EFFECT OF ENKEPHALINS ON THE INTRAMURAL INHIBITORY NON-ADRENERGIC NERVE RESPONSES OF SMOOTH-MUSCLE

The study concerned the effect of enkephalins and naloxone on the inhibitory non-adrenergic nerve responses of the taenia coli and the stomach smooth muscle cells of the guinea pig. Met-enkephalin, leu-enkephalin and D-ala-enkephalin (10-8-10-5 M) did not affect the muscle tension or membrane potential measured simultaneously using the sucrose-gap method. Naloxone (5 × 10-8-5 × 10-6 M) relaxed the stomach strip, but did not modify the inhibitory junction potential. These results indicate that enkephalins are not involved in the non-adrenergic inhibitory nervous system, except possibly as neuromodulators at an interneuronal synaptic level. © 1979.