Tachykinin, emesis

Substance P (SP) is a member of the family of tachykinin peptides that also includes neurokinin A and B. Their respective receptors are tachykinin NKl, tachykinin NK2 and tachykinin NK3. Substance P is best known as a pain neurotransmitter, but it also controls vomiting. In relation to emesis, its sites of localisation include the area postrema and the nucleus tractus solitarius. 

Substance P is the most important member of the tachykinin family. It exerts a variety of incompletely understood central actions that implicate the peptide in behavior, anxiety, depression, nausea, and emesis. It is a potent arteriolar vasodilator, producing marked hypotension in humans and several animal species. The vasodilation is mediated by release of nitric oxide from the endothelium. Conversely, substance P causes contraction of venous, intestinal, and bronchial smooth muscle. It also stimulates secretion by the salivary glands and causes diuresis and natriuresis by the kidneys. 

Antagonists of tachykinin receptors produce beneficial effects in several CNS disease states such as pain, asthma, emesis, and depression. 

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