Genetically engineered systems revealed the roles of basal ganglia in sleep-wake regulation

The basal ganglia(BG) act as a cohesive functional unit that regulates motor function,habit formation,and reward/addictive behaviors. However,it is still not well understood how the BG maintains wakefulness and suppresses sleep to achieve al these fundamental functions until genetical y engineered systems developed these years. Significant research efforts have recently been directed at developing genetic-molecular tools to achieve reversible and cell-type specific in vivo silencing or activation of neurons in behaving animals. Optogenetic tools can be used both to specifically activate or inhibit neurons of interest and identify functional synaptic connectivity between specific neuronal populations,both in vivo and in brain slices. Another recently developed system by Roth and colleagues permits the selective and ″remote″ manipulation(activation and silencing) of neuronal activity via all 3 major GPCR signaling pathways(G_i,G_s and G_q). These so-called ″ designer receptors exclusively activated by designer drugs″(DREADD) involve mutant GPCRs that do not respond to their endogenous ligands but are responsive to otherwise inert biological compounds. Recently,we demonstrated the essential roles and the neural pathways of the neurons expressing adenosine A_(2A) receptors or dopamine D_1 receptors in the BG for sleep-wake regulation using the genetically engineered systems including optogenetics and DREADD. We proposed a plausible model in which the caudate-putamen and the nucleus accumbens integrates behavioral processes with sleep/wakefulness through adenosine and dopamine receptors.

Adenosine A2A receptor-expressing neurons in the striatum regulate sleep behaviors

OBJECTIVE The high prevalence of sleep disturbance has been found in patients with striatum-related neurodegenerative disorders.In the striatum,there are abundant adenosine A2A receptors(A2ARs)whichhavebeen reported to mediatesleepbehavior for adenosine.We hypothesized that the A2AR-expressing neurons in the striatum are involved in sleep-wake regulation.METHODS We employed a chemogenetic technique,designer receptor exclusively activated by designer drug(DREADD),to specifically and non-invasively manipulate the neuron activity based on the principle of Cre/Lox P recombination,EEG/electromyogram recording for sleep-wake behaviors,the neural tracing approach toselectively visualize the perikarya of A2AR-expressing neurons and their axons by adeno-associated virus(AAV)encoding humanized Renilla green fluorescent(hr GFP)as a tracerin A2AR-Cre mice.In addition,we used immunoelectron microscopy,patch-clamp technique,and optogenetics in A2AR-Cre mice to selectively characterize the synapse and functional connectivity between the A2AR-expressing neurons and the neuron of their downstream targets in vitro.RESULTS The activation of A2AR-expressing neurons in rostral,centromedial and centrolateral striatum increased non-rapid eye movement(non-REM,NREM)sleep,concomitant with a reduction in wakefulness,whereas the activation of A2AR-expressing neurons in caudal striatum didn′t alter sleep-wake profiles at all.Topographical projections in the sagittal section showed that the axons of A2ARexpressing neurons from rostral striatum distributed in the rostral external globuspallidus(GPe)with a discoidal region paralleled to the striato-pallidal border,while the axons of the A2AR-expressing neurons from the central striatum not only distributed in the rostral GPe,but also in the caudal GPe with a similar distributing pattern as did in rostral neurons.However,the axons of A2ARexpressing neurons from caudal striatum just scattered in the caudal GPe.Based on our anatomical findings and patch-clamp technique combining with optogenetics,we found that A2AR neurons in the rostral striatum preferentially formed inhibitory synapses with parvalbumin(PV)-positive neurons in the rostral GPe,while A2AR neurons in the caudal striatum preferentially formed inhibitory synapses with PV-negative neurons in the caudal GPe.CONCLUSION The present results indicated that the A2AR-expressing neurons in rostral and central striatum are involved in sleep-wake regulation,probably via innervating PV-positive neurons in the GPe.

S6B-4 Roles of the Basal Ganglia in Sleep-Wake Regulation

The basal ganglia(BG)act as a cohesive functional unit that regulates motor function,habit formation,and reward/addictive behaviors.However,it is still not well understood how the BG maintains wakefulness and suppresses sleep to achieve all these fundamental functions until genetically engineered systems developed these years.We focused on the adenosine A2A and dopamine D1 Receptors(R)in the BG and obtained following 4 findings:①Nucleus accumbens(NAc)dopamine D1R-expressing neurons are essential in controlling wakefulness and are involved in physiological arousal via the lateral hypothalamus and midbrain circuits;②The rostromedial tegmental nucleus(RMTg),also called the GABAergic tail of the ventral tegmental area,projects to the midbrain dopaminergic system and other regions.Our findings reveal an essential role of the RMTg in the promotion of non-rapid eye movement(non-REM,NREM)sleep and homeostatic regulation;③Opposite to the D1R in the NAc,A2AR made a prominent contribution to sleep control associated with motivation.④Striatal adenosine A2AR neurons control active-period sleep via parvalbumin neurons in external globus pallidus.Taken together,we proposed a plausible model in which the caudate-putamen and NAc integrate behavioral processes with sleep/wakefulness through adenosine and dopamine receptors.The impacts of the BG in physiological sleep and insomnia will be discussed.

Chemogenetic and Optogenetic Manipulations of Microglia in Chronic Pain

Chronic pain relief remains an unmet medical need.Current research points to a substantial contribution of glia-neuron interaction in its pathogenesis.Particularly,microglia play a crucial role in the development of chronic pain.To better understand the microglial contribution to chronic pain,specific regional and temporal manipulations of microglia are necessary.Recently,two new approaches have emerged that meet these demands.Chemogenetic tools allow the expression of designer receptors exclusively activated by designer drugs(DREADDs)specifically in microglia.Similarly,optogenetic tools allow for microglial manipulation via the activation of artificially expressed,light-sensitive proteins.Chemo-and optogenetic manipulations of microglia in vivo are powerful in interrogating microglial function in chronic pain.This review summarizes these emerging tools in studying the role of microglia in chronic pain and highlights their potential applications in microglia-related neurological disorders.

Next-Generation Tools to Study Autonomic Regulation In Vivo

The recent development of tools to decipher the intricacies of neural networks has improved our understanding of brain function. Optogenetics allows one to assess the direct outcome of activating a geneticallydistinct population of neurons. Neurons are tagged with light-sensitive channels followed by photo-activation with an appropriate wavelength of light to functionally activate or silence them, resulting in quantifiable changes in the periphery. Capturing and manipulating activated neuron ensembles, is a recently-designed technique to permanently label activated neurons responsible for a physiological function and manipulate them. On the other hand, neurons can be transfected with genetically-encoded Ca2^+ indicators to capture the interplay between them that modulates autonomic end-points or somatic behavior. These techniques work with millisecond temporal precision. In addition, neurons can be manipulated chronically to simulate physiological aberrations by transfecting designer G-protein-coupled receptors exclusively activated by designer drugs. In this review, we elaborate on the fundamental concepts and applications of these techniques in research.

Prefrontal cortical circuits in anxiety and fear:an overview

Pathological anxiety is among the most difficult neuropsychiatric diseases to treat pharmacologically,and it represents a major societal problem.Studies have implicated structural changes within the prefrontal cortex(PFC)and functional changes in the communication of the PFC with distal brain structures in anxiety disorders.Treatments that affect the activity of the PFC,including cognitive therapies and transcranial magnetic stimulation,reverse anxiety-and fear-associated circuit abnormalities through mechanisms that remain largely unclear.While the subjective experience of a rodent cannot be precisely determined,rodent models hold great promise in dissecting well-conserved circuits.Newly developed genetic and viral tools and optogenetic and chemogenetic techniques have revealed the intricacies of neural circuits underlying anxiety and fear by allowing direct examination of hypotheses drawn from existing psychological concepts.This review focuses on studies that have used these circuit-based approaches to gain a more detailed,more comprehensive,and more integrated view on how the PFC governs anxiety and fear and orchestrates adaptive defensive behaviors to hopefully provide a roadmap for the future development of therapies for pathological anxiety.

化学遗传学技术在精神疾病研究中的应用

精神疾病具有机制复杂、复发率高等特点,一直是重大的医学和社会问题。在精准医疗方针的指导下,化学遗传学技术通过精确调控特定类型神经元或神经胶质细胞,为精神疾病中神经环路机制的研究模式带来重大变革,在探寻和证实精神疾病背后的神经生物学机制、药物作用靶点及新的治疗方法等方面具有不可或缺的作用。本文重点阐述了化学遗传学技术DREADD(designer receptors exclusively activated by designer drugs)在焦虑和抑郁障碍、睡眠觉醒障碍、创伤后应激障碍、药物成瘾等精神疾病机制研究中的应用,并对该技术今后的临床转化进行了展望。