The development of olfactory conditioned ejaculatory preferences in the male rat. II. Parametric manipulation of conditioning session number and duration.

We have previously demonstrated that repeated pairing of a neutral odor with copulation produces a subsequent conditioned ejaculatory preference (CEP) for females bearing that odor. The present study examines the course of CEP development. In Experiment 1, Long-Evans male rats were allowed access to almond-scented, sexually receptive females for either one, five, or nine conditioning sessions that were 30 min in duration. Males given five or nine sessions displayed significant CEPs. In Experiment 2, male rats were given a single conditioning session with multiple almond-scented females until either a duration (60, 120, 180, or 240 min) or copulatory criterion (two, four, or six ejaculatory series) was satisfied. Males that received 120-, 180-, or 240-min sessions or four ejaculations displayed significant CEPs; males that received two or six ejaculations displayed a trend for CEPs. Analysis of effect size estimates revealed that the strongest CEPs were produced by 120 min of copulation or four ejaculations. In Experiment 3, males receiving nine conditioning sessions each 30 min in duration displayed a more enduring CEP than did males receiving a single conditioning session 240 min in duration. These data suggest that early sexual experiences have particularly powerful influences on subsequent sexual preferences and that the development of sexual preferences are influenced by interactions between CS-UCS pairings and motivational variables.