Effects of neurotensin and neurotensin analogues on the migrating myoelectrical complexes in the small intestine of rats.

The purpose of the present experiments was to study the effect of neurotensin and neurotensin analogues on the migrating myoelectrical complexes in the small intestine of rats. Four bipolar electrodes were implanted into the muscular wall of the small intestine. The electrodes were placed 5, 15, 25 and 35 cm distal to the pylorus. 7-10 days after the operation the animals were fasted for 48 h with free access to water. Some experiments were performed on conscious rats and in others the rats were anesthetized with pentobarbital, 30 mg/kg. I.v. infusion of either neurotensin (NT) or (Gln4)-neurotensin at doses of 1.8, 3.6 and 7.1 pmol X kg-1 X min-1 abolished the migrating myoelectric complexes, which were replaced by increased spiking activity along the whole length of the small intestine from which activity was recorded. The changes in myoelectrical activity were observed within 2-4 min after commencement of the infusion. The activity returned to control levels within 5-15 min after the end of the infusion period. The neurotensin sequences NT 9-13, NT 8-13, NT 4 -13, NT 1-9 and (Gln4)-NT 1-11 did not induce any changes in the electrical activity in the small intestine. The effects of NT and (Gln4)-neurotensin on the myoelectrical activity in the small intestine were indistinguishable. The changes induced by NT or (Gln4)-NT resemble those found after the ingestion of food. The present data indicate that the intact NT sequence, rather than smaller NT fragments, is necessary to induce changes in myoelectrical activity in the small intestine.