title: Distinct classes of substance P receptors revealed by a comparison of the activities of substance P and some of its segments.
abstract: The contracting potency of Substance P and of its C-terminal fragments was studied using four isolated preparations of smooth muscle. The Substance P receptors in the four muscles studied can be differentiated on the basis of their interactions with Substance P and its C-terminal fragments. On the guinea pig ileum, the potency of Substance P is equal to that of the C-terminal octa- and heptapeptide segments and in the rat ileum the potency of Substance P is equal to that of the C-terminal octapeptide and even higher than that of the heptapeptide. In contrast, on the cow pupillary sphincter and guinea pig urinary bladder, Substance P is markedly less potent that the C-terminal octa-, hepta- and hexapeptides. These results suggest the existence of different classes of Substance P receptors and indicate that the N-terminal sequence may be important in regulating Substance P activity.
mesh_terms: D000818:Animals; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009842:Oligopeptides / Q000494:pharmacology*; D010446:Peptide Fragments / Q000494:pharmacology*; D011680:Pupil / Q000187:drug effects; D051381:Rats; D011956:Receptors, Cell Surface / Q000187:drug effects; D018040:Receptors, Neurokinin-1; D013329:Structure-Activity Relationship; D013373:Substance P / Q000494:pharmacology*; D001743:Urinary Bladder / Q000187:drug effects
chemical_list: D009842:Oligopeptides; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D018040:Receptors, Neurokinin-1; D013373:Substance P