| Institution: | Institut National de la Santé et de la Recherche Médicale (I.N.S.E.R.M.), Groupe de Recherches sur les Hormones Polypeptidiques et la Physiopathologie Endocrinienne, U. 145, Faculté de Médecine (Pasteur), 06034, Nice Cedex, France |
| Abstract: | The effects of neurotensin were investigated in intestinal smooth muscle preparations. Neurotensin relaxed the rat ileum, and contracted the guinea-pig ileum and taenia. Neurotensin induced a biphasic response (relaxation followed by contraction) in the contracted guinea-pig ileum. In all systems, half-maximal effects were obtained with 4–5 nM neurotensin and maximal responses with 30–60 nM; tachyphylaxis occurred with higher concentrations. Tetrodotoxin did not affect the responses to neurotensin in the rat ileum and the guinea-pig taenia. Tetrodotoxin abolished the contraction or the contraction phase (but not the relaxation phase) of the biphasic response induced by neurotensin in the guinea-pig ileum. Atropine partially inhibited the neurotensin-induced contraction in the guinea-pig ileum. These results suggest that neurotensin acts on intestinal smooth muscle both directly (relaxation of the rat and guinea-pig ileum, and contraction of the guinea-pig taenia) and through a nerve-mediated, partly cholinergic, process (contraction of the guinea-pig ileum). |
