Role of the striatum and nucleus accumbens in paced copulatory behavior in the female rat.

Female rats engage in a series of approach and avoidance behaviors (pacing behavior) directed at the male in order to achieve a preferred rate of intromissions that make pregnancy more likely to occur with insemination. The striatum and nucleus accumbens have been implicated in the modulation of pacing behavior. It is unclear, however, whether these areas of the brain are necessary for the display of pacing behavior. To address this question, ovariectomized female rats received either bilateral quinolinic acid lesions of the striatum or nucleus accumbens or sham surgeries. After hormone priming, rats were allowed to engage in mating behaviors in an apparatus in which they could pace the rate of the copulatory bout. There was a significant reduction in pacing efficiency after striatal lesions, in that females were less likely to leave the male's side of the chamber after a contact. Animals with lesions of the nucleus accumbens that included the shell were more likely to avoid sexual interaction altogether than animals with control lesions. Therefore, it is concluded that the striatum and nucleus accumbens modulate specific aspects of pacing behavior in the female rat.