Copyright © 2008 Elsevier B.V. All rights reserved.
Isoliquiritigenin suppresses cocaine-induced extracellular dopamine release in rat brain through GABAB receptor
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Eun Young Janga, Eun Sang Choec, Meeyul Hwangb, Sang Chan Kimb, Jong Rok Leeb, Sang Geon Kimd, Jae-Pil Jeone, Russell J. Buonof and Chae Ha Yanga, 
, 
aDepartment of Physiology, College of Oriental Medicine, Daegu Haany University, Daegu 706-828, South Korea
bThe Research Center for Biomedical Resource of Oriental Medicine, Daegu Haany University, Daegu, South Korea
cDepartment of Biological Sciences, Pusan National University, Pusan, South Korea
dCollege of Pharmacy and Research Institute of Pharmaceutical Sciences, Seoul National University, Seoul, South Korea
eDivision of Genome Resources, National Genome Research Institute, KNIH, Seoul, South Korea
fCoatesville Veteran's Affairs Medical Center, Coatesville, PA, USA
Available online 7 April 2008.
Abstract
Glycyrrhizae radix (licorice) comprises a variety of flavonoids as major constituents including 
isoliquiritigenin,
liquiritin, liquiritigenin, and glycyrrihizin. It has shown various biological activities such as anti-inflammatory, anti-carcinogenic and antihistamic. As very little is known in regard to drug addiction, we carried out a study on the effect of G. radix and its active component, isoliquiritigenin, on acute cocaine-induced extracellular dopamine release in moving rats. Male Sprague–Dawley rats were orally administered with methanolic extracts of G. radix or isoliquiritigenin 1 h prior to an injection of cocaine (20 mg/kg, intraperitoneal (i.p.)). Extracellular dopamine was measured by in vivo microdialysis. Extract of G. radix and isoliquiritigenin inhibited cocaine-induced extracellular dopamine level in the nucleus accumbens by dose-dependent manner. Inhibition of dopamine release by isoliquiritigenin resulted in attenuation of the expression of c-Fos, an immediately early gene induced by cocaine. Effect of isoliquiritigenin was completely prevented by a GABAB receptor antagonist. Thus, these results showed that G. radix and isoliquiritigenin inhibit cocaine-induced dopamine release by modulating GABAB receptor, suggesting that isoliquiritigenin might be effective in blocking the reinforcing effects of cocaine.
Keywords: Isoliquiritigenin; Cocaine; Nucleus accumbens; G. radix (licorice)
