Biology subjects

Bruchas, M. R.

Publications and source records attributed to Bruchas, M. R..

At least 19 recordsLinked to original sources

bioRxiv2026

Acute stress reorganizes pregenual cingulate and subthalamic coupling to approach-avoidance decisions in remitted depression

Major depressive disorder (MDD) is highly recurrent, and psychosocial stress is a central precipitant of relapses. Daily choices require weighing potential rewards against costs, a process disrupted in MDD that may contribute to relapse. Here, we tested whether a psychosocial stressor affects neural and computational mechanisms underlying approach-avoidance decision making in individuals with remitted MDD (rMDD, N=50) and healthy controls (N=74), prioritizing pregenual anterior cingulate cortex (pgACC) and subthalamic nucleus (STN) due to their roles in value integration and decision caution, respectively. Participants performed a dynamic approach-avoidance conflict task with fMRI before and after psychosocial stress. Hierarchical Bayesian drift-diffusion modeling evaluated whether stress modulated computational and neural mechanisms, with trial-wise pgACC and STN activity entered as neural regressors on evidence accumulation and decision threshold, respectively. Before stress, groups did not differ in any decision parameter, but pgACC activity contributed to evidence accumulation toward avoidance in controls only. After stress, rMDD showed larger increases than controls in the impact of both reward and aversiveness on accumulation toward approach and avoidance, respectively, predominantly for net-aversive offers. Furthermore, in rMDD, stress rendered both approach and avoidance decisions more sensitive to pgACC activity, and STN activity was more strongly coupled to the decision threshold than in controls. Finally, stress-induced increases in reward sensitivity in rMDD predicted one-year course of depressive symptoms. Thus, MDD remission is not characterized by a generalized blunting of decision-making, but by a latent circuit difference that acute stress reorganizes and predicts future symptoms.

neuroscience↗

bioRxiv2026

Parabrachial oxytocin receptor-expressing neurons link social observation of distress to defensive behavior

The ability to detect and respond to threat signals in the environment, including those conveyed by the distress of a familiar social partner, is fundamental to survival and disrupted in a range of neuropsychiatric conditions. This study identifies oxytocin receptor (Oxtr)-expressing neurons within the lateral parabrachial nucleus (lPBN) of mice as a key node in the neural circuitry underlying threat-related and social behaviors. These Oxtr neurons are activated by aversive stimuli and by observing demonstrator mice in stressful situations, including foot shock or inflammatory pain. Chemogenetic inhibition of these neurons alters social proximity and pain contagion in observers without affecting general anxiety-like behavior. Inhibition also transiently suppresses non-social central sensitization. Direct activation of lPBNOxtr neurons with a selective Oxtr agonist is anxiogenic and results in increased tactile sensitivity. Together, these findings suggest that lPBNOxtr neurons are poised to integrate information about environmental threat, whether experienced directly or witnessed in a conspecific to coordinate appropriate defensive behavioral responses.

neuroscience↗

bioRxiv2025

Nociceptin Orphanin F/Q Pathways are Dysregulated by Stress and Modulate Reward Learning and Motivation Across Species

Nociceptin orphanin F/Q has been implicated in stress-related depressive phenotypes. Specifically, exposure to chronic stressors upregulates nociceptin receptors (NOPR), whereas NOPR antagonism has anti-depressant/anti-anhedonic effects. The mechanisms underlying these effects remain, however, unclear. Here, we investigated the role of NOPR in depressive phenotypes alongside potentially prohedonic effects of NOPR antagonism across species. In Study 1, we evaluated whether exposure to early-life adversity (ELA) upregulated ventral tegmental area (VTA) and striatal prepronociceptin (Pnoc) gene expression in adult mice. In Study 2, we tested whether chronic social defeat altered Pnoc gene expression in reward-related regions. To establish whether direct NOPR modulation is implicated in reward-related behaviors, in Study 3, we assessed whether NOPR antagonism alters reward learning in rats. Finally, in Study 4, we tested whether NOPR antagonism boosts motivation among depressed humans. ELA induced anhedonic behavior and increased Pnoc expression in the VTA; in females (but not males), ELA increased Pnoc expression in the dorsal striatum (Study 1). Furthermore, chronic stress reduced Pnoc-expressing cells in the VTA, dorsal striatum and prefrontal cortex and susceptible rats showed reduced VTA NOPR gene (Oprl1)-expressing cells (Study 2). In a behavioral assay, a single 30-mg dose of a NOPR antagonist (BTRX-246040) boosted reward learning in rats (Study 3). Finally, in depressed humans, relative to placebo, 8-week treatment with BTRX-246040 increased incentive motivation (Study 4). Collectively, our findings indicate that chronic stressors alter Pnoc and mRNA levels of Pnoc-expressing cells in a sex-selective and region-specific manner impacting reward structures, and that NOPR antagonism shows anti-anhedonic properties.

neuroscience↗

bioRxiv2025

Identification of a stress-sensitive endogenous opioid-containing neuronal population in the paranigral ventral tegmental area.

Nociceptin/orphanin FQ (N/OFQ), an endogenous opioid neuropeptide, and its G-protein coupled receptor NOPR have been implicated in motivation, feeding behaviors, and aversion. Stress-induced dysfunction in these states is central to the development of numerous psychiatric disorders, and the N/OFQ-NOPR systems role in reward- and stress-related responses has driven broad interest in NOPR as a therapeutic target for anxiety and depression. However, the impact of stress on N/OFQ signaling in the context of its influence on discrete midbrain reward circuitry remains unknown. To this end, we focused on a possible candidate population of N/OFQ neurons in the paranigral ventral tegmental area (pnVTAPNOC) that have been shown to act locally on NOPR-containing VTA dopamine neurons to suppress motivation. Here we report and characterize pnVTAPNOC sensitivity to stress exposure and identify a functional excitatory and inhibitory afferent input to this subpopulation from the lateral hypothalamus (LH). Our results indicate that pnVTAPNOC neurons become recruited during exposure to a range of acute stressor types, whereas the GABAergic input from the LH to this population is suppressed by predator odor stress, providing a mechanism for disinhibition of these neurons. These findings suggest that this N/OFQ population in the pnVTA could act as a critical bridge between stress and motivation through interactions with upstream hypothalamic circuitry.

neuroscience↗

bioRxiv2025

Brainwide genetic capture for conscious state transitions

Neural circuits underlying unconsciousness remain poorly defined. We test the hypothesis that unconsciousness arises from specific, distributed circuits using general anesthesia in mice as a reproducible model. We identify a cortical-to-subcortical shift in neural activity during isoflurane anesthesia that is organized into nine discrete functional communities mapped at single-cell resolution. The lateral parabrachial nucleus (LPB) emerges as a central hub, exhibiting high interconnectivity, spontaneous firing under anesthesia, and preferential recruitment during reactivation of the brain-wide ensemble confirmed by single unit recordings. Chemogenetic reactivation of the captured brain-wide ensemble induces sedation, slow wave oscillations, hypothermia, and analgesia, which are components of anesthesia-induced unconsciousness. Reactivation of the LPB ensemble alone recapitulates a subset of these effects. Together, we define a global neural substrate for unconsciousness and recapitulate its dissociable autonomic, neurophysiologic, and behavioral effects using brain-wide ensemble manipulations. These results establish a neural circuit framework for anesthesia-induced unconsciousness in the mammalian brain.

neuroscience↗

bioRxiv2024

Dentate Gyrus Norepinephrine Ramping Facilitates Aversive Contextual Processing

Dysregulation in aversive contextual processing is believed to affect several forms of psychopathology, including post-traumatic stress disorder (PTSD). The dentate gyrus (DG) is an important brain region in contextual discrimination and disambiguation of new experiences from prior memories. The DG also receives dense projections from the locus coeruleus (LC), the primary source of norepinephrine (NE) in the mammalian brain, which is active during stressful events. However, how noradrenergic dynamics impact DG-dependent function during contextual discrimination and pattern separation remains unclear. Here, we report that aversive contextual processing in mice is linked to linear elevations in tonic norepinephrine release dynamics within the DG and report that this engagement of prolonged norepinephrine release is sufficient to produce contextual disambiguation, even in the absence of a salient aversive stimulus. These findings suggest that spatiotemporal ramping characteristics of LC-NE release in the DG during stress likely serve an important role in driving contextual processing.

neuroscience↗

bioRxiv2024

Endogenous opioid dynamics in the dorsal striatum sculpt neural activity to control goal-directed action

Endogenous neuropeptides are uniquely poised to regulate neuronal activity and behavior across multiple timescales. Traditional studies ascribing neuropeptide contributions to behavior lack spatiotemporal precision. The endogenous opioid dynorphin is highly enriched in the dorsal striatum, known to be critical for regulating goal-directed behavior. However, the locus, the precise timescale, or functional role of endogenous dyn-KOR signaling on goal-directed behavior is unknown. Here, we report that local, time-locked dynorphin release from the dorsomedial striatum is necessary and sufficient for goal-directed behavior using a suite of high resolution modern approaches including in vivo two-photon imaging, neuropeptide biosensor detection, conditional deletions and time-locked optogenetic manipulations. We discovered that glutamatergic axon terminals from the basolateral amygdala evoke striatal dynorphin release, resulting in retrograde presynaptic GPCR inhibition during behavior. Collectively, our findings isolate a causal role for endogenous neuropeptide release at rapid timescales, and subsequent GPCR activity for tuning and promoting fundamental goal-directed behaviors.

neuroscience↗

bioRxiv2024

Developmental and adult striatal patterning of nociceptin ligand marks striosomal population with direct dopamine projections

Circuit influences on the midbrain dopamine system are crucial to adaptive behavior and cognition. Recent developments in the study of neuropeptide systems have enabled high-resolution investigations of the intersection of neuromodulatory signals with basal ganglia circuitry, identifying the nociceptin/orphanin FQ (N/OFQ) endogenous opioid peptide system as a prospective regulator of striatal dopamine signaling. Using a prepronociceptin-Cre reporter mouse line, we characterized highly selective striosomal patterning of Pnoc mRNA expression in mouse dorsal striatum, reflecting early developmental expression of Pnoc. In the ventral striatum, Pnoc expression was was clustered across the nucleus accumbens core and medial shell, including in adult striatum. We found that PnoctdTomato reporter cells largely comprise a population of dopamine receptor D1 (Drd1) expressing medium spiny projection neurons localized in dorsal striosomes, known to be unique among striatal projections neurons for their direct innervation of midbrain dopamine neurons. These findings provide new understanding of the intersection of the N/OFQ system among basal ganglia circuits with particular implications for developmental regulation or wiring of striatal-nigral circuits.

neuroscience↗

bioRxiv2024

An integrated microfluidic and fluorescence platform for probing in vivo neuropharmacology

Neurotechnologies and genetic tools for dissecting neural circuit functions have advanced rapidly over the past decade, although the development of complementary pharmacological method-ologies has comparatively lagged. Understanding the precise pharmacological mechanisms of neuroactive compounds is critical for advancing basic neurobiology and neuropharmacology, as well as for developing more effective treatments for neurological and neuropsychiatric disorders. However, integrating modern tools for assessing neural activity in large-scale neural networks with spatially localized drug delivery remains a major challenge. Here, we present a dual microfluidic-photometry platform that enables simultaneous intracranial drug delivery with neural dynamics monitoring in the rodent brain. The integrated platform combines a wireless, battery-free, miniaturized fluidic microsystem with optical probes, allowing for spatially and temporally specific drug delivery while recording activity-dependent fluorescence using genetically encoded calcium indicators (GECIs), neurotransmitter sensors GRABNE and GRABDA, and neuropeptide sensors. We demonstrate the performance this platform for investigating neuropharmacological mechanisms in vivo and characterize its efficacy in probing precise mechanistic actions of neuroactive compounds across several rapidly evolving neuroscience domains.

neuroscience↗

bioRxiv2023

Long-Term In Vivo Molecular Monitoring Using Aptamer-Graphene Microtransistors

Long-term, real-time molecular monitoring in complex biological environments is critical for our ability to understand, prevent, diagnose, and manage human diseases. Aptamer-based electrochemical biosensors possess the promise due to their generalizability and a high degree of selectivity. Nevertheless, the operation of existing aptamer-based biosensors in vivo is limited to a few hours. Here, we report a first-generation long-term in vivo molecular monitoring platform, named aptamer-graphene microtransistors (AGMs). The AGM incorporates a layer of pyrene- (polyethylene glycol)5-alcohol and DNase inhibitor-doped polyacrylamide hydrogel coating to reduce biofouling and aptamer degradation. As a demonstration of function and generalizability, the AGM achieves the detection of biomolecules such as dopamine and serotonin in undiluted whole blood at 37 {degrees}C for 11 days. Furthermore, the AGM successfully captures optically evoked dopamine release in vivo in mice for over one week and demonstrates the capability to monitor behaviorally-induced endogenous dopamine release even after eight days of implantation in freely moving mice. The results reported in this work establish the potential for chronic aptamer-based molecular monitoring platforms, and thus serve as a new benchmark for molecular monitoring using aptamer-based technology.

bioengineering↗

bioRxiv2023

Development of a genetically-encoded sensor for probing endogenous nociceptin opioid peptide release

Nociceptin/orphanin-FQ (N/OFQ) is a recently appreciated critical opioid peptide with key regulatory functions in several central behavioral processes including motivation, stress, feeding, and sleep. The functional relevance of N/OFQ action in the mammalian brain remains unclear due to a lack of high-resolution approaches to detect this neuropeptide with appropriate spatial and temporal resolution. Here we develop and characterize NOPLight, a genetically encoded sensor that sensitively reports changes in endogenous N/OFQ release. We characterized the affinity, pharmacological profile, spectral properties, kinetics, ligand selectivity, and potential interaction with intracellular signal transducers of NOPLight in vitro. Its functionality was established in acute brain slices by exogeneous N/OFQ application and chemogenetic induction of endogenous N/OFQ release from PNOC neurons. In vivo studies with fibre photometry enabled direct recording of NOPLight binding to exogenous N/OFQ receptor ligands, as well as detection of endogenous N/OFQ release within the paranigral ventral tegmental area (pnVTA) during natural behaviors and chemogenetic activation of PNOC neurons. In summary, we show here that NOPLight can be used to detect N/OFQ opioid peptide signal dynamics in tissue and freely behaving animals.

neuroscience↗

bioRxiv2022

TRPV1-mediated sonogenetic neuromodulation of motor cortex in freely moving mice

BackgroundNoninvasive and cell-type-specific neuromodulation tools are critically needed for probing intact brain function. Sonogenetics for noninvasive activation of neurons engineered to express thermosensitive transient receptor potential vanilloid 1 (TRPV1) by transcranial focused ultrasound (FUS) was recently developed to address this need. However, using TRPV1-mediated sonogenetics to evoke behavior by targeting the cortex is challenged by its proximity to the skull due to high skull absorption of ultrasound and increased risks of thermal-induced tissue damage. ObjectiveThis study evaluated the feasibility and safety of TRPV1-mediated sonogenetics in targeting the motor cortex to modulate the locomotor behavior of freely moving mice. MethodsAdeno-associated virus was delivered to the mouse motor cortex via intracranial injection to express TRPV1 in excitatory neurons. A wearable FUS device was installed on the mouse head after a month to control neuronal activity by activating virally expressed TRPV1 through FUS sonication at different acoustic pressures. Immunohistochemistry staining of ex vivo brain slices was performed to verify neuron activation and evaluate safety. ResultsTRPV1-mediated sonogenetic stimulation at 0.7 MPa successfully evoked rotational behavior in the direction contralateral to the stimulation site, activated cortical neurons as indicated by the upregulation of c-Fos, and did not induce significant changes in inflammatory or apoptotic markers (GFAP, lba1, and Caspase-3). Sonogenetic stimulation of TRPV1 mice at a higher acoustic pressure, 1.1 MPa, induced significant changes in motor behavior and upregulation of c-Fos compared with FUS sonication of naive mice at 1.1 MPa. However, signs of damage at the meninges were observed at 1.1 MPa. ConclusionsTRPV1-mediated sonogenetics can achieve effective and safe neuromodulation at the cortex with carefully selected FUS parameters. These findings expand the application of this technique to include superficial brain targets.

bioengineering↗

bioRxiv2022

Glutamatergic Supramammillary Nucleus Neurons Promote Active Coping to Stress

Threat-response neural circuits are conserved across species and play roles in normal behavior and psychiatric diseases. Maladaptive changes in these neural circuits contribute to stress, mood, and anxiety disorders. Active coping in response to stressors is a psychosocial factor associated with resilience against stress-induced mood and anxiety disorders. The neural circuitry underlying active coping is poorly understood, but the functioning of these circuits could be key for overcoming anxiety and related disorders. The supramammillary nucleus (SuM) has been suggested to be engaged by threat. SuM has many projections and contains a poorly understood diversity of populations. We identified a unique population of glutamatergic SuM neurons (SuMVGLUT2+::POA) based on projection to the preoptic area of the hypothalamus (POA) and found SuMVGLUT2+::POA neurons have extensive arborizations. SuMVGLUT2+::POA neurons project to brain areas that mediate various features of the stress and threat responses including the paraventricular nucleus thalamus (PVT), periaqueductal gray (PAG), and the habenula (Hb). Thus, SuMVGLUT2+::POA neurons are positioned as a hub, connecting to areas implicated in regulating stress responses. Here we report SuMVGLUT2+::POA neurons are recruited by diverse threatening stressors, and recruitment of SuMVGLUT2+::POA neurons correlated with active coping behaviors. We found that selective photoactivation of the SuMVGLUT2+::POA population drove aversion but not anxiety like behaviors. Activation of SuMVGLUT2+::POA neurons in the absence of acute stressors evoked active coping like behaviors and drove instrumental behavior (selective port activations) (Figure 6). Also, activation of SuMVGLUT2+::POA neurons was sufficient to convert passive coping strategies to active behaviors during acute stress. In contrast, we found activation of GABAergic (VGAT+) SuM neurons (SuMVGAT+) neurons did not alter drive aversion or active coping, but termination of photostimulation was followed by increased mobility in the forced swim test. These findings establish a new node in stress response circuitry that has projections to many brain areas, evokes flexible active coping behaviors, and offers new opportunities for furthering our neurobiological understanding of stress. O_FIG O_LINKSMALLFIG WIDTH=134 HEIGHT=200 SRC="FIGDIR/small/507167v4_fig6.gif" ALT="Figure 6"> View larger version (30K): org.highwire.dtl.DTLVardef@717f84org.highwire.dtl.DTLVardef@16ad323org.highwire.dtl.DTLVardef@4ba5b6org.highwire.dtl.DTLVardef@6c811e_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOFigure 6.C_FLOATNO SuMVGLUT2+::POA neurons can drive instrumental action-outcome operant behavior (A) Schematic of injection and implant in VGLUT2+ Cre mice and paradigm of testing in 10-minute trials with four days before a progressive ratio (PR) trial on day five. (B) Illustration of the testing paradigm and set up. 10 Hz photostimulation was applied during the trials. Activation of the active port triggered the house light and paused stimulation for 10 seconds. Also shown is the progressive ratio used with number of required port activations per reward on vertical axis and reward number on the horizontal. (C) Cre+ mice (n=11) activated the active port triggering significantly (****p<0.0001) more pauses in stimulation than Cre- mice (n=11) mice on all four days of testing. (D) Cre+ mice activated the port significantly (****p<0.0001, ***p<0.001) more than the Cre- mice on all four trials. (E) The time to first activation of the active port was significantly (*p=0.046) different during the first trial, and Cre+ mice activated the active port significantly (**p<0.01, **p<0.01, **p=0.034) faster on subsequent trials. (F) On the fifth day after four 10-minute trials, mice were tested for 30 minutes using a progressive ratio. Cre+ performed significantly (****p<0.001) more active port activations than Cre- mice and activated the inactive port significantly more (**p=0.001) times. Cre+ mice also triggered significantly (****p<0.001) more pauses in photostimulation than Cre- mice. (G) Individual data for a representative (n=7) cohort of Cre+ mice showing cumulative active port activations as a function of time during the progressive ratio test show on-going engagement of the active port throughout the 30-minute trial. (H) The cumulative pauses in photostimulation (rewards) earned as a function of time during the progressive ratio trial are shown for individual Cre+ mice. Mice earned between 7 and 11 pause rewards during the trial. All data plotted as means {+/-}SEM. C_FIG

neuroscience↗

bioRxiv2022

Holographic stimulation of opposing amygdala ensembles bidirectionally modulates valence-specific behavior

The basolateral amygdala (BLA) is an evolutionarily conserved brain region, well known for valence processing. Despite this central role, the relationship between activity of BLA neuronal ensembles in response to appetitive and aversive stimuli and the subsequent expression of valence-specific behavior has remained elusive. Here we leverage 2-photon calcium imaging combined with single cell holographic photostimulation through an endoscopic lens implanted in the deep brain to demonstrate a direct causal role for discrete ensembles of BLA neurons in the control of oppositely valenced behavior. We report that targeted photostimulation of individual groups of appetitive or aversive BLA neurons shifts behavioral responses toward those behaviors which recruited a specific consumption or avoidance ensemble. Here we identify that neuronal encoding of valence in the BLA is graded and relies on the relative proportion of individual BLA neurons recruited in a stable appetitive or aversive ensemble.

neuroscience↗

bioRxiv2022

A diverse network of pericoerulear neurons control arousal states

As the primary source of norepinephrine (NE) in the brain, the locus coeruleus (LC) regulates arousal, avoidance and stress responses1,2. However, how local neuromodulatory inputs control LC function remains unresolved. Here we identify a population of transcriptionally, spatially and functionally diverse GABAergic neurons in the LC dendritic field that receive distant inputs and modulate modes of LC firing to control global arousal levels and arousal-related processing and behaviors. We define peri-LC anatomy using viral tracing and combine single-cell RNA sequencing with spatial transcriptomics to molecularly define both LC-NE and peri-LC cell types. We identify several neuronal cell types which underlie peri-LC functional diversity using a series of complementary neural circuit approaches in behaving mice. Our findings indicate that LC and peri-LC neurons are transcriptionally, functionally, and anatomically heterogenous neuronal populations which modulate arousal and avoidance states. Defining the molecular, cellular, and functional diversity of the LC and peri-LC provides a road map for understanding the neurobiological basis of arousal, motivation and neuropsychiatric disorders.

neuroscience↗

bioRxiv2022

Opto-MASS: a high-throughput engineering platform for genetically encoded fluorescentsensors enabling all optical in vivo detection of monoamines and neuropeptides

Fluorescent sensor proteins are instrumental for detecting biological signals in vivo with high temporal accuracy and cell-type specificity. However, engineering sensors with physiological ligand sensitivity and selectivity is difficult because they need to be optimized through individual mutagenesis in vitro to assess their performance. The vast mutational landscape proteins constitute an obstacle that slows down sensor development. This is particularly true for sensors that require mammalian host systems to be screened. Here, we developed a novel high-throughput engineering platform that functionally tests thousands of variants simultaneously in mammalian cells and thus allows the screening of large variant numbers. We showcase the capabilities of our platform, called Optogenetic Microwell Array Screening System (Opto-MASS), by engineering novel monoamine and neuropeptide in vivo capable sensors with distinct physiological roles at high-throughput.

bioengineering↗

bioRxiv2022

ABHD6 selectively controls Gq-dependent increases in 2-AG production

The most abundant endocannabinoid (eCB) in the brain, 2-arachidonoyl glycerol (2-AG), is hydrolyzed by /{beta}-hydrolase domain containing 6 (ABHD6); yet how ABHD6 controls stimuli-dependent increases in 2-AG production is unknown. To explore this question, we leveraged the recently developed 2-AG sensor, GRABeCB2.0, and found that stimulation of Neuro2a cells in culture with bradykinin (BK) acting at metabotropic B2K receptors and ATP acting at ionotropic P2X7 receptors led to differential increases in 2-AG levels. B2K triggered increases in 2-AG levels via diacylglycerol lipase (DAGL), and this mechanism was potentiated by increases in intracellular calcium and ABHD6 inhibition. By contrast, P2X7-triggered increases in 2-AG levels were dependent on DAGL and extracellular calcium but unaffected by ABHD6 inhibition. Thus, ABHD6 preferentially regulates metabotropic-dependent increases in 2-AG levels over ionotropic-dependent increases in 2-AG levels. Our study indicates that ABHD6 selectively controls stimuli-dependent increases in 2-AG production and emphasizes its specific role in eCB signaling.

cell biology↗

bioRxiv2021

A photoswitchable GPCR-based opsin for presynaptic silencing

Optical manipulations of genetically defined cell types have generated significant insights into the dynamics of neural circuits. While optogenetic activation has been relatively straightforward, rapid and reversible synaptic inhibition has been far more difficult to achieve. Instead of relying on unpredictable ion manipulations or slow photoactivatable toxins at axon terminals, we took a different approach to leverage the natural ability of inhibitory presynaptic GPCRs to silence synaptic transmission. Here we characterize parapinopsin (PPO), a photoswitchable non-visual opsin from lamprey pineal gland that couples to Gi/o-signaling cascades. PPO can be rapidly activated by pulsed blue light, switched off with amber light, and is effective for repeated or prolonged inhibition. We developed viral vectors for cell-specific expression of PPO, which traffics very effectively in numerous neuron types. At presynaptic terminals, PPO can silence glutamate release and suppress dopamine-dependent reward and cocaine place preference behaviors in vivo. PPO immediately fills a significant gap in the neuroscience toolkit for rapid and reversible synaptic inhibition, and has broader utility for achieving spatiotemporal control of inhibitory GPCR signaling cascades in other biological and pharmacological applications.

neuroscience↗