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Planta Med 2013; 79(15): 1408-1412
DOI: 10.1055/s-0033-1350698
Biological and Pharmacological Activity
Original Papers
Georg Thieme Verlag KG Stuttgart · New York

Potentiating Effect of Glabridin on GABAA Receptor-Mediated Responses in Dorsal Raphe Neurons

Zhenhua Jin
1   Department of Physiology, School of Medicine, Kyung Hee University, Seoul, Republic of Korea
,
Sojin Kim
1   Department of Physiology, School of Medicine, Kyung Hee University, Seoul, Republic of Korea
,
Suengmok Cho
2   Korea Food Research Institute, Seongnam, Republic of Korea
,
In-Ho Kim
2   Korea Food Research Institute, Seongnam, Republic of Korea
,
Daeseok Han
2   Korea Food Research Institute, Seongnam, Republic of Korea
,
Young-Ho Jin
1   Department of Physiology, School of Medicine, Kyung Hee University, Seoul, Republic of Korea
› Author Affiliations
Further Information

Publication History

received 24 May 2013
revised 03 July 2013

accepted 08 July 2013

Publication Date:
23 August 2013 (online)

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Abstract

Flavonoid-rich ethanol extracts of licorice root have sedative and anxiolytic effects. Glabridin is a major flavonoid component from licorice which we evaluated by examining GABA responses in acutely isolated dorsal raphe neurons of the rat. Neurons were recorded with patch-clamp methods at a holding potential of − 50 mV. Glabridin potentiated GABA-induced responses by positively modulating GABAA receptor responses with different concentration range. GABA (2 × 10−6 M)-evoked currents were potentiated in a stepwise pattern increasing glabridin concentration. Between 10−12 and 10−8 M glabridin increased GABA responses by about 140 % of the control. At concentrations above 10− 7 M, a much larger, dose-dependent potentiation occurred before reaching a plateau at 3 × 10−6 M glabridin. A hypnotic drug, zolpidem, also induced biphasic concentration-potentiation relationship. The glabridin potentiation ratio was 2.2 times larger than the maximum potentiation to the benzodiazepine receptor full agonist diazepam. Benzodiazepine receptor antagonist, flumazenil (3 × 10−7 M), failed to inhibit glabridin (3 × 10−7 M)-induced potentiation. This result implies that glabridin may exhibit sedative and hypnotic effects by potentiating GABAergic inhibition in dorsal raphe neurons by GABAA receptor actions.

Key words

licorice - flavonoid - benzodiazepine receptor - flumazenil - sedative-hypnotic activity - GABAA receptor - Glycyrrhiza glabra - Fabaceae
 

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