Neurally mediated contraction of ileal longitudinal muscle by substance P.
The time course of the spasmogenic effect of substance P (SP) on the longitudinal muscle (LM) of the guinea-pig ileum was investigated. Maximum effective concentrations of SP (greater than or equal to 10 ng/ml) produced a fast initial response which subsequently declined to about 50% of the initial contraction. This remaining half-maximum contraction was increased by physostigmine and decreased by tropicamide, morphine, and tetrodotoxin; hexamethonium had no effect. The results indicate that SP, apart from its direct action on the LM, also activates cholinergic neurones innervating the LM.
D000818:Animals; D002799:Cholinergic Fibers / Q000187:drug effects*; D004347:Drug Interactions; D005260:Female; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000294:innervation; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D009469:Neuromuscular Junction / Q000502:physiology; D013373:Substance P / Q000008:administration & dosage / Q000494:pharmacology*
D013373:Substance P