Publications by authors named "Michael R Bruchas"

92 Publications

Sonothermogenetics for noninvasive and cell-type specific deep brain neuromodulation.

Brain Stimul 2021 May 11. Epub 2021 May 11.

Department of Biomedical Engineering, Washington University in St. Louis, Saint Louis, MO, 63130, USA; Department of Radiation Oncology, Washington University School of Medicine, Saint Louis, MO, 63108, USA. Electronic address:

Background: Critical advances in the investigation of brain functions and treatment of brain disorders are hindered by our inability to selectively target neurons in a noninvasive manner in the deep brain.

Objective: This study aimed to develop sonothermogenetics for noninvasive, deep-penetrating, and cell-type-specific neuromodulation by combining a thermosensitive ion channel TRPV1 with focused ultrasound (FUS)-induced brief, non-noxious thermal effect.

Methods: The sensitivity of TRPV1 to FUS sonication was evaluated in vitro. It was followed by in vivo assessment of the success rate of sonothermogenetics in the activation of genetically defined neurons in the mouse brain by two-photon microscopic calcium imaging. Behavioral response evoked by sonothermogenetic stimulation at a deep brain target was recorded in freely moving mice. Immunohistochemistry staining of ex vivo brain slices was performed to evaluate the safety of FUS sonication.

Results: TRPV1 was found to be an ultrasound-sensitive ion channel. FUS sonication at the mouse brain in vivo selectively activated neurons that were genetically modified to express TRPV1. Temporally precise activation of TRPV1-expressing neurons was achieved with its success rate linearly correlated with the peak temperature within the FUS-targeted brain region as measured by in vivo magnetic resonance thermometry. FUS stimulation of TRPV1-expressing neurons at the striatum repeatedly evoked locomotor behavior in freely moving mice. FUS sonication was confirmed to be safe based on inspection of neuronal integrity, inflammation, and apoptosis markers.

Conclusions: This noninvasive and cell-type-specific neuromodulation approach with the capability to target the deep brain has the promise to advance the study of the intact nervous system and uncover new ways to treat neurological disorders.
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http://dx.doi.org/10.1016/j.brs.2021.04.021DOI Listing
May 2021

A photoswitchable GPCR-based opsin for presynaptic inhibition.

Neuron 2021 May 10. Epub 2021 May 10.

Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO, USA; Department of Neuroscience, Washington University School of Medicine, St. Louis, MO, USA; Center of Excellence in the Neurobiology of Addiction, Pain, and Emotion, Departments of Anesthesiology and Pain Medicine, and Pharmacology, University of Washington, Seattle, WA, USA. Electronic address:

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 proven more elusive. Here, we leveraged the natural ability of inhibitory presynaptic GPCRs to suppress synaptic transmission and characterize parapinopsin (PPO) as a GPCR-based opsin for terminal inhibition. PPO is a photoswitchable opsin that couples to G signaling cascades and is rapidly activated by pulsed blue light, switched off with amber light, and effective for repeated, prolonged, and reversible inhibition. PPO rapidly and reversibly inhibits glutamate, GABA, and dopamine release at presynaptic terminals. Furthermore, PPO alters reward behaviors in a time-locked and reversible manner in vivo. These results demonstrate that PPO fills a significant gap in the neuroscience toolkit for rapid and reversible synaptic inhibition and has broad utility for spatiotemporal control of inhibitory GPCR signaling cascades.
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http://dx.doi.org/10.1016/j.neuron.2021.04.026DOI Listing
May 2021

Parabrachial opioidergic projections to preoptic hypothalamus mediate behavioral and physiological thermal defenses.

Elife 2021 Mar 5;10. Epub 2021 Mar 5.

Center for the Neurobiology of Addiction, Pain and Emotion, Departments of Anesthesiology and Pharmacology, University of Washington, Seattle, United States.

Maintaining stable body temperature through environmental thermal stressors requires detection of temperature changes, relay of information, and coordination of physiological and behavioral responses. Studies have implicated areas in the preoptic area of the hypothalamus (POA) and the parabrachial nucleus (PBN) as nodes in the thermosensory neural circuitry and indicate that the opioid system within the POA is vital in regulating body temperature. In the present study we identify neurons projecting to the POA from PBN expressing the opioid peptides dynorphin and enkephalin. Using mouse models, we determine that warm-activated PBN neuronal populations overlap with both prodynorphin (Pdyn) and proenkephalin (Penk) expressing PBN populations. Here we report that in the PBN () and () mRNA expressing neurons are partially overlapping subsets of a glutamatergic population expressing () (VGLUT2). Using optogenetic approaches we selectively activate projections in the POA from PBN Pdyn, Penk, and VGLUT2 expressing neurons. Our findings demonstrate that Pdyn, Penk, and VGLUT2 expressing PBN neurons are critical for physiological and behavioral heat defense.
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http://dx.doi.org/10.7554/eLife.60779DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7935488PMC
March 2021

Extended amygdala-parabrachial circuits alter threat assessment and regulate feeding.

Sci Adv 2021 Feb 26;7(9). Epub 2021 Feb 26.

Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA.

An animal's evolutionary success depends on the ability to seek and consume foods while avoiding environmental threats. However, how evolutionarily conserved threat detection circuits modulate feeding is unknown. In mammals, feeding and threat assessment are strongly influenced by the parabrachial nucleus (PBN), a structure that responds to threats and inhibits feeding. Here, we report that the PBN receives dense inputs from two discrete neuronal populations in the bed nucleus of the stria terminalis (BNST), an extended amygdala structure that encodes affective information. Using a series of complementary approaches, we identify opposing BNST-PBN circuits that modulate neuropeptide-expressing PBN neurons to control feeding and affective states. These previously unrecognized neural circuits thus serve as potential nodes of neural circuitry critical for the integration of threat information with the intrinsic drive to feed.
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http://dx.doi.org/10.1126/sciadv.abd3666DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7909877PMC
February 2021

Cold-induced hyperphagia requires AgRP neuron activation in mice.

Elife 2020 12 15;9. Epub 2020 Dec 15.

UW Medicine Diabetes Institute, Department of Medicine, University of Washington, Seattle, United States.

To maintain energy homeostasis during cold exposure, the increased energy demands of thermogenesis must be counterbalanced by increased energy intake. To investigate the neurobiological mechanisms underlying this cold-induced hyperphagia, we asked whether agouti-related peptide (AgRP) neurons are activated when animals are placed in a cold environment and, if so, whether this response is required for the associated hyperphagia. We report that AgRP neuron activation occurs rapidly upon acute cold exposure, as do increases of both energy expenditure and energy intake, suggesting the mere perception of cold is sufficient to engage each of these responses. We further report that silencing of AgRP neurons selectively blocks the effect of cold exposure to increase food intake but has no effect on energy expenditure. Together, these findings establish a physiologically important role for AgRP neurons in the hyperphagic response to cold exposure.
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http://dx.doi.org/10.7554/eLife.58764DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7837681PMC
December 2020

Prepronociceptin-Expressing Neurons in the Extended Amygdala Encode and Promote Rapid Arousal Responses to Motivationally Salient Stimuli.

Cell Rep 2020 11;33(6):108362

Department of Psychiatry, University of North Carolina, Chapel Hill, NC 72599, USA; Neuroscience Center, University of North Carolina, Chapel Hill, NC 72599, USA; Neuroscience Curriculum, University of North Carolina, Chapel Hill, NC 72599, USA; Department of Cell Biology and Physiology, University of North Carolina, Chapel Hill, NC 72599, USA. Electronic address:

Motivational states consist of cognitive, emotional, and physiological components controlled by multiple brain regions. An integral component of this neural circuitry is the bed nucleus of the stria terminalis (BNST). Here, we identify that neurons within BNST that express the gene prepronociceptin (Pnoc) modulate rapid changes in physiological arousal that occur upon exposure to motivationally salient stimuli. Using in vivo two-photon calcium imaging, we find that Pnoc neuronal responses directly correspond with rapid increases in pupillary size when mice are exposed to aversive and rewarding odors. Furthermore, optogenetic activation of these neurons increases pupillary size and anxiety-like behaviors but does not induce approach, avoidance, or locomotion. These findings suggest that excitatory responses in Pnoc neurons encode rapid arousal responses that modulate anxiety states. Further histological, electrophysiological, and single-cell RNA sequencing data reveal that Pnoc neurons are composed of genetically and anatomically identifiable subpopulations that may differentially tune rapid arousal responses to motivational stimuli.
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http://dx.doi.org/10.1016/j.celrep.2020.108362DOI Listing
November 2020

Imaging stress.

Neurobiol Stress 2020 Nov 13;13:100228. Epub 2020 May 13.

Center of Excellence for Stress and Mental Health, VA San Diego Healthcare System and Department of Psychiatry, University of California San Diego, San Diego, CA, USA.

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http://dx.doi.org/10.1016/j.ynstr.2020.100228DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7276484PMC
November 2020

The Complex Role of Nociceptin Signaling in Stress: Clarity Through Neuroimaging?

Biol Psychiatry 2020 03;87(6):489-491

Center for Neurobiology of Addiction, Pain, and Emotion, University of Washington, Seattle, Washington; Department of Anesthesiology, University of Washington, Seattle, Washington. Electronic address:

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http://dx.doi.org/10.1016/j.biopsych.2020.01.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7875195PMC
March 2020

Battery-free, lightweight, injectable microsystem for in vivo wireless pharmacology and optogenetics.

Proc Natl Acad Sci U S A 2019 10 10;116(43):21427-21437. Epub 2019 Oct 10.

Department of Materials Science and Engineering, Northwestern University, Evanston, IL 60208;

Pharmacology and optogenetics are widely used in neuroscience research to study the central and peripheral nervous systems. While both approaches allow for sophisticated studies of neural circuitry, continued advances are, in part, hampered by technology limitations associated with requirements for physical tethers that connect external equipment to rigid probes inserted into delicate regions of the brain. The results can lead to tissue damage and alterations in behavioral tasks and natural movements, with additional difficulties in use for studies that involve social interactions and/or motions in complex 3-dimensional environments. These disadvantages are particularly pronounced in research that demands combined optogenetic and pharmacological functions in a single experiment. Here, we present a lightweight, wireless, battery-free injectable microsystem that combines soft microfluidic and microscale inorganic light-emitting diode probes for programmable pharmacology and optogenetics, designed to offer the features of drug refillability and adjustable flow rates, together with programmable control over the temporal profiles. The technology has potential for large-scale manufacturing and broad distribution to the neuroscience community, with capabilities in targeting specific neuronal populations in freely moving animals. In addition, the same platform can easily be adapted for a wide range of other types of passive or active electronic functions, including electrical stimulation.
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http://dx.doi.org/10.1073/pnas.1909850116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6815115PMC
October 2019

Neurobiological links between stress and anxiety.

Neurobiol Stress 2019 Nov 13;11:100191. Epub 2019 Aug 13.

Neurocentre Magendie, INSERM 1215, Université de Bordeaux, 146 Rue Léo Saignat, 33000 Bordeaux, France.

Stress and anxiety have intertwined behavioral and neural underpinnings. These commonalities are critical for understanding each state, as well as their mutual interactions. Grasping the mechanisms underlying this bidirectional relationship will have major clinical implications for managing a wide range of psychopathologies. After briefly defining key concepts for the study of stress and anxiety in pre-clinical models, we present circuit, as well as cellular and molecular mechanisms involved in either or both stress and anxiety. First, we review studies on divergent circuits of the basolateral amygdala (BLA) underlying emotional valence processing and anxiety-like behaviors, and how norepinephrine inputs from the locus coeruleus (LC) to the BLA are responsible for acute-stress induced anxiety. We then describe recent studies revealing a new role for mitochondrial function within the nucleus accumbens (NAc), defining individual trait anxiety in rodents, and participating in the link between stress and anxiety. Next, we report findings on the impact of anxiety on reward encoding through alteration of circuit dynamic synchronicity. Finally, we present work unravelling a new role for hypothalamic corticotropin-releasing hormone (CRH) neurons in controlling anxiety-like and stress-induce behaviors. Altogether, the research reviewed here reveals circuits sharing subcortical nodes and underlying the processing of both stress and anxiety. Understanding the neural overlap between these two psychobiological states, might provide alternative strategies to manage disorders such as post-traumatic stress disorder (PTSD).
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http://dx.doi.org/10.1016/j.ynstr.2019.100191DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6712367PMC
November 2019

Wireless optofluidic brain probes for chronic neuropharmacology and photostimulation.

Nat Biomed Eng 2019 08 5;3(8):655-669. Epub 2019 Aug 5.

School of Electrical Engineering, Korea Advanced Institute of Science and Technology, Daejeon, Republic of Korea.

Both in vivo neuropharmacology and optogenetic stimulation can be used to decode neural circuitry, and can provide therapeutic strategies for brain disorders. However, current neuronal interfaces hinder long-term studies in awake and freely behaving animals, as they are limited in their ability to provide simultaneous and prolonged delivery of multiple drugs, are often bulky and lack multifunctionality, and employ custom control systems with insufficiently versatile selectivity for output mode, animal selection and target brain circuits. Here, we describe smartphone-controlled, minimally invasive, soft optofluidic probes with replaceable plug-like drug cartridges for chronic in vivo pharmacology and optogenetics with selective manipulation of brain circuits. We demonstrate the use of the probes for the control of the locomotor activity of mice for over four weeks via programmable wireless drug delivery and photostimulation. Owing to their ability to deliver both drugs and photopharmacology into the brain repeatedly over long time periods, the probes may contribute to uncovering the basis of neuropsychiatric diseases.
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http://dx.doi.org/10.1038/s41551-019-0432-1DOI Listing
August 2019

A Paranigral VTA Nociceptin Circuit that Constrains Motivation for Reward.

Cell 2019 07;178(3):653-671.e19

Departments of Anesthesiology, Division of Basic Research, Anatomy and Neurobiology, and Washington University Pain Center, Washington University School of Medicine, St. Louis, MO, USA; Department of Biomedical Engineering, Washington University in St. Louis, St. Louis, MO 63130, USA; Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, MO, USA; Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA. Electronic address:

Nociceptin and its receptor are widely distributed throughout the brain in regions associated with reward behavior, yet how and when they act is unknown. Here, we dissected the role of a nociceptin peptide circuit in reward seeking. We generated a prepronociceptin (Pnoc)-Cre mouse line that revealed a unique subpopulation of paranigral ventral tegmental area (pnVTA) neurons enriched in prepronociceptin. Fiber photometry recordings during progressive ratio operant behavior revealed pnVTA neurons become most active when mice stop seeking natural rewards. Selective pnVTA neuron ablation, inhibition, and conditional VTA nociceptin receptor (NOPR) deletion increased operant responding, revealing that the pnVTA nucleus and VTA NOPR signaling are necessary for regulating reward motivation. Additionally, optogenetic and chemogenetic activation of this pnVTA nucleus caused avoidance and decreased motivation for rewards. These findings provide insight into neuromodulatory circuits that regulate motivated behaviors through identification of a previously unknown neuropeptide-containing pnVTA nucleus that limits motivation for rewards.
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http://dx.doi.org/10.1016/j.cell.2019.06.034DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7001890PMC
July 2019

Achieving tight control of a photoactivatable Cre recombinase gene switch: new design strategies and functional characterization in mammalian cells and rodent.

Nucleic Acids Res 2019 09;47(17):e97

Department of Pharmacology, University of Colorado School of Medicine, Aurora, CO 80045, USA.

A common mechanism for inducibly controlling protein function relies on reconstitution of split protein fragments using chemical or light-induced dimerization domains. A protein is split into fragments that are inactive on their own, but can be reconstituted after dimerization. As many split proteins retain affinity for their complementary half, maintaining low activity in the absence of an inducer remains a challenge. Here, we systematically explore methods to achieve tight regulation of inducible proteins that are effective despite variation in protein expression level. We characterize a previously developed split Cre recombinase (PA-Cre2.0) that is reconstituted upon light-induced CRY2-CIB1 dimerization, in cultured cells and in vivo in rodent brain. In culture, PA-Cre2.0 shows low background and high induced activity over a wide range of expression levels, while in vivo the system also shows low background and sensitive response to brief light inputs. The consistent activity stems from fragment compartmentalization that shifts localization toward the cytosol. Extending this work, we exploit nuclear compartmentalization to generate light-and-chemical regulated versions of Cre recombinase. This work demonstrates in vivo functionality of PA-Cre2.0, describes new approaches to achieve tight inducible control of Cre DNA recombinase, and provides general guidelines for further engineering and application of split protein fragments.
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http://dx.doi.org/10.1093/nar/gkz585DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6753482PMC
September 2019

Loss of CELF6 RNA binding protein impairs cocaine conditioned place preference and contextual fear conditioning.

Genes Brain Behav 2019 09 19;18(7):e12593. Epub 2019 Jun 19.

Department of Genetics, Washington University School of Medicine, St. Louis, Missouri.

In addition to gene expression differences in distinct cell types, there is substantial post-transcriptional regulation driven in part by RNA binding proteins (RBPs). Loss-of-function RBP mutations have been associated with neurodevelopmental disorders, such as Fragile-X syndrome and syndromic autism. Work performed in animal models to elucidate the influence of neurodevelopmental disorder-associated RBPs on distinct behaviors has showed a connection between normal post-transcriptional regulation and conditioned learning. We previously reported cognitive inflexibility in a mouse model null for the RBP CUG-BP, Elav-like factor 6 (CELF6), which we also found to be associated with human autism. Specifically, these mice failed to potentiate exploratory hole-poking behavior in response to familiarization to a rewarding stimuli. Characterization of Celf6 gene expression showed high levels in monoaminergic populations such as the dopaminergic midbrain populations. To better understand the underlying behavioral disruption mediating the resistance to change exploratory behavior in the holeboard task, we tested three hypotheses: Does Celf6 loss lead to global restricted patterns of behavior, failure of immediate response to reward or failure to alter behavior in response to reward (conditioning). We found the acute response to reward was intact, yet Celf6 mutant mice exhibited impaired conditioned learning to both reward and aversive stimuli. Thus, we found that the resistance to change by the Celf6 mutant in the holeboard was most parsimoniously explained as a failure of conditioning, as the mice had blunted responses even to potent rewarding stimuli such as cocaine. These findings further support the role of RBPs in conditioned learning.
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http://dx.doi.org/10.1111/gbb.12593DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7059558PMC
September 2019

NOP Receptor Signaling Cascades.

Handb Exp Pharmacol 2019 ;254:131-139

Department of Anesthesiology and Pain Medicine, Center for Neurobiology of Addiction, Pain, and Emotion, University of Washington, Seattle, WA, USA.

The nociceptin/orphanin FQ (N/OFQ) peptide (NOP) receptor is a G protein-coupled receptor with wide distribution throughout the peripheral and central nervous system. Similar to other opioid receptors, NOP receptors couple to intracellular second messengers and regulatory proteins to affect biological systems. In this chapter, we review the current literature for NOP signaling cascades including their role as classic GPCRs, the investigation of their kinase and arrestin signaling pathways, and the importance of examining biased signaling to critically evaluate the therapeutic potential of novel NOP agonists.
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http://dx.doi.org/10.1007/164_2019_215DOI Listing
July 2019

A Motivational and Neuropeptidergic Hub: Anatomical and Functional Diversity within the Nucleus Accumbens Shell.

Neuron 2019 05;102(3):529-552

Center for Neurobiology of Addiction, Pain, and Emotion, University of Washington, Seattle, WA 98195, USA; Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98195, USA; Department of Pharmacology, University of Washington, Seattle, WA 98195, USA. Electronic address:

The mesocorticolimbic pathway is canonically known as the "reward pathway." Embedded within the center of this circuit is the striatum, a massive and complex network hub that synthesizes motivation, affect, learning, cognition, stress, and sensorimotor information. Although striatal subregions collectively share many anatomical and functional similarities, it has become increasingly clear that it is an extraordinarily heterogeneous region. In particular, the nucleus accumbens (NAc) medial shell has repeatedly demonstrated that the rules dictated by more dorsal aspects of the striatum do not apply or are even reversed in functional logic. These discrepancies are perhaps most easily captured when isolating the functions of various neuromodulatory peptide systems within the striatum. Endogenous peptides are thought to play a critical role in modulating striatal signals to either amplify or dampen evoked behaviors. Here we describe the anatomical-functional backdrop upon which several neuropeptides act within the NAc to modulate behavior, with a specific emphasis on nucleus accumbens medial shell and stress responsivity. Additionally, we propose that, as the field continues to dissect fast neurotransmitter systems within the NAc, we must also provide considerable contextual weight to the roles local peptides play in modulating these circuits to more comprehensively understand how this important subregion gates motivated behaviors.
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http://dx.doi.org/10.1016/j.neuron.2019.03.003DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6528838PMC
May 2019

Central Amygdala Prepronociceptin-Expressing Neurons Mediate Palatable Food Consumption and Reward.

Neuron 2019 06 24;102(5):1037-1052.e7. Epub 2019 Apr 24.

Bowles Center for Alcohol Studies, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA; Department of Pharmacology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC 27599, USA. Electronic address:

Food palatability is one of many factors that drives food consumption, and the hedonic drive to feed is a key contributor to obesity and binge eating. In this study, we identified a population of prepronociceptin-expressing cells in the central amygdala (Pnoc) that are activated by palatable food consumption. Ablation or chemogenetic inhibition of these cells reduces palatable food consumption. Additionally, ablation of Pnoc cells reduces high-fat-diet-driven increases in bodyweight and adiposity. Pnoc neurons project to the ventral bed nucleus of the stria terminalis (vBNST), parabrachial nucleus (PBN), and nucleus of the solitary tract (NTS), and activation of cell bodies in the central amygdala (CeA) or axons in the vBNST, PBN, and NTS produces reward behavior but did not promote feeding of palatable food. These data suggest that the Pnoc network is necessary for promoting the reinforcing and rewarding properties of palatable food, but activation of this network itself is not sufficient to promote feeding.
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http://dx.doi.org/10.1016/j.neuron.2019.03.037DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6750705PMC
June 2019

Defining circuit-specific roles for G protein-coupled receptors in aversive learning.

Curr Opin Behav Sci 2019 Apr 8;26:146-156. Epub 2019 Feb 8.

Department of Anesthesiology and Pain Medicine, University of Washington, Seattle, WA 98195.

The encoding of negative valence in response to noxious stimuli/experiences and in turn, the behavioral representation of negative affective states is essential for survival. Recent advances in neuroscience have determined multiple sites of neural plasticity and key circuits of connectivity across these regions in mediating aversive behavior. G protein-coupled receptors (GPCRs), owing to their neuromodulatory role, are especially important to refining our understanding of the molecular substrates involved in these circuits. In this review, we will focus on recent, contemporary findings that explore neural circuit-specific roles for neurotransmitter/peptide GPCRs and the importance of using novel approaches to illuminate the molecular mechanisms central to aversive learning.
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http://dx.doi.org/10.1016/j.cobeha.2019.01.002DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7449380PMC
April 2019

Agonist-selective NOP receptor phosphorylation correlates in vitro and in vivo and reveals differential post-activation signaling by chemically diverse agonists.

Sci Signal 2019 03 26;12(574). Epub 2019 Mar 26.

Institute of Pharmacology and Toxicology, Jena University Hospital, Friedrich Schiller University Jena, Drackendorfer Str. 1, Jena 07747, Germany.

Agonists of the nociceptin/orphanin FQ opioid peptide (NOP) receptor, a member of the opioid receptor family, are under active investigation as novel analgesics, but their modes of signaling are less well characterized than those of other members of the opioid receptor family. Therefore, we investigated whether different NOP receptor ligands showed differential signaling or functional selectivity at the NOP receptor. Using newly developed phosphosite-specific antibodies to the NOP receptor, we found that agonist-induced NOP receptor phosphorylation occurred primarily at four carboxyl-terminal serine (Ser) and threonine (Thr) residues, namely, Ser, Ser, Thr, and Ser, and proceeded with a temporal hierarchy, with Ser as the first site of phosphorylation. G protein-coupled receptor kinases 2 and 3 (GRK2/3) cooperated during agonist-induced phosphorylation, which, in turn, facilitated NOP receptor desensitization and internalization. A comparison of structurally distinct NOP receptor agonists revealed dissociation in functional efficacies between G protein-dependent signaling and receptor phosphorylation. Furthermore, in NOP-eGFP and NOP-eYFP mice, NOP receptor agonists induced multisite phosphorylation and internalization in a dose-dependent and agonist-selective manner that could be blocked by specific antagonists. Our study provides new tools to study ligand-activated NOP receptor signaling in vitro and in vivo. Differential agonist-selective NOP receptor phosphorylation by chemically diverse NOP receptor agonists suggests that differential signaling by NOP receptor agonists may play a role in NOP receptor ligand pharmacology.
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http://dx.doi.org/10.1126/scisignal.aau8072DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6934085PMC
March 2019

Pain-Induced Negative Affect Is Mediated via Recruitment of The Nucleus Accumbens Kappa Opioid System.

Neuron 2019 05 13;102(3):564-573.e6. Epub 2019 Mar 13.

Department of Anesthesiology, Washington University Pain Center, Washington University in St. Louis, School of Medicine, St. Louis, MO 63110, USA; Department of Neuroscience, Washington University in St. Louis, St. Louis, MO 63110, USA. Electronic address:

Negative affective states affect quality of life for patients suffering from pain. These maladaptive emotional states can lead to involuntary opioid overdose and many neuropsychiatric comorbidities. Uncovering the mechanisms responsible for pain-induced negative affect is critical in addressing these comorbid outcomes. The nucleus accumbens (NAc) shell, which integrates the aversive and rewarding valence of stimuli, exhibits plastic adaptations in the presence of pain. In discrete regions of the NAc, activation of the kappa opioid receptor (KOR) decreases the reinforcing properties of rewards and induces aversive behaviors. Using complementary techniques, we report that in vivo recruitment of NAc shell dynorphin neurons, acting through KOR, is necessary and sufficient to drive pain-induced negative affect. Taken together, our results provide evidence that pain-induced adaptations in the kappa opioid system within the NAc shell represent a functional target for therapeutic intervention that could circumvent pain-induced affective disorders. VIDEO ABSTRACT.
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http://dx.doi.org/10.1016/j.neuron.2019.02.029DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6509001PMC
May 2019

Pain Wars: A New Hope.

Neuron 2018 12;100(6):1280-1282

Department of Anesthesiology, Division of Basic Research, Washington University School of Medicine, St. Louis, MO, USA; Center for the Neurobiology of Addiction, Pain, and Emotion, Departments of Anesthesiology and Pain Medicine, Department of Pharmacology, University of Washington, Seattle, WA, USA. Electronic address:

Nociceptin opioid peptide receptor agonists interact with mu-opioid receptor agonists for pain relief. A new study by Ding et al. (2018) examines a bifunctional nociceptin- and mu-opioid receptor agonist, AT-121, that provides analgesia without physiological side effects or abuse liability, offering a promising new hope toward better analgesics.
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http://dx.doi.org/10.1016/j.neuron.2018.11.045DOI Listing
December 2018

In vivo detection of optically-evoked opioid peptide release.

Elife 2018 09 3;7. Epub 2018 Sep 3.

Department of Anesthesiology, Division of Basic Research, Washington University School of Medicine, St. Louis, United States.

Though the last decade has seen accelerated advances in techniques and technologies to perturb neuronal circuitry in the brain, we are still poorly equipped to adequately dissect endogenous peptide release in vivo. To this end we developed a system that combines in vivo optogenetics with microdialysis and a highly sensitive mass spectrometry-based assay to measure opioid peptide release in freely moving rodents.
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http://dx.doi.org/10.7554/eLife.36520DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6135606PMC
September 2018

Nicotine aversion is mediated by GABAergic interpeduncular nucleus inputs to laterodorsal tegmentum.

Nat Commun 2018 07 13;9(1):2710. Epub 2018 Jul 13.

Committee on Neurobiology, University of Chicago, Chicago, IL, 60637, USA.

Nicotine use can lead to dependence through complex processes that are regulated by both its rewarding and aversive effects. Recent studies show that aversive nicotine doses activate excitatory inputs to the interpeduncular nucleus (IPN) from the medial habenula (MHb), but the downstream targets of the IPN that mediate aversion are unknown. Here we show that IPN projections to the laterodorsal tegmentum (LDTg) are GABAergic using optogenetics in tissue slices from mouse brain. Selective stimulation of these IPN axon terminals in LDTg in vivo elicits avoidance behavior, suggesting that these projections contribute to aversion. Nicotine modulates these synapses in a concentration-dependent manner, with strong enhancement only seen at higher concentrations that elicit aversive responses in behavioral tests. Optogenetic inhibition of the IPN-LDTg connection blocks nicotine conditioned place aversion, suggesting that the IPN-LDTg connection is a critical part of the circuitry that mediates the aversive effects of nicotine.
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http://dx.doi.org/10.1038/s41467-018-04654-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6045623PMC
July 2018

Endogenous and Exogenous Opioids in Pain.

Annu Rev Neurosci 2018 07 31;41:453-473. Epub 2018 May 31.

Department of Anesthesiology, Perioperative and Pain Medicine, Stanford University, Palo Alto, California 94304, USA; email:

Opioids are the most commonly used and effective analgesic treatments for severe pain, but they have recently come under scrutiny owing to epidemic levels of abuse and overdose. These compounds act on the endogenous opioid system, which comprises four G protein-coupled receptors (mu, delta, kappa, and nociceptin) and four major peptide families (β-endorphin, enkephalins, dynorphins, and nociceptin/orphanin FQ). In this review, we first describe the functional organization and pharmacology of the endogenous opioid system. We then summarize current knowledge on the signaling mechanisms by which opioids regulate neuronal function and neurotransmission. Finally, we discuss the loci of opioid analgesic action along peripheral and central pain pathways, emphasizing the pain-relieving properties of opioids against the affective dimension of the pain experience.
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http://dx.doi.org/10.1146/annurev-neuro-080317-061522DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6428583PMC
July 2018

Molecular and Functional Sex Differences of Noradrenergic Neurons in the Mouse Locus Coeruleus.

Cell Rep 2018 05;23(8):2225-2235

Department of Genetics and Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA. Electronic address:

Preclinical work has long focused on male animals, though biological sex clearly influences risk for certain diseases, including many psychiatric disorders. Such disorders are often treated by drugs targeting the CNS norepinephrine system. Despite roles for noradrenergic neurons in behavior and neuropsychiatric disease models, their molecular characterization has lagged. We profiled mouse noradrenergic neurons in vivo, defining over 3,000 high-confidence transcripts expressed therein, including druggable receptors. We uncovered remarkable sex differences in gene expression, including elevated expression of the EP3 receptor in females-which we leverage to illustrate the behavioral and pharmacologic relevance of these findings-and of Slc6a15 and Lin28b, both major depressive disorder (MDD)-associated genes. Broadly, we present a means of transcriptionally profiling locus coeruleus under baseline and experimental conditions. Our findings underscore the need for preclinical work to include both sexes and suggest that sex differences in noradrenergic neurons may underlie behavioral differences relevant to disease.
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http://dx.doi.org/10.1016/j.celrep.2018.04.054DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6070358PMC
May 2018

Non-canonical Opioid Signaling Inhibits Itch Transmission in the Spinal Cord of Mice.

Cell Rep 2018 Apr;23(3):866-877

Center for the Study of Itch, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Anesthesiology, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Psychiatry, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Developmental Biology, Washington University School of Medicine, St. Louis, MO 63110, USA. Electronic address:

Chronic itch or pruritus is a debilitating disorder that is refractory to conventional anti-histamine treatment. Kappa opioid receptor (KOR) agonists have been used to treat chronic itch, but the underlying mechanism remains elusive. Here, we find that KOR and gastrin-releasing peptide receptor (GRPR) overlap in the spinal cord, and KOR activation attenuated GRPR-mediated histamine-independent acute and chronic itch in mice. Notably, canonical KOR-mediated G signaling is not required for desensitizing GRPR function. In vivo and in vitro studies suggest that KOR activation results in the translocation of Ca-independent protein kinase C (PKC)δ from the cytosol to the plasma membrane, which in turn phosphorylates and inhibits GRPR activity. A blockade of phospholipase C (PLC) in HEK293 cells prevented KOR-agonist-induced PKCδ translocation and GRPR phosphorylation, suggesting a role of PLC signaling in KOR-mediated GRPR desensitization. These data suggest that a KOR-PLC-PKCδ-GRPR signaling pathway in the spinal cord may underlie KOR-agonists-induced anti-pruritus therapies.
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http://dx.doi.org/10.1016/j.celrep.2018.03.087DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5937707PMC
April 2018

Contemporary strategies for dissecting the neuronal basis of neurodevelopmental disorders.

Neurobiol Learn Mem 2019 11 14;165:106835. Epub 2018 Mar 14.

Departmentof Anesthesiology, Division of Basic Research, Washington University School of Medicine, St. Louis, MO 63110, United States; Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110, United States; Department of Psychiatry, Washington University School of Medicine, St. Louis, MO 63110, United States; Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, MO 63110, United States; Washington University Pain Center, Washington University School of Medicine, St. Louis, MO 63110, United States. Electronic address:

Great efforts in clinical and basic research have shown progress in understanding the neurobiological mechanisms of neurodevelopmental disorders, such as autism, schizophrenia, and attention-deficit hyperactive disorders. Literature on this field have suggested that these disorders are affected by the complex interaction of genetic, biological, psychosocial and environmental risk factors. However, this complexity of interplaying risk factors during neurodevelopment has prevented a complete understanding of the causes of those neuropsychiatric symptoms. Recently, with advances in modern high-resolution neuroscience methods, the neural circuitry analysis approach has provided new solutions for understanding the causal relationship between dysfunction of a neural circuit and behavioral alteration in neurodevelopmental disorders. In this review we will discuss recent progress in developing novel optogenetic and chemogenetic strategies to investigate neurodevelopmental disorders.
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http://dx.doi.org/10.1016/j.nlm.2018.03.015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6138573PMC
November 2019

Wireless optoelectronic photometers for monitoring neuronal dynamics in the deep brain.

Proc Natl Acad Sci U S A 2018 02 29;115(7):E1374-E1383. Epub 2018 Jan 29.

Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801;

Capabilities for recording neural activity in behaving mammals have greatly expanded our understanding of brain function. Some of the most sophisticated approaches use light delivered by an implanted fiber-optic cable to optically excite genetically encoded calcium indicators and to record the resulting changes in fluorescence. Physical constraints induced by the cables and the bulk, size, and weight of the associated fixtures complicate studies on natural behaviors, including social interactions and movements in environments that include obstacles, housings, and other complex features. Here, we introduce a wireless, injectable fluorescence photometer that integrates a miniaturized light source and a photodetector on a flexible, needle-shaped polymer support, suitable for injection into the deep brain at sites of interest. The ultrathin geometry and compliant mechanics of these probes allow minimally invasive implantation and stable chronic operation. In vivo studies in freely moving animals demonstrate that this technology allows high-fidelity recording of calcium fluorescence in the deep brain, with measurement characteristics that match or exceed those associated with fiber photometry systems. The resulting capabilities in optical recordings of neuronal dynamics in untethered, freely moving animals have potential for widespread applications in neuroscience research.
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http://dx.doi.org/10.1073/pnas.1718721115DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5816195PMC
February 2018

Tuning Biased GPCR Signaling for Physiological Gain.

Cell 2017 11;171(5):989-991

Department of Anesthesiology, Division of Basic Research, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Neuroscience, Washington University School of Medicine, St. Louis, MO 63110, USA; Department of Psychiatry, Washington University School of Medicine, St. Louis, MO 63110, USA; Division of Biology and Biomedical Sciences, Washington University School of Medicine, St. Louis, MO 63110, USA; Washington University Pain Center, Washington University School of Medicine, St. Louis, MO 63110, USA. Electronic address:

Effective and safe doses of opiate painkillers, like morphine, can be limited by respiratory depression. Schmid et al. (2017) now present a quantitative method to design ligands and correlate GPCR signaling bias to the dose separation between therapeutic and adverse effects in animals.
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http://dx.doi.org/10.1016/j.cell.2017.10.046DOI Listing
November 2017