Rice bran component γ‐oryzanol promotes sleep in mice by antagonism of histamine H1 receptor

Abstract

γ-Oryzanol, a unique component of rice bran, has been shown to exert anti-anxiety and anti-depressive effects. Evidence suggests that γ-oryzanol may affect sleep; however, sedative-hypnotic effects have not been reported. In this study, a pentobarbital-induced sleep test and sleep-wake profile assessment using recorded electroencephalography are used. Also, the molecular mechanism of γ-oryzanol’s sleep effects is evaluated in histamine H1 receptor (H1R)-knockout (KO) mice. γ-Oryzanol gave a dose-dependent reduction in sleep latency and increased the amount of non-rapid eye movement sleep (NREMS). The hypnotic effects of γ-oryzanol were comparable to those of the positive control doxepin, an H1R antagonist. In an in vivo mechanistic study, its hypnotic effects were completely blocked by the H1R agonist 2-pyridylethylamine. Additionally, neither γ-oryzanol nor doxepin increased NREMS or decreased sleep latency in H1R-KO mice. The results demonstrate that γ-oryzanol reduces sleep latency and promotes NREMS in mice via H1R antagonism.

Keywords

• γ‐Oryzanol
• Sedative-hypotonic
• Histamine H1 receptor
• Non-rapid eye movement sleep