Effects of (-)-epigallocatechin-3-gallate on the activity of substantia nigra dopaminergic neurons.
Despite many studies on the biological and pharmacological properties of (-)-epigallocatechin-3-gallate (EGCG), an active component of green tea, information on neuronal modulation by EGCG is limited. This study was designed to investigate the effects of EGCG on the electrical activity of rat substantia nigra dopaminergic neurons using whole-cell patch clamp recordings. The spike frequency was increased to 6.33+/-0.23 (p<0.05) and 7.15+/-0.29 (p<0.05) by 5 and 10 microM EGCG, respectively, from the control level of 5.49+/-0.19 spikes/second, respectively (n=18). The resting membrane potential of the cells was decreased to -45.66+/-0.45 and -43.99+/-0.87 (p<0.05), by 5 and 10 microM EGCG, respectively, from -47.82+/-0.57 mV. The amplitude of afterhyperpolarization was decreased to 12.73+/-0.45 (p<0.05) and 11.60+/-0.57 (p<0.05) by 5 and 10 microM EGCG, respectively, from 13.80+/-0.31 mV. The neuronal activity of dopaminergic neurons is closely linked to dopamine release. When neurons switch from a single-spike firing to bursts of action potentials, the release of dopamine increases. The above experimental results suggest that EGCG increases the neuronal activity via inhibition of calcium-dependent potassium currents underlying the afterhyperpolarization, and it could act as a facilitating factor that elicits NMDA-dependent bursts of action potentials like apamin or bicuculline methiodide.
Jeong
Han-Seong
HS
Department of Physiology, Chonnam National University Medical School, Gwangju 501-190, Korea.
Jang
Sujeong
S
Jang
Myung-Joo
MJ
Lee
Sam-Gyu
SG
Kim
Tae-Sun
TS
Tag-Heo
Lee
Jae-Hyuk
JH
Jun
Jae Yeoul
JY
Park
Jong-Seong
JS
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D002392:Catechin / Q000031:analogs & derivatives* / Q000494:pharmacology; D004298:Dopamine / Q000378:metabolism*; D007150:Immunohistochemistry; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D018408:Patch-Clamp Techniques; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013378:Substantia Nigra / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism
D000975:Antioxidants; D002392:Catechin; C045651:epigallocatechin gallate; D011505:Protein-Tyrosine Kinases; D004298:Dopamine