Partner preference for strain of female in Long-Evans male rats.

Although male rats are reported to show greater sexual arousal and mating preference for a novel female compared to a familiar one, we have shown that after repeated copulation to ejaculation with a female bearing a neutral odor in bilevel pacing chambers, or unilevel pacing chambers bisected by a 1-hole divider, male rats display a conditioned ejaculatory preference for a female bearing the odor relative to a female not bearing the odor. The aim of the present study was to examine whether males might also develop a conditioned ejaculatory preference for the strain characteristics of the female after repeated copulation with the same female in a pacing chamber bisected by either a 1-hole or 4-hole divider. In this experiment, male Long-Evans rats were given 10 copulatory trials with the same Long-Evans or Wistar female in either the 1-hole or 4-hole condition. Copulatory preferences were then examined in an open field where males had the choice to copulate with either the familiar female or a novel one of a different strain from the familiar female. Results indicated that Long-Evans males trained in the 1-hole condition with the same Long-Evans female displayed a conditioned ejaculatory preference for the familiar vs. novel female. However, males trained in the 1-hole condition with the same Wistar female at every trial copulated indiscriminately with the familiar and novel females. No preference was detected in males trained in the 4-hole condition. These findings suggest that, following training in a 1-hole pacing chamber, males displayed an ejaculatory preference only if the familiar female is of their own strain.