Tea catechin, (-)-epigallocatechin gallate, causes membrane depolarizations of myenteric neurons in the guinea-pig small intestine.
Intracellular recordings were made from enteric neurons in the myenteric plexus of the guinea-pig small intestine to examine actions of one of tea catechins, (-)-epigallocatechin gallate (EGCG), on neuronal activity. EGCG at concentrations from 1 to 20 microM depolarized about 60% of both of S and AH neurons in a concentration-dependent manner, although EGCG-induced depolarizations were largely varied in amplitude from neuron to neuron. The depolarizations started passing off during the presence of EGCG at higher concentrations, and became smaller or almost abolished with repeated applications, indicating the EGCG-induced response shows desensitization-like characteristics. The EGCG-depolarization was associated with a decrease in input membrane resistance, and their reversal potential was estimated about -30 mV. Since the EGCG-depolarization was recorded in the absence of external Ca(2+), it is concluded that one of tea catechins has direct depolarizing effects on a population of myenteric neurons.
Homma
T
T
Department of Autonomic Physiology, Medical Research Institute, Tokyo Medical and Dental University, 2-3-10 Kandasurugadai, Chiyoda-ku, Tokyo, 101-0062, Japan.
Hirai
K
K
Hara
Y
Y
Katayama
Y
Y
D000200:Action Potentials / Q000187:drug effects; D000818:Animals; D002392:Catechin / Q000031:analogs & derivatives / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D016166:Free Radical Scavengers / Q000494:pharmacology*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007421:Intestine, Small / Q000294:innervation; D008297:Male; D009197:Myenteric Plexus / Q000166:cytology / Q000187:drug effects*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D013662:Tea
D016166:Free Radical Scavengers; D013662:Tea; D002392:Catechin; C045651:epigallocatechin gallate