Central noradrenergic control of penile erection

Penile erection is completely dependent on commands from the central nervous system. Spinal centers controlling penile erection are located in the thoracolumbar and lumbosacral spinal cord. These centers are activated by information from the periphery and supraspinal nuclei so as to elicit penile erection in a variety of physiological contexts. A small number of nuclei including the locus coeruleus located in the pons sends noradrenergic fibers to the forebrain and spinal cord, including those areas controlling penile erection. Recent morphological techniques such as in situ hybridization and autoradiography using radioligand binding permit investigation of the brain and spinal pathways utilizing alpha adrenoceptor subtypes. Furthermore, pharmacological experiments suggest a modulatory role for noradrenaline in the control of penile erection either in the brain or in the spinal cord. The most robust evidence is that central inhibition of alpha-2 adrenoceptors facilitates sexual function. Taken together, the data propose new directions in the physiological exploration of penile erection and the therapeutic approach of erectile dysfunction.