Neurotensin contracts the guinea-pig longitudinal ileal smooth muscle by inducing acetylcholine release.

Neurotensin contracted the isolated longitudinal smooth muscle strip of the guinea-pig ileum, but was only 22% as effective as histamine. Neostigmine (0.1 micrometer) increased the effectiveness of neurotensin 4-fold. Atropine (0.1 micrometer) completely inhibited the contracting effect of neurotensin measured in the presence of neostigmine, whereas hexamethonium (0.1 micrometer) was without effect. It is concluded that in the longitudinal smooth muscle of the guinea-pig ileum, the contracting effect of neurotensin is mediated by the release of acetylcholine from nerve endings in response to a postganglionic stimulation of cholinergic nerve fibers.