Oxytocin Proerectile projections from the supraoptic area of the hypothalamus and the PVN travel to the spinal centers for erection and oxytocin has been shown to be a key neurotransmitter in these neurons. In lab animals, intracerebroventricular or intrathecal injection of oxytocin antagonists blocks the induction of erection that is seen with intrathecal oxytocin injection. Additionally, antagonist injection into the lateral ventricles leads to a dose dependant reduction in noncontact erections.

This has led to the belief that oxytocin plays a role in facilitating nonreflexive erections. Dopamine Dopaminergic neurons project to the MPOA and PVN  and also have been discovered to travel from the caudal hypothalamus to the lumbosacral spinal cord.

Dopamine is thought to participate in central regulation of the autonomic and somatic penile reflexes. The dopamine receptor agonist, apomorphine, induces penile erection in rats when administered systemically. Additionally, apomorphine injection into the MPOA facilitated erections while dopaminergic antagonist injection into the MPOA decreased penile reflexes.

In the PVN, dopaminergic neurons appear to stimulate oxytocinergic neurons, which then more directly account for the erectile response. This is supported by the prevention of apomorphine-induced erections in the presence of oxytocin receptor antagonists.

Serotonin In experimental animal models, bulbospinal neurons containing serotonin (5-HT) project to the lumbar spinal cord. Serotonergic fibers have been demonstrated in close proximity to retrogradely labeled sacral preganglionic neurons.

One study showed 5-HT in general had an inhibitory effect on male sexual behavior. However, there have been conflicting reports with another study showing that the stimulation of 5-HT2c receptors mediated the erectile response. Thus, the full function of 5-HT in erectile function has not been fully elucidated. It appears to serve various functions likely acting as a major modulator of the central control of erection.