Enkephalinergic modulation of non-cholinergic transmission in mammalian prevertebral ganglia.

The non-cholinergic excitatory potential elicited in neurons of the isolated inferior mesenteric ganglia was depressed by bath application of Met- or Leu-enkephalin and enhanced by naloxone or naltrexone. The membrane depolarization induced by exogenously applied putative transmitter substance P was not appreciably affected by either enkephalin (Enk) or opiate antagonists. Our results indicate that the non-cholinergic excitatory transmission which may be mediated by substance P in prevertebral ganglia is modulated presynaptically by endogenously released Enk in a manner that may resemble the interaction between these two peptides in the spinal cord.