Biology subjects

Kalyanaraman, V.

Publications and source records attributed to Kalyanaraman, V..

5 recordsLinked to original sources

bioRxiv2026

The role of mu opioid receptors on excitatory and inhibitory neurons in the rostral ventromedial medulla in neuropathic pain

Descending projections from the brain to the spinal cord can regulate painful stimulus processing and are modulated by endogenous and exogenous opioids. We investigated the role of mu opioid receptors (MORs) in GABAergic vs. glutamatergic neurons of the rostral ventral medulla (RVM) in a mouse model of chronic neuropathic pain. We found that activating glutamatergic and GABAergic neurons in the RVM both result in antinociception [BC1.1]at baseline, but glutamatergic neurons enhance pain responses after nerve injury. [BC2.1]We then interrogated the role of RVM MOR signaling on neuropathic pain by using CRISPR/Cas9 to delete MOR in glutamatergic or GABAergic RVM neurons. We found that MOR knockout in glutamatergic and GABAergic RVM neurons precipitates early neuropathic pain onset with no effect on chronic pain intensity. These results suggest that RVM MOR signaling modulates hypersensitivity in the early phase of injury, but chronic neuropathic pain is largely independent of mu opioid receptor signaling.

neuroscience↗

bioRxiv2025

Reduced SK channel control of mesolimbic dopamine neuron firing drives reward seeking adaptations in chronic pain

Patients with chronic neuropathic pain typically experience affective symptoms that drive reduced quality of life and negatively impact pain management. Mesolimbic dopamine is necessary for reward valuation and learning, and the existence of a hypodopaminergic state has been proposed to underlie these affective symptoms of chronic pain. However, direct functional evidence for this hypodopaminergic state is lacking, and the mechanisms underlying its emergence over the acute to chronic pain transition are unknown. Here, we find a selective deficit in the ability of mesolimbic dopamine neurons to sustain burst firing, which is apparent uniquely at chronic timepoints following neuropathic injury. As a result, animals are unable to sustain effortful pursuit of rewards under conditions of high effort or time costs. Convergent biophysical modeling and experimental electrophysiology establish that in a spared nerve injury (SNI) model of chronic neuropathic pain, calcium-activated, small-conductance potassium (SK) channel function is impaired, resulting in lower peak firing and earlier entry into depolarization block of mesolimbic dopamine neurons. Critically, dopamine dependent reward learning, formation of cue-reward associations and locomotor activity remain intact, arguing against the interpretation of a generalized hypodopaminergic state. These results elucidate a circuit-level basis for selective motivational deficits emerging in chronic neuropathic pain.

neuroscience↗

bioRxiv2024

Projection-TAGs enable multiplex projection tracing and multi-modal profiling of projection neurons

Single-cell multiomic techniques have sparked immense interest in developing a comprehensive multi-modal map of diverse neuronal cell types and their brain-wide projections. However, investigating the complex wiring diagram, spatial organization, transcriptional, and epigenetic landscapes of brain-wide projection neurons is hampered by the lack of efficient and easily adoptable tools. Here we introduce Projection-TAGs, a retrograde AAV platform that allows multiplex tagging of projection neurons using RNA barcodes. By using Projection-TAGs, we performed multiplex projection tracing of the cortex and high-throughput single-cell profiling of the transcriptional and epigenetic landscapes of the cortical projection neurons in female mice. Projection-TAGs can be leveraged to obtain a snapshot of activity-dependent recruitment of distinct projection neurons and their molecular features in the context of a specific stimulus. Given its flexibility, usability, and compatibility, we envision that Projection-TAGs can be readily applied to build a comprehensive multi-modal map of brain neuronal cell types and their projections.

neuroscience↗

bioRxiv2023

Cell specific single viral vector CRISPR/Cas9 editing and genetically encoded tool delivery in the central and peripheral nervous systems

Gene manipulation strategies using germline knockout, conditional knockout, and more recently CRISPR/Cas9 are crucial tools for advancing our understanding of the nervous system. However, traditional gene knockout approaches can be costly and time consuming, may lack cell-type specificity, and can induce germline recombination. Viral gene editing presents and an exciting alternative to more rapidly study genes of unknown function; however, current strategies to also manipulate or visualize edited cells are challenging due to the large size of Cas9 proteins and the limited packaging capacity of adeno-associated viruses (AAVs). To overcome these constraints, we have developed an alternative gene editing strategy using a single AAV vector and mouse lines that express Cre-dependent Cas9 to achieve efficient cell-type specific editing across the nervous system. Expressing Cre-dependent Cas9 in specific cell types in transgenic mouse lines affords more space to package guide RNAs for gene editing together with Cre-dependent, genetically encoded tools to manipulate, map, or monitor neurons using a single virus. We validated this strategy with three commonly used tools in neuroscience: ChRonos, a channelrhodopsin, for manipulating synaptic transmission using optogenetics; GCaMP8f for recording Ca2+ transients using fiber photometry, and mCherry for anatomical tracing of axonal projections. We tested these tools in multiple brain regions and cell types, including GABAergic neurons in the nucleus accumbens (NAc), glutamatergic neurons projecting from the ventral pallidum (VP) to the lateral habenula (LHb), dopaminergic neurons in the ventral tegmental area (VTA), and parvalbumin (PV)-positive proprioceptive neurons in the periphery. This flexible approach should be useful to identify novel genes that affect synaptic transmission, circuit activity, or morphology with a single viral injection.

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↗