Interazione dopamina-ossitocina nel controllo centrale della risposta erettile

We investigated: 1) the effect of a pro-erectile dose of apomorphine, a mixed dopamine receptor agonist, injected into the PVN on the release of dopamine by mesolimbic dopaminergic neurons in the “shell” of the nucleus accumbens; 2) the effect of oxytocin injected into the VTA on penile erection and on the concentration of dopamine into the “shell” of the nucleus accumbens and into the PVN; 3) the mechanism responsible for the pro-erectile effect of oxytocin injection into the VTA, mainly the role of the NO-GMPc system; and 4) the relationship between oxytocinergic fibers/axons, mesolimbic dopaminergic cell bodies, NO synthase and guanylyl cyclase into the VTA. The results obtained suggest the existence of a neural circuit where dopaminergic and oxytocinergic neurons play a key role in the motivational/rewarding and consummatory aspects of male sexual behavior. When activated, this circuit facilitates not only the copulatory behavior through the activation of paraventricular oxytocinergic neurons projecting to the spinal cord, but also the mechanisms controlling sexual motivation and sexual reward through the activation of paraventricular oxytocinergic neurons projecting to the VTA. Infact, oxytocin released here activates the NO-cGMP system localized into the cell bodies of the mesolimbic dopaminergic neurons and this, in turn, lead to the release of dopamine into the nucleus accumbens. This neural circuit may play a key role in the integration of the activity of neural pathways controlling the consummatory (erection-ejaculation) and anticipatory (motivation and reward) aspects of the male sexual behavior in physiological contexts.