Non-neuronal excitatory neurotensin receptors on the taenia coli of the guinea pig: lack of influence of tetrodotoxin and dynorphin

Picomoles of neurotensin caused contractions of the smooth muscles of the taenia coli and the myenteric plexus preparation of the guinea pig ileum. The musculotropic effect of neurotensin on the taenia coli was resistant to tetrodotoxin and to treatment with dynorphin. In contrast, the contractile activity of the neuropeptide in the ileum was substantially modified by pretreatment with tetrodotoxin or dynorphin. It is concluded that, whereas neurotensin causes a direct muscular response on the taenia coli via activation of selective peptide receptors probably located on the muscle membrane, the neuropeptide causes a predominant indirect action on the ileum mediated apparently via the release of acetylcholine from the nerve terminals of the myenteric plexus. Neurotensin may play a role in the control of gut peristalis either by modifying the release of neurotransmitters or by directly influencing the smooth muscles of the intestines.