Dual Effect of Substance P on Canine Antral Muscle

Substance P (SP) is widely distributed in neuronal structures of the mammalian gut. The peptide is known to have excitatory effects on various gastrointestinal tissues both in vivo and in vitro and this effect appears to be partially mediated by acetylcholine release from the myenteric plexus. In this study we sought (1) to describe the SP effect on the canine antral muscle in vitro and (2) to characterize its mechanism of action. Longitudinal (LAM) and circular (CAM) antral muscle strips from 30 mongrel dogs were studied using conventional organ bath techniques as previously described (Am. J. Physiol., 242: G141, 1982).