Biology subjects

Prescott, S. A.

Publications and source records attributed to Prescott, S. A..

18 recordsLinked to original sources

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

Physiologically realistic gamma activity produced in silico by weakening the PING attractor state

Network oscillations in the gamma (30-80 Hz) frequency range are implicated in many vital neurological functions. The seminal Pyramidal Interneuron Network Gamma (PING) mechanism produces gamma oscillations in silico with dynamics associated with a strongly attracting limit cycle. However, this activity is stronger and more stable than what is observed during in vivo gamma oscillations, which are transient and driven by sparse spiking activity. Here we describe multiple biophysically motivated changes degenerately driving PING-motivated networks to produce more realistic gamma activity. Increased heterogeneity, synapse-like noise, and a depolarized chloride reversal potential each destabilize the attractor represented by PING-driven activity: minor alterations disrupt the unrealistic organization of idealized PING oscillations, while larger changes entirely prevent this overly-synchronous network activity. This allows new dynamics to emerge: spontaneous and transient increases in gamma-band oscillatory power with excitatory cells only weakly entrained to the population rhythm. These features, better approximating the in vivo reality, mirror a systems oscillatory return to a stable focus following noise-induced perturbations. In fact, dynamical systems with both a stable focus and limit cycle are associated with Hopf bifurcations, which have been characterized in models of reciprocally connected excitatory and inhibitory neuronal populations as required for PING. We therefore propose a revised explanation for physiologically-realistic gamma activity that retains the key elements of the PING mechanism--strong reciprocal connection between excitatory and inhibitory neurons--but where biophysical phenomena bias the system towards damped oscillations around a weakly stable focus rather than a stable limit cycle. Significance StatementThe mechanisms underlying network oscillations at gamma frequencies have long been a focus of computational neuroscience. This research has produced idealized mechanisms yielding highly synchronous, active, and stable oscillations; however, in vivo gamma rhythms are transient with sparse neuronal spiking. Here, we illustrate minimal, biophysically relevant adjustments to established Pyramidal Interneuron Network Gamma (PING) networks that bridge a major divide between these traditional in silico systems and the experimental reality. Uncorrelated noisy input and a depolarized chloride reversal potential disrupt stereotyped PING rhythms and promote more realistic transient increased gamma power in network activity. This important step forward in the modeling of gamma oscillations illustrates how including biophysical detail can promote more realistic activity in computational systems.

neuroscience↗

bioRxiv2025

Functional implications of compartment-specific homeostatic regulation and the feasibility of independent local feedback signals

Neurons regulate their average firing rate by adjusting their synaptic strength and intrinsic excitability. Intracellular calcium is implicated as an error signal for both types of homeostatic regulation. Past studies have focused on global calcium but two properties cannot be independently regulated by one error signal. Here, we computationally tested the implications of local vs global feedback and the feasibility of local (compartment-specific) error signals based on spatially segregated calcium changes. Simulations in a simple two-compartment model confirmed that a perturbation applied to one compartment induces local compensation only if feedback is compartment-specific. Simulations in a biophysically detailed multicompartment model with realistic calcium handling confirmed that dendritic and somatic calcium signals remain relatively segregated and can, therefore, encode separate error signals. Strong perturbations (as often tested experimentally) triggered widespread compensation because local compensation was overwhelmed. Non-local compensation also occurred when the spatial segregation of calcium signals was weakened. Our results demonstrate the plausibility of compartment-specific feedback using calcium-based error signals. Furthermore, whereas local homeostatic regulation nullifies local perturbations through compensation within the affected compartment, non-local regulation causes widespread compensatory changes that, while restoring the neurons overall input-output relationship, distorts the input-output relationship of individual compartments, with potentially important consequences.

neuroscience↗

bioRxiv2025

Adaptation in somatosensory afferents improves rate and temporal coding of vibrotactile stimulus features

Adaptation is a common neural phenomenon wherein sustained stimulation evokes fewer action potentials (spikes) over time. Rather than simply reduce firing rate, adaptation may help neurons form better (i.e. more discriminable) representations of sensory input. To study effects of adaptation in low-threshold mechanoreceptors (LTMRs), we recorded single unit LTMR responses to 30-second-long vibrotactile stimuli with different intensities and frequencies applied to the hind paw of rats. To assess the impact of adaptation on somatosensory encoding, decoders were applied to the initial and late (adapted) phases of population-level responses to assess the decodability (discrimination) of stimulus intensity and frequency. Adaptation-mediated changes in the rate and timing (phase-locking) of spikes were quantified. Rate coding of stimulus intensity was improved by the nonuniform reduction in firing rate across responses to different stimuli, and across neurons. This improvement was absent in simulations with uniform reductions in firing rate, thus revealing the necessity of stimulus-dependent variability in adaptation effects. Spike timing (quantified as interspike intervals) remained highly informative about stimulus frequency throughout stimulation despite the progressive reduction in spike count over time. When the drop in spike count was accounted for, adaptation was found to improve temporal coding of stimulus frequency by increasing the precision of phase-locking. In other words, adaptation improved the precision of spike timing, and this increased the information about stimulus frequency conveyed by each spike. These results show that adaptation, by modulating spiking in different ways, can improve encoding of different stimulus features using different coding schemes. SIGNIFICANCE STATEMENTFiring rate adaptation refers to the progressive reduction in spiking during sustained stimulation. Adaptation is often ascribed to fatigue and could conceivably introduce ambiguity into neural representations by causing (the probability or timing of) spike generation to depend not only on the current stimulus, but also on past stimulation. By recording from rat primary somatosensory afferents during vibrotactile stimulation of the paw, we show that nonuniform adaptation across sets of afferents improves rate-based coding of stimulus intensity. We also show that adaptation improves spike timing (phase-locking to a periodic stimulus) which, in turn, improves temporal coding of stimulus frequency. These results demonstrate that early-stage adaptation improves somatosensory signals relayed centrally.

neuroscience↗

bioRxiv2025

Nociceptor clock genes control excitability and pain perception in a sex- and time-dependent manner

Nociception is critical for pain perception and survival and begins with the activation of nociceptors, specialized sensory neurons located in the dorsal root ganglia (DRGs). Both sex and circadian rhythms, governed by clock genes, seem to play a significant role in modulating pain perception. However, the potential interaction between circadian rhythms and sex differences in nociception at the peripheral level has been largely overlooked. Here, we first report that DRGs from mice express clock genes in a time- and sex-dependent manner. Using whole-cell recordings in whole-mounted DRGs and optogenetic stimulation of Nav1.8-expressing neurons, we demonstrate that male nociceptors exhibit reduced excitability during the night, while female nociceptor excitability remains stable across time points. Disruption of the core clock gene Bmal1 in Nav1.8-expressing neurons not only diminished nociceptor activity but also abolished the nighttime reduction in heat sensitivity, highlighting a pivotal role for the molecular clock in regulating nociception. Transcriptomic analyses, voltage-clamp recordings, and pharmacological experiments identified the voltage-gated chloride channel ClC-2, controlled by Bmal1, as a key mediator for the observed fluctuations in male nociceptor excitability. This work opens new avenues for chronobiology-inspired strategies in pain management tailored to sex-specific mechanisms.

neuroscience↗

bioRxiv2025

Spinal processing of spatiotemporally diverse tactile stimuli: Implications for allodynia and spinal cord stimulation

Touch is mistakenly perceived as painful when inhibition in the spinal dorsal horn (SDH) is weakened. Disinhibition un-gates a polysynaptic spinal circuit but why mechanical allodynia is predominantly evoked by certain stimuli, like dynamic brushing, remains unclear. To answer this, we incorporated receptive fields (RFs) into a computational model of the SDH to study the processing of stimuli with different spatiotemporal features. Broad stimuli normally suppress output spiking by engaging inhibition from the RF surround, but the efficacy of inhibition depends on the inputs temporal pattern. This is critical since excitatory and inhibitory spinal neurons are preferentially sensitive to synchronous and asynchronous input, respectively. Furthermore, spikes driven by synchronous input are resistant to feedforward inhibition. The combined results explain why broad dynamic touch (e.g. brush or vibration) evokes more allodynia than punctate static touch. Our results also show that asynchronous and spatially disordered input evoked by kilohertz-frequency spinal cord stimulation preferentially activates inhibitory neurons, thus explaining its anti-allodynic effects.

neuroscience↗

bioRxiv2024

Quantifying the contribution of somatosensory afferent types and changes therein to pain sensitivity using transcutaneous optogenetic stimulation in behaving mice

Optogenetics provides an unprecedented opportunity to delineate how different somatosensory afferents contribute to sensation, including pain. Afferents expressing channelrhodopsin-2 (ChR2) can be selectively activated by transcutaneous photostimuli applied to behaving mice. Despite care taken to precisely target expression of ChR2 to specific cell types, imprecise photostimulation has hindered quantitative optogenetic-based behavioral testing. Here, we used a robot to reproducibly apply transcutaneous optogenetic stimuli to the hind paw of mice while measuring nocifensive withdrawal. Different photostimulus waveforms (pulses and ramps) and response metrics (threshold and latency) were compared in mice expressing ChR2 in all afferents (Advillin-ChR2) or preferentially in nociceptors (NaV1.8-ChR2). CFA-induced inflammation caused withdrawal from ramped photostimuli to become faster relative to baseline and to vehicle-injected controls whereas pulsed photostimuli revealed a modest increase in threshold. Analgesia caused by NaV1.7 and 1.8 channel blockade was evident in both testing protocols. Overall, ramp-based testing was more effective and more efficient (i.e. required less time and total stimulation) than pulse-based testing. Electrophysiological measurements confirmed that inflammation increases nociceptor excitability without affecting phototransduction, and suggests that withdrawal latency depends on the number of nociceptors activated rather than how strongly each nociceptor is activated. Consistent with changes described in nociceptor somata, the behavioral consequences of peripherally blocking different voltage-gated sodium (NaV) channels showed that nociceptor axons normally rely on NaV1.8 but upregulate NaV1.7 after inflammation, with important clinical implications for drug efficacy. Collectively, these results demonstrate the utility of optogenetic pain testing when reproducibly delivered and strategically designed photostimuli are used.

neuroscience↗

bioRxiv2024

Impact of extracellular current flow on action potential propagation in myelinated axons

Myelinated axons conduct action potentials, or spikes, in a saltatory manner. Inward current caused by a spike occurring at one node of Ranvier spreads axially to the next node, which regenerates the spike when depolarized enough for voltage-gated sodium channels to activate, and so on. The rate at which this process progresses dictates the velocity at which the spike is conducted, and depends on several factors including axial resistivity and axon diameter that directly affect axial current. Here we show through computational simulations in modified double-cable axon models that conduction velocity also depends on extracellular factors whose effects can be explained by their indirect influence on axial current. Specifically, we show that a conventional double-cable model, with its outside layer connected to ground, transmits less axial current than a model whose outside layer is less absorptive. A more resistive barrier exists when an axon is packed tightly between other myelinated fibers, for example. We show that realistically resistive boundary conditions can significantly increase the velocity and energy efficiency of spike propagation, while also protecting against propagation failure. Certain factors like myelin thickness may be less important than typically thought if extracellular conditions are more resistive than normally considered. We also show how realistically resistive boundary conditions affect ephaptic interactions. Overall, these results highlight the unappreciated importance of extracellular conditions for axon function. SIGNIFICANCE STATEMENTAxons transmit spikes over long distances. Transmission is sped up and made more efficient by myelination, which allows spikes to jump between nodes of Ranvier without activating the intervening (internodal) membrane. Conduction velocity depends on the current transmitted axially from one node to the next. Axial current is known to depend on a variety of features intrinsic to myelinated fibers (e.g. axon diameter, myelin thickness) but we show here, through detailed biophysical simulations, how extracellular conditions (e.g. axon packing density) are also important. The effects ultimately boil down to the variety of paths current can follow, and the amount of current taking alternative paths rather than flowing directly from one node to the next.

neuroscience↗

bioRxiv2024

Encoding of vibrotactile stimuli by mechanoreceptors in rodent glabrous skin

Somatosensory coding in rodents has been mostly studied in the whisker system and hairy skin, whereas the function of low-threshold mechanoreceptors (LTMRs) in rodent glabrous skin has received scant attention, unlike in primates where glabrous skin has been the focus. The relative activation of different LTMR subtypes carries information about vibrotactile stimuli, as does the rate and temporal patterning of LTMR spikes. Rate coding depends on the probability of a spike occurring on each stimulus cycle (reliability) whereas temporal coding depends on the timing of spikes relative to the stimulus cycle (precision). Using in vivo extracellular recordings in rats and mice, we measured the reliability and precision of LTMR responses to different tactile stimuli including sustained pressure and vibration. Similar to other species, rodent LTMRs were separated into rapid-adapting (RA) or slow-adapting (SA) based on their response to sustained pressure. However, unlike the dichotomous frequency preference characteristic of RAI and RAII afferents in other species, rodent RAs fell along a continuum. Fitting generalized linear models (GLMs) to experimental data reproduced the reliability and precision of rodent RAs. The resulting model parameters highlight key mechanistic differences across the RA spectrum; specifically, the integration window of different RAs transitions from wide to narrow as tuning preferences across the population move from low to high frequencies. Our results show that rodent RAs can support both rate and temporal coding, but their heterogeneity suggests that co-activation patterns play a greater role in population coding than for dichotomously tuned primates RAs. Significance StatementOur sense of touch starts with activation of nerve fibres in the skin. Although response properties of various fibre types are well-established in other species (e.g. primates), quantitative characterization in rats and mice is limited. To fill this gap, we performed a comprehensive electrophysiological investigation into the coding properties of tactile fibres in rodent non-hairy skin and then simulated these fibres to explain differences in their responses. We show that rodent tactile fibres resemble those from other species, but that their heterogeneity at the population level may differ, with potentially important implications for encoding of touch. Simulations reveal intrinsic mechanisms that support this heterogeneity and provide a useful tool to explore somatosensation in rodents.

neuroscience↗

bioRxiv2023

Reproducible and fully automated testing of nocifensive behavior in mice

Pain in rodents is often inferred from their withdrawal to noxious stimulation, using the threshold stimulus intensity or response latency to quantify pain sensitivity. This usually involves applying stimuli by hand and measuring responses by eye, which limits reproducibility and throughput to the detriment of preclinical pain research. Here, we describe a device that standardizes and automates pain testing by providing computer-controlled aiming, stimulation, and response measurement. Optogenetic and thermal stimuli are applied to the hind paw using blue and infrared light, respectively. Red light delivered through the same light path assists with aiming, and changes in its reflectance off the paw are used to measure paw withdrawal latency with millisecond precision at a fraction of the cost and data processing associated with high-speed video. Using standard video, aiming was automated by training a neural network to recognize the paws and move the stimulator using motorized linear actuators. Real-time data processing allows for closed-loop control of stimulus initiation and termination. We show that stimuli delivered with this device are significantly less variable than hand-delivered stimuli, and that reducing stimulus variability is crucial for resolving stimulus-dependent variations in withdrawal. Slower stimulus waveforms whose stable delivery is made possible with this device reveal details not evident with typical photostimulus pulses. Moreover, the substage video reveals a wealth of "spontaneous" behaviors occurring before and after stimulation that can considered alongside withdrawal metrics to better assess the pain experience. Automation allows comprehensive testing to be standardized and carried out efficiently.

animal behavior and cognition↗

bioRxiv2023

Paresthesia during spinal cord stimulation depends on synchrony of dorsal column axon activation

Spinal cord stimulation (SCS) reduces chronic pain. Conventional (40-60 Hz) SCS engages spinal inhibitory mechanisms by activating low-threshold mechanoreceptive afferents with axons in the dorsal columns (DCs). But activating DC axons typically causes a buzzing sensation (paresthesia) that can be uncomfortable. Kilohertz-frequency (1-10 kHz) SCS produces analgesia without paresthesia and is thought, therefore, not to activate DC axons, leaving its mechanism unclear. Here we show in rats that kilohertz-frequency SCS activates DC axons but causes them to spike less synchronously than conventional SCS. Spikes desynchronize because axons entrain irregularly when stimulated at intervals shorter than their refractory period, a phenomenon we call overdrive desynchronization. Effects of overdrive desynchronization on evoked compound action potentials were verified in simulations, rats, pigs, and a chronic pain patient. Whereas synchronous spiking in DC axons is necessary for paresthesia, asynchronous spiking is sufficient to produce analgesia. Asynchronous activation of DC axons thus produces paresthesia-free analgesia.

neuroscience↗

bioRxiv2022

Equivalent excitability through different sodium channel subtypes and implications for analgesia by subtype-selective drugs

Nociceptive sensory neurons convey pain-related signals to the CNS using action potentials. Loss-of-function mutations in the voltage-gated sodium channel NaV1.7 cause insensitivity to pain (presumably by reducing nociceptor excitability) but efforts to treat pain by inhibiting NaV1.7 pharmacologically have largely failed. This may reflect the variable contribution of NaV1.7 to nociceptor excitability. Contrary to claims that NaV1.7 is necessary for nociceptors to initiate action potentials, we show that nociceptors can achieve equivalent excitability using different combinations of NaV1.3, NaV1.7, and NaV1.8. Selectively blocking one of those NaV subtypes reduces nociceptor excitability only if the other two subtypes are weakly expressed. For example, excitability relies on NaV1.8 in acutely dissociated nociceptors but responsibility shifts to NaV1.7 and NaV1.3 by the fourth day in culture. A similar shift in NaV dependence occurs in vivo after inflammation, impacting ability of the NaV1.7-selective inhibitor PF-05089771 to reduce pain in behavioral tests. Flexible use of different NaV subtypes exemplifies degeneracy - equivalent function using different components - and compromises the reliable modulation of nociceptor excitability by subtype-selective inhibitors. Identifying the dominant NaV subtype to predict drug efficacy is not trivial. Degeneracy at the cellular level must be considered when choosing drug targets at the molecular level. SIGNIFICANCE STATEMENTNociceptors can achieve equivalent excitability using different sodium channel subtypes. The analgesic efficacy of subtype-selective drugs hinges on which subtype controls excitability. This contingency likely contributes to poor clinical outcomes.

neuroscience↗

bioRxiv2021

Spike initiation properties in the axon support high-fidelity signal transmission

The axon initial segment (AIS) converts graded depolarization into all-or-none spikes that are transmitted by the axon to downstream neurons. Analog-to-digital transduction and digital signal transmission call for distinct spike initiation properties (filters) and those filters should, therefore, differ between the AIS and distal axon. Here we show that unlike the AIS, which spikes repetitively during sustained depolarization, the axon spikes transiently and only if depolarization reaches threshold before KV1 channels activate. Rate of depolarization is critical. This was shown by optogenetically evoking spikes in the distal axon of CA1 pyramidal neurons using different photostimulus waveforms and pharmacological conditions while recording antidromically propagated spikes at the soma, thus circumventing the prohibitive difficulty of patching intact axons. Computational modeling shows that KV1 channels in the axon implement a high-pass filter that is matched to the axial current waveform associated with spike propagation, thus maximizing the signal-to-noise ratio to ensure high-fidelity transmission of spike-based signals.

neuroscience↗

bioRxiv2021

Physiological noise optimizes multiplexed coding of vibrotactile-like signals in somatosensory cortex

Neurons can use different aspects of their spiking to simultaneously represent (multiplex) different features of a stimulus. For example, some pyramidal neurons in primary somatosensory cortex (S1) use the rate and timing of their spikes to respectively encode the intensity and frequency of vibrotactile stimuli. Doing so has several requirements. Because they fire at low rates, pyramidal neurons cannot entrain 1:1 with high-frequency (100-600 Hz) inputs and instead must skip (i.e. not respond to) some stimulus cycles. The proportion of skipped cycles must vary inversely with stimulus intensity for firing rate to encode stimulus intensity. Spikes must phase lock to the stimulus for spike times (intervals) to encode stimulus frequency but, in addition, skipping must occur irregularly to avoid aliasing. Using simulations and in vitro experiments in which S1 pyramidal neurons were stimulated with inputs emulating those induced by vibrotactile stimuli, we show that fewer cycles are skipped as stimulus intensity increases, as required for rate coding, and that physiological noise induces irregular skipping without disrupting phase locking, as required for temporal coding. This occurs because the reliability and precision of spikes evoked by small- amplitude, fast-onset signals are differentially sensitive to noise. Simulations confirmed that differences in stimulus intensity and frequency can be well discriminated based on differences in spike rate or timing, respectively, but only in the presence of noise. Our results show that multiplexed coding by S1 pyramidal neurons is facilitated rather than degraded by physiological levels of noise. In fact, multiplexing is optimal under physiologically noisy conditions.

neuroscience↗

bioRxiv2021

Multiscale computer model of the spinal dorsal horn reveals changes in network processing associated with chronic pain

Pain-related sensory input is processed in the spinal dorsal horn (SDH) before being relayed to the brain. That processing profoundly influences whether stimuli are correctly or incorrectly perceived as painful. Significant advances have been made in identifying the types of excitatory and inhibitory neurons that comprise the SDH, and there is some information about how neuron types are connected, but it remains unclear how the overall circuit processes sensory input or how that processing is disrupted under chronic pain conditions. To explore SDH function, we developed a computational model of the circuit that is tightly constrained by experimental data. Our model comprises conductance-based neuron models that reproduce the characteristic firing patterns of spinal neurons. Excitatory and inhibitory neuron populations, defined by their expression of genetic markers, spiking pattern, or morphology, were synaptically connected according to available qualitative data. Using a genetic algorithm, synaptic weights were tuned to reproduce projection neuron firing rates (model output) based on primary afferent firing rates (model input) across a range of mechanical stimulus intensities. Disparate synaptic weight combinations could produce equivalent circuit function, revealing degeneracy that may underlie heterogeneous responses of different circuits to perturbations or pathological insults. To validate our model, we verified that it responded to reduction of inhibition (i.e. disinhibition) and ablation of specific neuron types in a manner consistent with experiments. Thus validated, our model offers a valuable resource for interpreting experimental results and testing hypotheses in silico to plan experiments for examining normal and pathological SDH circuit function. Significance StatementWe developed a multiscale computer model of the posterior part of spinal cord gray matter (spinal dorsal horn), involved in perception of touch and pain. The model reproduces several experimental observations and makes predictions about how specific types of spinal neurons and synapses influence projection neurons that send information to the brain. Misfiring of these projection neurons can produce anomalous sensations associated with chronic pain. Our computer model will not only assist in planning future experiments, but will also be useful for developing new pharmacotherapy for chronic pain disorders, connecting the effect of drugs acting at the molecular scale with emergent properties of neurons and circuits that shape the pain experience.

neuroscience↗

bioRxiv2020

Simultaneously regulating many properties requires that neurons adjust diverse ion channels

Neurons regulate their excitability by adjusting their ion channel levels. Degeneracy - achieving equivalent outcomes (excitability) using different solutions (channel combinations) - facilitates this regulation by enabling a disruptive change in one channel to be offset by compensatory changes in other channels. But neurons must co-regulate many properties. Pleiotropy - the impact of one channel on more than one property - complicates regulation because a compensatory ion channel change that restores one property to its target value often disrupts other properties. How then does a neuron simultaneously regulate multiple properties? Here we demonstrate that of the many channel combinations producing the target value for one property (the single-output solution set), few combinations produce the target value for other properties. Combinations producing the target value for two or more properties (the multi-output solution set) correspond to the intersection between single-output solution sets. Properties can be effectively co-regulated only if the number of adjustable channels (nin) exceeds the number of regulated properties (nout). Ion channel correlations emerge during homeostatic regulation when the dimensionality of solution space (nin - nout) is low. Even if each property can be regulated to its target value when considered in isolation, regulation as a whole fails if single-output solution sets do not intersect. Our results also highlight that ion channels must be co-adjusted with different ratios to regulate different properties, which suggests that each error signal drives modulatory changes independently, despite those changes ultimately affecting the same ion channels.

neuroscience↗

bioRxiv2019

Excitatory neurons are more disinhibited than inhibitory neurons by chloride dysregulation in the spinal dorsal horn

Neuropathic pain is a debilitating condition caused by the abnormal processing of somatosensory input. Synaptic inhibition in the spinal dorsal horn plays a key role in that processing. Mechanical allodynia - the misperception of light touch as painful - occurs when inhibition is compromised. Disinhibition is due primarily to chloride dysregulation caused by hypofunction of the potassium-chloride co-transporter KCC2. Here we show, in rats, that excitatory neurons are disproportionately affected. This is not because chloride is differentially dysregulated in excitatory and inhibitory neurons, but, rather, because excitatory neurons rely more heavily on inhibition to counterbalance strong excitation. Receptive fields in both cell types have a center-surround organization but disinhibition unmasks more excitatory input to excitatory neurons. Differences in intrinsic excitability also affect how chloride dysregulation affects spiking. These results deepen understanding of how excitation and inhibition are normally balanced in the spinal dorsal horn, and how their imbalance disrupts somatosensory processing.

neuroscience↗

bioRxiv2019

Control iPSC lines with clinically annotated genetic variants for versatile multi-lineage differentiation

Induced Pluripotent Stem Cells (iPSC) derived from healthy individuals are important controls for disease modeling studies. To create a resource of genetically annotated iPSCs, we reprogrammed footprint-free lines from four volunteers in the Personal Genome Project Canada (PGPC). Multilineage directed differentiation efficiently produced functional cortical neurons, cardiomyocytes and hepatocytes. Pilot users further demonstrated line versatility by generating kidney organoids, T-lymphocytes and sensory neurons. A frameshift knockout was introduced into MYBPC3 and these cardiomyocytes exhibited the expected hypertrophic phenotype. Whole genome sequencing (WGS) based annotation of PGPC lines revealed on average 20 coding variants. Importantly, nearly all annotated PGPC and HipSci lines harboured at least one pre-existing or acquired variant with cardiac, neurological or other disease associations. Overall, PGPC lines were efficiently differentiated by multiple users into cell types found in six tissues for disease modeling, and clinical annotation highlighted variant-preferred lines for use as unaffected controls in specific disease settings.

developmental biology↗