HCN channels in the lateral habenula regulate pain and comorbid depressive-like behaviors in mice.

AIMS: Comorbid anxiodepressive-like symptoms (CADS) in chronic pain are closely related to the overactivation of the lateral habenula (LHb). Hyperpolarization-activated cyclic nucleotide-gated (HCN) channels have been implicated to play a key role in regulating neuronal excitability. However, the role of HCN channels in the LHb during CADS has not yet been characterized. This study aimed to investigate the effect of HCN channels in the LHb on CADS during chronic pain. METHODS: After chronic neuropathic pain induction by spared nerve injury (SNI), mice underwent a sucrose preference test, forced swimming test, tail suspension test, open-field test, and elevated plus maze test to evaluate their anxiodepressive-like behaviors. Electrophysiological recordings, immunohistochemistry, Western blotting, pharmacological experiments, and virus knockdown strategies were used to investigate the underlying mechanisms. RESULTS: Evident anxiodepressive-like behaviors were observed 6w after the SNI surgery, accompanied by increased neuronal excitability, enhanced HCN channel function, and increased expression of HCN2 isoforms in the LHb. Either pharmacological inhibition or virus knockdown of HCN2 channels significantly reduced LHb neuronal excitability and ameliorated both pain and depressive-like behaviors. CONCLUSION: Our results indicated that the LHb neurons were hyperactive under CADS in chronic pain, and this hyperactivation possibly resulted from the enhanced function of HCN channels and up-regulation of HCN2 isoforms.

Causal relationship between coffee intake and neurological diseases: a Mendelian randomization study.

BACKGROUND: Previous observational studies focused on the association of coffee consumption and neurological disease. However, it is not known whether these associations are causal. METHODS: We used Mendelian randomization (MR) study to assess the causal relationship of coffee intake with the risk of neurological diseases, including Alzheimer's disease, Parkinson's disease, amyotrophic lateral sclerosis, multiple sclerosis, epilepsy, stroke, and migraine. Single-nucleotide polymorphisms (SNPs) which had genetic statistical significance with coffee intake were used as instrumental variable (IV). Genetic instruments were stretched from the MRC-IEU (MRC Integrative Epidemiology Unit) analysis on the UK Biobank. We performed MR analyses using the inverse variance weighted (IVW) method as the main approach. Sensitivity analyses were further performed using MR-Egger and MR-PRESSO to assess the robustness. RESULTS: In the MR analysis, 40 SNPs were selected as IV, the F statistics for all SNPs ranged from 16 to 359. In IVW approach, our results provide genetic evidence supporting a potential causal association between coffee intake and a lower risk of migraine (OR = 0.528, 95% CI = 0.342-0.817, P = 0.004) and migraine with aura (OR = 0.374, 95% CI = 0.208-0.672, P = 0.001). However, we found no significant association between coffee intake and other neurological diseases along with their subtypes in this MR study. CONCLUSION: Using genetic data, our MR study found significant evidence supporting a causal association between coffee intake and migraine. This suggests that coffee consumption is likely a trigger or a prevention strategy for migraine.

Clinical efficacy of transforaminal endoscopic discectomy in the treatment of recurrent lumbar disc herniation: a single-center retrospective analysis.

PURPOSE: To investigate the clinical efficacy of transforaminal endoscopic discectomy (TED) in treating recurrent lumbar disc herniation. METHODS: Clinical datal of 31 patients who were hospitalized in the Department of Pain Management, First Affiliated Hospital of Nanchang University, between 2015 and 2018 due to recurrent lumbar disc herniation were collected and analyzed retrospectively. Visual analogue scale (VAS) scores and Japanese Orthopedic Association (JOA) scores were used to assess alterations of patients' leg pain intensity and nerve function, respectively. The Modified MacNab criteria were used to evaluate patients' excellent and good rates. RESULTS: Compared to clinical data before surgery, there was a significant reduction in VAS scores (P < 0.01) along with a significant improvement in JOA scores (P < 0.01) at 2 years after revision surgery. The patients' excellent and good rates were 83.9% at the 2 years after surgery. CONCLUSION: The TED is safe and effective in the long term and is applicable to the treatment of recurrent lumbar disc herniation.

Thalamocortical Circuit Controls Neuropathic Pain via Up-regulation of HCN2 in the Ventral Posterolateral Thalamus.

The thalamocortical (TC) circuit is closely associated with pain processing. The hyperpolarization-activated cyclic nucleotide-gated (HCN) 2 channel is predominantly expressed in the ventral posterolateral thalamus (VPL) that has been shown to mediate neuropathic pain. However, the role of VPL HCN2 in modulating TC circuit activity is largely unknown. Here, by using optogenetics, neuronal tracing, electrophysiological recordings, and virus knockdown strategies, we showed that the activation of VPL TC neurons potentiates excitatory synaptic transmission to the hindlimb region of the primary somatosensory cortex (S1HL) as well as mechanical hypersensitivity following spared nerve injury (SNI)-induced neuropathic pain in mice. Either pharmacological blockade or virus knockdown of HCN2 (shRNA-Hcn2) in the VPL was sufficient to alleviate SNI-induced hyperalgesia. Moreover, shRNA-Hcn2 decreased the excitability of TC neurons and synaptic transmission of the VPL-S1HL circuit. Together, our studies provide a novel mechanism by which HCN2 enhances the excitability of the TC circuit to facilitate neuropathic pain.

Exploring gene signatures and regulatory networks in a rat model of sciatica: implications and validation in neuropathic pain.

Background: Sciatica (neuropathic pain [NP]) is a common disease characterized by pain from radiation along the sciatic nerve. The aim of this study was to study the genes associated with chronic systolic injury of sciatic nerve (SCN-CCI) in rats by RNA-Seq technique, and to explore their potential as therapeutic targets. Methods: Sciatic nerve rat model was obtained by ligation of sciatic nerve and divided into two groups: SCN-CCI group and Sham group. Behavioral assessments were performed to evaluate pain sensitivity, following which their spinal cord dorsal horn were resected and RNA sequencing was conducted to identify differentially expressed genes (DEGs). Bioinformatics and functional enrichment analysis was performed to identify promising DEGs and their related biological processes and pathways associated with SCN-CCI. PPI network analysis and hub gene identification were conducted. QRT-PCR, western blot, ELISA, and immunofluorescence staining were performed on rat models to validate the expression of these hub genes and investigate related proteins and inflammatory markers. Results: The SCN-CCI rat model was successfully obtained, exhibiting increased pain sensitivity compared to the Sham group, as indicated by decreased mechanical allodynia thresholds, thermal latencies, and increased paw withdrawals. RNA-Seq analysis identified 117 DEGs in the SCN-CCI rat model, involved in various biological processes and pathways related to sciatica. PPI network analysis revealed hub genes, including Ly6g6e, which exhibited significant differential expression. QRT-PCR and Western blot analysis confirmed the expression patterns of these hub genes. Pain behavior assessment demonstrated reduced pain thresholds and increased paw flinching responses in the SCN-CCI group. Furthermore, the SCN-CCI group showed upregulated expression of Ly6g6e, increased protein levels of Ly6g6e, CGRP, and NGF, as well as elevated levels of IL-1ß, MCP-1, and IL-6, and microglial cell activation in the spinal dorsal horn. ELISA results confirmed the increased levels of IL-1ß, MCP-1, and IL-6 in the spinal dorsal horn. Conclusion: These comprehensive findings provide valuable insights into the SCN-CCI rat model, DEGs associated with sciatica, hub genes (Ly6g6e as promising targets), pain behavior changes and molecular alterations.

MiR-199-3p Suppressed Inflammatory Response by Targeting MECP2 to Alleviate TRX-Induced PHN in Mice.

Varicella zoster virus-induced postherpetic neuralgia (PHN) can be alleviated by limited medications with serious side effects. This study aims to investigate the underlying molecular mechanism of miR-199-3p in mediating PHN in mice. 293T cells were transfected with miR-199-3p vectors (mimic/inhibitor). The target relationship between miR-199-3p and MECP2 was confirmed using luciferase reporter assay. PHN mouse model was established by TRX injection. Animal behaviors were evaluated using Hargreaves test and Von Frey test. Western blot was used for protein analysis, and quantitative reverse transcription polymerase chain reaction was performed for messenger RNA quantification. Serum levels of inflammatory mediators were determined using ELISA. Paw withdrawal latency (PWL) and mechanical withdrawal threshold (MWT) were decreased in resiniferatoxin-induced PHN mice. Downregulated miR-199-3p and upregulated MECP2 were found in PHN mice. Upregulated miR-199-3p increased PWL and MWT, but inhibited MECP2 in PHN mice. Besides, increased miR-199-3p suppressed proinflammatory indicators and activated anti-inflammatory mediators. It also found that MECP2 was the target of miR-199-3p. Further study showed miR-199-3p enhanced PWL and MWT, and supported inflammatory response via targeting MECP2. miR-199-3p regulated inflammation by targeting MECP2 to alleviate TRX-induced PHN in mice.

Clinical significance of methyl-CpG binding protein 2 in postherpetic neuralgia: an observational study / Importancia clínica de la proteína 2 de unión a metil-CpG (MECP2) en la neuralgia posherpética: un estudio observacional

Abstract The present study was aimed to investigate the clinical significance of methyl-CpG binding protein 2 (MECP2) in patients with postherpetic neuralgia (PHN). This prospective case control study enrolled 319 cases of PHN patients from April 2017~December 2019. The patients' sleep quality and quality of life were evaluated using the Pittsburgh sleep quality score and the SF- 36 scale, respectively. The serum levels of MECP2, CRP, IL -6 and TNF-α were tested using enzyme linked immunosorbent assay (ELISA). The pain condition of the patients was evaluated using the visual analogue scale (VAS). The levels of MECP2 were significantly increased in PHN patients compared with the patients without PHN. Serum MECP2 levels were the highest in patients with severe pain, and were the lowest in patients with mild pain. Similarly, the frequency of severe pain in patients with low expression of MECP2 was significantly lower than the patients with higher MECP2 expression. Besides, serum levels of inflammatory factors CRP, IL -6 and TNF-α were markedly increased in PHN patients, which were also increased with the increase of the severity of pain. CRP, IL -6 and TNF-α were positively correlated with serum levels of MECP2 in PHN patients. Before the study, patients with lower MECP2 levels showed a significantly higher SF-36 score and lower Pittsburgh and VAS scores than patients with higher levels of MECP2. However, after one month, no significant difference was found between the patients. ROC curve showed MECP2 had the potential as a diagnostic biomarker for PHN. In conclusion, higher serum MECP2 levels are associated with a more severe pain condition and increased release of inflammatory factors.

Resumen El objetivo de este estudio fue investigar la importancia clínica de la MECP2 en pacientes con neuralgia posherpética (NPH). Este estudio observacional prospectivo incluyó 319 pacientes con NPH entre abril de 2017 y diciembre de 2019. La calidad del sueño y la calidad de vida de los pacientes se evaluaron con la escala de calidad del sueño de Pittsburgh y la escala SF - 36, respectivamente. Los niveles séricos de MECP2, PCR, IL -6 y TNF-α fueron determinados por ELISA. Se utilizó la escala visual analógica (EVA) para evaluar la intensidad del dolor. Los niveles de MECP2 en pacientes con NPH aumentaron significativamente en comparación con los pacientes sin NPH. El nivel sérico de MECP2 fue más alto en pacientes con dolor grave y el más bajo en pacientes con dolor leve. Además, la incidencia de dolor grave en pacientes con baja expresión de MECP2 fue significativamente menor que en pacientes con alta expresión de MECP2. Además, los niveles séricos de PCR, IL -6 y TNF-α aumentaron significativamente en pacientes con NPH, y se incrementaron con el aumento del grado de dolor. Los niveles séricos de PCR, IL -6 y TNF-α en pacientes con NPH se correlacionaron positivamente con los niveles séricos de MECP2. Antes del estudio, los pacientes con niveles más bajos de MECP2 tenían puntuaciones significativamente más altas de SF - 36, y puntuaciones más bajas de Pittsburgh y EVA que los pacientes con niveles más altos de MECP2. Sin embargo, no se encontraron diferencias significativas entre los pacientes un mes después. Las curvas ROC mostraron que la MECP2 podría ser un biomarcador de diagnóstico para la NPH. En general, los niveles séricos más altos de la MECP2 se asociaron con condiciones de dolor más graves y un aumento de la liberación de factores inflamatorios.

Electrophysiological and Morphological Features of Rebound Depolarization Characterized Interneurons in Rat Superficial Spinal Dorsal Horn.

Substantia gelatinosa (SG) neurons, which are located in the spinal dorsal horn (lamina II), have been identified as the "central gate" for the transmission and modulation of nociceptive information. Rebound depolarization (RD), a biophysical property mediated by membrane hyperpolarization that is frequently recorded in the central nervous system, contributes to shaping neuronal intrinsic excitability and, in turn, contributes to neuronal output and network function. However, the electrophysiological and morphological properties of SG neurons exhibiting RD remain unclarified. In this study, whole-cell patch-clamp recordings were performed on SG neurons from parasagittal spinal cord slices. RD was detected in 44.44% (84 out of 189) of the SG neurons recorded. We found that RD-expressing neurons had more depolarized resting membrane potentials, more hyperpolarized action potential (AP) thresholds, higher AP amplitudes, shorter AP durations, and higher spike frequencies in response to depolarizing current injection than neurons without RD. Based on their firing patterns and morphological characteristics, we propose that most of the SG neurons with RD mainly displayed tonic firing (69.05%) and corresponded to islet cell morphology (58.82%). Meanwhile, subthreshold currents, including the hyperpolarization-activated cation current (I h ) and T-type calcium current (I T ), were identified in SG neurons with RD. Blockage of I h delayed the onset of the first spike in RD, while abolishment of I T significantly blunted the amplitude of RD. Regarding synaptic inputs, SG neurons with RD showed lower frequencies in both spontaneous and miniature excitatory synaptic currents. Furthermore, RD-expressing neurons received either Aδ- or C-afferent-mediated monosynaptic and polysynaptic inputs. However, RD-lacking neurons received afferents from monosynaptic and polysynaptic Aδ fibers and predominantly polysynaptic C-fibers. These findings demonstrate that SG neurons with RD have a specific cell-type distribution, and may differentially process somatosensory information compared to those without RD.

Oxidative stress induced by NOX2 contributes to neuropathic pain via plasma membrane translocation of PKCε in rat dorsal root ganglion neurons.

BACKGROUND: Nicotinamide adenine dinucleotide phosphate oxidase 2 (NOX2)-induced oxidative stress, including the production of reactive oxygen species (ROS) and hydrogen peroxide, plays a pivotal role in neuropathic pain. Although the activation and plasma membrane translocation of protein kinase C (PKC) isoforms in dorsal root ganglion (DRG) neurons have been implicated in multiple pain models, the interactions between NOX2-induced oxidative stress and PKC remain unknown. METHODS: A spared nerve injury (SNI) model was established in adult male rats. Pharmacologic intervention and AAV-shRNA were applied locally to DRGs. Pain behavior was evaluated by Von Frey tests. Western blotting and immunohistochemistry were performed to examine the underlying mechanisms. The excitability of DRG neurons was recorded by whole-cell patch clamping. RESULTS: SNI induced persistent NOX2 upregulation in DRGs for up to 2 weeks and increased the excitability of DRG neurons, and these effects were suppressed by local application of gp91-tat (a NOX2-blocking peptide) or NOX2-shRNA to DRGs. Of note, the SNI-induced upregulated expression of PKCε but not PKC was decreased by gp91-tat in DRGs. Mechanical allodynia and DRG excitability were increased by ψεRACK (a PKCε activator) and reduced by εV1-2 (a PKCε-specific inhibitor). Importantly, εV1-2 failed to inhibit SNI-induced NOX2 upregulation. Moreover, the SNI-induced increase in PKCε protein expression in both the plasma membrane and cytosol in DRGs was attenuated by gp91-tat pretreatment, and the enhanced translocation of PKCε was recapitulated by H2O2 administration. SNI-induced upregulation of PKCε was blunted by phenyl-N-tert-butylnitrone (PBN, an ROS scavenger) and the hydrogen peroxide catalyst catalase. Furthermore, εV1-2 attenuated the mechanical allodynia induced by H2O2 CONCLUSIONS: NOX2-induced oxidative stress promotes the sensitization of DRGs and persistent pain by increasing the plasma membrane translocation of PKCε.

A plant-by-plant strategy for high-ambition coal power phaseout in China.

More than half of current coal power capacity is in China. A key strategy for meeting China's 2060 carbon neutrality goal and the global 1.5 °C climate goal is to rapidly shift away from unabated coal use. Here we detail how to structure a high-ambition coal phaseout in China while balancing multiple national needs. We evaluate the 1037 currently operating coal plants based on comprehensive technical, economic and environmental criteria and develop a metric for prioritizing plants for early retirement. We find that 18% of plants consistently score poorly across all three criteria and are thus low-hanging fruits for rapid retirement. We develop plant-by-plant phaseout strategies for each province by combining our retirement algorithm with an integrated assessment model. With rapid retirement of the low-hanging fruits, other existing plants can operate with a 20- or 30-year minimum lifetime and gradually reduced utilization to achieve the 1.5 °C or well-below 2 °C climate goals, respectively, with complete phaseout by 2045 and 2055.

Different approaches to percutaneous endoscopic lumbar discectomy for L5/S1 lumbar disc herniation: a retrospective study.

OBJECTIVE: To observe the surgical procedure and outcome of percutaneous endoscopic lumbar discectomy for L5/S1 lumbar disc herniation (LDH) by the interlaminar and transforaminal approach. METHODS: A total of 153 patients with L5/S1 LDH who were treated using percutaneous endoscopic transforaminal discectomy (PETD, n = 84) or percutaneous endoscopic interlaminar discectomy (PEID, n = 69) from January 2016 to January 2018 were enrolled in this retrospective study. The time of puncture, operation under the endoscope, total operation and number of fluoroscopy of the two groups were compared. All groups were followed up for two years by using the Oswestry disability index (ODI) and the Visual Analogue Scale (VAS). Additionally, the incidence of complications, reoperation and postoperative low back pain were compared between the two groups. RESULTS: There were no significant difference in general information between the two groups. Compared to the PEID group, the PETD group had a decreased operation time under the endoscope and an increased puncture time, total operation time, and the number of fluoroscopy (p < 0.05). The preoperative VAS and ODI scores of the PETD and PEID group were decreased at the last follow-up (p < 0.05). There were no difference in the preoperative or last follow-up VAS and ODI scores, as well as complications, reoperation between the two groups (p > 0.05). The incidence of postoperative low back pain in the PETD group was lower than that in the PEID group (p > 0.05). CONCLUSIONS: The two-year clinical outcome of PETD is equal to that of PEID for L5/S1 LDH. Compared to those with PETD, the puncture time, total operation time and radiation exposure are lower with PEID, but the incidence of postoperative low back pain is higher.

Silencing of lncRNA Gm14461 alleviates pain in trigeminal neuralgia through inhibiting astrocyte activation.

Our previous study showed that silencing of lncRNA Gm14461 alleviated pain in a murine model of trigeminal neuralgia (TN), but the molecular mechanism remains not fully understood. Evidence indicates that astrocyte activation and autophagy are involved in the development of TN. Herein, this study aimed to elucidate whether the pain-relief effect of Gm14461 silencing in TN involved regulation of astrocyte activation and autophagy. A murine model of TN was induced by chronic constriction injury of the infraorbital nerve surgery. The mechanical withdrawal threshold (MWT) was measured to assess the analgesic effect of Gm14461 silencing. Mouse astrocytes were treated with lipopolysaccharide (LPS) as a cell model. Astrocyte activation was evaluated by glial fibrillary acidic protein (GFAP) immunofluorescence and western blot analysis of GFAP. Autophagy was evaluated by LC3 immunofluorescence and western blot analysis of autophagy-related proteins. The results showed that Gm14461 silencing increased MWT value in TN model mice. Meanwhile, Gm14461 silencing inhibited astrocyte activation and enhanced autophagy in both TN mice and LPS-treated astrocytes. The enhancement of autophagy by Gm14461 silencing involved the activation of the AMPK signaling and the suppression of the Akt/mTOR signaling. Collectively, the analgesic effect of Gm14461 silencing in TN was related to attenuation of astrocyte activation via enhancement of autophagy.

The treatment of V2 + V3 idiopathic trigeminal neuralgia using peripheral nerve radiofrequency thermocoagulation via the foramen rotundum and foramen ovale compared with semilunar ganglion radiofrequency thermocoagulation.

OBJECTIVES: To compare the advantages and disadvantages of V2 + V3 idiopathic trigeminal neuralgia using peripheral nerve radiofrequency (RF) thermocoagulation (PRF) via the foramen rotundum (FR) and foramen ovale (FO) with those of semilunar ganglion RF thermocoagulation (GRF) under local anesthesia, for exploring a new and available surgical method for patients with V2 + V3 idiopathic trigeminal neuralgia. PATIENTS AND METHODS: 102 patients with V2 + V3 idiopathic trigeminal neuralgia were enrolled in this prospective randomized controlled clinical trial, and they were divided into the PRF and GRF group randomly (n = 51 in both groups). The outcome of pain relief was assessed using the Barrow Neurological Institute (BNI) pain score, and grouped as good (BNI Class I or II, no medication required) and bad (BNI Class III-V, medication required or failed). Recurrence was defined as a relapse to a previous lower level after attainment of any higher level of pain relief. The immediate effective rate, the 2-year postoperative effective rate, the 2-year postoperative recurrence rate, and the number of complications were observed and recorded. RESULTS: Their basic conditions (age, gender ratio, side of pain, and disease duration) were similar. Furthermore, we found that the 2-year postoperative effective rate between them had no significant difference. By comparing the two groups, PRF group had the better immediate effective rate of the V2 branch and no severe complications such as corneal ulcer, however, GRF group had lower 2-year postoperative recurrence rate of the V3 branch and fewer facial swelling. CONCLUSION: The PRF surgery, like GRF, is another prospective treatment for V2 + V3 idiopathic trigeminal neuralgia by virtue of its excellent immediate effect, accurate positioning and high safety.

Effects of long non-coding RNA Gm14461 on pain transmission in trigeminal neuralgia.

BACKGROUND: This study aims to investigate the role of long non-coding RNA Gm14461 in regulating pain transmission in trigeminal neuralgia (TN). The mouse TN model was produced by chronic constriction injury of the infraorbital nerve (CCI-ION). The values of mechanical withdrawal threshold (MWT) were measured to assess the nociception of mice at different times after CCI-ION surgery (0, 1, 3, 5, 7, 9, 11, 13, 15 d). The primary mouse trigeminal ganglion neurons (TGNs) were isolated from C57BL/6 J mice and treated with TNF-α to mimic a TN cellular model. The expression of Gm14461, TNF-α, IL-1ß, and IL-6 was examined using qRT-PCR. The protein levels of CGRP and P2X3/7 receptor were measured using western blot. RESULTS: Gm14461 expression was increased in trigeminal ganglia (TGs) of TN mice on the operation side. Furthermore, Gm14461 knockdown in TGs increased, whereas Gm14461 overexpression decreased MWT in TN mice. Moreover, Gm14461 knockdown downregulated, whereas Gm14461 overexpression upregulated mRNA levels of TNF-α, IL-1ß, and IL-6 and protein levels of CGRP and P2X3/7 receptor in TGs from TN mice. In vitro assay showed that Gm14461 was upregulated by TNF-α, IL-1ß, and IL-6. Additionally, Gm14461 knockdown decreased protein levels of CGRP and P2X3/7 receptor in TNF-α-treated TGNs, whereas Gm14461 overexpression exerted the opposite effect. CONCLUSION: Gm14461 promoted pain transmission (reduced MWT value) in a CCI-ION-induced mouse TN model. The underlying mechanisms might involve the regulation of pro-inflammatory cytokines, CGRP and P2X3/7 receptor.

Preparation of Acute Spinal Cord Slices for Whole-cell Patch-clamp Recording in Substantia Gelatinosa Neurons.

Recent whole-cell patch-clamp studies from substantia gelatinosa (SG) neurons have provided a large body of information about the spinal mechanisms underlying sensory transmission, nociceptive regulation, and chronic pain or itch development. Implementations of electrophysiological recordings together with morphological studies based on the utility of acute spinal cord slices have further improved our understanding of neuronal properties and the composition of local circuitry in SG. Here, we present a detailed and practical guide for the preparation of spinal cord slices and show representative whole-cell recording and morphological results. This protocol permits ideal neuronal preservation and can mimic in vivo conditions to a certain extent. In summary, the ability to obtain an in vitro preparation of spinal cord slices enables stable current- and voltage-clamp recordings and could thus facilitate detailed investigations into the intrinsic membrane properties, local circuitry and neuronal structure using diverse experimental approaches.

Nerve injury elevates functional Cav3.2 channels in superficial spinal dorsal horn.

Cav3 channels play an important role in modulating chronic pain. However, less is known about the functional changes of Cav3 channels in superficial spinal dorsal horn in neuropathic pain states. Here, we examined the effect of partial sciatic nerve ligation (PSNL) on either expression or electrophysiological properties of Cav3 channels in superficial spinal dorsal horn. Our in vivo studies showed that the blockers of Cav3 channels robustly alleviated PSNL-induced mechanical allodynia and thermal hyperalgesia, which lasted at least 14 days following PSNL. Meanwhile, PSNL triggered an increase in both mRNA and protein levels of Cav3.2 but not Cav3.1 or Cav3.3 in rats. However, in Cav3.2 knockout mice, PSNL predominantly attenuated mechanical allodynia but not thermal hyperalgesia. In addition, the results of whole-cell patch-clamp recordings showed that both the overall proportion of Cav3 current-expressing neurons and the Cav3 current density in individual neurons were elevated in spinal lamina II neurons from PSNL rats, which could not be recapitulated in Cav3.2 knockout mice. Altogether, our findings reveal that the elevated functional Cav3.2 channels in superficial spinal dorsal horn may contribute to the mechanical allodynia in PSNL-induced neuropathic pain model.

Cell-Type Specific Distribution of T-Type Calcium Currents in Lamina II Neurons of the Rat Spinal Cord.

Spinal lamina II (substantia gelatinosa, SG) neurons integrate nociceptive information from the primary afferents and are classified according to electrophysiological (tonic firing, delayed firing, single spike, initial burst, phasic firing, gap firing and reluctant firing) or morphological (islet, central, vertical, radial and unclassified) criteria. T-type calcium (Cav3) channels play an essential role in the central mechanism of pathological pain, but the electrophysiological properties and the cell-type specific distribution of T-type channels in SG neurons have not been fully elucidated. To investigate the electrophysiological and morphological features of T-type channel-expressing or -lacking neurons, voltage- and current-clamp recordings were performed on either transverse or parasagittal spinal cord slices. Recording made in transverse spinal cord slices showed that an inward current (I T) was observed in 44.5% of the SG neurons that was fully blocked by Ni2+ and TTA-A2. The amplitude of I T depended on the magnitude and the duration of hyperpolarization pre-pulse. The voltage for eliciting and maximizing I T were -70 mV and -35 mV, respectively. In addition, we found that most of the I T-expressing neurons are tonic firing neurons and exhibit more negative action potential (AP) threshold and smaller difference of AP threshold and resting membrane potential (RMP) than those neurons lacking I T. Consistently, a specific T-type calcium channel blocker TTA-P2 increased the AP threshold and enlarged the difference between AP threshold and membrane potential (Ihold = 0). Meanwhile, the morphological analysis indicated that most of the I T-expressing neurons are islet neurons. In conclusion, we identify a cell-type specific distribution and the function of T-type channels in SG neurons. These findings might provide new insights into the mechanisms underlying the contribution of T-type channels in sensory transmission.

Overexpression of TUSC7 inhibits the inflammation caused by microglia activation via regulating miR-449a/PPAR-γ.

OBJECTIVE: The aim of this study was to investigate the mechanisms of TUSC7/miR-449a/PPAR-γ axis on the inflammation induced by microglia activation. METHODS: A compressive spinal cord injury (SCI) model was established. The expressions of TUSC7, miR-449a PPAR-γ, TNF-α and IL-1ß in spinal cord tissues of SCI rats and HAPI cells were determined. The interaction of TUSC7 and miR-449a was tested by RIP and RNA pull-down assays. The regulatory relationship between miR-449a and PPAR-γ was tested by dual luciferase reporter gene assay. RESULTS: In the spinal cord tissue of SCI rats and HAPI cells induced by LPS, TUSC7 expression was reduced and miR-449a expression was increased. Overexpression of TUSC7 inhibited microglial activation and the expression of inflammatory factors (TNF-α and IL-1ß). Moreover, we have found a targeting regulatory relation between TUSC7 and miR-449a, and a negative regulatory relationship between miR-449a and PPAR-γ. In the study of molecular mechanism, we found that TUSC7 could regulate PPAR-γ through miR-449a, and overexpression of TUSC7 inhibited microglial activation and the expression of inflammatory factors through miR-449a. CONCLUSION: Overexpression of TUSC7 inhibited microglial activation and the expression of inflammatory factors in microglia cells by regulating miR-449a/PPAR-γ.

Shank3-deficient thalamocortical neurons show HCN channelopathy and alterations in intrinsic electrical properties.

KEY POINTS: Shank3 increases the HCN channel surface expression in heterologous expression systems. Shank3Δ13-16 deficiency causes significant reduction in HCN2 expression and Ih current amplitude in thalamocortical (TC) neurons. Shank3Δ13-16 - but not Shank3Δ4-9 -deficient TC neurons share changes in basic electrical properties which are comparable to those of HCN2-/- TC neurons. HCN channelopathy may critically mediate events downstream from Shank3 deficiency. ABSTRACT: SHANK3 is a scaffolding protein that is highly enriched in excitatory synapses. Mutations in the SHANK3 gene have been linked to neuropsychiatric disorders especially the autism spectrum disorders. SHANK3 deficiency is known to cause impairments in synaptic transmission, but its effects on basic neuronal electrical properties that are more localized to the soma and proximal dendrites remain unclear. Here we confirmed that in heterologous expression systems two different mouse Shank3 isoforms, Shank3A and Shank3C, significantly increase the surface expression of the mouse hyperpolarization-activated, cyclic-nucleotide-gated (HCN) channel. In Shank3Δ13-16 knockout mice, which lack exons 13-16 in the Shank3 gene (both Shank3A and Shank3C are removed) and display a severe behavioural phenotype, the expression of HCN2 is reduced to an undetectable level. The thalamocortical (TC) neurons from the ventrobasal (VB) complex of Shank3Δ13-16 mice demonstrate reduced Ih current amplitude and correspondingly increased input resistance, negatively shifted resting membrane potential, and abnormal spike firing in both tonic and burst modes. Impressively, these changes closely resemble those of HCN2-/- TC neurons but not of the TC neurons from Shank3Δ4-9 mice, which lack exons 4-9 in the Shank3 gene (Shank3C still exists) and demonstrate moderate behavioural phenotypes. Additionally, Shank3 deficiency increases the ratio of excitatory/inhibitory balance in VB neurons but has a limited impact on the electrical properties of connected thalamic reticular (RTN) neurons. These results provide new understanding about the role of HCN channelopathy in mediating detrimental effects downstream from Shank3 deficiency.

CT-guided selective percutaneous radiofrequency thermocoagulation via the foramen rotundum for isolated maxillary nerve idiopathic trigeminal neuralgia.

OBJECTIVE Although CT-guided selective percutaneous radiofrequency thermocoagulation (PRFT) via the foramen rotundum (FR) has been used in the clinic as a novel successful treatment for isolated, second division (maxillary nerve [V2]), idiopathic trigeminal neuralgia (ITN), there is only very limited related literature published to date. This report aims to provide more detail for physicians about this technique. METHODS Between March 2013 and April 2014, 20 patients with isolated V2 ITN refractory to or intolerant of drug treatment were treated by CT-guided selective PRFT via the FR at the First Affiliated Hospital of Nanchang University. The outcome of pain relief was assessed using the Barrow Neurological Institute (BNI) pain score, and grouped as good (BNI Class I or II, no medication required) and bad (BNI Class III-V, medication required or failed). Recurrence was defined as a relapse to a previous lower level after attainment of any higher level of pain relief. Adverse effects and complications were also monitored and recorded. RESULTS All patients (100%) obtained good pain relief including BNI Class I in 17 patients (85%) and BNI Class II in 3 patients (15%) immediately postoperatively. None of the patients were lost to follow-up. During the mean follow-up period of 24.3 months (range 18-30 months), 2 patients (10%) experienced recurring pain and the mean time until recurrence was 10.5 months (range 8-13 months). No adverse effects or complications occurred except for transient numbness restricted to the V2 dermatome in all patients (100%) and facial hematoma in 3 patients (15%). CONCLUSIONS In the current study, CT-guided selective PRFT via the FR not only achieved absolute selective lesioning to V2, but also helped patients attain successful pain relief with few adverse effects. These limited data suggest that CT-guided selective PRFT via the FR appears to be a feasible, safe, effective, and even relatively ideal treatment for isolated V2 ITN, but these findings need confirmation from further studies.