PPT Slide
The sympathetic [alpha]-adrenergic receptors are thought to mediate, in part, corpus cavernosum tone maintained in flaccidity. All 3 subtypes of [alpha]1-adrenergic receptors and [alpha]2-adrenergic receptors are expressed in human corpus cavernosum. Blockage of these receptors by [alpha]1-, [alpha]2-, or mixed [alpha]-adrenergic receptor antagonists has been used to treat ED. Specifically, phentolamine (an [alpha]1- and [alpha]2-selective antagonist) has been used alone and in combination with other agents.