Novel pharmacology of substance K-binding sites: a third type of tachykinin receptor

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Science  23 Nov 1984:
Vol. 226, Issue 4677, pp. 987-989
DOI: 10.1126/science.6095447


The tachykinins are a family of peptides with the carboxyl terminal amino acid sequence Phe-X-Gly-Leu-Met-NH2. Three major mammalian tachykinins have been identified--substance K, neuromedin K, and substance P--but only two tachykinin receptors have been postulated. Three tachykinins were labeled with radioiodinated Bolton-Hunter reagent and their binding characteristics were determined in crude membrane suspensions from several tissues. In cerebral cortex labeled eledoisin exhibited high-affinity binding that was inhibited by tachykinins in a manner indicating a definitive SP-E receptor site. In gastrointestinal smooth muscle and bladder, high-affinity binding of labeled substance P was inhibited in a pattern indicating a definitive SP-P site. In intestinal smooth muscle and bladder, however, labeled substance K and labeled eledoisin were both bound in a pattern indicating a preference for substance K itself. The results suggest the existence of three distinct types of tachykinin receptors: SP-P, SP-E, and SP-K.