ABSTRACT
Erections occur by one of three mechanisms (Table 1). First, erotic stimuli can lead to an erection. Such stimuli can be visual, auditory, olfactory or imaginative, and they appear to originate in the cerebral cortex before stimulating the hypothalamus, from where descending pathways pass into the spinal cord. A number of neurotransmitters have a role in this process, including dopamine, serotonin, oxytocin and noradrenaline (norepinephrine), and of these, dopamine appears to be particularly important. It is present within the hypothalamus, and when released in response to a sexual stimulus it appears to be proerectile (Figure 1). It is this mechanism that has been exploited by the use of apomorphine, a dopaminergic drug, as an oral therapy for men with ED. From the hypothalamus, the descending oxytocinergic neurons to the spinal cord
Table 1 Types of erections.
