PMID: 6291266Aug 1, 1982

The effects of leucine-enkephalin on the spontaneous motility of the circular muscle of the cat colon

Zeitschrift für Gastroenterologie
M Wienbeck, R G Dünzen


Since the effects of endogenously occurring opiates in the regulation of colonic motility are unknown, we set out to study the actions of leucine-enkephalin on the spontaneous contractile and electrical activity of the isolated circular muscle of the cat colon. The muscle strips exhibited regular rhythmic contractions and myoelectrical slow waves 3.67 +/- 0.16 (SEM) times/min. Mean contraction force was 1.20 +/- 0.09 mN. Leucine-enkephalin caused a dose-dependent increase in contractile activity by a factor of 8.24 +/- 2.68; ED50 was 2.23 X 10(-9) M, ED100 4.33 X 10(-8) M. Methionine-enkephalin was equally effective, but morphine was much less effective. Naloxone acted as a specific antagonist. Concentrations of 10(-8) and 10(-7) M shifted the dose-response curve to the right, at the ED50 of leucine-enkephalin by 0.66 and 1.63 log units, respectively. Naloxone exhibited the characteristics of competitive antagonism; pA2 was -8.69, the slope was 1.06. Other antagonists did not affect the enkephalin actions on the muscle. The results of this study suggest that leucine-enkephalin acts on specific receptors of the circular muscle of the cat colon. It is conceivable, therefore, that leucine-enkephalin exerts its effects under physio...Continue Reading

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Enkephalin, Leucine
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