Pharmacology of Penile Erection

• Published in: Pharmacological reviews Vol. 53; no. 3; pp. 417 - 450
• Main Author: Andersson, K E
• Format: Journal Article
• Language: English
• Published: United States American Society for Pharmacology and Experimental Therapeutics 01-09-2001
• Subjects: Animals; Erectile Dysfunction - drug therapy; Erectile Dysfunction - etiology; Humans; Male; Muscle, Smooth - drug effects; Penile Erection - drug effects; Penile Erection - physiology; Penile Erection - psychology; Rats; Risk Factors
• ISSN: 0031-6997; 1521-0081

Erection is basically a spinal reflex that can be initiated by recruitment of penile afferents, but also by visual, olfactory,
and imaginary stimuli. The reflex involves both autonomic and somatic efferents and is modulated by supraspinal influences.
Several central transmitters involved in the erectile control have been identified. Dopamine, acetylcholine, nitric oxide
(NO), and peptides, such as oxytocin and adrenocorticotropic/α-melanocyte-stimulating hormone, seem to have a facilitatory
role, whereas serotonin may be either facilitatory or inhibitory, and enkephalins are inhibitory. Peripherally, the balance
between contractant and relaxant factors controls the degree of contraction of the smooth muscle of the corpora cavernosa
and determines the functional state of the penis. Noradrenaline contracts both corpus cavernosum and penile vessels via stimulation
of α 1 -adrenoceptors. Neurogenic NO is considered the most important factor for relaxation of penile vessels and corpus cavernosum.
The role of other mediators released from nerves or endothelium has not been definitely established. Erectile dysfunction
(ED) may be due to inability of penile smooth muscles to relax. This inability can have multiple causes. However, patients
with ED respond well to the pharmacological treatments that are currently available. The drugs used are able to substitute,
partially or completely, the malfunctioning endogenous mechanisms that control penile erection. Most drugs have a direct action
on penile tissue facilitating penile smooth muscle relaxation, including prostaglandin E 1 , NO donors, phosphodiesterase inhibitors, and α-adrenoceptor antagonists. Dopamine receptors in central nervous centers participating
in the initiation of erection have been targeted for the treatment of ED. Apomorphine, administered sublingually, is the first
of such drugs.