Pathophysiology of Erectile Dysfunction

Physiology of erection and pathophysiology erectile dysfunction is reviewed. Analysis is obtained from basic and clinical research including animals studies, anatomical studies, and molecular and cellular research on corporal tissue obtained during penile prosthesis implantation. Supraspinal influences and spinal influence on penile erection has been learned from spinal cord injury patient. Corporal smooth muscle relaxation of penile arteries and corpus cavernosum leads to penile erection, results from parasympathetic/nonadrenergic noncholinergic neural pathway activation and simultaneous inhibition of sympathetic outflow. Anatomical studies taught understanding of the mechanism for restriction of blood outflow from the corpora cavernosa. The change of smooth muscle tone has emerged as a key factor in erection and detumescence. Many independent factors converge on the modulation of corporal smooth muscle tone. Neuronal and local neurotransmitter effects via gap junction, potassium channels, and calcium channel. A nitric oxide/cyclic guanosine monophosphate mechanism as well as cyclic aminomonophosphate has an important role in mediating the corporal smooth muscle relaxation necessary for erectile function. Erectile dysfunction can be due to vasculogenic, neurogenic, hormonal, veno-occlusive, psychogenic and/or pharmacogenic factors as well as alterations in the nitric oxide/cyclic guanosine monophosphate (cGMP) or cyclic aminophosphate (cAMP) pathway or other regulatory mechanisms including gap junction or ionic channel resulting in an imbalance in corporal smooth muscle contraction and relaxation. Our present knowledge of the hemodynamics, functional anatomy, neurophysiology, and neuropharmacology of penile erection and dysfunction at the cellular and molecular level has led to better understanding of physiology and pathophysiology of erectile dysfunction.