5-HT1A receptor binding in the dorsal raphe nucleus is implicated in the anxiolytic-like effects of Cinnamomum cassia

Abstract

Previously we reported that the 50% EtOH extract of Cinnamomum cassia (C. cassia) possesses anxiolytic-like activity in the mouse elevated plus maze (EPM) test. This activity was blocked by the 5-HT1A receptor antagonist, WAY 100635. Therefore, in order to investigate the effect of C. cassia on 5-HT1A receptor binding, quantitative autoradiography of 5-HT1A receptors was carried out in brains of mice treated acutely and repeatedly with C. cassia. Binding of [H-3]8-OH-DPAT to the 5-HT1A receptor was investigated in the mouse brain. After a single treatment of C. cassia (750 mg/kg, p.o.), [H-3]8-OH-DPAT binding showed a significant increase in the dorsal raphe nucleus (DRN). After repeated treatment with C. cassia (100 mg/kg, once a day for 5 days. p.o.), [H-3]8-OH-DPAT binding showed no significant change in any brain region. Taken together, the anxiolytic-like effect of the 50% EtOH extract of C. cassia might be mediated by region specific change of 5-HT1A receptors in the dorsal raphe nucleus. (C) 2012 Published by Elsevier Inc.