The nature of the conditioned response mediating olfactory conditioned ejaculatory preference in the male rat

We have developed a model to study the influence of conditioning on sexual partner preference in the rat. In this model, pairing a neutral odor (almon d) with copulation to ejaculation produces a subsequent preference to ejacu late with females bearing that odor. We refer to this phenomenon as a condi tioned ejaculatory preference (CEP). The present study investigates the nat ure of the conditioned response that mediates CEP. Given equal mount and in tromission distributions, but an unequal ejaculation distribution, we hypot hesized that two mechanisms could account for CEP: facilitated ejaculation or selective ejaculation. To test these hypotheses, we examined the effect of omitting the olfactory conditioned stimulus (CS) or applying it to a non receptive female. Males trained with the CS paired with copulation (paired- trained males) failed to display evidence of delayed ejaculation when copul ating with unscented females. Conversely, paired-trained males displayed CS -elicited copulatory behavior with CS-bearing nonreceptive females. In addi tion, we re-analyzed the data from the copulatory preference tests of previ ous experiments for CEP-displaying males. Again, we failed to find evidence of facilitated ejaculation with the scented female. However, the time betw een the last mount or intromission and ejaculation was increased if either occurred with the scented female. Furthermore, more mounts were directed to wards the scented female near the end, but not at other points, of an ejacu latory series. These findings suggest that the paired-trained males attend to the scented female near the point of ejaculation, and are consistent wit h the hypothesis that CEP is mediated by selective ejaculation. (C) 2001 El sevier Science B.V. All rights reserved.