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The cholinergic neurons in the nucleus basalis of Meynert (NBM) are a key structure in cognition, the dysfunction of which is associated with various neurological disorders, especially dementias. However, the whole‐brain neural connectivity to cholinergic neurons in the NBM remains to be further and comprehensively researched. Using virus‐based, specific, retrograde, and anterograde tracing, we illustrated the monosynaptic inputs and axon projections of NBM cholinergic neurons in choline acetyltransferase (ChAT)‐Cre transgenic mice. Our results showed that NBM cholinergic neurons received mainly inputs from the caudate putamen and the posterior limb of the anterior commissure in the subcortex. Moreover, the majority of cholinergic terminals from the NBM were observed in the cortex mantle, including the motor cortex, sensory cortex, and visual cortex. Interestingly, although NBM cholinergic neurons received input projections from the caudate putamen, interstitial nucleus of the posterior limb of the anterior commissure, and central amygdaloid nucleus, NBM cholinergic neurons sparsely sent axon projection to innervate these areas. Furthermore, primary motor cortex, secondary motor cortex, and primary somatosensory cortex received abundant inputs from the NBM but sent few outputs to the NBM. Taken together, our results reveal the detailed and specific connectivity of cholinergic neurons of the NBM and provide a neuroanatomic foundation for further studies to explore the important physiological functions of NBM cholinergic neurons. [ABSTRACT FROM AUTHOR]

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 D 1 receptor (D 1 R)-expressing neurons are essential for behavioral arousal. Using in vivo fiber photometry in mice, we find arousal-dependent increases in population activity of NAc D 1 R neurons. Optogenetic activation of NAc D 1 R 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 D 1 R 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 D 1 R neurons suppresses arousal, with increased nest-building behaviors. Collectively, our data indicate that NAc D 1 R 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 A 2A receptors (A 2A Rs), which are essential for adenosine-induced sleep. Here we showed that chemogenetic activation of A 2A R 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 A 2A R 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 A 2A R neurons. In addition, chemogenetic inhibition of striatal A 2A R 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 A 2A R neuron/GPe PV neuron circuit in sleep control.

Ethanol has extensive effects on sleep and daytime alertness, causing premature disability and death. Adenosine, as a potent sleep-promoting substance, is involved in many cellular and behavioral responses to ethanol. However, the mechanisms of hypnotic effects of ethanol remain unclear. In this study, we investigated the role of adenosine in ethanol-induced sleep using C57BL/6Slac mice, adenosine A 2A receptor (A 2A R) knockout mice, and their wild-type littermates. The results showed that intraperitoneal injection of ethanol (3.0 g/kg) at 21:00 decreased the latency to non-rapid eye movement (NREM) sleep and increased the duration of NREM sleep for 5 h. Ethanol dose-dependently increased NREM sleep, which was consistent with decreases in wakefulness in C57BL/6Slac mice compared with their own control. Caffeine (5, 10, or 15 mg/kg), a nonspecific adenosine receptor antagonist, dose-dependently and at high doses completely blocked ethanol-induced NREM sleep when administered 30 min prior to (but not after) ethanol injection. Moreover, ethanol-induced NREM sleep was completely abolished in A 2A R knockout mice compared with wild-type mice. These findings strongly indicate that A 2A R is a key receptor for the hypnotic effects of ethanol, and pretreatment of caffeine might be a strategy to counter the hypnotic effects of ethanol.