Midbrain lesions, dopamine and male sexual behavior

Destruction of the medial preoptic area (MPOA) eliminates mating in male rats and this region is believed to play a major role in the control of male sexual behavior. Efferents from the MPOA pass through and/or terminate in 4 midbrain regions: the dorsolateral tegmentum (DLT), the central gray, and the A9 and A10 areas. The present study reports the effects of bilateral destruction of each of these midbrain regions on brain catecholamines and sexual behavior in male rats. DLT lesions eliminated mating, reproducing the effect of bilateral preoptic lesions. The sexual activity of males with central gray lesions was accelerated in the sense that the mounting rate for these males was significantly faster than for controls and lesioned males ejaculated more frequently and with shorter latencies than did controls. A9 lesions impaired mating--lesioned males mounted at a slower rate and ejaculated less frequently than controls. Males with A10 lesions took longer to re-initiate mating after an ejaculation than controls, but copulation per se (as reflected in mount rate, ejaculation frequency and latency to ejaculate) was not affected by A10 damage. Brain catecholamine levels were not affected by either DLT or central gray lesions. A9 lesions produced a significant depletion in neostriatal dopamine which was highly correlated with mount latency, mount rate, ejaculation latency and ejaculation frequency. A10 lesions produced a significant depletion of dopamine in the nucleus accumbens and cingulate cortex, but these effects were not significantly correlated with any measure of sexual behavior.