The influence of substance P on the response of guinea-pig isolated ileum to periarterial nerve stimulation

Open Access
Publisher Website
Google Scholar
Abstract
1 The effects of substance P (SP) on the responses of the guinea-pig isolated ileum to periarterial nerve stimulation were studied. Electrical stimulation (2–50 Hz) of mesenteric periarterial nerves resulted in contraction of preparations pre treated with guanethidine. The responses were abolished by atropine and morphine, but unaffected by hexamethonium. 2 SP in a high concentration (0.65 μmol) inhibited reversibly, by about 40%, the responses of the guinea-pig isolated ileum to periarterial nerve stimulation. 3 SP in a very low concentration (0.18 pmol) potentiated (by about 20%) the responses of the guinea-pig isolated ileum to periarterial nerve stimulation. 4 In the presence of low concentrations (0.06–0.32 pmol) of SP, morphine (2.65 μmol) produced less inhibition of the responses to periarterial nerve stimulation, and recovery from morphine inhibition of contraction was accelerated. 5 These results indicate that SP may act as a modulator on prejunctional acetylcholine release in the guinea-pig ileum.