Haloperidol challenge during copulation prevents subsequent increase in male sexual motivation

Male rats manifest an increase in sexual motivation following sexual experience. The current experiment was devised to investigate the role of dopamine in this process by assessing whether sexual behavior occurring in the presence of the dopamine receptor antagonist, haloperidol, would continue to alter the subjects' subsequent sexual motivation. Four groups of male Long-Evans rats (total N=34) traversed an operant runway once per day for one of two goalbox targets: a nonestrous or estrous female. Following establishment of baseline run times (10 trials), all males received one ejaculation with a receptive female in a separate testing environment. Subjects were pretreated with vehicle or one of three doses of haloperidol (0.05, 0.075, 0.10 mg/kg) 45 min prior to being paired with the receptive female. All subjects successfully achieved ejaculation under these conditions. Subjects were then re-tested within the runway for their motivation to approach the two types of female targets (10 trials). Vehicle-treated subjects expressed the expected increase in sexual motivation following sexual experience, while haloperidol treatment dose-dependently attenuated this effect. Subjects that received the highest haloperidol dose subsequently manifested increased run times and intra-runway "retreat" behaviors, suggesting that female cues may have become associated with an aversive sexual experience. These results are consistent with the view that dopamine systems play a role in the rewarding or reinforcing consequences of male sexual behavior.