Evidence for neurotensin as a non-adrenergic, non-cholinergic neurotransmitter in guinea pig ileum.
Neurotensin is a 13-amino acid peptide that is widely distributed in central and peripheral tissues of various mammalian species. In peripheral tissues, the highest concentration of neurotensin-like immunoreactivity is found in the ileum, where it is present in endocrine-like cells and nerve fibres. The longitudinal smooth muscle layer of the guinea pig ileum, where neurotensin has both a direct relaxant and an indirect contractile action, has been used extensively as a biological assay system for neurotensin. We report here that the majority of specific 3H-neurotensin binding sites is present in the guinea pig ileum circular smooth muscle layer, which is known to be innervated by a large proportion of the ileal non-adrenergic inhibitory nerves. Neurotensin produces a dose-dependent, tetrodotoxin-resistant relaxation, whereas the relaxation produced by field stimulation of the inhibitory nerves is frequency-dependent and tetrodotoxin-sensitive. The calcium-dependent potassium channel blocker apamin inhibits both the neurotensin- and nerve stimulation-induced muscle relaxation. Incubation of the circular smooth muscle preparation with a neurotensin antiserum substantially inhibited the nerve stimulation-induced relaxation, indicating a direct relationship between the effects of neurotensin and of nerve stimulation.
D000818:Animals; D001345:Autoradiography; D001681:Biological Assay; D002462:Cell Membrane / Q000378:metabolism; D007082:Ileum / Q000032:analysis* / Q000378:metabolism; D007700:Kinetics; D051379:Mice; D009496:Neurotensin / Q000032:analysis* / Q000378:metabolism; D018377:Neurotransmitter Agents; D011956:Receptors, Cell Surface / Q000032:analysis* / Q000378:metabolism; D018028:Receptors, Neurotensin; D014316:Tritium
D018377:Neurotransmitter Agents; D011956:Receptors, Cell Surface; D018028:Receptors, Neurotensin; D014316:Tritium; D009496:Neurotensin