Chemogenetic Tools Research Articles

Chemogenetic emulation of intraneuronal oxidative stress affects synaptic plasticity

Oxidative stress, a state of disrupted redox signaling, reactive oxygen species (ROS) overproduction, and oxidative cell damage, accompanies numerous brain pathologies, including aging-related dementia and Alzheimer's disease, the most common neurodegenerative disorder of the elderly population. However, a causative role of neuronal oxidative stress in the development of aging-related cognitive decline and neurodegeneration remains elusive because of the lack of approaches for modeling isolated oxidative injury in the brain. Here, we present a chemogenetic approach based on the yeast flavoprotein d-amino acid oxidase (DAAO) for the generation of intraneuronal hydrogen peroxide (H2O2). To validate this chemogenetic tool, DAAO and HyPer7, an ultrasensitive genetically encoded H2O2 biosensor, were targeted to neurons. Changes in the fluorescence of HyPer7 upon treatment of neurons expressing DAAO with d-norvaline (D-Nva), a DAAO substrate, confirmed chemogenetically induced production of intraneuornal H2O2. Then, using the verified chemogenetic tool, we emulated isolated intraneuronal oxidative stress in acute brain slices and, using electrophysiological recordings, revealed that it does not alter basal synaptic transmission and the probability of neurotransmitter release from presynaptic terminals but reduces long-term potentiation (LTP). Moreover, treating neurons expressing DAAO with D-Nva via the patch pipette also decreases LTP. This observation indicates that isolated oxidative stress affects synaptic plasticity at single cell level. Our results broaden the toolset for studying normal redox regulation in the brain and elucidating the role of oxidative stress to the pathogenesis of cognitive aging and the early stages of aging-related neurodegenerative diseases. The proposed approach is useful for identification of early markers of neuronal oxidative stress and may be used in screens of potential antioxidants effective against neuronal oxidative injury.

Simultaneous Manipulation and Imaging of Chemogenetically Induced Hydrogen Peroxide in Hardly Transfectable Endothelial Cells

Hydrogen peroxide (H2O2) is a critical signaling molecule in vascular cells, which controls signaling events, yet it can cause pathological oxidative stress in excess. The lack of suitable tools undermined experimental approaches to study the role of oxidative eu- and distress in cellular ultra-locales. This study exploits a yeast-derived D-amino acid oxidase (mDAAO) as a chemogenetic tool to induce, visualize and test the cytotoxicity of H2O2 in hardly transfectable endothelial cells. Due to the poor transfectability of endothelial cells, lentiviral vectors have been used to generate cell lines stably expressing mDAAOs. mDAAOs are substrate-based chemogenetic enzymes that convert D-amino acids to their corresponding alpha-keto acids and generate H2O2 as a byproduct, which can be visualized with a novel ultrasensitive, and ratiometric H2O2 biosensor termed HyPer7. This study tested the suitability of two different D-amino acids, including D-alanine and D-methionine, to induce oxidative stress in endothelial cells. Live-cell imaging experiments unveiled that 10 mM D-methionine generated significantly higher and faster H2O2 signals than D-alanine. However, both D-amino acids induced comparable levels of cell death documented by a colorimetric cell metabolic activity assay (MTT). This study provides a guide for manipulating and monitoring the cytotoxic effect of H2O2 in endothelial cells.

Molecular basis for selective activation of DREADD-based chemogenetics.

Designer receptors exclusively activated by designer drugs (DREADDs) represent a powerful chemogenetic technology for the remote control of neuronal activity and cellular signalling1-4. The muscarinic receptor-based DREADDs are the most widely used chemogenetic tools in neuroscience research. The Gq-coupled DREADD (hM3Dq) is used to enhance neuronal activity, whereas the Gi/o-coupled DREADD (hM4Di) is utilized to inhibit neuronal activity5. Here we report four DREADD-related cryogenic electron microscopy high-resolution structures: a hM3Dq-miniGq complex and a hM4Di-miniGo complex bound to deschloroclozapine; a hM3Dq-miniGq complex bound to clozapine-N-oxide; and a hM3R-miniGq complex bound to iperoxo. Complemented with mutagenesis, functional and computational simulation data, our structures reveal key details of the recognition of DREADD chemogenetic actuators and the molecular basis for activation. These findings should accelerate the structure-guided discovery of next-generation chemogenetic tools.

O013 / #694 LOCAL SUPPRESSION OF BRAIN EXCITABILITY USING GI-MEDIATED CHEMOGENETIC AND OPTICAL NEUROMODULATION TECHNIQUES: TRACK 2: BRAIN STIMULATION FOR TREATMENT RESISTANT DEPRESSION, PAIN, AND PARKINSON'S DISEASE

A large subset of patients with epilepsy suffer from seizures originating from a specific region in the brain, the seizure focus. Patients are commonly treated with anti-epileptic drugs which interfere with neuronal excitability and/or neurotransmission. These drugs affect the whole body while only a small part of the brain (i.e., seizure focus) needs to be treated. Side effects are therefore common and severe. The goal of this preclinical research was to investigate the efficacy of suppressing seizures with chemogenetic and optopharmacogical tools, targeting the Gi signaling pathway for inhibition of neurotransmission and neuronal excitability.

Multiparametric imaging with genetic biosensors and chemogenetic tools: Golden keys to redox biology

Multiparametric imaging with genetic biosensors and chemogenetic tools: Golden keys to redox biology

Clozapine-Induced Chemogenetic Neuromodulation Rescues Post-Stroke Deficits After Chronic Capsular Infarct

Long-term disabilities induced by stroke impose a heavy burden on patients, families, caregivers, and public health systems. Extensive studies have demonstrated the therapeutic value of neuromodulation in enhancing post-stroke recovery. Among them, chemogenetic neuromodulation activated by clozapine-N-oxide (CNO) has been proposed as the potential tool of neuromodulation. However, recent evidence showed that CNO does not cross the blood − brain barrier and may in fact have low binding affinity for chemogenetic tool. Thus, clozapine (CLZ) has been suggested for use in chemogenetic neuromodulation, in place of CNO, because it readily crosses the blood–brain barrier. Previously we reported that low doses of CLZ (0.1 mg/kg) successfully induced neural responses without off-target effects. Here, we show that low-dose clozapine (0.1 mg/kg) can induce prolonged chemogenetic activation while avoiding permeability issues and minimizing off-target effects. In addition, clozapine-induced excitatory chemogenetic neuromodulation (CLZ-ChemoNM) of sensory-parietal cortex with hsyn-hM3Dq-YFP-enhanced motor recovery in a chronic capsular infarct model of stroke in rats, improving post-stroke behavioral scores to 56% of pre-infarct levels. Longitudinal 2-deoxy-2-[18F]-fluoro-D-glucose microPET (FDG-microPET) scans showed that a reduction in diaschisis volume and activation of corticostriatal circuits were both correlated with post-stroke recovery. We also found c-Fos increases in bilateral cortices and BDNF increases in the cortices and striatum after CLZ-ChemoNM, indicating an increase in neural plasticity. These findings suggest the translational feasibility of CLZ-ChemoNM for augmenting recovery in chronic stroke.

DEVELOPMENT OF AN ADRENOCORTICAL CELL MODEL OF CALCIUM SIGNALING MODULATION TO DECIPHER THE MOLECULAR MECHANISMS RESPONSIBLE FOR PRIMARY ALDOSTERONISM

Objective: Primary aldosteronism (PA) is the most frequent form of secondary hypertension. The identification of germline or somatic mutations in different genes coding for ion channels (KCNJ5, CACNA1D, CACNA1H and CLCN2) and ATPases (ATP1A1 and ATP2B3) defines PA as a channelopathy. These mutations promote activation of calcium signaling, the main trigger for aldosterone biosynthesis. The objective of our work was to elucidate, using chemogenetic tools, the molecular mechanisms underlying the development of PA by modulating sodium entry into the cells, mimicking some of known mutations identified in PA. Design and method: We have developed an adrenocortical H295R_S2 cell line stably expressing a chimeric ion channel receptor formed by the extracellular ligand-binding domain of the α7 nicotinic acetylcholine receptor fused to the ion pore domain of the serotonin receptor 5HT3α and named α7–5HT3. Mutations have been introduced in the ligand binding domain to allow only synthetic drugs to activate this channel receptor. Activation of α7–5HT3 by a specific drug, PSEM-817 leads to sodium entry into the cells. This cell line was characterized in terms of intracellular calcium concentrations, cell proliferation, aldosterone production, steroidogenic expression and electrophysiological properties. Results: Treatment of α7–5HT3 expressing cells with increasing concentration of PSEM-817 (from 10–9 to 10–5 M) induced a significant increase in intracellular calcium concentrations, similarly to potassium (12 mM) or angiotensin II (10–8 M). This stimulation of calcium signaling did not affect cell proliferation, but was responsible for an increase in CYP11B2 expression and aldosterone production after 24 h of treatment. However, while increased intracellular calcium concentrations were observed starting from 10–8 M of PSEM-817, CYP11B2 expression and aldosterone production were only affected starting from 10–7 M, suggesting a dose dependent effect. Finally, whereas cells were hyperpolarized in absence of stimulation (around -60 mV), PSEM-817 induced a strong depolarization, cells rising to a membrane potential around -10 mV. Conclusions: This cell line, in which we can modulate the intracellular calcium concentration “on demand”, is a useful tool for a better understanding of the alterations of intracellular ion balance and calcium signaling in the pathophysiology of PA.

Development of an adrenocortical cell model of calcium signaling modulation to decipher the molecular mechanisms responsible for primary aldosteronism

Primary aldosteronism (PA) is the most frequent form of secondary hypertension. The identification of germline or somatic mutations in different genes coding for ion channels and defines PA as a channelopathy. These mutations promote activation of calcium signaling, the main trigger for aldosterone biosynthesis. The objective of our work was to elucidate, using chemogenetic tools, the molecular mechanisms underlying the development of PA by modulating sodium entry into the cells, mimicking some of known mutations identified in PA. We have developed an adrenocortical H295R-S2 cell line stably expressing a chimeric ion channel receptor formed by the extracellular ligand-binding domain of the α7 nicotinic acetylcholine receptor fused to the ion pore domain of the serotonin receptor 5HT3α and named α7-5HT3. Mutations have been introduced in the ligand-binding domain to allow only synthetic drugs to activate this channel receptor. Activation of α7-5HT3 by a specific drug, PSEM-817 leads to sodium entry into the cells. This cell line was characterized in terms of intracellular calcium concentrations, cell proliferation, aldosterone production, steroidogenic expression and electrophysiological properties. Treatment of α7-5HT3 expressing cells with increasing concentration of PSEM-817 (from 10-9 to 10-5 M) induced a significant increase in intracellular calcium concentrations, similarly to potassium (12 mM) or angiotensin II (10-8 M). This stimulation of calcium signaling did not affect cell proliferation, but was responsible for an increase in CYP11B2 expression and aldosterone production after 24 h of treatment. However, while increased intracellular calcium concentrations were observed starting from 10-8 M of PSEM-817, CYP11B2 expression and aldosterone production were only affected starting from 10-7 M, suggesting a dose-dependent effect. Finally, whereas cells were hyperpolarized in absence of stimulation (around −60 mV), PSEM-817 induced a strong depolarization, cells rising to a membrane potential around −10 mV. This cell line, in which we can modulate the intracellular calcium concentration “on demand”, is a useful tool for a better understanding of the alterations of intracellular ion balance and calcium signaling in the pathophysiology of PA.

Exercise Training and Chemogenetic Activation of the Dorsal Motor Nucleus of the Vagus Rescue the Changes in the Hepatic Vein Glucose Concentration by Central Action of Insulin in SHR

The Dorsal Motor Nucleus of the Vagus (DMNV) is the main parasympathetic output from CNS as part of the brain‐liver axis that participates on glucose homeostasis. Previously, we have shown that icv injection of insulin elicited a decrease the hepatic vein glucose concentration (HVGC) of Wistar, but not in SHR. Here we aimed to investigate whether the deficiency of central action of insulin to control the HVGC of SHR is due to a dysfunction in the cholinergic neurotransmission in the DMNV and which putative neurotransmitter could play a role in this circuitry. To this, we used in vivo and in vitro studies using chemogenetic tools, and the whole‐cell patch‐clamp recordings. Ethical approval: CEUA/ICB‐USP #8336131119). IN VIVO STUDIES: Male SHR (12 weeks old) received an injection of DREADD (LVV‐Gq‐hM3q‐PRSx8‐eGFP) to selectively activate de DMNV neurons with clozapine‐N‐oxide (CNO). After 10 days of CNO treatment, the animals received icv injection of insulin and the HVGC was monitored in freely moving rats. IN VITRO STUDIES: to identify liver‐projecting DMVN neurons, age‐matched (12 weeks old) of Wistar and sedentary and exercised trained SHR (SHRt) received, 5 days prior to the experiments, injections of Fluorogold (FG) on the liver parenchyma. At the day of the electrophysiological studies, the FG‐labeled DMVN neurons was visualized and recorded in whole‐cell patch‐clamp mode, before and after application of oxytocin (OT) in the bath. The results of in vivo studies have shown that in the DREADD group the icv insulin was able to reduce the HVGC when compared to the control group (Control: 113,6±14,9 mg/dL n=5; vs DREADD: 74,2±6,16mg/dL; p≤0,05). As for the in vitro studies, the application of OT in liver projecting‐DMNV depolarized the resting membrane potential (Basal: −59.4± 0.7 mV vs OT: −56.2 ± 1.2 mV, n = 10; t = 2.403, df = 9; P = 0.0397) and increased the firing frequency (baseline: 1.9±0.8 vs OT: 3.0 ± 0.9 Hz, n=10; P = 0.002) in Wistar, but not in sedentary SHR. Interestingly, in SHR trained for 4 weeks, the OT caused depolarization of resting membrane potential (baseline: −61.3 ± 1.3 vs OT: −59.6 ± 1.5 mV, n=18; P=0.0177) and an increase in the firing frequency (baseline: 3.9±0.7 vs OT: 4.7±0.6 Hz, n=18, P=0.0012). As conclusion, the selective activation of parasympathetic preganglionic neurons of the DMNV rescues the changes in the HVGC elicited by central action of insulin, which used to be defective in SHR, indicating that the circuitry involving DMNV‐liver pathway is somehow dysfunctional, which could be due to the autonomic unbalance observed in this strain. Moreover, OT elicits similar changes in the electrophysiological properties of liver‐projecting DMNV neurons of Wistar and exercise‐trained but not sedentary SHR. These results indicate that exercise training can restore the sensitivity of liver‐projecting DMNV neurones of exercise trained SHR to OT.

Probing the Cellular Basis of Spinal Kappa Opioid Receptor Inhibition of Itch

The kappa opioid receptor (KOR, encoded by Oprk1) is an extremely attractive target for the treatment of chronic itch. The KOR agonist nalfurafine is used to treat chronic itch associated with kidney and liver disease in Japan, with additional KOR agonists in development for atopic dermatitis and neuropathic itch. Despite the clinical promise of KOR agonists, the cellular basis of KOR inhibition of itch remains unknown. Previous work from our lab demonstrated that KOR inhibition of itch occurs – at least in part – at the level of the spinal cord, raising the question: how does KOR signaling inhibit itch spinal circuits? We are addressing this fundamental gap in knowledge through a combination of molecular, genetic, behavioral, and physiological approaches in mice. First, we used fluorescent in situ hybridization to determine which spinal neuron populations express Oprk1. We show that Oprk1 is expressed within a heterogenous population of spinal neurons, but primarily those that express the neuropeptide substance P or the neurokinin-1 receptor, which drive itch behavior. Moreover, retrograde viral labeling revealed that Oprk1 is expressed in spinoparabrachial neurons that relay itch input from the spinal cord to the brain. Next, we tested whether Oprk1 spinal neurons contribute to itch behaviors. We selectively expressed excitatory chemogenetic tools in Oprk1-Cre spinal neurons and found that chemogenetic activation of these neurons potentiated itch behaviors. Finally, we used ex vivo two-photon calcium imaging of the spinal cord to visualize the neuron networks activated by spinal itch neuropeptides and investigated how KOR agonists inhibit these networks. Notably, these data are the first in-depth look into the cellular basis of spinal KOR inhibition of itch and provide fundamental mechanistic insights into KOR agonists that are clinically effective in alleviating chronic itch. Supported by NIH grants F32NS110155 (TDS) and R01NS0967905 (SER).

DREADDs in Epilepsy Research: Network-Based Review.

Epilepsy can be interpreted as altered brain rhythms from overexcitation or insufficient inhibition. Chemogenetic tools have revolutionized neuroscience research because they allow “on demand” excitation or inhibition of neurons with high cellular specificity. Designer Receptors Exclusively Activated by Designer Drugs (DREADDs) are the most frequently used chemogenetic techniques in epilepsy research. These engineered muscarinic receptors allow researchers to excite or inhibit targeted neurons with exogenous ligands. As a result, DREADDs have been applied to investigate the underlying cellular and network mechanisms of epilepsy. Here, we review the existing literature that has applied DREADDs to understand the pathophysiology of epilepsy. The aim of this review is to provide a general introduction to DREADDs with a focus on summarizing the current main findings in experimental epilepsy research using these techniques. Furthermore, we explore how DREADDs may be applied therapeutically as highly innovative treatments for epilepsy.

Oxytocin Receptor-Expressing Neurons in the Paraventricular Thalamus Regulate Feeding Motivation through Excitatory Projections to the Nucleus Accumbens Core.

Oxytocin receptors (OTR) have been found in the paraventricular thalamus (PVT) for the regulation of feeding and maternal behaviors. However, the functional projections of OTR-expressing PVT neurons remain largely unknown. Here, we used chemogenetic and optogenetic tools to test the role of OTR-expressing PVT neurons and their projections in the regulation of food intake in both male and female OTR-Cre mice. We found chemogenetic activation of OTR-expressing PVT neurons promoted food seeking under trials with a progressive ratio schedule of reinforcement. Using Feeding Experimentation Devices for real-time meal measurements, we found chemogenetic activation of OTR-expressing PVT neurons increased meal frequency but not cumulative food intake because of a compensatory decrease in meal sizes. In combination with anterograde neural tracing and slice patch-clamp recordings, we found optogenetic stimulation of PVT OTR terminals excited neurons in the posterior basolateral amygdala (pBLA) and nucleus accumbens core (NAcC) as well as local PVT neurons through monosynaptic glutamatergic transmissions. Photostimulation of OTR-expressing PVT-NAcC projections promoted food-seeking, whereas selective activation of PVT-pBLA projections produced little effect on feeding. In contrast to selective activation of OTR terminals, photostimulation of a broader population of glutamatergic PVT terminals exerted direct excitation followed by indirect lateral inhibition on neurons in both NAcC and anterior basolateral amygdala. Together, these results suggest that OTR-expressing PVT neurons are a distinct population of PVT glutamate neurons that regulate feeding motivation through projections to NAcC.SIGNIFICANCE STATEMENT The paraventricular thalamus plays an important role in the regulation of feeding motivation. However, because of the diversity of paraventricular thalamic neurons, the specific neuron types promoting food motivation remain elusive. In this study, we provide evidence that oxytocin receptor-expressing neurons are a specific group of glutamate neurons that primarily project to the nucleus accumbens core and posterior amygdala. We found that activation of these neurons promotes the motivation for food reward and increases meal frequency through projections to the nucleus accumbens core but not the posterior amygdala. As a result, we postulate that oxytocin receptor-expressing neurons in the paraventricular thalamus and their projections to the nucleus accumbens core mainly regulate feeding motivation but not food consumption.

All-optical monitoring of excitation-secretion coupling demonstrates that SV2A functions downstream of evoked Ca2+ entry.

SV2A, an essential transporter-like synaptic vesicle protein, is a major target for antiepileptic drugs and a receptor for clostridial neurotoxins including Botox. While SV2A is required for normal levels of evoked neurotransmitter release, the mechanism underlying this role remains unclear. Here, we introduce a new chemogenetic approach for all-optical monitoring of excitation-secretion coupling, and we demonstrate its use in characterizing the SV2A knockout (KO) phenotype in cultured hippocampal neurons. This method employs the HaloTag system to target a robust small-molecule Ca2+ indicator, JF646 -BAPTA, to the presynaptic compartment. The far-red fluorescence of this indicator enables multiplexing with the fluorescent glutamate sensor iGluSnFR for detection of presynaptic Ca2+ influx and glutamate release at the same axonal boutons. Evoked glutamate release probability was reduced in SV2A KO neurons without a change in presynaptic Ca2+ entry, suggesting that SV2A supports vesicle fusion by increasing the functional availability, or efficiency, of the Ca2+ -regulated membrane fusion machinery. KEY POINTS: One of the most prescribed antiepileptic medications, levetiracetam, acts by binding a protein of uncertain molecular function. This transporter-like protein, SV2A, is trafficked to synaptic vesicles and acts to support neurotransmitter release, but the mechanism underlying this function has not been determined In this study, we sought to establish whether SV2A changes Ca2+ signalling at nerve terminals, which is a key regulatory system for synaptic vesicle exocytosis. To do so, we adapted new chemogenetic tools to perform all-optical measurements of presynaptic Ca2+ and glutamate release in neurons lacking SV2A. Our measurements showed that loss of SV2A reduces glutamate release without reducing Ca2+ influx at hippocampal nerve terminals, demonstrating that SV2A increases the likelihood that Ca2+ will trigger synaptic vesicle fusion.

A novel ligand for chemogenetic receptors, Deschloroclozapine, enables rapid and selective modulation of neuronal activity and behavior in living animals

A brain function is manifested by harmonizing some brain regions responsible for the function. Since pathological conditions in neuropsychiatric disorders are induced by the failure of this mechanism, it is crucial to identify the affected function by manipulating the specific brain regions. Designer receptors exclusively activated by designer drugs (DREADDs) are one of the chemogenetic tools that offer a means to repeatedly reversible control of the activity of a target neural population expressing a "designer receptor" by systemic injection of "designer drug," which is biologically inert. The most widely used DREADDs are muscarinic-based receptors, such as hM3Dq (excitatory) and hM4Di (inhibitory), which can be activated by clozapine-N-oxide (CNO). However, CNO has some concerns. First, because CNO has a modest brain penetrability, the effect is slow. Second, since CNO is metabolized to clozapine, an antipsychotic drug that acts on numerous endogenous receptors, the systemic administration may produce off-target actions. Therefore, we developed a new compound, deschloroclozapine (DCZ), to solve these issues. DCZ has a higher affinity and greater agonist potency than CNO with reduced off-target actions and can rapidly modulate the neuronal activity and behavior with muscarinic-based DREADDs in living animals. Given the potential weak point of CNO, DCZ affords clear benefits to many users of muscarinic-based DREADD, with increased reliability by removing concerns about possible off-target responses.

Chemically oligomerizable TDP-43: a novel chemogenetic tool for studying the pathophysiology of amyotrophic lateral sclerosis.

Chemically oligomerizable TDP-43: a novel chemogenetic tool for studying the pathophysiology of amyotrophic lateral sclerosis.

Neural circuit control of innate behaviors.

All animals possess a plethora of innate behaviors that do not require extensive learning and are fundamental for their survival and propagation. With the advent of newly-developed techniques such as viral tracing and optogenetic and chemogenetic tools, recent studies are gradually unraveling neural circuits underlying different innate behaviors. Here, we summarize current development in our understanding of the neural circuits controlling predation, feeding, male-typical mating, and urination, highlighting the role of genetically defined neurons and their connections in sensory triggering, sensory to motor/motivation transformation, motor/motivation encoding during these different behaviors. Along the way, we discuss possible mechanisms underlying binge-eating disorder and the pro-social effects of the neuropeptide oxytocin, elucidating the clinical relevance of studying neural circuits underlying essential innate functions. Finally, we discuss some exciting brain structures recurrently appearing in the regulation of different behaviors, which suggests both divergence and convergence in the neural encoding of specific innate behaviors. Going forward, we emphasize the importance of multi-angle and cross-species dissections in delineating neural circuits that control innate behaviors.

Multiparametric imaging approaches to dissect the role of ROS and RNS signaling pathways using chemogenetic tools and genetically encoded biosensors

Multiparametric imaging approaches to dissect the role of ROS and RNS signaling pathways using chemogenetic tools and genetically encoded biosensors

Systematic Input-Output Mapping Reveals Structural Plasticity of VTA Dopamine Neurons-Zona Incerta Loop Underlying the Social Buffering Effects in Learned Helplessness.

A common phenomenon called social buffering (SB), communication within conspecific animals is a benefit for a stressed individual to better recover from aversive events, is crucial to all mammals. Although the dopamine reward system has been implicated in SB, it is not clear which neuronal populations are relevant and how they contribute. Here, we adopted a learned helplessness (LH) animal model of depression and found that LH subjects housed with a conspecific partner show better performance in the shuttle box test, showing that SB improves the stress-coping abilities to deal with stress. Bidirectional manipulation of ventral tegmental area (VTA) dopamine neurons by chemogenetic tools can mimic or block the SB effect in LH mice. To screen for SB-induced structure plasticity of VTA dopamine neurons, we employed viral genetic tools for mapping input and output architecture and found LH- and SB-triggered circuit-level changes in neuronal ensembles. Zona incerta (ZI), an overlapping brain region, was significantly changed in both anterograde and retrograde tracing during LH and SB. These results reveal a neural loop with structural plasticity between VTA dopamine neurons and ZI underlies the SB effects in LH and lays a foundation for studying how VTA dopamine neurons regulate SB-related neural circuits.

Clozapine is my favorite color: Chemogenetic modulation of anxiety-related behavior in primates

The development of technologies to reversibly manipulate neural circuitry has given rise to the prospect of more precisely targeted therapies to normalize brain function in neuropsychiatric disorders. These approaches must be feasible using viral vector-mediated gene transfer to be practical in primates. Chemogenetic tools have great potential in fulfilling this goal. Chemogenetic neuromodulation changes neuronal activity via a systemically administered drug that triggers artificial receptors placed in anatomically defined neuronal populations via viral vectors.

Behavioral Engagement With Playable Objects Resolves Stress-Induced Adaptive Changes by Reshaping the Reward System

BackgroundThe reward system regulates motivated behavior, and repeated practice of specific motivated behavior might conversely modify the reward system. However, the detailed mechanisms by which they reciprocally regulate each other are not clearly understood. MethodsMice subjected to chronic restraint stress show long-lasting depressive-like behavior, which is rescued by continual engagement with playable objects. A series of molecular, pharmacological, genetic, and behavioral analyses, combined with microarray, liquid chromatography, and chemogenetic tools, are used to investigate the neural mechanisms of antidepressive effects of playable objects. ResultsHere, we show that repeated restraint induces dopamine surges into the nucleus accumbens–lateral shell (NAc-lSh), which cause upregulation of the neuropeptide PACAP in the NAc-lSh. As repeated stress is continued, the dopamine surge by stressors is adaptively suppressed without restoring PACAP upregulation, and the resulting enhanced PACAP inputs from NAc-lSh neurons to the ventral pallidum facilitate depressive-like behaviors. Continual engagement with playable objects in mice subjected to chronic stress remediates reduced dopamine response to new stressors, enhanced PACAP upregulation, and depressive-like behaviors. Overactivation of dopamine D1 receptors over the action of D2 receptors in the NAc-lSh promotes depressive-like behaviors. Conversely, inhibition of D1 receptors or PACAP upregulation in the NAc-lSh confers resilience to chronic stress–induced depressive-like behaviors. Histochemical and chemogenetic analyses reveal that engagement with playable objects produces antidepressive effects by reshaping the ventral tegmental area–to–NAc-lSh and NAc-lSh–to–ventral pallidum circuits. ConclusionsThese results suggest that behavioral engagement with playable objects remediates depressive-like behaviors by resolving stress-induced maladaptive changes in the reward system.