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Eur J Pharmacol. 2009 Feb 14;604(1-3):20-6. doi: 10.1016/j.ejphar.2008.12.015. Epub 2008 Dec 16.

Effects of (-) epigallocatechin-3-gallate on Na(+) currents in rat dorsal root ganglion neurons.

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1
Department of Pharmacology, College of Medicine, Chung-Ang University, Seoul 156-756, Republic of Korea.

Abstract

The natural product (-) epigallocatechin-3-gallate (EGCG) is the major polyphenolic constituent found in green tea. Dorsal root ganglion neurons are primary sensory neurons, and express tetrodotoxin-sensitive and tetrodotoxin-resistant Na(+) currents, which are both actively involved in the generation and propagation of nociceptive signals. Effects of EGCG on tetrodotoxin-sensitive and tetrodotoxin-resistant Na(+) currents in rat dorsal root ganglion neurons were investigated using the whole-cell variation of the patch-clamp techniques. EGCG inhibited both types of Na(+) currents potently and in a concentration-dependent manner. The apparent dissociation constant, K(d), was estimated to be 0.74 and 0.80 microM for tetrodotoxin-sensitive and tetrodotoxin-resistant Na(+) currents, respectively. (-) Epigallocatechin (EGC) was far less potent to inhibit Na(+) currents than EGCG, suggesting that gallate moiety of EGCG is an important functional group to modulate Na(+) currents. EGCG had little or no effect on the activation or steady-state inactivation voltage of either type of Na(+) current. EGCG simply reduced the availability of Na(+) channels for activation. Thus, EGCG appears to bind to resting Na(+) channels to inhibit them. EGCG slowed the recovery of tetrodotoxin-sensitive Na(+) current from inactivation. The property of EGCG to inhibit sensory Na(+) currents can be utilized to develop an analgesic agent.

PMID:
19111536
DOI:
10.1016/j.ejphar.2008.12.015
[Indexed for MEDLINE]

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