Biology subjects

Samineni, V. K.

Publications and source records attributed to Samineni, V. K..

12 recordsLinked to original sources

bioRxiv2025

A Neural Circuit for Modular Gating of Organ Somatosensation

End-organs such as the bladder rely on a delicate balance between internal urgency and voluntary restraint. However, the specific spinal circuits coordinating these functions remain poorly defined. Here, we identify a genetically defined population of lumbosacral spinal interneurons marked by Trpc4 expression that gate bladder sensory input and regulate micturition reflexes. Single-cell transcriptomics and in situ physiology reveal molecularly distinct Trpc4 subtypes. Functional manipulation reveals that Trpc4 neurons are essential for coordinating bladder-sphincter activity and gating visceral pain. Their ablation leads to bladder hypersensitivity and voiding dysfunction, while targeted activation reverses these maladaptive states. Circuit tracing reveals convergence of primary afferent and descending brainstem inputs onto Trpc4 neurons. These findings establish Trpc4 interneurons are critical for bladder sensory-motor integration and extend classical spinal gating models to encompass visceral pain and organ reflex control.

neuroscience↗

bioRxiv2025

Central Amygdala Neuronal Ensembles Coordinate Visceral Pain and Its Affective Behaviors

Visceral pain and its affective component associated with cystitis remain poorly understood. Here, we delineate the role of central amygdala (CeA) neuronal ensembles in encoding and modulating cystitis-induced bladder pain and its affective components. Utilizing a multidisciplinary approach combining behavioral assays, optogenetic manipulations, whole-cell electrophysiology, and activity-dependent genetic labeling, we identified functionally discrete CeA subpopulations that are selectively recruited during bladder inflammation. Bidirectional optogenetic modulation of these ensembles produced opposing effects on nocifensive and anxiety-like behaviors, indicating their causal involvement. Single-nucleus RNA sequencing of FosTRAP-labeled neurons revealed distinct transcriptional signatures associated with inflammatory activation. Integrating electrophysiological and transcriptomic data, we demonstrate that cystitis drives cell type-specific adaptations in CeA circuits. These findings provide mechanistic insight and uncover a molecularly and functionally defined CeA ensemble that orchestrates the sensory and affective dimensions of visceral pain.

neuroscience↗

bioRxiv2025

A brainstem-thalamic circuitry for affective-motivational responses to cold pain

The medial thalamus is crucial for the sensory and affective-motivational responses to chronic pain. However, a mechanistic understanding of how the distinct subnuclei of the medial thalamus mediate behavioral responses to pain remains lacking. Taking advantage of intersectional viral genetics, chemogenetics, optogenetics, in-vivo imaging, and ex-vivo physiology, we reveal that the neurons in the parafascicular (PF) nuclei of the medial thalamus receive monosynaptic inputs from the lateral parabrachial nuclei (LPBN) in mice. LPBN is an essential nucleus in the ascending pain pathway, receiving projections from the dorsal horn of the spinal cord. The PF neurons downstream of LPBN (PFpost-LPBN) are nociceptive, sensitized by peripheral neuropathy, acutely aversive, and, when activated, drive both sensory and affective-motivational responses to cold pain. In contrast, the LPBN target neurons in the intralaminar centromedian thalamus (CMpost-LPBN), another nociceptive nucleus of the medial thalamus, are primarily involved in the affective-motivational aspects of pain. Together, we reveal that the LPBN, through two closely related thalamic nuclei, influences behavior in mice with cold hypersensitivity due to peripheral neuropathies.

neuroscience↗

bioRxiv2025

Convergent state-control of endogenous opioid analgesia

Pain is a dynamic and nonlinear experience shaped by injury and contextual factors, including expectations of future pain or relief1. While {micro} opioid receptors are central to the analgesic effects of opioid drugs, the endogenous opioid neurocircuitry underlying pain and placebo analgesia remains poorly understood. The ventrolateral column of the posterior periaqueductal gray is a critical hub for nociception and endogenous analgesia mediated by opioid signaling2. However, significant gaps remain in understanding the cell-type identities, the sub-second neural dynamics involved in pain modulation, the role of endogenous peptide neuromodulators, and the contextual factors influencing these processes. Using spatial mapping with single-nuclei RNA sequencing of pain-active neurons projecting to distinct long-range brain targets, alongside cell type-specific and activity-dependent genetic tools for in vivo optical recordings and modulation of neural activity and opioid peptide release, we identified a functional dichotomy in the ventrolateral periaqueductal gray. Neurons expressing {micro} opioid receptors encode active nociceptive states, whereas enkephalin-releasing neurons drive pain relief during recovery from injury, in response to learned fear predictions, and during placebo analgesia. Finally, by leveraging the functional effects of placebo analgesia, we used direct optogenetic activation of vlPAG enkephalin neurons to drive opioid peptide release, resulting in a robust reduction in pain. These findings show that diverse need states converge on a shared midbrain circuit that releases endogenous opioids with high spatiotemporal precision to suppress nociceptive activity and promote analgesia.

neuroscience↗

bioRxiv2024

Transcriptomic landscape of mammalian ventral pallidum at single-cell resolution

The ventral pallidum (VP) is critical for motivated behaviors. While contemporary work has begun to elucidate the functional diversity of VP neurons, the molecular heterogeneity underlying this functional diversity remains incompletely understood. We used snRNA-seq and in situ hybridization to define the transcriptional taxonomy of VP cell types in mice, macaques, and baboons. We found transcriptional conservation between all three species, within the broader neurochemical cell types. Unique dopaminoceptive and cholinergic subclusters were identified and conserved across both primate species but had no homolog in mice. This harmonized consensus VP cellular atlas will pave the way for understanding the structure and function of the VP and identified key neuropeptides, neurotransmitters, and neuro receptors that could be targeted within specific VP cell types for functional investigations. TeaserGenetic identity of ventral pallidum cell types is conserved across rodents and primates at the transcriptional level

neuroscience↗

bioRxiv2024

Norepinephrine Signals Through Astrocytes To Modulate Synapses

AbstractLocus coeruleus (LC)-derived norepinephrine (NE) drives network and behavioral adaptations to environmental saliencies by reconfiguring circuit connectivity, but the underlying synapse-level mechanisms are elusive. Here, we show that NE remodeling of synaptic function is independent from its binding on neuronal receptors. Instead, astrocytic adrenergic receptors and Ca2+ dynamics fully gate the effect of NE on synapses as the astrocyte-specific deletion of adrenergic receptors and three independent astrocyte-silencing approaches all render synapses insensitive to NE. Additionally, we find that NE suppression of synaptic strength results from an ATP-derived and adenosine A1 receptor-mediated control of presynaptic efficacy. An accompanying study from Chen et al. reveals the existence of an analogous pathway in the larval zebrafish and highlights its importance to behavioral state transitions. Together, these findings fuel a new model wherein astrocytes are a core component of neuromodulatory systems and the circuit effector through which norepinephrine produces network and behavioral adaptations, challenging an 80-year-old status quo.

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↗

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↗

bioRxiv2021

Cellular, Circuit and Transcriptional Framework for Modulation of Itch in the Central Amygdala

Itch is an unpleasant sensation that elicits robust scratching and active avoidance. However, the identity of the cells and neural circuits that organize this information remains elusive. Here we show the necessity and sufficiency of itch-activated neurons in the central amygdala (CeA) for both itch sensation and active avoidance. Further, we show that itch-activated CeA neurons play important roles in itch-related comorbidities, including anxiety-like behaviors, but not in some aversive and appetitive behaviors previously ascribed to CeA neurons. RNA-sequencing of itch-activated CeA neurons identified several differentially expressed genes as well as potential key signaling pathways in regulating pruritis. Finally, viral tracing experiments demonstrate that these neurons send a critical projection to the periaqueductal gray to mediate modulation of itch. These findings reveal a cellular and circuit signature of CeA neurons orchestrating behavioral and affective responses to pruritus in mice.

neuroscience↗

bioRxiv2018

Cell type-specific modulation of sensory and affective components of itch in the periaqueductal gray

Itch is a distinct aversive sensation that elicits a strong urge to scratch. Despite recent advances in our understanding of the peripheral basis of itch, we know very little regarding how central neural circuits modulate acute and chronic itch processing. Here we establish the causal contributions of defined periaqueductal gray (PAG) neuronal populations in itch modulation. Chemogenetic manipulations demonstrate bidirectional modulation of scratching by neurons in the PAG. Fiber photometry studies show that activity of GABAergic and glutamatergic neurons in the PAG is modulated in an opposing manner during chloroquine-evoked scratching. Furthermore, activation of PAG GABAergic neurons or inhibition of glutamatergic neurons resulted in attenuation of scratching in both acute and chronic pruritis. Surprisingly, PAG GABAergic neurons, but not glutamatergic neurons, seem to encode the aversive component of itch. Thus, the PAG represents a neuromodulatory hub that regulates both the sensory and affective aspects of acute and chronic itch.

neuroscience↗

bioRxiv2017

Macrophage-to-sensory neuron crosstalk mediated by Angiotensin II type-2 receptor elicits neuropathic pain

Peripheral nerve damage initiates a complex series of cellular and structural processes that culminate in chronic neuropathic pain. Our study defines local angiotensin signaling via activation of the Angiotensin II (Ang II) type-2 receptor (AT2R) on macrophages as the critical trigger of neuropathic pain. An AT2R-selective antagonist attenuates neuropathic, but not inflammatory pain hypersensitivity in mice, and requires the cell damage-sensing ion channel transient receptor potential family-A member-1 (TRPA1). Mechanical and cold pain hypersensitivity that are characteristic of neuropathic conditions can be attenuated by chemogenetic depletion of peripheral macrophages and AT2R-null hematopoietic cell transplantation. Our findings show no AT2R expression in mouse or human sensory neurons, rather AT2R expression and activation in macrophages triggers production of reactive oxygen/nitrogen species, which trans-activate TRPA1 on sensory neurons. Our study defines the precise neuro-immune crosstalk underlying nociceptor sensitization at the site of nerve injury. This form of cell-to-cell signaling represents a critical peripheral mechanism for chronic neuropathic pain, and therefore identifies multiple analgesic targets.

neuroscience↗

bioRxiv2017

Optogenetic silencing of primary afferents reduces evoked and ongoing bladder pain

Patients with interstitial cystitis/bladder pain syndrome (IC/BPS) suffer from chronic pain that severely affects quality of life. Although the underlying pathophysiology is not well understood, inhibition of bladder sensory afferents temporarily relieves pain. Here, we explored the possibility that optogenetic inhibition of bladder sensory afferents could be used to modulate bladder pain. Specifically, we chose to study the role of Nav1.8+ sensory afferents before and after induction of a mouse model of bladder pain. The light-activated inhibitory proton pump Archaerhodopsin (Arch) was expressed under control of the Nav1.8+ promoter to selectively silence these neurons. Optically silencing Nav1.8+ afferents significantly blunted the evoked visceromotor response to bladder distension and led to small but significant changes in bladder function. To study of the role of these fibers in freely behaving mice, we developed a fully implantable, flexible, wirelessly powered optoelectronic system for the long-term manipulation of bladder afferent expressed opsins. We found that optogenetic inhibition of Nav1.8+ fibers reduced both ongoing pain and evoked cutaneous hypersensitivity in the context of cystitis, but had no effect in uninjured, naive mice. These results suggest that selective optogenetic silencing of bladder afferents may represent a potential future therapeutic strategy for the treatment of bladder pain.

neuroscience↗