Female rats develop conditioned place preferences for sex at their preferred interval

Female rats engage in approach and avoidance behaviors directed toward the male to "pace" the rate of copulation. These pacing behaviors result in a pattern of vaginocervical stimulation that triggers a neuroendocrine reflex that is important for pregnancy to result from insemination. Each female rat has a preferred pacing interval, and females develop conditioned place preferences for paced sex versus nonpaced sex. Research from this laboratory has reported that extracellular dopamine concentrations in striatum and nucleus accumbens are greater in female rats that are engaging in paced sex compared with those engaging in nonpaced sex. Furthermore, females who have males removed at their preferred intervals during a copulatory bout show extracellular dopamine concentrations comparable to females engaging in paced sex. It is unclear, however, whether they would also develop a conditioned place preference for sex under such conditions. This experiment was designed to address this question. Female rats had six exposures each to a chamber in which they engaged in nonpaced sex and a chamber in which they engaged in paced or preferred pacing interval sex. Following conditioning trials, females were tested for a conditioned place preference. The findings indicate that female rats develop conditioned place preferences for paced sex and for sex in which the male is removed at her preferred interval. This suggests that sexual behavior is reinforcing to female rats when their preferred interval is achieved, whether or not they are actively controlling the rate of copulation.