Nucleus accumbens (NAc) is involved in behaviors that depend on heightened wakefulness, but its impact on arousal remains unclear. Here, we demonstrate that NAc dopamine D1 receptor (D1R)-expressing neurons are essential for behavioral arousal. Using in vivo fiber photometry in mice, we find arousal-dependent increases in population activity of NAc D1R neurons. Optogenetic activation of NAc D1R neurons induces immediate transitions from non-rapid eye movement sleep to wakefulness, and chemogenetic stimulation prolongs arousal, with decreased food intake. Patch-clamp, tracing, immunohistochemistry, and electron microscopy reveal that NAc D1R neurons project to the midbrain and lateral hypothalamus, and might disinhibit midbrain dopamine neurons and lateral hypothalamus orexin neurons. Photoactivation of terminals in the midbrain and lateral hypothalamus is sufficient to induce wakefulness. Silencing of NAc D1R neurons suppresses arousal, with increased nest-building behaviors. Collectively, our data indicate that NAc D1R neuron circuits are essential for the induction and maintenance of wakefulness.

Dysfunction of the striatum is frequently associated with sleep disturbances. However, its role in sleep-wake regulation has been paid little attention even though the striatum densely expresses adenosine A2A receptors (A2ARs), which are essential for adenosine-induced sleep. Here we showed that chemogenetic activation of A2AR neurons in specific subregions of the striatum induced a remarkable increase in non-rapid eye movement (NREM) sleep. Anatomical mapping and immunoelectron microscopy revealed that striatal A2AR neurons innervated the external globus pallidus (GPe) in a topographically organized manner and preferentially formed inhibitory synapses with GPe parvalbumin (PV) neurons. Moreover, lesions of GPe PV neurons abolished the sleep-promoting effect of striatal A2AR neurons. In addition, chemogenetic inhibition of striatal A2AR neurons led to a significant decrease of NREM sleep at active period, but not inactive period of mice. These findings reveal a prominent contribution of striatal A2AR neuron/GPe PV neuron circuit in sleep control.

The rostromedial tegmental nucleus (RMTg), also called the GABAergic tail of the ventral tegmental area, projects to the midbrain dopaminergic system, dorsal raphe nucleus, locus coeruleus, and other regions. Whether the RMTg is involved in sleep–wake regulation is unknown. In the present study, pharmacogenetic activation of rat RMTg neurons promoted non-rapid eye movement (NREM) sleep with increased slow-wave activity (SWA). Conversely, rats after neurotoxic lesions of 8 or 16 days showed decreased NREM sleep with reduced SWA at lights on. The reduced SWA persisted at least 25 days after lesions. Similarly, pharmacological and pharmacogenetic inactivation of rat RMTg neurons decreased NREM sleep. Electrophysiological experiments combined with optogenetics showed a direct inhibitory connection between the terminals of RMTg neurons and midbrain dopaminergic neurons. The bidirectional effects of the RMTg on the sleep–wake cycle were mimicked by the modulation of ventral tegmental area (VTA)/substantia nigra compacta (SNc) dopaminergic neuronal activity using a pharmacogenetic approach. Furthermore, during the 2-hour recovery period following 6-hour sleep deprivation, the amount of NREM sleep in both the lesion and control rats was significantly increased compared with baseline levels; however, only the control rats showed a significant increase in SWA compared with baseline levels. Collectively, our findings reveal an essential role of the RMTg in the promotion of NREM sleep and homeostatic regulation.

BackgroundNonalcoholic fatty liver disease (NAFLD) is a common liver disorder that currently lacks effective treatment. Berberine (BBR), a botanic compound isolated from traditional Chinese medicine, exhibits a potent therapeutic potential for the metabolic disease. The current study aimed to understand the mechanisms underlying the therapeutic effect of BBR in NAFLD.MethodsWe performed systematical analyses on hepatic expression profiles of mRNAs and long noncoding RNAs (lncRNAs) in a high-fat diet (HFD)-induced steatotic animal model with or without BBR treatment. The study was conducted by using the methods of bioinformatics, including hierarchical clustering, gene enrichment and gene co-expression networks analysis. The effect of BBR on the expression profile of some interesting genes was confirmed by quantitative RT-PCR and further studied in a human hepatic cell line, Huh7.ResultsWe found that a large group of genes including 881 mRNAs and 538 lncRNAs whose expression in the steatotic liver was reversed by BBR treatment, suggesting a global effect of BBR in modulating hepatic gene expression profiles. Among the BBR-regulated genes, we identified several modules and numerous significant genes that were associated with liver metabolism and NAFLD-related functions. Specifically, a conserved lncRNA, MRAK052686, was found strongly correlated with the antioxidant factor Nrf2, and both genes were down-regulated by the steatotic liver. Moreover, the reduced expression of MRAK052686 and Nrf2 was completely reversed by BBR treatment, suggesting a new mechanism accounting for the therapeutic effect of BBR.ConclusionsThe findings for the first time provide a new genetic insight into the pharmaceutical mechanism of BBR in protecting against NAFLD.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-015-0383-6) contains supplementary material, which is available to authorized users.