Neurotensin Enhances Gastric Motility in Antral Circular Muscle Strip of Guinea-pig

Neurotensin Enhances Gastric Motility in Antral Circular Muscle Strip of Guinea-pig

<P> Many reports suggest that neurotensin (NT) in the gastrointestinal tract may play a possible role as a neurotransmitter, a circulating hormone, or a modulator of motor activity. NT exerts various actions in the intestine; it produces contractile and relaxant responses in intestinal smooth muscle. This study was designed to investigate the effect of NT on motility of antral circular muscle strips in guinea-pig stomach. To assess the role of Ca<SUP>2&#8290;</SUP> influx in underlying mechanism, slow waves were simultaneously recorded with spontaneous contractions using conventional intracellular microelectrode technique. At the concentration of 10<SUP>&#8291;7</SUP> M, where NT showed maximum response, NT enhanced the magnitude (863&#8273;198%, mean&#8273;SEM, n=13) and the frequency (154&#8273;10.3%, n=11) of spontaneous contractions. NT evoked a slight hyperpolarization of membrane potential, tall and steep slow waves with abortive spikes (278&#8273;50%, n=4). These effects were not affected by atropine (2μM), guanethidine (2μM) and tetrodotoxin (0.2μM). NT-induced contractile responses were abolished in Ca<SUP>2&#8290;</SUP>-free solution and reduced greatly to near abolition by 10μM of verapamil or 0.2 mM of CdCl<SUB>2</SUB>. Verapamil attenuated the effects of NT on frequency and amplitude of the slow waves. Taken together, these results indicate that NT enhances contractility in guinea-pig gastric antral circular muscle and Ca<SUP>2&#8290;</SUP> influx through the voltage-operated Ca<SUP>2&#8290;</SUP> channel appears to play an important role in the NT-induced contractile mechanism.