Effect of enkephalins on colonic mechanoreceptor synaptic input to inferior mesenteric ganglion

H. D. Shu, J. A. Love, J. H. Szurszewski

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11 Scopus citations


The effects of leucine-enkephalin (Leu-Enk) on colonic mechanoreceptor input to the inferior mesenteric ganglion (IMG) and on colonic intraluminal pressure of the guinea pig were studied in vitro. Superfusion of the IMG with Leu-Enk decreased colonic, afferent mechanoreceptor synaptic input. In neurons in which mechanoreceptor input caused postsynaptic spikes, Leu-Enk decreased synaptic input and increased the basal intraluminal pressure of the colon. When mechanoreceptor input consisted of singly occurring excitatory postsynaptic potentials (EPSPs), Leu-Enk decreased the frequency of EPSPs but did not cause a change in colonic pressure. The inhibitory effects of Leu-Enk on synaptic transmission were antagonized by naloxone. In the isolated IMG, Leu-Enk converted synchronous action potentials in response to electrical stimulation of intermesenteric nerves to subthreshold EPSPs without a change in the resting membrane potential or input resistance. Action potentials elicited by depolarizing current pulses or by exogenous acetylcholine were unaltered by Leu-Enk. These data suggest that Leu-Enk increased colonic intraluminal pressure by acting on the presynaptic terminals of colonic mechanoreceptive neurons to reduce synaptic input to and output from the inhibitory neurons of the IMG.

Original languageEnglish (US)
Pages (from-to)G128-G135
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Issue number1 (15/1)
StatePublished - 1987

ASJC Scopus subject areas

  • Physiology
  • Hepatology
  • Gastroenterology
  • Physiology (medical)


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