Tea catechin, (−)-epigallocatechin gallate, facilitates cholinergic ganglion transmission in the myenteric plexus of the guinea-pig small intestine

Intracellular recordings were made from myenteric S neurons of the guinea-pig ileum. One of the major tea catechins, (−)-epigallocatechin gallate (EGCG at concentrations from 1 to 20 μM), was applied by superfusion to examine its effect on cholinergic ganglion transmission in the myenteric plexus. Fast excitatory postsynaptic potentials (EPSPs) evoked by electrical stimulation to ganglia and/or internodal fiber tracts were augmented in amplitude by EGCG in about 60% of tested neurons without changing the postsynaptic sensitivity to acetylcholine (ACh) applied by ionophoresis. Furthermore, the amplitude-ratio of paired fast EPSPs was increased by EGCG. These results indicated that the site at which EGCG augmented the fast EPSPs was presynaptic. It is concluded that EGCG can facilitate the cholinergic ganglion transmission possibly by increasing the amount of ACh released and, together with its previously described depolarizing action on myenteric neurons, may modulate the activity of the myenteric plexus of the guinea-pig ileum.