Microinjection of the dopamine antagonist cis-flupenthixol into the MPOA impairs copulation, penile reflexes and sexual motivation in male rats

Microinjection of the dopamine antagonist cis-flupenthixol into the medial preoptic area was previously shown to impair male rat copulatory behavior. The present experiments provide further evidence of cis-flupenthixol's inhibitory effects on male sexual behavior. Following microinjections of moderate to high doses of cis-flupenthixol, males exhibited slower copulatory rates and fewer ejaculations in copula, fewer ex copula erections and penile movements, and reduced sexual motivation in an X-maze. Locomotion in the X-maze was not significantly affected. Microinjections of the inactive isomer trans-flupenthixol produced no change in any behavioral measure, indicating that cis-flupenthixol's effects were receptor mediated. We suggest that dopamine receptors in the MPOA influence copulation primarily by regulating reflexive and motivational factors, but not locomotion.