scholarly journals Involvement of ASIC1a channels in the spinal processing of pain information by deep projection neurons

2021 ◽  
Author(s):  
Magda Chafai ◽  
Ariane Delrocq ◽  
Perrine Inquimbert ◽  
Ludivine Pidoux ◽  
Kevin Delanoe ◽  
...  
Keyword(s):  
Dynamic Range ◽  
Ex Vivo ◽  
Computational Modelling ◽  
Functional Expression ◽  
Spinal Pain ◽  
Projection Neurons ◽  
Positive Contribution ◽  
Calcium Dependent ◽  
Wdr Neurons

Dorsal horn of the spinal cord is an important crossroad of pain neuraxis, especially for the neuronal plasticity mechanisms that can lead to chronic pain states. Windup is a well-known spinal pain facilitation process initially described several decades ago, but which exact mechanism is still not fully understood. Here, we combine both ex vivo and in vivo electrophysiological recordings of spinal neurons with computational modelling to demonstrate a role for ASIC1a-containing channels in the windup process. Spinal application of the ASIC1a inhibitory venom peptides mambalgin-1 and psalmotoxin-1 (PcTx1) significantly reduces the ability of deep wide dynamic range (WDR) neurons to develop windup in vivo. All deep WDR-like neurons recorded from spinal slices exhibit an ASIC current with biophysical and pharmacological characteristics consistent with functional expression of ASIC1a/ASIC2 heteromeric channels. A computational model of WDR neuron supplemented with heteromeric ASIC1a/ASIC2 channel parameters accurately reproduces the experimental data, further supporting a positive contribution of these channels to windup. It also predicts a calcium-dependent windup decrease for elevated ASIC conductances, a phenomenon that was experimentally validated using either a combination of calcium-activated potassium channel inhibitory peptides (apamin and iberiotoxin), or the Texas coral snake ASIC-activating toxin (MitTx). This study demonstrates a possible dual contribution to windup of calcium permeable ASIC1a/ASIC2 channels in deep laminae projecting neurons, promoting it upon moderate channel activity, but ultimately leading to calcium-dependent windup inhibition associated to potassium channels when activity increases.

scholarly journals Enhanced food motivation in obese mice is controlled by D1R expressing spiny projection neurons in the nucleus accumbens.

2022 ◽  
Author(s):  
Bridget A Matikainen-Ankney ◽  
Alex A Legaria ◽  
Yvan M Vachez ◽  
Caitlin A Murphy ◽  
Yiyan A Pan ◽  
...  
Keyword(s):  
Nucleus Accumbens ◽  
Food Reward ◽  
Ex Vivo ◽  
D1 Receptor ◽  
Physical Work ◽  
Projection Neurons ◽  
Food Motivation ◽  
Obese Mice ◽  
Food Seeking

Obesity is a chronic relapsing disorder that is caused by an excess of caloric intake relative to energy expenditure. In addition to homeostatic feeding mechanisms, there is growing recognition of the involvement of food reward and motivation in the development of obesity. However, it remains unclear how brain circuits that control food reward and motivation are altered in obese animals. Here, we tested the hypothesis that signaling through pro-motivational circuits in the core of the nucleus accumbens (NAc) is enhanced in the obese state, leading to invigoration of food seeking. Using a novel behavioral assay that quantifies physical work during food seeking, we confirmed that obese mice work harder than lean mice to obtain food, consistent with an increase in the relative reinforcing value of food in the obese state. To explain this behavioral finding, we recorded neural activity in the NAc core with both in vivo electrophysiology and cell-type specific calcium fiber photometry. Here we observed greater activation of D1-receptor expressing NAc spiny projection neurons (NAc D1SPNs) during food seeking in obese mice relative to lean mice. With ex vivo slice physiology we identified both pre- and post-synaptic mechanisms that contribute to this enhancement in NAc D1SPN activity in obese mice. Finally, blocking synaptic transmission from D1SPNs decreased physical work during food seeking and attenuated high-fat diet-induced weight gain. These experiments demonstrate that obesity is associated with a selective increase in the activity of D1SPNs during food seeking, which enhances the vigor of food seeking. This work also establishes the necessity of D1SPNs in the development of diet-induced obesity, identifying a novel potential therapeutic target.

scholarly journals Opposing Influence of Sensory and Motor Cortical Input on Striatal Circuitry and Choice Behavior

2018 ◽  
Author(s):  
Christian R. Lee ◽  
Alex J. Yonk ◽  
Joost Wiskerke ◽  
Kenneth G. Paradiso ◽  
James M. Tepper ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Dorsal Striatum ◽  
Behavioral Effect ◽  
Projection Neurons ◽  
Cortical Input ◽  
Optogenetic Stimulation ◽  
Main Input ◽  
Opposing Effects ◽  
Stimulation Of

SummaryThe striatum is the main input nucleus of the basal ganglia and is a key site of sensorimotor integration. While the striatum receives extensive excitatory afferents from the cerebral cortex, the influence of different cortical areas on striatal circuitry and behavior is unknown. Here we find that corticostriatal inputs from whisker-related primary somatosensory (S1) and motor (M1) cortex differentially innervate projection neurons and interneurons in the dorsal striatum, and exert opposing effects on sensory-guided behavior. Optogenetic stimulation of S1-corticostriatal afferents in ex vivo recordings produced larger postsynaptic potentials in striatal parvalbumin (PV)-expressing interneurons than D1- or D2-expressing spiny projection neurons (SPNs), an effect not observed for M1-corticostriatal afferents. Critically, in vivo optogenetic stimulation of S1-corticostriatal afferents produced task-specific behavioral inhibition, which was bidirectionally modulated by striatal PV interneurons. Optogenetic stimulation of M1 afferents produced the opposite behavioral effect. Thus, our results suggest opposing roles for sensory and motor cortex in behavioral choice via distinct influences on striatal circuitry.

scholarly journals Dysregulation of the basal ganglia indirect pathway prior to cell loss in the Q175 mouse model of Huntington's disease

2021 ◽  
Author(s):  
Joshua Callahan ◽  
David L Wokosin ◽  
Mark D Bevan
Keyword(s):  
Basal Ganglia ◽  
Huntington's Disease ◽  
Huntington’S Disease ◽  
Ex Vivo ◽  
Cell Loss ◽  
Projection Neurons ◽  
Indirect Pathway ◽  
Cortical Input ◽  
Psychomotor Symptoms

The psychomotor symptoms of Huntington's disease (HD) are linked to degeneration of the basal ganglia indirect pathway. To determine how this pathway is perturbed prior to cell loss, optogenetic- and reporter-guided electrophysiological interrogation approaches were applied to early symptomatic 6-month-old Q175 HD mice. Although cortical activity was unaffected, indirect pathway striatal projection neurons were hypoactive in vivo, consistent with reduced cortical input strength and dendritic excitability. Downstream parvalbumin-expressing prototypic external globus pallidus (GPe) neurons were hyperactive in vivo and exhibited elevated autonomous firing ex vivo. Optogenetic inhibition of prototypic GPe neurons ameliorated the abnormal hypoactivity of postsynaptic subthalamic nucleus (STN) and putative arkypallidal neurons in vivo. In contrast to STN neurons, autonomous arkypallidal activity was unimpaired ex vivo. Together with previous studies, these findings demonstrate that basal ganglia indirect pathway neurons are highly dysregulated in Q175 mice through changes in presynaptic activity and/or intrinsic properties 6-12 months before cell loss.

scholarly journals Neuronal hyperexcitability in the ventral posterior thalamus of neuropathic rats: modality selective effects of pregabalin

2016 ◽  
Vol 116 (1) ◽  
pp. 159-170 ◽  
Author(s):  
Ryan Patel ◽  
Anthony H. Dickenson
Keyword(s):  
Dynamic Range ◽  
Spinal Nerve ◽  
Population Coding ◽  
Mechanical Stimuli ◽  
Spinothalamic Tract ◽  
Noxious Heat ◽  
Posterior Thalamus ◽  
Central Processing ◽  
Wdr Neurons

Neuropathic pain represents a substantial clinical challenge; understanding the underlying neural mechanisms and back-translation of therapeutics could aid targeting of treatments more effectively. The ventral posterior thalamus (VP) is the major termination site for the spinothalamic tract and relays nociceptive activity to the somatosensory cortex; however, under neuropathic conditions, it is unclear how hyperexcitability of spinal neurons converges onto thalamic relays. This study aimed to identify neural substrates of hypersensitivity and the influence of pregabalin on central processing. In vivo electrophysiology was performed to record from VP wide dynamic range (WDR) and nociceptive-specific (NS) neurons in anesthetized spinal nerve-ligated (SNL), sham-operated, and naive rats. In neuropathic rats, WDR neurons had elevated evoked responses to low- and high-intensity punctate mechanical stimuli, dynamic brushing, and innocuous and noxious cooling, but less so to heat stimulation, of the receptive field. NS neurons in SNL rats also displayed increased responses to noxious punctate mechanical stimulation, dynamic brushing, noxious cooling, and noxious heat. Additionally, WDR, but not NS, neurons in SNL rats exhibited substantially higher rates of spontaneous firing, which may correlate with ongoing pain. The ratio of WDR-to-NS neurons was comparable between SNL and naive/sham groups, suggesting relatively few NS neurons gain sensitivity to low-intensity stimuli leading to a “WDR phenotype.” After neuropathy was induced, the proportion of cold-sensitive WDR and NS neurons increased, supporting the suggestion that changes in frequency-dependent firing and population coding underlie cold hypersensitivity. In SNL rats, pregabalin inhibited mechanical and heat responses but not cold-evoked or elevated spontaneous activity.

scholarly journals The Antiallodynic Action of Pregabalin May Depend on the Suppression of Spinal Neuronal Hyperexcitability in Rats with Spared Nerve Injury

2014 ◽  
Vol 19 (4) ◽  
pp. 205-211 ◽  
Author(s):  
Lei Ding ◽  
Jie Cai ◽  
Xiang-Yang Guo ◽  
Xiu-Li Meng ◽  
Guo-Gang Xing
Keyword(s):  
Neuropathic Pain ◽  
Dorsal Horn ◽  
Nerve Injury ◽  
Dynamic Range ◽  
Inhibitory Effect ◽  
Electrophysiological Recording ◽  
Spared Nerve Injury ◽  
Withdrawal Threshold ◽  
Wdr Neurons

BACKGROUND: Pregabalin (PGB) is a novel antiepileptic drug and is also used as a first-line medication for the treatment of neuropathic pain. However, the mechanisms of its analgesic effects remain largely unknown.OBJECTIVES: To elucidate the mechanisms underlying the antiallodynic action of PGB in rats with neuropathic pain.METHODS: In a rat model of neuropathic pain induced by spared nerve injury, mechanical allodynia, as a behavioural sign of neuropathic pain, was assessed by measuring 50% paw withdrawal threshold with von Frey filaments. Activities of dorsal horn wide dynamic range (WDR) neurons were examined by extracellular electrophysiological recording in vivo.RESULTS: Spinal administration of PGB exerted a significant antiallodynic effect and a prominent inhibitory effect on the hypersensitivity of dorsal horn WDR neurons in rats with spared nerve injury.CONCLUSION: The antiallodynic action of PGB is likely dependent on the suppression of WDR neuron hyperexcitability in rats with neuropathic pain.

scholarly journals Slowly Reducible Genetically Encoded Green Fluorescent Indicator for In Vivo and Ex Vivo Visualization of Hydrogen Peroxide

2019 ◽  
Vol 20 (13) ◽  
pp. 3138 ◽  
Author(s):  
Oksana M. Subach ◽  
Tatiana A. Kunitsyna ◽  
Olga A. Mineyeva ◽  
Alexander A. Lazutkin ◽  
Dmitri V. Bezryadnov ◽  
...  
Keyword(s):  
Hydrogen Peroxide ◽  
Single Cell ◽  
Hela Cells ◽  
Dynamic Range ◽  
Ex Vivo ◽  
Neuronal Cultures ◽  
Half Time ◽  
Fluorescent Indicator ◽  
Green Fluorescent

Hydrogen peroxide (H2O2) plays an important role in modulating cell signaling and homeostasis in live organisms. The HyPer family of genetically encoded indicators allows the visualization of H2O2 dynamics in live cells within a limited field of view. The visualization of H2O2 within a whole organism with a single cell resolution would benefit from a slowly reducible fluorescent indicator that integrates the H2O2 concentration over desired time scales. This would enable post hoc optical readouts in chemically fixed samples. Herein, we report the development and characterization of NeonOxIrr, a genetically encoded green fluorescent indicator, which rapidly increases fluorescence brightness upon reaction with H2O2, but has a low reduction rate. NeonOxIrr is composed of circularly permutated mNeonGreen fluorescent protein fused to the truncated OxyR transcription factor isolated from E. coli. When compared in vitro to a standard in the field, HyPer3 indicator, NeonOxIrr showed 5.9-fold higher brightness, 15-fold faster oxidation rate, 5.9-fold faster chromophore maturation, similar intensiometric contrast (2.8-fold), 2-fold lower photostability, and significantly higher pH stability both in reduced (pKa of 5.9 vs. ≥7.6) and oxidized states (pKa of 5.9 vs.≥ 7.9). When expressed in the cytosol of HEK293T cells, NeonOxIrr demonstrated a 2.3-fold dynamic range in response to H2O2 and a 44 min reduction half-time, which were 1.4-fold lower and 7.6-fold longer than those for HyPer3. We also demonstrated and characterized the NeonOxIrr response to H2O2 when the sensor was targeted to the matrix and intermembrane space of the mitochondria, nucleus, cell membranes, peroxisomes, Golgi complex, and endoplasmic reticulum of HEK293T cells. NeonOxIrr could reveal endogenous reactive oxygen species (ROS) production in HeLa cells induced with staurosporine but not with thapsigargin or epidermal growth factor. In contrast to HyPer3, NeonOxIrr could visualize optogenetically produced ROS in HEK293T cells. In neuronal cultures, NeonOxIrr preserved its high 3.2-fold dynamic range to H2O2 and slow 198 min reduction half-time. We also demonstrated in HeLa cells that NeonOxIrr preserves a 1.7-fold ex vivo dynamic range to H2O2 upon alkylation with N-ethylmaleimide followed by paraformaldehyde fixation. The same alkylation-fixation procedure in the presence of NP-40 detergent allowed ex vivo detection of H2O2 with 1.5-fold contrast in neuronal cultures and in the cortex of the mouse brain. The slowly reducible H2O2 indicator NeonOxIrr can be used for both the in vivo and ex vivo visualization of ROS. Expanding the family of fixable indicators may be a promising strategy to visualize biological processes at a single cell resolution within an entire organism.

scholarly journals Citrullinated myelin induces microglial TNFα and inhibits endogenous repair in the cuprizone model of demyelination

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Miranda M. Standiford ◽  
Ethan M. Grund ◽  
Charles L. Howe
Keyword(s):  
Microglial Activation ◽  
Primary Motor Cortex ◽  
Ex Vivo ◽  
Arginine Deiminase ◽  
Calcium Dependent ◽  
Cingulum Bundle ◽  
Normal Chow ◽  
Demyelinating Disorders

Abstract Background Microglia are the primary phagocytes of the central nervous system and are responsible for removing damaged myelin following demyelination. Previous investigations exploring the consequences of myelin phagocytosis on microglial activation overlooked the biochemical modifications present on myelin debris. Such modifications, including citrullination, are increased within the inflammatory environment of multiple sclerosis lesions. Methods Mouse cortical myelin isolated by ultracentrifugation was citrullinated ex vivo by incubation with the calcium-dependent peptidyl arginine deiminase PAD2. Demyelination was induced by 6 weeks of cuprizone (0.3%) treatment and spontaneous repair was initiated by reversion to normal chow. Citrullinated or unmodified myelin was injected into the primary motor cortex above the cingulum bundle at the time of reversion to normal chow and the consequent impact on remyelination was assessed by measuring the surface area of myelin basic protein-positive fibers in the cortex 3 weeks later. Microglial responses to myelin were characterized by measuring cytokine release, assessing flow cytometric markers of microglial activation, and RNAseq profiling of transcriptional changes. Results Citrullinated myelin induced a unique microglial response marked by increased tumor necrosis factor α (TNFα) production both in vitro and in vivo. This response was not induced by unmodified myelin. Injection of citrullinated myelin but not unmodified myelin into the cortex of cuprizone-demyelinated mice significantly inhibited spontaneous remyelination. Antibody-mediated neutralization of TNFα blocked this effect and restored remyelination to normal levels. Conclusions These findings highlight the role of post-translation modifications such as citrullination in the determination of microglial activation in response to myelin during demyelination. The inhibition of endogenous repair induced by citrullinated myelin and the reversal of this effect by neutralization of TNFα may have implications for therapeutic approaches to patients with inflammatory demyelinating disorders.

scholarly journals Functional expression of SGLTs in rat brain

2010 ◽  
Vol 299 (6) ◽  
pp. C1277-C1284 ◽  
Author(s):  
Amy S. Yu ◽  
Bruce A. Hirayama ◽  
Gerald Timbol ◽  
Jie Liu ◽  
Ernest Basarah ◽  
...  
Keyword(s):  
Ex Vivo ◽  
Brain Slices ◽  
Glucose Transporters ◽  
Functional Expression ◽  
Positron Emission ◽  
Health And Disease ◽  
Pass Through ◽  
The Brain

This work provides evidence of previously unrecognized uptake of glucose via sodium-coupled glucose transporters (SGLTs) in specific regions of the brain. The current understanding of functional glucose utilization in brain is largely based on studies using positron emission tomography (PET) with the glucose tracer 2-deoxy-2-[F-18]fluoro-d-glucose (2-FDG). However, 2-FDG is only a good substrate for facilitated-glucose transporters (GLUTs), not for SGLTs. Thus, glucose accumulation measured by 2-FDG omits the role of SGLTs. We designed and synthesized two high-affinity tracers: one, α-methyl-4-[F-18]fluoro-4-deoxy-d-glucopyranoside (Me-4FDG), is a highly specific SGLT substrate and not transported by GLUTs; the other one, 4-[F-18]fluoro-4-deoxy-d-glucose (4-FDG), is transported by both SGLTs and GLUTs and will pass through the blood brain barrier (BBB). In vitro Me-4FDG autoradiography was used to map the distribution of uptake by functional SGLTs in brain slices with a comparable result from in vitro 4-FDG autoradiography. Immunohistochemical assays showed that uptake was consistent with the distribution of SGLT protein. Ex vivo 4-FDG autoradiography showed that SGLTs in these areas are functionally active in the normal in vivo brain. The results establish that SGLTs are a normal part of the physiology of specific areas of the brain, including hippocampus, amygdala, hypothalamus, and cerebral cortices. 4-FDG PET imaging also established that this BBB-permeable SGLT tracer now offers a functional imaging approach in humans to assess regulation of SGLT activity in health and disease.

Computational Model of Radiofrequency Ablation of Cardiac Tissues Incorporating Thermo-Electro-Mechanical Interactions

2020 ◽  
Author(s):  
Sundeep Singh ◽  
Roderick Melnik
Keyword(s):  
Radiofrequency Ablation ◽  
Cardiac Tissue ◽  
A Priori Estimates ◽  
Ex Vivo ◽  
Numerical Study ◽  
Experimental Studies ◽  
Computational Modelling ◽  
Cardiac Ablation ◽  
Fully Coupled

Abstract The application of radiofrequency ablation (RFA) has been widely explored in treating various types of cardiac arrhythmias. Computational modelling provides a safe and viable alternative to ex vivo and in vivo experimental studies for quantifying the effects of different variables efficiently and reliably, apart from providing a priori estimates of the ablation volume attained during cardiac ablation procedures. In this contribution, we report a fully coupled thermo-electro-mechanical model for a more accurate prediction of the treatment outcomes during the radiofrequency cardiac ablation. A numerical model comprising of cardiac tissue and the cardiac chamber has been developed in which an electrode has been inserted perpendicular to the cardiac tissue to simulate actual clinical procedures. Temperature-dependent heat capacity, electrical and thermal conductivities, and blood perfusion rate have been considered to model more realistic scenarios. The effects of blood flow and contact force of the electrode tip on the efficacy of a fully coupled model of RFA have been systematically investigated. The numerical study predicts that the efficacy of RFA is significantly dependent on the thermo-electro-mechanical parameters of the cardiac tissue.

scholarly journals Phytochemicals of Cinnamomi Cortex: Cinnamic Acid, but not Cinnamaldehyde, Attenuates Oxaliplatin-Induced Cold and Mechanical Hypersensitivity in Rats

Nutrients ◽  
2019 ◽  
Vol 11 (2) ◽  
pp. 432 ◽  
Author(s):  
Hyeon Kyeong Chae ◽  
Woojin Kim ◽  
Sun Kwang Kim
Keyword(s):  
Neuropathic Pain ◽  
Cinnamic Acid ◽  
Mechanical Allodynia ◽  
Dynamic Range ◽  
Spinal Pain ◽  
Analgesic Action ◽  
Mechanical Hypersensitivity ◽  
Pain Transmission ◽  
Cinnamomi Cortex

A chemotherapy drug, oxaliplatin, induces cold and mechanical hypersensitivity, but effective treatments for this neuropathic pain without side effects are still lacking. We previously showed that Cinnamomi Cortex suppresses oxaliplatin-induced pain behaviors in rats. However, it remains unknown which phytochemical of Cinnamomi Cortex plays a key role in that analgesic action. Thus, here we investigated whether and how cinnamic acid or cinnamaldehyde, major components of Cinnamomi Cortex, alleviates cold and mechanical allodynia induced by a single oxaliplatin injection (6 mg/kg, i.p.) in rats. Using an acetone test and the von Frey test for measuring cold and mechanical allodynia, respectively, we found that administration of cinnamic acid, but not cinnamaldehyde, at doses of 10, 20 and 40 mg/kg (i.p.) significantly attenuates the allodynic behaviors in oxaliplatin-injected rats with the strongest effect being observed at 20 mg/kg. Our in vivo extracellular recordings also showed that cinnamic acid (20 mg/kg, i.p.) inhibits the increased activities of spinal wide dynamic range neurons in response to cutaneous mechanical and cold stimuli following the oxaliplatin injection. These results indicate that cinnamic acid has an effective analgesic action against oxaliplatin-induced neuropathic pain through inhibiting spinal pain transmission, suggesting its crucial role in mediating the effect of Cinnamomi Cortex.

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