Spinosin enhances non-rapid eye movement sleep and alters c-Fos expression in sleep-wake regulatory brain regions in mice.

PURPOSE

Spinosin, a key flavonoids component found in Semen Zizhiphi spinosae, is known to enhance pentobarbital-induced sleep, which is primarily assessed with the loss-of-righting reflex (LORR). This research focused on investigating the impact of spinosin on sleep regulation in typical murine models.

METHODS

We used electroencephalogram (EEG) and electromyogram (EMG) recordings to evaluate the effects of spinosin (10, 20, 40 mg/kg, i.p.) on sleep-wake state. Immunohistochemical techniques were employed to investigate the c-Fos expression in various sleep-wake brain regions following the injection of spinosin.

RESULTS

In the initial three-hour period following administration, spinosin administered at a dose of 40 mg/kg exhibited a notable augmentation in the duration of non-rapid eye movement (NREM) sleep, with a 2.04-fold increase (P < 0.0001), accompanied by a reduction in wakefulness by approximately 42.84% (P < 0.0001) compared to the vehicle group. Immunohistochemical analysis revealed an enhancement in c-Fos expression within the accumbens nucleus (Acb) when treated with spinosin at 40 mg/kg. In contrast, a notable reduction in c-Fos expression was detected across various brain regions, including the paraventricular thalamic nucleus (PV), lateral hypothalamic area (LHA), ventrolateral periaqueductal gray (VLPAG), dorsal raphe nucleus (DR), and lateral parabrachial nucleus (LPB) (P < 0.05). In addition, the treatment resulted in an increase in c-Fos expression within gamma-aminobutyric acid (GABAergic) neurons in the Acb, while simultaneously decreasing c-Fos expression in orexin neurons within the LHA.

CONCLUSIONS

The results indicate that spinosin (40 mg/kg, i.p.) enhances NREM sleep in mice. Moreover, heightened activity of GABAergic neurons in the Acb and reduced activity of orexin neurons in the LHA may be the pathway through which spinosin promotes sleep.