Effects of quercetin on the sleep–wake cycle in rats: Involvement of gamma-aminobutyric acid receptor type A in regulation of rapid eye movement sleep

The bioflavonoid quercetin is widely found in plants and exerts a large number of biological activities such as anti-hypertensive and anti-inflammatory properties. However, the effect of quercetin on the sleep–wake cycle has not been investigated. In the present study, we investigated the effect of quercetin on sleep–wake regulation. Intraperitoneal administration of quercetin (200 mg/kg) significantly increased non-rapid eye movement (non-REM) sleep during dark period in rats, while it significantly decreased REM sleep. The decrease in REM sleep induced by quercetin was blocked by intracerebroventricular (i.c.v.) injection of bicuculline, a GABA(A) receptor antagonist. In contrast, the increase in non-REM sleep induced by quercetin was not affected by i.c.v. injection of bicuculline. Therefore, the present results suggest that quercetin alters the sleep–wake cycle partly through activation of GABA(A) receptors.