Substance P stimulates and inhibits intestinal peristalsis via distinct receptors

The tachykinins substance P (SP) and neurokinin A participate in the neural control of intestinal peristalsis. This study aimed at elucidating the types of tachykinin receptors involved in SP's ability first to stimulate and then to inhibit propulsive activity. Peristalsis in the guinea pig isolated ileum was triggered by fluid-induced distension of the intestinal wall. Unlike SP, the neurokinin (NK)-1 receptor-selective agonist SP methyl ester (1-100 nM) failed to facilitate peristalsis but caused a delayed inhibition of peristaltic activity. In contrast, the NK-2 receptor-selective agonist [beta-Ala8]-NKA-(4-10) (BANKA, 1-100 nM) stimulated, but did not inhibit, peristalsis. The NK-3 receptor-selective agonist succinyl-[Asp6,N-MePhe8]-substance P-(6-11) (SENKTIDE, 0.1-10 nM) was most potent in facilitating propulsive activity, and only with 10 nM SENKTIDE was a delayed inhibition of peristalsis seen. The receptors responsible for the tachykinin-evoked stimulation and inhibition of peristaltic activity were further characterized by use of the NK-1 receptor-selective antagonist (+)-(2S,3S)-3-(2-methoxybenzylamino)-2-phenylpiperidine (CP-99,994, 300 nM) and the NK-2 selective antagonist (-)-N-methyl-N[4-acetylamino-4-phenyl-piperidino-2 (3,4 dichlorophenyl)butyl]-benzamide (SR-48,968, 100 nM). CP-99,994 antagonized the inhibitory effects of SP (100 nM) and SP methyl ester (100 nM) on peristalsis but did not alter the facilitation of propulsive motility brought about by SP or BANKA (100 nM). Conversely, SR-48,968 (100 nM) suppressed the ability of SP and BANKA to stimulate persitaltic activity but did not attenuate the inhibitory motor effects of SP and SP methyl ester.(ABSTRACT TRUNCATED AT 250 WORDS)