Biology subjects

Darmohray, D.

Publications and source records attributed to Darmohray, D..

6 recordsLinked to original sources

bioRxiv2026

Brainwide dopamine dynamics across sleep-wake transitions

Dopaminergic signaling plays a critical role in regulating arousal and transitions between sleep states, yet brainwide dynamics underlying these transitions remain incompletely characterized. Here, we employed multi-site fiber photometry with the dopamine sensor GRAB-DA2m, combined with electroencephalogram (EEG)/electromyogram (EMG) recordings, to systematically assess regional dopamine (DA) dynamics across sleep-wake states in the medial prefrontal cortex (mPFC), striatal subregions, central amygdala (CeA), and midbrain nuclei in mice. We found that DA levels prominently increased in the mPFC, dorsolateral striatum (DLS), ventral tegmental area (VTA), substantia nigra pars compacta (SNc), and dorsal raphe nucleus (DRN) during transitions from non-rapid eye movement (NREM) sleep to wakefulness (WAKE), supporting their role in arousal. Conversely, DA decreased in the CeA and nucleus accumbens lateral parts (NAc-L) during these transitions. During transitions from NREM to rapid eye movement sleep (REM), DA elevations were observed in the CeA and middle accumbens subregion (NAc-M), rather than NAc-L, while other regions exhibited decreases. Cross-regional DA correlations revealed synchronized network activity across sleep-wake transitions. Optogenetic activation of VTA and DRN dopamine neurons induced robust DA release in cortical and subcortical regions, and chemogenetic activation promoted wakefulness selectively via VTA and DRN, but not SNc DA neurons. These results elucidate distinct brainwide DA dynamics across state transitions and highlight differential roles for DA signaling in modulating sleep-wake states.

neuroscience↗

bioRxiv2025

Brainstem circuit for sickness-induced sleep

Increased sleep induced by immune activation plays a crucial role in facilitating recovery from illness. However, the neural mechanisms underlying sickness-induced sleep remain poorly understood. Here, we identify a brainstem circuit originating in the nucleus of the solitary tract (NST) that mediates sickness-induced sleep. Using activity-dependent genetic labeling, we tagged NST neurons activated by lipopolysaccharide (LPS) injection and showed that their chemogenetic activation strongly promotes non-rapid eye movement (NREM) sleep. These NST neurons project extensively to the parabrachial nucleus (PB), where LPS-activated neurons also promote NREM sleep. Fiber photometry imaging of several wake-promoting neuromodulators using their biosensors showed that evoked norepinephrine (NE) release from locus coeruleus (LC) neurons is markedly reduced by either LPS injection or direct activation of NST or PB sickness neurons. These results suggest that sickness-induced sleep is mediated in part by a brainstem circuit that regulates neuromodulator signaling.

neuroscience↗

bioRxiv2024

Restoration of locus coeruleus noradrenergic transmission during sleep

Sleep is indispensable for health and wellbeing, but its basic function remains elusive. The locus coeruleus (LC) powerfully promotes arousal by releasing noradrenaline. We found that noradrenaline transmission is reduced by prolonged wakefulness and restored during sleep. Fiber-photometry imaging of noradrenaline using its biosensor showed that its release evoked by optogenetic LC neuron activation was strongly attenuated by three hours of sleep deprivation and restored during subsequent sleep. This is accompanied by the reduction and recovery of the wake-promoting effect of the LC neurons. The reduction of both LC evoked noradrenaline release and wake-inducing potency is activity dependent, and the rate of noradrenaline transmission recovery depends on mammalian target of rapamycin (mTOR) signaling. The decline and recovery of noradrenaline transmission also occur in spontaneous sleep-wake cycles on a timescale of minutes. Together, these results reveal an essential role of sleep in restoring transmission of a key arousal-promoting neuromodulator.

neuroscience↗

bioRxiv2024

Activation of locus coeruleus noradrenergic neuronsrapidly drives homeostatic sleep pressure

Homeostatic sleep regulation is essential for optimizing the amount and timing of sleep, but the underlying mechanism remains unclear. Optogenetic activation of locus coeruleus noradrenergic neurons immediately increased sleep propensity following transient wakefulness. Fiber photometry showed that repeated optogenetic or sensory stimulation caused rapid declines of locus coeruleus calcium activity and noradrenaline release. This suggests that functional fatigue of noradrenergic neurons, which reduces their wake-promoting capacity, contributes to sleep pressure.

neuroscience↗

bioRxiv2019

Changes in behavioral state account for the modulation of cerebellar learning by cannabinoid receptors

Cannabinoids are notorious and profound modulators of behavioral state. In the brain, endocannabinoids act via Type 1-cannabinoid receptors (CB1) to modulate synaptic transmission and mediate multiple forms of synaptic plasticity. CB1 knockout (CB1KO) mice display a range of behavioral phenotypes, in particular hypoactivity and various deficits in learning and memory, including cerebellumdependent delay eyeblink conditioning. Here we find that the apparent effects of CB1 deletion on cerebellar learning are not due to direct effects on CB1-dependent plasticity, but rather, arise as a secondary consequence of altered behavioral state. Hypoactivity of CB1KO mice accounts for their impaired eyeblink conditioning across both animals and trials. Moreover, learning in these mutants is rescued by walking on a motorized treadmill during training. Finally, cerebellar granule cell-specific CB1KOs exhibit normal eyeblink conditioning, and both global and granule cell-specific CB1KOs display normal cerebellum-dependent locomotor coordination and learning. These findings highlight the modulation of behavioral state as a powerful independent means through which individual genes contribute to complex behaviors.

neuroscience↗

bioRxiv2018

Spatial and temporal locomotor learning in mouse cerebellum

Stable and efficient locomotion requires precise coordination of whole-body movements. Learned changes in interlimb coordination can be induced by exposure to a split-belt treadmill that imposes different speeds under each side of the body. Here we show that mice adapt to split-belt walking in a way that is remarkably similar to humans, suggesting that this form of locomotor learning is highly conserved across vertebrates. Like human learning, mouse locomotor adaptation is specific to measures of interlimb coordination, has spatial and temporal components that adapt at different rates, and is highly context-specific. Using a variety of approaches, we demonstrate that split-belt adaptation in mice specifically depends on intermediate cerebellum, but is insensitive to large lesions of cerebral cortex. Finally, cell-type specific chemogenetics combined with quantitative behavioral analysis reveal distinct neural circuit mechanisms underlying spatial vs. temporal components of locomotor adaptation.

neuroscience↗