Neurochemical correlates of male sexual behavior

This report presents evidence of changes in the concentration of monoamine neurotransmitters and their metabolites in homogenates of spinal cord and brain areas of male rats related to specific events of their mating behavior. Intact male rats were allowed to copulate with receptive females and decapitated immediately after either the first intromission or the first ejaculation. Non-mating control animals were exposed to other males, instead of females. The concentration of monoamines (norepinephrine, dopamine and serotonin) and some of their major metabolites (DOPAC and HIAA) in homogenates of discrete brain areas (parietal cortex, preoptic region, mediobasal hypothalamus) and lumbosacral spinal cord were measured by HPLC-ED. Results suggest that sexual arousal is associated with both increased dopaminergic activity in the preoptic region and inhibition of descending monoaminergic signals to the lumbosacral cord, whereas ejaculation is accompanied by increased activity of the serotonergic, as well as dopaminergic, innervation of the preoptic region. These findings give neurochemical support to notions of central monoamines involvement in sexual behavior suggested by previous pharmacological studies.