behaviors were observed for all experimental groups, behavioral measures obtained during conditioning trials revealed significant group differences. Experimental groups displayed different amounts of agitated behaviors (paw treading and chin rubbing) during conditioning trials and the subsequent copulation test session. Differential paw treading and chin rubbing may reflect the relative salience of cues that serve as potential conditioned stimuli in each experimental condition. Groups also differed in the amount of time spent near the inaccessible stimulus animals during conditioning trials. Rats in Group E-LiCl were the only rats to develop a preference for the side of the chamber away from the stimulus animal. Preferences demonstrated by rats in Groups M-LiCl and NR-LiCl varied with the structural features of the test chamber. These experiments demonstrate that male rats that have received multiple pairings of LiCl-induced illness in the presence of various stimulus conditions (inaccessible estrous and nonestrous female rats, inaccessible male rats, contextual cues of the chamber, almond odor) display copulatory decrements during subsequent encounters with an estrous female.