Dietary natural cocoa ameliorates disrupted circadian rhythms in locomotor activity and sleep-wake cycles in mice with chronic sleep disorders caused by psychophysiological stress

Abstract Cocoa contains many chemical compounds that affect physiological functions in experimental animals and in humans. The present study used a mouse model characterized by disrupted circadian rhythms of locomotor activity and sleep-wake cycles to determine whether natural cocoa improves chronic sleep disorders (CSD) induced by psychophysiological stress. Mice were fed with a high-fat high-sucrose diet supplemented with 2.0% natural cocoa and stressed for 30 days to induce CSD. Dietary cocoa restored the amplitude reduction of day-night activity rhythms by improving reduced nocturnal wheel-running activities during CSD. Electroencephalography (EEG) revealed that dietary cocoa significantly ameliorated CSD-induced increases in wakefulness during the first half of the inactive phase and in non-rapid eye movement (NREM) sleep during the first half of the active phase. The attenuation of circadian REM sleep rhythms and increased EEG slow wave activity (a marker of NREM sleep intensity) induced by CSD were ameliorated in mice supplemented with cocoa. Dietary cocoa notably did not affect wheel-running activity rhythms or sleep-wake cycles under normal conditions. Dietary cocoa significantly increased the hypothalamic mRNA expression of Hspa1a that encodes HSP70 and is associated with sleep regulation. Furthermore, Hspa1a expression was not induced by CSD in mice supplemented with cocoa. These findings suggest that dietary cocoa exerts beneficial effects on insomnia and circadian sleep disorders induced by psychophysiological stress.