11.06 Nitric Oxide

Nitric oxide (NO) is a biological gas that is involved in a range of cell signalling events, including vascular regulation, neurotransmission and regulation of inflammation. NO activates soluble guanylate cyclase (sGC) to produce the second messenger cGMP, resulting in activation of a cascade of events leading to vasorelaxation.

Nitrovasodilators are drugs that donate NO, which then elicits vasodilation. They are used to treat angina and heart failure associated with acute myocardial infarction (glyceryl trinitrate and isosorbide dinitrate)

Drugs used in the treatment of erectile dysfunction inhibit phosphodiesterase (PDE), which breaks down cGMP, effectively prolonging the vasodilator action of cGMP. PDEV is preferentially located in the corpus cavenosum, thus inhibitors of this enzyme enhance and prolong penile erection (e.g. sildenafil).