Biology subjects

Gowrishankar, R.

Publications and source records attributed to Gowrishankar, R..

6 recordsLinked to original sources

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↗

bioRxiv2023

Kappa Opioid Receptor Antagonism Rescues Genetic Perturbation of Dopamine Homeostasis: Molecular, Physiological and Behavioral Consequences

Aberrant dopamine (DA) signaling is implicated in schizophrenia, bipolar disorder (BPD), autism spectrum disorder (ASD), substance use disorder, and attention-deficit/hyperactivity disorder (ADHD). Treatment of these disorders remains inadequate, as exemplified by the therapeutic use of d-amphetamine and methylphenidate for the treatment of ADHD, agents with high abuse liability. In search for an improved and non-addictive therapeutic approach for the treatment of DA-linked disorders, we utilized a preclinical mouse model expressing the human DA transporter (DAT) coding variant DAT Val559, previously identified in individuals with ADHD, ASD, or BPD. DAT Val559, like several other disease-associated variants of DAT, exhibits anomalous DA efflux (ADE) that can be blocked by d-amphetamine and methylphenidate. Kappa opioid receptors (KORs) are expressed by DA neurons and modulate DA release and clearance, suggesting that targeting KORs might also provide an alternative approach to normalizing DA-signaling disrupted by perturbed DAT function. Here we demonstrate that KOR stimulation leads to enhanced surface trafficking and phosphorylation of Thr53 in wildtype DAT, effects achieved constitutively by the Val559 mutant. Moreover, these effects can be rescued by KOR antagonism of DAT Val559 in ex vivo preparations. Importantly, KOR antagonism also corrected in vivo DA release as well as sex-dependent behavioral abnormalities observed in DAT Val559 mice. Given their low abuse liability, our studies with a construct valid model of human DA associated disorders reinforce considerations of KOR antagonism as a pharmacological strategy to treat DA associated brain disorders.

neuroscience↗

bioRxiv2023

An Open-Source Platform for Head-Fixed Operant and Consummatory Behavior

Head-fixed behavioral experiments in rodents permit unparalleled experimental control, precise measurement of behavior, and concurrent modulation and measurement of neural activity. Here we present OHRBETS (Open-Source Head-fixed Rodent Behavioral Experimental Training System; pronounced Orbitz), a low-cost, open-source ecosystem of hardware and software to flexibly pursue the neural basis of a variety of motivated behaviors. Head-fixed mice tested with OHRBETS displayed operant conditioning for caloric reward that replicates core behavioral phenotypes observed during freely moving conditions. OHRBETS also permits for optogenetic intracranial self-stimulation under positive or negative operant conditioning procedures and real-time place preference behavior, like that observed in freely moving assays. In a multi-spout brief-access consumption task, mice displayed licking as a function of concentration of sucrose, quinine, and sodium chloride, with licking modulated by homeostatic or circadian influences. Finally, to highlight the functionality of OHRBETS, we measured mesolimbic dopamine signals during the multi-spout brief-access task that display strong correlations with relative solution value and magnitude of consumption. All designs, programs, and instructions are provided freely online. This customizable ecosystem enables replicable operant and consummatory behaviors and can be incorporated with methods to perturb and record neural dynamics in vivo. Impact StatementA customizable open-source hardware and software ecosystem for conducting diverse head-fixed behavioral experiments in mice.

neuroscience↗

bioRxiv2022

Medial accumbens shell spiny projection neurons encode relative reward preference

Medial nucleus accumbens shell (mNAcSh) is a critical brain region for driving motivated behaviors. Despite this well-established role, the underlying reward processing of individual neurons, circuits and cell-types within mNAcSh remains largely unknown. Here, we leverage deep brain 2-photon calcium imaging through endoscopic lenses to record mNAcSh spiny projection neuron (SPN) ensemble responses to rewards of different concentrations and to reward-predictive cues across cue-reward learning. Reward responses were found to be heterogeneous and particularly differentiated based on reward concentration and cell type. A large subpopulation of reward-excited enkephalinergic SPNs were found to be specifically recruited during consumption of high concentration, unpreferred reward. A major enkephalinergic efferent projection from mNAcSh to ventral pallidum (VP) was also found to be recruited to high concentration but unpreferred reward and to causally drive low positive reward preference. Enkephalin and dynorphinergic SPNs in mNAcSh distinctly represent rewards of different preference and propagate distinct signals through efferent projections to drive consummatory behavior.

neuroscience↗

bioRxiv2021

Sex and Circuit Specific Dopamine Transporter Regulation Underlies Unique Behavioral Trajectories of Functional SLC6A3 Coding Variation

Virtually all neuropsychiatric disorders display sex differences in prevalence, age of onset, and/or clinical symptomology. In sex-biased disorders, one sex is often suggested to harbor protective mechanisms, rendering them resilient to genetic and/or environmental risk factors. Here, we demonstrate sex-biased molecular, pharmacological and behavioral effects induced by the dopamine (DA) transporter (DAT) coding variant Ala559Val, previously identified in subjects diagnosed with the male-biased disorders attention-deficit/hyperactivity disorder and autism spectrum spectrum disorder. In DAT Val559 mice, we identified sex differences in response to psychostimulants, social behavior, and cognitive traits. We reveal a sex by circuit dissociation in D2-type autoreceptor (D2AR) regulation of DAT wherein D2AR-dependent DAT phosphorylation and trafficking, detectable in the male dorsal striatum, does not occur in females but rather is a property of the ventral striatum, predicting sex-specific changes in behavior. Consequently, we found that a subset of altered behaviors can be normalized using the D2R antagonist sulpiride in DAT Val559 mice. Our studies provide a cogent example of how sex shapes the behavioral trajectory of DA signaling perturbations and identify the sex-dependent, locality-selective capacity for D2AR regulation of DAT as an unrecognized determinant of this trajectory. Rather than identifying one sex as resilient, we find that sex can drive alterative behavioral patterns from shared signaling perturbations that may result in females being underreported. Our work underscores the utility of model systems to study the functional intrusions of rare genetic variation to gain insights into pathways underlying normal and perturbed trait domains associated with common neuropsychiatric conditions.

neuroscience↗

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↗