Layer-specific pain relief pathways originating from primary motor cortex.

The primary motor cortex (M1) is involved in the control of voluntary movements and is extensively mapped in this capacity. Although the M1 is implicated in modulation of pain, the underlying circuitry and causal underpinnings remain elusive. We unexpectedly unraveled a connection from the M1 to the nucleus accumbens reward circuitry through a M1 layer 6-mediodorsal thalamus pathway, which specifically suppresses negative emotional valence and associated coping behaviors in neuropathic pain. By contrast, layer 5 M1 neurons connect with specific cell populations in zona incerta and periaqueductal gray to suppress sensory hypersensitivity without altering pain affect. Thus, the M1 employs distinct, layer-specific pathways to attune sensory and aversive-emotional components of neuropathic pain, which can be exploited for purposes of pain relief.

Brain Mechanisms of Pain and Dysautonomia in Diabetic Neuropathy: Connectivity Changes in Thalamus and Hypothalamus.

CONTEXT: About one-third of diabetic patients suffer from neuropathic pain, which is poorly responsive to analgesic therapy and associated with greater autonomic dysfunction. Previous research on diabetic neuropathy mainly links pain and autonomic dysfunction to peripheral nerve degeneration resulting from systemic metabolic disturbances, but maladaptive plasticity in the central pain and autonomic systems following peripheral nerve injury has been relatively ignored. OBJECTIVE: This study aimed to investigate how the brain is affected in painful diabetic neuropathy (PDN), in terms of altered structural connectivity (SC) of the thalamus and hypothalamus that are key regions modulating nociceptive and autonomic responses. METHODS: We recruited 25 PDN and 13 painless (PLDN) diabetic neuropathy patients, and 27 healthy adults as controls. The SC of the thalamus and hypothalamus with limbic regions mediating nociceptive and autonomic responses was assessed using diffusion tractography. RESULTS: The PDN patients had significantly lower thalamic and hypothalamic SC of the right amygdala compared with the PLDN and control groups. In addition, lower thalamic SC of the insula was associated with more severe peripheral nerve degeneration, and lower hypothalamic SC of the anterior cingulate cortex was associated with greater autonomic dysfunction manifested by decreased heart rate variability. CONCLUSION: Our findings indicate that alterations in brain structural connectivity could be a form of maladaptive plasticity after peripheral nerve injury, and also demonstrate a pathophysiological association between disconnection of the limbic circuitry and pain and autonomic dysfunction in diabetes.

Component-target network and mechanism of Qufeng Zhitong capsule in the treatment of neuropathic pain.

ETHNOPHARMACOLOGICAL RELEVANCE: Qufeng Zhitong capsule (QFZTC) is a traditional Chinese medicine (TCM) clinically used for treating pain. However, the active ingredients of QFZTC and its pharmacological mechanism in the treatment of neuropathic pain (NP) remain unclear. AIM OF THE STUDY: We aimed to identify the active ingredients of QFZTC and reveal its target genes and underlying mechanism of action in NP. MATERIALS AND METHODS: High-performance liquid chromatography (HPLC) was used to identify the active ingredients of QFZTC. Network pharmacology analysis was conducted to determine the core targets and pathway enrichment of QFZTC. An NP mice model was established through chronic compression injury (CCI) surgery of the sciatic nerve, while von Frey instrumentation and a thermal stimulator were employed to measure the sensitivity of mice to mechanical and thermal stimuli. Immunofluorescence was used to observe the expression of TLR4 and p-P65 in microglia. Western blotting was used to detect the levels of protein expression of Iba-1, TLR4, MyD88, P65, p-P65, and c-Fos, while ELISA kits were used to detect the release of TNF-α, IL-6, and IL-1ß. RESULTS: Seven active ingredients were identified in QFZTC: gallic acid, loganylic acid, syringin, corilagin, loganin, ellagic acid, and osthole. Network analysis identified TLR4, TNF, IL6, IL1ß, and c-Fos as core targets, and Toll-like receptors and NF-κB as core signaling pathways. Treatment with QFZTC significantly relieved mechanical allodynia and thermal hyperalgesia in CCI mice models. CCI induced an increase in the expression of TLR4 and p-P65 in microglia, whereas QFZTC dose-dependently reduced the expression of Iba-1, TLR4, MyD88, and p-P65 in the spinal cord. QFZTC inhibited the expression of the c-Fos pain marker and reduced the expression of the TNF-α, IL-6, and IL-1ß inflammatory factors. CONCLUSION: We combined the active ingredients of QFZTC with network pharmacology research to clarify its biological mechanism in the treatment of NP. We demonstrated that QFZTC reduced NP in mice probably through regulating the spinal microglia via the TLR4/MyD88/NF-κB signaling pathway. Hence, QFZTC could be regarded as a potential drug for relieving NP.

Efficacy of 5% Dextrose Water Injection for Peripheral Entrapment Neuropathy: A Narrative Review.

Current non-surgical treatment for peripheral entrapment neuropathy is considered insignificant and unsustainable; thus, it is essential to find an alternative novel treatment. The technique of perineural injection therapy using 5% dextrose water has been progressively used to treat many peripheral entrapment neuropathies and has been proven to have outstanding effects in a few high-quality studies. Currently, the twentieth edition of Harrison's Principles of Internal Medicine textbook recommends this novel injection therapy as an alternative local treatment for carpal tunnel syndrome (CTS). Hence, this novel approach has become the mainstream method for treating CTS, and other studies have revealed its clinical benefit for other peripheral entrapment neuropathies. In this narrative review, we aimed to provide an insight into this treatment method and summarize the current studies on cases of peripheral entrapment neuropathy treated by this method.

Emerging Benefits: Pathophysiological Functions and Target Drugs of the Sigma-1 Receptor in Neurodegenerative Diseases.

The sigma-1 receptor (Sig-1R) is encoded by the SIGMAR1 gene and is a nonopioid transmembrane receptor located in the mitochondrial-associated endoplasmic reticulum membrane (MAM). It helps to locate endoplasmic reticulum calcium channels, regulates calcium homeostasis, and acts as a molecular chaperone to control cell fate and participate in signal transduction. It plays an important role in protecting neurons through a variety of signaling pathways and participates in the regulation of cognition and motor behavior closely related to neurodegenerative diseases. Based on its neuroprotective effects, Sig-1R has now become a breakthrough target for alleviating Alzheimer's disease and other neurodegenerative diseases. This article reviews the most cutting-edge research on the function of Sig-1R under normal or pathologic conditions and target drugs of the sigma-1 receptor in neurodegenerative diseases.

Motor cortex stimulation for chronic neuropathic pain: results of a double-blind randomized study.

Motor cortex stimulation via surgically implanted electrodes has been used as an off-label treatment for chronic neuropathic pain, but its efficacy has not been fully established. We aimed to objectively study the efficacy of motor cortex stimulation and characterize potential predictors of response. In this randomized, double-blind, sham-controlled, single centre trial, we recruited 18 patients with chronic neuropathic pain who did not adequately respond to conventional treatment and had a numerical pain rating scale (NRS) score ≥6. Patients were initially assigned to receive 3 months of active ('on') or sham ('off') stimulation in a double-blind cross-over phase. This was followed by a 3-month single-blind phase, and 6 months of open-label follow-up. A meaningful response in our trial was defined as a ≥30% or 2-point reduction in NRS scores during active stimulation. Using Bayesian statistics, we found a 41.4% probability of response towards on versus off motor cortex stimulation. The probability of improvement during active stimulation (double-blind, single-blind and open-label phases) compared to baseline was 47.2-68.5%. Thirty nine per cent of the patients were considered long-term responders, 71.4% of whom had facial pain, phantom limb pain or complex regional pain syndrome. In contrast, 72.7% of non-responders had either post-stroke pain or pain associated with brachial plexus avulsion. Thirty-nine per cent of patients had a substantial postoperative analgesic effect after electrode insertion in the absence of stimulation. Individuals with diagnoses associated with a good postoperative outcome or those who developed an insertional effect had a near 100% probability of response to motor cortex stimulation. In summary, we found that ∼40% of patients responded to motor cortex stimulation, particularly those who developed an insertional effect or had specific clinical conditions that seemed to predict an appropriate postoperative response.

Classification of circadian pain rhythms and pain characteristics in chronic pain patients: An observational study.

ABSTRACT: This study aimed to perform cluster analysis in patients with chronic pain to extract groups with similar circadian rhythms and compare neuropathic pain and psychological factors among these groups to identify differences in pain-related outcomes. A total of 63 community-dwellers with pain lasting at least 3 months and Numerical Rating Scale scores of ≥2 were recruited from 3 medical institutions. Their pain circadian rhythms were evaluated over 7 days by measuring pain intensity at 6-time points per day using a 10-cm visual analog scale. Cluster analysis was performed using 6 variables with standardized visual analog scale values at 6-time points for individual participants to extract groups with similar pain circadian rhythms. The results of the Neuropathic Pain Symptom Inventory and psychological evaluations in each group were compared using the Kruskal-Wallis test. The results revealed 3 clusters with different circadian rhythms of pain. The total and evoked pain subscale Neuropathic Pain Symptom Inventory scores differed among the 3 clusters. The results suggest that a thorough understanding of circadian pain rhythms in chronic pain patients may facilitate the performance of activities of daily living and physical exercise from the perspective of pain management.

Electroacupuncture inhibits the interaction between peripheral TRPV1 and P2X3 in rats with different pathological pain.

Chronic pain is regarded to be one of the common and refractory diseases to cure in the clinic. One hundred Hz electroacupuncture (EA) is commonly used for inflammatory pain and 2 Hz for neuropathic pain possibly by modulating the transient receptor potential vanilloid subtype 1 (TRPV1) or the purinergic P2X3 related pathways. To clarify the mechanism of EA under various conditions of pathological pain, rats received a subcutaneous administration of complete Freund's adjuvant (CFA) for inflammatory pain and spared nerve injury (SNI) for neuropathic pain. The EA was performed at the bilateral ST36 and BL60 1 d after CFA or SNI being successfully established for 3 consecutive days. The mechanical hyperalgesia test was measured at baseline, 1 d after model establishment, 1 d and 3 d after EA. The co-expression changes, co-immunoprecipitation of TRPV1 and P2X3, and spontaneous pain behaviors (SPB) test were performed 3 d after EA stimulation. One hundred Hz EA or 2Hz EA stimulation could effectively down-regulate the hyperalgesia of CFA or SNI rats. The increased co-expression ratio between TRPV1 and P2X3 at the dorsal root ganglion (DRG) in two types of pain could be reduced by 100Hz or 2Hz EA intervention. While 100Hz or 2Hz EA was not able to eliminate the direct physical interaction between TRPV1 and P2X3. Moreover, EA could significantly inhibit the SPB induced by the co-activation of peripheral TRPV1 and P2X3. All results indicated that EA could significantly reduce the hyperalgesia and the SPB, which was partly related to inhibiting the co-expression and indirect interaction between peripheral TRPV1 and P2X3.

Supraspinal nociceptive networks in neuropathic pain after spinal cord injury.

Neuropathic pain following spinal cord injury involves plastic changes along the whole neuroaxis. Current neuroimaging studies have identified grey matter volume (GMV) and resting-state functional connectivity changes of pain processing regions related to neuropathic pain intensity in spinal cord injury subjects. However, the relationship between the underlying neural processes and pain extent, a complementary characteristic of neuropathic pain, is unknown. We therefore aimed to reveal the neural markers of widespread neuropathic pain in spinal cord injury subjects and hypothesized that those with greater pain extent will show higher GMV and stronger connectivity within pain related regions. Thus, 29 chronic paraplegic subjects and 25 healthy controls underwent clinical and electrophysiological examinations combined with neuroimaging. Paraplegics were demarcated based on neuropathic pain and were thoroughly matched demographically. Our findings indicate that (a) spinal cord injury subjects with neuropathic pain display stronger connectivity between prefrontal cortices and regions involved with sensory integration and multimodal processing, (b) greater neuropathic pain extent, is associated with stronger connectivity between the posterior insular cortex and thalamic sub-regions which partake in the lateral pain system and (c) greater intensity of neuropathic pain is related to stronger connectivity of regions involved with multimodal integration and the affective-motivational component of pain. Overall, this study provides neuroimaging evidence that the pain phenotype of spinal cord injury subjects is related to the underlying function of their resting brain.

Effects of Curcumin and Its Different Formulations in Preclinical and Clinical Studies of Peripheral Neuropathic and Postoperative Pain: A Comprehensive Review.

Lesion or disease of the somatosensory system leads to the development of neuropathic pain. Peripheral neuropathic pain encompasses damage or injury of the peripheral nervous system. On the other hand, 10-15% of individuals suffer from acute postoperative pain followed by persistent pain after undergoing surgeries. Antidepressants, anticonvulsants, baclofen, and clonidine are used to treat peripheral neuropathy, whereas opioids are used to treat postoperative pain. The negative effects associated with these drugs emphasize the search for alternative therapeutics with better efficacy and fewer side effects. Curcumin, a polyphenol isolated from the roots of Curcuma longa, possesses antibacterial, antioxidant, and anti-inflammatory properties. Furthermore, the low bioavailability and fast metabolism of curcumin have led to the advent of various curcumin formulations. The present review provides a comprehensive analysis on the effects of curcumin and its formulations in preclinical and clinical studies of neuropathic and postoperative pain. Based on the positive outcomes from both preclinical and clinical studies, curcumin holds the promise of mitigating or preventing neuropathic and postoperative pain conditions. However, more clinical studies with improved curcumin formulations are required to involve its use as adjuvant to neuropathic and postoperative drugs.

Can chronopharmacology improve the therapeutic management of neurological diseases?

The importance of circadian rhythm dysfunctions in the pathophysiology of neurological diseases has been highlighted recently. Chronopharmacology principles imply that tailoring the timing of treatments to the circadian rhythm of individual patients could optimize therapeutic management. According to these principles, chronopharmacology takes into account the individual differences in patients' clocks, the rhythmic changes in the organism sensitivity to therapeutic and side effects of drugs, and the predictable time variations of disease. This review examines the current literature on chronopharmacology of neurological diseases focusing its scope on epilepsy, Alzheimer and Parkinson diseases, and neuropathic pain, even if other neurological diseases could have been analyzed. While the results of the studies discussed in this review point to a potential therapeutic benefit of chronopharmacology in neurological diseases, the field is still in its infancy. Studies including a sufficiently large number of patients and measuring gold standard markers of the circadian rhythmicity are still needed to evaluate the beneficial effect of administration times over the 24-hour day but also of clock modulating drugs.

Electroacupuncture may alleviate neuropathic pain via suppressing P2X7R expression.

Neuropathic pain is a severe problem that is difficult to treat clinically. Reducing abnormal remodeling of dendritic spines/synapses and increasing the anti-inflammatory effects in the spinal cord dorsal horn are potential methods to treat this disease. Previous studies have reported that electroacupuncture (EA) could increase the pain threshold after peripheral nerve injury. However, the underlying mechanism is unclear. P2X7 receptors (P2X7R) mediate the activation of microglia and participate in the occurrence and development of neuropathic pain. We hypothesized that the effects of EA on relieving pain may be related to the downregulation of the P2X7R. Spinal nerve ligation (SNL) rats were used as a model in this experiment, and 2'(3')-O-(4-benzoyl)benzoyl ATP (BzATP) was used as a P2X7R agonist. We found that EA treatment decreased dendritic spine density, inhibited synaptic reconstruction and reduced inflammatory response, which is consistent with the decrease in P2X7R expression as well as the improved neurobehavioral performance. In contrast to the beneficial effects of EA, BzATP enhanced abnormal remodeling of dendritic spines/synapses and inflammation. Furthermore, the EA-mediated positive effects were reversed by BzATP, which is consistent with the increased P2X7R expression. These findings indicated that EA improves neuropathic pain by reducing abnormal dendritic spine/synaptic reconstruction and inflammation via suppressing P2X7R expression.

Anti-nociceptive effects of Sedum Lineare Thunb. on spared nerve injury-induced neuropathic pain by inhibiting TLR4/NF-κB signaling in the spinal cord in rats.

Neuropathic pain is still a critical public health problem worldwide. Thereby, the search for novel and more effective strategies against neuropathic pain is urgently considered. It is known that neuroinflammation plays a crucial role in the pathogenesis of neuropathic pain. SedumLineare Thunb. (SLT), a kind of Chinese herb originated from the whole grass of Crassulaceae plant, was reported to possess anti-inflammatory activity. However, whether SLT has anti-nociceptive effect on neuropathic pain and its possible underlying mechanisms remains poorly elucidated. In this study, a rat model of neuropathic pain induced by spared nerve injury (SNI)was applied. SLT (p.o.) was administered to SNI rats once every day lasting for 14 days. Pain-related behaviors were assessed by using paw withdrawal threshold (PWT) and CatWalk gait parameters. Expression levels of inflammatory mediators and pain-related signaling molecules in the spinal cord were detected using western blotting assay. The results revealed that SLT (30, 100, and 300 mg/kg, p.o.) treatment for SNI rats ameliorated mechanical hypersensitivity in a dose-dependent manner. Application of SLT at the most effective dose of 100 mg/kg to SNI rats not only significantly blocked microglial activation, but also markedly reduced the protein levels of spinal HMGB1, TLR4, MyD88, TRAF6, IL-1ß, IL-6, and TNF-α, along with an enhancement in gait parameters. Furthermore, SLT treatment dramatically inhibited the phosphorylation levels of both IKK and NF-κB p65 but obviously improved both IκB and IL-10 protein expression in the spinal cord of SNI rats. Altogether, these data suggested that SLT could suppress spinal TLR4/NF-κB signaling pathway in SNI rats, which might at least partly contribute to its anti-nociceptive action, indicating that SLT may serveas a potential therapeutic agent for neuropathic pain.

An overview of ongoing clinical trials assessing pharmacological therapeutic strategies to manage chemotherapy-induced peripheral neuropathy, based on preclinical studies in rodent models.

Chemotherapy-induced peripheral neuropathy (CIPN) is a major dose-limiting side effect induced by a variety of chemotherapeutic agents. Symptoms are mainly sensory: pain, tingling, numbness, and temperature sensitivity. They may require the tapering of chemotherapy regimens or even their cessation; thus, the prevention/treatment of CIPN is critical to increase effectiveness of cancer treatment. However, CIPN management is mainly based on conventional neuropathic pain treatments, with poor clinical efficacy. Therefore, significant effort is made to identify new pharmacological targets to prevent/treat CIPN. Animal modeling is a key component in predicting human response to drugs and in understanding the pathophysiological mechanisms underlying CIPN. In fact, studies performed in rodents highlighted several pharmacological targets to treat/prevent CIPN. This review provides updated information about ongoing clinical trials testing drugs for the management of CIPN and presents some of their proof-of-concept studies conducted in rodent models. The presented drugs target oxidative stress, renin-angiotensin system, glutamatergic neurotransmission, sphingolipid metabolism, neuronal uptake transporters, nicotinamide adenine dinucleotide metabolism, endocannabinoid system, transient receptor potential channels, and serotoninergic receptors. As some clinical trials focus on the effect of the drugs on pain, others evaluate their efficacy by assessing general neuropathy. Moreover, based on studies conducted in rodent models, it remains unclear if some of the tested drugs act in an antinociceptive fashion or have neuroprotective properties. Thus, further investigations are needed to understand their mechanism of action, as well as a global standardization of the methods used to assess efficacy of new therapeutic strategies in the treatment of CIPN.

The Effect of Optogenetic Inhibition of the Anterior Cingulate Cortex in Neuropathic Pain Following Sciatic Nerve Injury.

Cortical disinhibition is the underlying pathological alteration contributing to neuropathic pain associated with peripheral nerve injury. Nerve injury resulting in disinhibition of the anterior cingulate cortex has been reported. However, the effect of optogenetic inhibition of the anterior cingulate cortex (ACC) on the sensory component of nerve injury-induced neuropathic pain has not been well studied. To investigate the feasibility of optogenetic ACC modulation, we injected an optogenetic virus or a null virus into the ACC of a nerve injury-induced neuropathic pain model. The unilateral ACC was modulated, and the optogenetic effect was measured by mechanical and thermal sensitivity tests. The assessment was performed in "pre-light off," "stimulation-yellow light on," and "post-light off" states. Optogenetic inhibition of the ACC in injury models revealed improved mechanical and thermal latencies with profound pain-relieving effects against nerve injury-induced neuropathic pain. The sensory thalamic discharge in electrophysiological in vivo recordings was also altered during laser stimulation. This finding indicates that hyperactivity of the ACC in nerve injury increases output to the spinothalamic tract through direct or indirect pathways. The direct photoinhibition of ACC neurons could play a vital role in restoring equilibrium and provide novel insight into techniques that can assuage peripheral nerve injury-induced neuropathic pain.

Positive Regulatory Domain I-binding Factor 1 Mediates Peripheral Nerve Injury-induced Nociception in Mice by Repressing Kv4.3 Channel Expression.

BACKGROUND: The transcriptional repressor positive regulatory domain I-binding factor 1 (PRDM1) is expressed in adult mouse dorsal root ganglion and regulates the formation and function of peripheral sensory neurons. The authors hypothesized that PRDM1 in the dorsal root ganglion may contribute to peripheral nerve injury-induced nociception regulation and that its mechanism may involve Kv4.3 channel transcriptional repression. METHODS: Nociception was induced in C57BL/6 mice by applying chronic constriction injury, complete Freund's adjuvant, or capsaicin plantar injection. Nociceptive response was evaluated by mechanical allodynia, thermal hyperalgesia, cold hyperalgesia, or gait analysis. The role of PRDM1 was evaluated by injection of Prdm1 knockdown and overexpression adeno-associated viruses. The interaction of PRDM1 at the Kv4.3 (Kcnd3) promoter was evaluated by chromatin immunoprecipitation assay. Excitability of dorsal root ganglion neurons was evaluated by whole cell patch clamp recordings, and calcium signaling in spinal dorsal horn neurons was evaluated by in vivo two-photon imaging. RESULTS: Peripheral nerve injury increased PRDM1 expression in the dorsal root ganglion, which reduced the activity of the Kv4.3 promoter and repressed Kv4.3 channel expression (injured vs. uninjured; all P < 0.001). Knockdown of PRDM1 rescued Kv4.3 expression, reduced the high excitability of injured dorsal root ganglion neurons, and alleviated peripheral nerve injury-induced nociception (short hairpin RNA vs. Scram; all P < 0.05). In contrast, PRDM1 overexpression in naive mouse dorsal root ganglion neurons diminished Kv4.3 channel expression and induced hyperalgesia (PRDM1 overexpression vs. control, mean ± SD; n = 13; all P < 0.0001) as evaluated by mechanical allodynia (0.6 ± 0.3 vs. 1.2 ± 0.2 g), thermal hyperalgesia (5.2 ± 1.3 vs. 9.8 ± 1.7 s), and cold hyperalgesia (3.4 ± 0.5 vs. 5.3 ± 0.6 s). Finally, PRDM1 downregulation in naive mice reduced the calcium signaling response of spinal dorsal horn neurons to thermal stimulation. CONCLUSIONS: PRDM1 contributes to peripheral nerve injury-induced nociception by repressing Kv4.3 channel expression in injured dorsal root ganglion neurons.

Electroacupuncture Modulates Spinal BDNF/TrκB Signaling Pathway and Ameliorates the Sensitization of Dorsal Horn WDR Neurons in Spared Nerve Injury Rats.

Neuropathic pain is more complex and severely affects the quality of patients' life. However, the therapeutic strategy for neuropathic pain in the clinic is still limited. Previously we have reported that electroacupuncture (EA) has an attenuating effect on neuropathic pain induced by spared nerve injury (SNI), but its potential mechanisms remain to be further elucidated. In this study, we designed to determine whether BDNF/TrκB signaling cascade in the spinal cord is involved in the inhibitory effect of 2 Hz EA on neuropathic pain in SNI rats. The paw withdrawal threshold (PWT) of rats was used to detect SNI-induced mechanical hypersensitivity. The expression of BDNF/TrκB cascade in the spinal cord was evaluated by qRT-PCR and Western blot assay. The C-fiber-evoked discharges of wide dynamic range (WDR) neurons in spinal dorsal horn were applied to indicate the noxious response of WDR neurons. The results showed that 2 Hz EA significantly down-regulated the levels of BDNF and TrκB mRNA and protein expression in the spinal cord of SNI rats, along with ameliorating mechanical hypersensitivity. In addition, intrathecal injection of 100 ng BDNF, not only inhibited the analgesic effect of 2 Hz EA on pain hypersensitivity, but also reversed the decrease of BDNF and TrκB expression induced by 2 Hz EA. Moreover, 2 Hz EA obviously reduced the increase of C-fiber-evoked discharges of dorsal horn WDR neurons by SNI, but exogenous BDNF (100 ng) effectively reversed the inhibitory effect of 2 Hz EA on SNI rats, resulting in a remarkable improvement of excitability of dorsal horn WDR neurons in SNI rats. Taken together, these data suggested that 2 Hz EA alleviates mechanical hypersensitivity by blocking the spinal BDNF/TrκB signaling pathway-mediated central sensitization in SNI rats. Therefore, targeting BDNF/TrκB cascade in the spinal cord may be a potential mechanism of EA against neuropathic pain.

Reduced activity of GAD67 expressing cells in the reticular thalamus enhance thalamic excitatory activity and varicella zoster virus associated pain.

Within the reticular thalamic nucleus neurons express gamma aminobutyric acid (GABA) and these cells project to the ventral posteromedial thalamic nucleus. When GABA activity decreases the activity of excitatory cells in the ventral posteromedial nucleus would be expected to increase. In this study, we addressed the hypothesis that attenuating GABAergic cells in the reticular thalamic nucleus increases excitatory activity in the ventral posteromedial nucleus increasing varicella zoster virus (VZV) associated pain in the orofacial region. Adeno-associated virus (AAV) was infused in the reticular thalamic nucleus of Gad1-Cre rats. This virus transduced a G inhibitory designer receptor exclusively activated by designer drugs (DREADD) gene that was Cre dependent. A dose of estradiol that was previously shown to reduce VZV pain and increase GABAergic activity was administered to castrated and ovariectomized rats. Previous studies suggest that estradiol attenuates herpes zoster pain by increasing the activity of inhibitory neurons and decreasing the activity of excitatory cells within the lateral thalamic region. The ventral posteromedial nucleus was infused with AAV containing a GCaMP6f expression construct. A glass lens was implanted for miniscope imaging. Our results show that the activity of GABA cells within the reticular thalamic region decreased with clozapine N-oxide treatment concomitant with increased calcium activity of excitatory cells in the ventral posteromedial nucleus and an increased orofacial pain response. The results suggest that estradiol attenuates herpes zoster pain by increasing the activity of inhibitory neurons within the reticular thalamus that then inhibit excitatory activity in ventral posteromedial nucleus causing a reduction in orofacial pain.

Fluoroquinolone prophylaxis does not increase risk of neuropathy in children with acute lymphoblastic leukemia.

BACKGROUND: Fluoroquinolone antibiotics are frequently utilized in pediatric oncology patients as prophylaxis or step-down therapy following broad spectrum beta-lactam therapy for febrile neutropenia. Concerns regarding neurotoxicity limit the use of these agents. No studies have evaluated the association between fluoroquinolone use and neurotoxicity in pediatric oncology patients receiving other neurotoxic agents such as vincristine. METHODS: An observational cohort study comprising patients aged 0-18 at diagnosis enrolled on a prospective study for treatment of acute lymphoblastic leukemia (ALL) at a pediatric comprehensive cancer center between October 2007 and November 2018. Data for neuropathic pain and sensory or motor neuropathy were collected prospectively, and a Cox proportional hazards regression model was used to evaluate associations between administration of fluoroquinolone antibiotics during induction therapy and subsequent development of vincristine-induced peripheral neurotoxicity (VIPN). RESULTS: A total of 598 participants were enrolled, including 338 (57%) who received fluoroquinolones during induction therapy; of these 470 (79%) were diagnosed with VIPN and 139 (23%) were diagnosed with high-grade (Grade 3+) VIPN. On unadjusted analyses, and analyses adjusted for age and race, there was no evidence of an association between fluoroquinolone exposure and subsequent VIPN (hazard ratio [HR] 0.8, 95% CI 0.5-1.04, P = .08) or high-grade VIPN (HR 1.1, 95% CI 0.4-2.2, P = .87). CONCLUSIONS: The results of this observational study do not show an association between exposure to fluoroquinolone antibiotics during induction therapy for ALL and subsequent development of vincristine-induced peripheral neuropathies, and suggest that a large increase in VIPN is unlikely.

An integrated strategy for discovering effective components of Shaoyao Gancao decoction for treating neuropathic pain by the combination of partial least-squares regression and multi-index comprehensive method.

ETHNOPHARMACOLOGICAL RELEVANCE: Neuropathic pain, the incidence of which ranges from 5 to 8% in the general population, remains challenge in the treatment. Shaoyao Gancao decoction (SGD) is a Chinese classical formula used to relieve pain for thousands of years and has been applied for neuropathic pain nowadays. However, the effective components of SGD for the treatment of neuropathic pain remains unclear. AIMS OF STUDY: To investigate the effect and potential mechanism of SGD against neuropathic pain and further reveal the effective components of SGD in the treatment of neuropathic pain. MATERIALS AND METHODS: Spared nerve injury (SNI) model rats of neuropathic pain were orally given SGD to intervene, the components in vivo after SGD administration were determined, behavior indicators, biochemical parameters, and metabolomics were applied for assessing the efficacy. Then correlation between components and biomarkers was analyzed by pearson correlation method. To further measure the contribution of components to efficacy, the combination of partial least-squares regression (PLSR) and multi-index comprehensive method was carried out, according to the corresponding contribution degree of the results, the components with large contribution degree were considered as the effective components. RESULTS: SGD exhibited a significant regulatory effect on neuropathic pain, which could increase the pain threshold and decrease the levels of SP, ß-EP, PGE2 and NO. With the high resolution of UPLC-Q-TOF/MS technology, a total of 128 compounds from SGD were identified and 44 of them were absorbed in blood. Besides, 40 serum biomarkers were identified after intervention of SGD and the metabolic pathways were constructed. The key metabolic pathways including Glycerophospholipid metabolism, Linoleic acid metabolism, Alpha-linolenic acid metabolism, Glycosylphosphatidylinositol-anchor biosynthesis and Arachidonic acid metabolism may be related to the regulation of neuropathic pain. Metabolomics combined with PLSR and multi-index comprehensive method was utilized to discover 5 components including paeonol, DL-Arabinose, benzoic acid, hispaglabridin A and paeonilactone C as effective components of SGD in the treatment of neuropathic pain. This strategy was used to explore the effective components of SGD and elucidate its possible analgesic mechanism. CONCLUSION: This study demonstrate that SGD significantly relieved neuropathic pain and elucidated the effective components of SGD for treating neuropathic pain, the strategy as an illustrative case study can be applied to other classical formula and is beneficial to improve the quality and efficacy.