Abstract
Intracellular microelectrode and standard organ bath techniques were used to study in vitro the effects of neurotensin on the electrical and mechanical activities of canine antral circular smooth muscle. Neurotensin reduced or abolished spontaneous contractions. Muscarinic and adrenergic antagonists and tetrodotoxin did not block the effects of neurotensin, suggesting that the action of neurotensin was due to a direct action on the smooth muscle cell. Although the inhibitory effect of norepinephrine and neurotensin was similar, the effect of neurotensin did not appear to occur by an adrenergic mechanism because alpha- and beta-receptor blockade had no effect. Neurotensin also reduced or abolished contractions stimulated by pentagastrin and acetylcholine. The inhibitory effect of neurotensin on spontaneous acetylcholine- and pentagastrin-stimulated contractions was associated with a decrease in the amplitude and duration of the plateau potential of the gastric action potential. The data suggest that modulation of antral contractions by neurotensin occurs through a voltage-dependent mechanism that operates during the plateau potential.
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