Biology subjects

De Koninck, Y.

Publications and source records attributed to De Koninck, Y..

16 recordsLinked to original sources

bioRxiv2026

Superficial spinal Tac1-lineage neurons are polymodal nociceptive

Tac1-lineage neurons in the spinal dorsal horn have been implicated in coping behavior in response to sustained noxious stimuli, but their developmental origin, cellular heterogeneity, and functional contribution remain incompletely understood. Here, we characterized the molecular identity, developmental trajectory, electrophysiological properties, and sensory responses of spinal Tac1-lineage neurons. In adults, Tac1-lineage neurons comprised a heterogeneous population of excitatory and inhibitory interneurons and excitatory projection neurons distributed across the superficial dorsal horn. In contrast, at embryonic day 16.5, Tac1-lineage neurons in laminae I/IIo were exclusively projection neurons, revealing a marked developmental transition in the composition of the Tac1 lineage. Electrophysiological recordings from spinal cord slices further demonstrated substantial functional heterogeneity, with most Tac1-lineage neurons exhibiting phasic or single-spike firing and smaller populations displaying tonic or reluctant firing. In vivo calcium imaging in anesthetized mice revealed prominent responses to noxious mechanical and thermal stimulation. Interestingly, Tac1-lineage neurons used distinct strategies to encode cold and heat intensity. Together, these findings reveal pronounced developmental and functional heterogeneity within the Tac1 lineage and demonstrate that adult Tac1-lineage neurons are predominately polymodal nociceptive.

neuroscience↗

bioRxiv2026

Spinotrode: long-term intraspinal electrophysiological recordings to unravel dorsal horn neuron dynamics in behaving mice

Recording single-unit neural activity in the spinal cord in freely moving rodents is crucial for understanding spinal network dynamics but remains challenging due to specific biomechanical constraints. So far, the vast majority of studies have been conducted in anesthetized or restrained animals, limiting the correlation of neuronal activity with naturalistic behaviours. Here we introduce the Spinotrode, a vertebral implant able to stably record signals (over several weeks) at the single-cell level in the bilateral dorsal horns of adult mice. It is engineered to minimize postural constraints and interrogate spinal activity during sensory stimulation and motor behaviours. No functional impairment or tissue damage was apparent. Spinotrode recordings allowed identification of distinct functional types of neurons associated with paw withdrawal, revealed dorsal horn activity during locomotor behaviour distinct from proprioception and touch, and uncovered contralateral sensory activation upon nociceptive reflex responses, which forces reassessment of data obtained in anesthetized animals.

neuroscience↗

bioRxiv2026

Multimodal transcriptomics and calcium imaging reveal a novel subset of polymodal nociceptors expressing the interleukin 1 receptor in mice

We previously established that sensory neurons in the mouse dorsal root ganglia (DRG) express a functional receptor for the proinflammatory cytokine interleukin (IL)-1. We also demonstrated that deletion of the IL-1 receptor type 1 gene, Il1r1, in TRPV1-expressing (+) neurons prevented pain in models of chronic inflammatory diseases such as multiple sclerosis, rheumatoid arthritis and osteoarthritis. Here, we found a marked sex difference in the abundance of IL-1R1+ neurons, which represented approximately 10% of all DRG neurons in females but only 5% in males. However, male mice exhibited stronger, longer-lasting mechanical hypersensitivity than females after IL-1{beta} injection into the cerebrospinal fluid. In vivo calcium imaging revealed that IL-1{beta}- responsive DRG neurons responded to cutaneous mechanical and capsaicin stimulation. By integrating spatial transcriptomics with single-cell RNA sequencing (scRNA-Seq), we identified a gene signature uniquely marking IL-1R1+ neurons, including genes such as Ada, Cysltr2, Gpr139, Htr1a, Htr1f, Il31ra, Nppb, Npy2r, Nts, P2rx2, Pde4c, and Sst, with Ada and Sst validated at the protein level. Omics analysis revealed that IL-1R1+ DRG neurons form a subset of non-peptidergic type 3 (NP3) sensory neurons, which are linked to inflammatory pain and itch. However, Il1r1 deletion did not affect itch responses to serotonin, histamine, or chloroquine, and these mediators failed to induce calcium activity in IL-1{beta}-responsive DRG neurons. Finally, scRNA-seq identified several genes upregulated in NP3 neurons after IL-1{beta} injection, including Alkal2, Bdnf, and Lcn2, associated with chronic inflammatory pain. Thus, our study unveils novel markers for IL-1R1+ nociceptors and reaffirms their selective role in inflammatory pain.

neuroscience↗

bioRxiv2026

Differential regulation of KCC2 function, trafficking, and degradation by Ca2+-dependent signaling pathways

Regulation of the K+-Cl- cotransporter KCC2 is a critical determinant of the efficacy of inhibition in the central nervous system and KCC2 hypofunction appears at the root of several neurological disorders. Both BDNF-TrkB and NMDAR signaling regulate KCC2, but how they interact remains unknown. Here we show that these two signaling pathways act synergistically to differentially modulate KCC2 function and expression through post-translational regulation, via distinct Ca2+ signalling modes. Blocking ryanodine-dependent intracellular Ca2+ release prevented TrkB-, but not NMDAR-mediated downregulation. TrkB-signalling in absence of NMDAR activation modulated KCC2 function but not expression. In contrast, NMDAR activation induced KCC2 internalization dependent on extracellular Ca2+ influx. In turn, calpain-mediated KCC2 degradation, but not internalization, required Ca2+ influx through voltage-gated Ca2+ channels. While TrkB-activation potentiated the effect of NMDAR on KCC2, the reverse was not true. Yet, strong NMDAR activation was sufficient to cause TrkB-independent KCC2 downregulation. Finally, prolonged, but not short-term inhibition of KCC2 activity caused NMDAR-dependent KCC2 downregulation. These findings reveal, for the first time, that a co-transporter function can be regulated through other means than membrane expression: through a continuum of interwoven synergistic processes, from function to internalization to degradation, scaling with time and stimulus strength.

neuroscience↗

bioRxiv2026

A neuronal pathway for the supraspinal relay of warm and cool sensation

Cutaneous thermosensation is a fundamental sense allowing discrimination of external temperature changes and driving adaptive responses essential for survival and well-being. This sensory process begins with the activation of peripheral thermoreceptors, which encode the quality and intensity of thermal stimuli into neuronal activity that is further integrated by spinal cord circuits and relayed to supraspinal centres through the anterolateral tract (ALT). While classical experiments identified thermal responsive ALT neurons in the superficial spinal dorsal horn, the functional logic of innocuous temperature relay remains poorly understood. We show that, in mice, the majority of Phox2a-lineage lamina I ALT are selectively tuned to innocuous warming or cooling, and receive direct inputs from peripheral thermoreceptors. Their genetic ablation, chemogenetic or optogenetic manipulation impaired temperature discrimination. Our findings contrast with the previous finding that the majority of ALT neurons being mechano- and thermo-nociceptive and provide novel evidence for the existence of a large ensemble of genetically defined warming- and cooling- responsive ALT neurons. The large representation of innocuous temperature in supraspinal-relaying ALT neurons indicates substantial spinal amplification of thermal information and underscores the importance of innocuous thermosensation in the ascending sensory pathway.

neuroscience↗

bioRxiv2025

Nucleus raphe magnus serotonin neurons bidirectionally control spinal mechanical pain transmission

BackgroundNoxious stimuli are conveyed to and integrated in the dorsal horn of the spinal cord (DHSC) before being transmitted to supraspinal centers, where pain perception is generated. Descending pathways from the brainstem dynamically modulate this integration, either facilitating or inhibiting nociceptive information based on physiological, emotional, genetic and environmental factors. Serotonergic neurons in the nucleus raphe magnus (NRM), activating different spinal 5-HT receptors, exert bidirectional control, both facilitatory and inhibitory, but the underlying mechanisms of this control remain unclear. MethodsWe investigated in adult mice, the NRM serotonergic modulation of nociception using imaging, behavioral, pharmacological, electrophysiological, chemogenetic and optogenetic approaches. ResultsWe have demonstrated that the action of serotonergic neurons in the NRM on spinal nociceptive transmission depends on their activation pattern, which targets different spinal 5-HT receptors likely associated with different spinal microcircuits. Serotonergic neurons of the NRM exert a tonic analgesic effect mediated by 5-HT2c receptor. Low increase in 5-HT activity leads to an increased analgesia through spinal inhibitory interneurons expressing 5-HT2c and 5-HT2A receptors. Finally, prolonged stimulation of serotonergic neurons led to hyperalgesia mediated by 5-HT3 receptor. Comparison of 5-HT receptors in spinal tissue from mice and human shows that 5-HT2c receptor has a very high expression level, comparable between both species. ConclusionsThese results propose a model of bidirectional action of serotonin neurons on nociceptive transmission depending on their level of activity and show that 5-HT2c receptor is the main mediator of serotonin-induced analgesia.

neuroscience↗

bioRxiv2025

Decreased KCC2 expression in the human spinal dorsal horn associated with chronic pain and long-term opioid use

Loss of GABAergic and glycinergic inhibitory efficacy in the spinal dorsal horn is associated with neuropathic pain and opioid-induced hyperalgesia in rodent models. Downregulation of the KCC2 chloride extrusion transporter is a key mechanism underlying this decreased inhibitory efficacy, but to-date there is no evidence supporting or opposing this hypothesis in humans. Here we demonstrate that KCC2 expression is decreased in superficial dorsal horn neurons of organ donors who died with a documented history of pain, or of long-term opioid use. We show profoundly decreased KCC2 dorsal horn membrane expression in a primary cohort associated with either chronic pain or opioid use, and in a replication cohort of mixed chronic pain and opioid use history. These results show that decreased dorsal horn inhibitory efficacy likely promotes chronic pain in humans and support the development of therapeutics augmenting KCC2 function as a treatment for chronic pain and opioid use disorders.

neuroscience↗

bioRxiv2024

Distinct Excitability Properties of Cardiac Calbindin Neurons: Identifying a Unique Neuronal Population

The intrinsic cardiac nervous system is a complex system that plays a critical role in the regulation of cardiac physiological parameters and has been shown to contribute to cardiac arrhythmias. To date, several types of neurons with distinct neurochemical and electrophysiological phenotypes have been identified. However, no study has correlated the neurochemical phenotype to a specific electrophysiological behavior. Calbindin-D28k, a calcium binding protein, is expressed in numerous cardiac neurons. Given that changes in neuronal excitability have been associated with arrhythmia susceptibility and that calbindin expression has been associated with modulations of neuronal excitability, our objective is to assess whether the cardiac calbindin neuronal population has specific properties that could be involved in cardiac modulation and arrhythmias. By using a Cre-Lox mouse model to specifically target calbindin neurons with a fluorescent reporter, we characterized the neurochemical and the electrophysiological phenotype of this cardiac neuronal population. Calbindin neurons exhibit a specific neurochemical profile and a larger soma with shorter neurite length compared to other neurons. This was combined with a distinct electrophysiological signature characterized by a lower excitability with a predominantly phasic profile associated to a lower N-type calcium current density. These properties resemble to the cardiac neuronal remodeling observed in pathologies such as type II diabetes and heart failure. Therefore, we believe that this specific neuronal population deserves investigations in the context of these pathologies.

physiology↗

bioRxiv2023

Chronic pain mediated changes in the appetitive value of affective touch in mice

The existence of skin-to-brain circuits for rewarding gentle touch highlight its critical nature across species. However, this gentle affective touch is not always appetitive and can produce aversion or negative affect in disorders such as chronic pain. Sensory neurons expressing the protein MrgprB4 detect gentle stroking in mice and their activation of these neurons known to be positively reinforcing. Here we assess whether activation of channelrhodopsin (ChR2) expressing MrgprB4 afferents signal positively valenced tactile information and whether this is altered in models of chronic pain. We further interrogate how this this sensory information is reflected in the downstream circuits recruited. Optogenetic activation of MrgprB4 lineage afferents was found to be appetitive in control and capsaicin sensitized mice but not nerve injured mice, indicating that the appetitive value is diminished in neuropathic pain. Remarkably, this appetitive value was partially recovered in male nerve injured mice by treatment with the analgesic gabapentin. These behavioral changes were also accompanied by different patterns of neuronal activity throughout the brain, including altered activation of sites that receive direct projections from the spinal cord between sham and nerve injured mice. Together, these findings highlight the plastic nature of these affective tactile circuits under pathological conditions.

neuroscience↗

bioRxiv2023

Gut microbiota promotes pain in fibromyalgia

Fibromyalgia is a chronic syndrome characterized by widespread pain in the absence of evident tissue injury or pathology, making it one of the most mysterious chronic pain conditions. Despite affecting 2-4% of the population, primarily women1, the cause and underlying mechanisms of fibromyalgia remain elusive, and effective targeted treatments are currently unavailable. The gut microbiota of women with fibromyalgia differs from healthy controls2,3. However, it is unknown whether changes in gut microbiota have a causal role in mediating pain and other symptoms of fibromyalgia. Here, we show that fecal microbiota transplantation (FMT) from individuals with fibromyalgia, but not from healthy controls, into germ-free mice induces persistent pain hypersensitivity. FMT from fibromyalgia patients led to a reduction in intraepidermal nerve fiber density and alterations in the peripheral immune profile, and induced activation of spinal microglia, which contributed to the development of pain in mice. Notably, the pain hypersensitivity in mice that were administered microbiota from fibromyalgia patients resolved after FMT from healthy controls. Consistent with these findings, an open-label pilot study showed that transplanting microbiota from healthy individuals to humans with fibromyalgia alleviated pain and reduced overall symptom severity. Thus, altered gut microbiota has a causal role in fibromyalgia pain, highlighting it as a promising target for therapeutic interventions.

neuroscience↗

bioRxiv2023

Chronic optogenetic activation of hippocampal pyramidal neurons replicates the proteome footprint of Alzheimer's disease-like pathology

Neuronal overexcitability can elicit synaptic changes, leading to neuronal hyperactivity and abnormal neural circuit processing. Such network disruption impairs neuronal function and survival, initiating neurodegeneration and Alzheimers disease (AD). Yet, the sequence of synaptic changes resulting from excessive neuronal activity remains elusive. We employed optogenetics to induce sustained neuronal hyperactivity in the hippocampi of wild-type and AD-like 5xFAD mice. Surprisingly, after a month of daily optogenetic stimulation, the proteomic profiles of photoactivated wild-type and 5xFAD mice exhibited remarkable similarity. Proteins involved in translation, protein transport, autophagy, and notably in the AD pathology were upregulated in wild-type mice. Conversely, both glutamatergic and GABAergic synaptic proteins were downregulated. These hippocampal proteomic and signaling alterations in wild-type mice resulted in spatial memory loss and augmented A{beta}42 secretion. Collectively, these findings indicate that sustained neuronal hyperactivity alone replicates proteome changes seen in AD-linked mutant mice. Therefore, prolonged neuronal hyperactivity may contribute to synaptic transmission disruption, memory deficits and the neurodegenerative process associated with AD.

neuroscience↗

bioRxiv2023

KCC2 as a novel biomarker and therapeutic target for motoneuron degenerative disease

Hyperexcitability in cells throughout the corticospinal tract is a presymptomatic feature of amyotrophic lateral sclerosis (ALS) associated with lethal motor degeneration 1-6. Disinhibition is a possible cause of this hyperexcitability, potentially implicating the central nervous system-specific potassium-chloride cotransporter, KCC2, a core regulator of the strength of GABAergic neurotransmission linked to several neurological disorders 7-11. Here, we show that KCC2 is downregulated in the membrane of motor cortex neurons from post-mortem SOD1-, C9orf72- and sporadic ALS is patients. Increased protein levels of KCC2 were found in plasma and cerebral spinal fluid of ALS patients and mice harbouring the SOD1*G93A mutation. Longitudinal analysis of disease progression in both SOD1*G93A and Prp-TDP43*A315T mice revealed a decrease of KCC2 membrane levels in cortical and spinal motor neurons which were already present at the presymptomatic phase. Using KCC2-enhancing compounds, CLP290 and prochlorperazine (PCPZ) restored KCC2 membrane expression and function, delayed motor deficit onset, and extended lifespan up to two months in mutant mice. Human-derived neurons differentiated from iPSC harbouring the SOD1*G93A mutation displayed KCC2 deficits which PCPZ treatment rescued. Acute administration of KCC2 enhancers restored chloride transport in presymptomatic and symptomatic mice and reversed motor neuron hyperexcitability in awake behaving mutant mice. These findings identify KCC2 as both an early biomarker and a disease-modifying therapeutic target for ALS.

neuroscience↗

bioRxiv2023

Assessing spontaneous sensory neuron activity using in vivo calcium imaging

Heightened spontaneous activity in sensory neurons is often reported in individuals living with chronic pain. It is possible to study this activity in rodents using electrophysiology, but these experiments require great skill and can be prone to bias. Here, we have examined whether in vivo calcium imaging with GCaMP6s can be used as an alternative approach. We show that spontaneously active calcium transients can be visualised in the fourth lumbar dorsal root ganglion (L4 DRG) via in vivo imaging in a mouse model of pain. Application of lidocaine to the nerve, between the inflamed site and the DRG, silenced spontaneous firing and revealed the true baseline level of calcium for spontaneously active neurons. We used this data to train a machine leaning algorithm to predict when a neuron is spontaneously active. We show that our algorithm is accurate in two different models of pain: intraplantar Complete Freunds Adjuvant and antigen-induced arthritis, with accuracies of 90.0% +/-1.2 and 85.9 % +/-2.1, respectively, assessed against visual inspection by an experienced observer. The algorithm can also detect neuronal activity in imaging experiments generated in a different lab using a different microscope configuration (Accuracy = 94.0 % +/2.2). We provide a Google Colaboratory Notebook to allow anyone easy access to this novel tool, for assessment of peripheral neuron activity in their own calcium imaging setups.

neuroscience↗

bioRxiv2021

Sexual dimorphism in a neuronal mechanism of spinal hyperexcitability across rodent and human models of pathological pain

The prevalence and severity of many chronic pain syndromes differ across sex, and recent studies have identified differences in immune signalling within spinal nociceptive circuits as a potential mediator. Although it has been proposed that sex-specific pain mechanisms converge once they reach neurons within the superficial dorsal horn (SDH), direct investigations using rodent and human preclinical pain models have been lacking. Here, we discovered that in the Freunds Adjuvant in vivo model of inflammatory pain, where both male and female rats display tactile allodynia, a pathological coupling between KCC2-dependent disinhibition and NMDA receptor potentiation within SDH neurons was observed in male but not female rats. Unlike males, the neuroimmune mediator, BDNF, failed to downregulate inhibitory signalling elements (KCC2 and STEP61) and upregulate excitatory elements (pFyn, GluN2B, and pGluN2B) in female rats, resulting in no effect of ex vivo BDNF on synaptic NMDA receptor responses in female lamina I neurons. Importantly, this sex difference in spinal pain processing was conserved from rodents to humans. As in rodents, ex vivo spinal treatment with BDNF downregulated markers of disinhibition and upregulated markers of facilitated excitation in SDH neurons from male but not female human organ donors. Ovariectomy in female rats recapitulated the male pathological pain neuronal phenotype, with BDNF driving a coupling between disinhibition and NMDA receptor potentiation in adult lamina I neurons following the prepubescent elimination of sex hormones in females. This discovery of sexual dimorphism in a central neuronal mechanism of chronic pain across species provides a foundational step towards a better understanding and treatment for pain in both sexes.

neuroscience↗

bioRxiv2021

A female-specific role for Calcitonin Gene-Related Peptide (CGRP) in rodent pain models

We aimed to investigate a potentially sexually dimorphic role of Calcitonin Gene-Related Peptide (CGRP) in mouse and rat models of pain. Based on findings in migraine where CGRP has a preferential pain-promoting effect in female rodents, we hypothesized that CGRP antagonists and antibodies would attenuate pain sensitization more efficaciously in female than male mice and rats. In hyperalgesic priming induced by activation of interleukin 6 (IL-6) signaling, CGRP receptor antagonists, olcegepant and CGRP8-37, both given intrathecally, blocked and reversed hyperalgesic priming only in females. A monoclonal antibody against CGRP, given systemically, blocked priming specifically in female rodents but failed to reverse it. In the spared nerve injury (SNI) model, there was a transient effect of both CGRP antagonists, given intrathecally, on mechanical hypersensitivity in female mice only. Consistent with these findings, intrathecally applied CGRP caused a long-lasting, dose-dependent mechanical hypersensitivity in female mice but more transient effects in males. This CGRP-induced mechanical hypersensitivity was reversed by the KCC2 activator, CLP257 suggesting a role for anionic plasticity in the dorsal horn in the pain-promoting effects of CGRP in females. In spinal dorsal horn slices, CGRP shifted GABAA reversal potentials to significantly more positive values but, again, only in female mice. Therefore, CGRP may regulate KCC2 expression and/or activity specifically in females. However, KCC2 hypofunction promotes mechanical pain hypersensitivity in both sexes because CLP257 alleviated hyperalgesic priming in male and female mice. We conclude that CGRP promotes pain plasticity in female mice, but has a limited impact in male mice. Significance StatementThe majority of patients impacted by chronic pain are women. Mechanistic studies in rodents are creating a clear picture that molecular events promoting chronic pain are different in male and female animals. Far more is known about chronic pain mechanisms in male animals. We sought to build on recent evidence showing that CGRP is a more potent and efficacious promoter of headache pain in female than in male rodents. To test this, we used hyperalgesic priming and the spared nerve injury (SNI) neuropathic pain models in mice. Our findings show a clear sex dimorphism wherein CGRP promotes pain in female but not male mice. Our work suggests that CGRP antagonists could be tested for efficacy in women for a broader variety of pain conditions.

neuroscience↗

bioRxiv2017

Native KCC2 Interactome Reveals PACSIN1 As A Critical Regulator Of Synaptic Inhibition

KCC2 is a neuron-specific K+-Cl- cotransporter essential for establishing the Cl- gradient required for hyperpolarizing inhibition. KCC2 is highly localized to excitatory synapses where it regulates spine morphogenesis and AMPA receptor confinement. Aberrant KCC2 function contributes to numerous human neurological disorders including epilepsy and neuropathic pain. Using unbiased functional proteomics, we identified the KCC2-interactome in the mouse brain to determine KCC2-protein interactions that regulate KCC2 function. Our analysis revealed that KCC2 interacts with a diverse set of proteins, and its most predominant interactors play important roles in postsynaptic receptor recycling. The most abundant KCC2 interactor is a neuronal endocytic regulatory protein termed PACSIN1 (SYNDAPIN1). We verified the PACSIN1-KCC2 interaction biochemically and demonstrated that shRNA knockdown of PACSIN1 in hippocampal neurons significantly increases KCC2 expression and hyperpolarizes the reversal potential for Cl-. Overall, our global native-KCC2 interactome and subsequent characterization revealed PACSIN1 as a novel and potent negative regulator of KCC2.

neuroscience↗