Etifoxine provides benefits in nerve repair with acellular nerve grafts

The effectiveness of acellular nerve allografts compared to autografts in animal models: A systematic review and meta-analysis

BACKGROUND

Treatment of nerve injuries proves to be a worldwide clinical challenge. Acellular nerve allografts are suggested to be a promising alternative for bridging a nerve gap to the current gold standard, an autologous nerve graft.

OBJECTIVE

To systematically review the efficacy of the acellular nerve allograft, its difference from the gold standard (the nerve autograft) and to discuss its possible indications.

MATERIAL AND METHODS

PubMed, Embase and Web of Science were systematically searched until the 4th of January 2022. Original peer reviewed paper that presented 1) distinctive data; 2) a clear comparison between not immunologically processed acellular allografts and autologous nerve transfers; 3) was performed in laboratory animals of all species and sex. Meta analyses and subgroup analyses (for graft length and species) were conducted for muscle weight, sciatic function index, ankle angle, nerve conduction velocity, axon count diameter, tetanic contraction and amplitude using a Random effects model. Subgroup analyses were conducted on graft length and species.

RESULTS

Fifty articles were included in this review and all were included in the meta-analyses. An acellular allograft resulted in a significantly lower muscle weight, sciatic function index, ankle angle, nerve conduction velocity, axon count and smaller diameter, tetanic contraction compared to an autologous nerve graft. No difference was found in amplitude between acellular allografts and autologous nerve transfers. Post hoc subgroup analyses of graft length showed a significant reduced muscle weight in long grafts versus small and medium length grafts. All included studies showed a large variance in methodological design.

CONCLUSION

Our review shows that the included studies, investigating the use of acellular allografts, showed a large variance in methodological design and are as a consequence difficult to compare. Nevertheless, our results indicate that treating a nerve gap with an allograft results in an inferior nerve recovery compared to an autograft in seven out of eight outcomes assessed in experimental animals. In addition, based on our preliminary post hoc subgroup analyses we suggest that when an allograft is being used an allograft in short and medium (0-1cm, > 1-2cm) nerve gaps is preferred over an allograft in long (> 2cm) nerve gaps.

Revisiting the Role of Biologically Active Natural and Synthetic Compounds as an Intervention to Treat Injured Nerves

Traumatic lesions in nerves present high incidence and may culminate in sensorimotor and/or autonomic dysfunctions or a total loss of function, affecting the patient's quality of life. Although the microenvironment favors peripheral nerve regeneration, the regenerative process is not always successful. Some herbs, natural products, and synthetic drugs have been studied as potential pro-regenerative interventions. We reviewed and discussed the most recent articles published over the last ten years in high impact factor journals. Even though most of the articles contemplated in this review were in vitro and animal model studies, those with herbs showed promising results. Most of them presented antioxidant and anti-inflammatory effects. Drugs of several pharmacological classes also showed optimistic outcomes in nerve functional recovery, including clinical trials. The results are hopeful; however, mechanisms of action need to be elucidated, and there is a need for more high-quality clinical studies. The study presents careful compilation of findings of dozens of compounds with consistent pro-regenerative evidence published in respected scientific journals. It may be valuable for health professionals and researchers in the field.

The non-benzodiazepine anxiolytic etifoxine limits mechanical allodynia and anxiety-like symptoms in a mouse model of streptozotocin-induced diabetic neuropathy

More than 450 million people worldwide suffer from diabetes, or 1 in 11 people. Chronic hyperglycemia degrades patients’ quality of life and the development of neuropathic pain contributes to the burden of this disease. In this study, we used the mouse model of streptozocin-induced diabetic type 1 neuropathy to assess the analgesic potential of etifoxine. Etifoxine is a prescribed anxiolytic that increases GABAAA receptor function through a direct positive allosteric modulation effect and, indirectly, by stimulating the production of endogenous GABAA receptor positive modulators such as allopregnanolone-type neurosteroids. We show that a post-symptomatic or preventive treatment strongly and durably reduces mechanical hyperalgesia and anxiety in diabetic neuropathic mice. This analgesic and neuroprotective effect on painful symptoms and emotional comorbidities is promising and should now be clinically evaluated.

Decellularization of Nervous Tissues and Clinical Application

The nervous system is an ensemble of organs that transmit and process external information and are responsible for the adaption to the external environment and homeostasis control of the internal environment. The nervous system of vertebrates is divided into the central nervous system (CNS) and peripheral nervous system (PNS) due to its structural features. The CNS, which includes the brain and the spinal cord, processes information from external stimuli and assembles orders suitable for these stimuli. The CNS then sends signals to control other organs/tissues. On the other hand, the PNS connects the CNS to other organs/tissues and functions as a signal pathway. Therefore, the decline and loss of various functions due to injuries of the nervous system cause an impaired quality of life (QOL) and eventually the termination of life activities. Here, we report mainly on decellularized neural tissue and its application as a substrate for the regeneration of the nervous system.

Tissue Engineering and Regenerative Medicine: Achievements, Future, and Sustainability in Asia

Exploring innovative solutions to improve the healthcare of the aging and diseased population continues to be a global challenge. Among a number of strategies toward this goal, tissue engineering and regenerative medicine (TERM) has gradually evolved into a promising approach to meet future needs of patients. TERM has recently received increasing attention in Asia, as evidenced by the markedly increased number of researchers, publications, clinical trials, and translational products. This review aims to give a brief overview of TERM development in Asia over the last decade by highlighting some of the important advances in this field and featuring major achievements of representative research groups. The development of novel biomaterials and enabling technologies, identification of new cell sources, and applications of TERM in various tissues are briefly introduced. Finally, the achievement of TERM in Asia, including important publications, representative discoveries, clinical trials, and examples of commercial products will be introduced. Discussion on current limitations and future directions in this hot topic will also be provided.

A novel mouse model of contralateral C7 transfer via the pretracheal route: A feasibility study

BACKGROUND

Contralateral seventh cervical nerve transfer (contralateral C7 transfer) is a novel treatment for patients with spastic paralysis, including stroke and traumatic brain injury. However, little is known on changes in plasticity that occur in the intact hemisphere after C7 transfer. An appropriate surgical model is required.

NEW METHOD

We described in detail the anatomy of the C7 in a mouse model. We designed a pretracheal route by excising the contralateral C6 lamina ventralis, and the largest nerve defect necessary for direct neurorrhaphy was compared with defect lengths in a prespinal route. To test feasibility, we performed in-vivo surgery and assessed nerve regeneration by immunofluorescence, histology, electrophysiology, and behavioral examinations.

RESULTS

Two types of branching were found in the anterior and posterior divisions of C7, both of which were significantly larger than the sural nerve. The length of the nerve defect was drastically reduced after contralateral C6 lamina ventralis excision. Direct tension-free neurorrhaphy was achieved in 66.7% of mice. The expression of neurofilament in the distal segment of the regenerated C7 increased. Histological examination revealed remyelination. Behavioral tests and electrophysiology tests showed functional recovery in a traumatic brain injury mouse.

COMPARISON WITH EXISTING METHODS

This is the first direct tension-free neurorrhaphy mouse model of contralateral C7 transfer which shortened the time of nerve regeneration; previous models have used nerve grafting.

CONCLUSIONS

This paper describes a simple, reproducible, and effective mouse model of contralateral C7 transfer for studying brain plasticity and exploring potential new therapies after unilateral cerebral injury.

Reduction of Traumatic Brain Damage by Tspo Ligand Etifoxine

Experimental studies have shown that ligands of the 18 kDa translocator protein can reduce neuronal damage induced by traumatic brain injury by protecting mitochondria and preventing metabolic crisis. Etifoxine, an anxiolytic drug and 18 kDa translocator protein ligand, has shown beneficial effects in the models of peripheral nerve neuropathy. The present study investigates the potential effect of etifoxine as a neuroprotective agent in traumatic brain injury (TBI). For this purpose, the effect of etifoxine on lesion volume and modified neurological severity score at 4 weeks was tested in Sprague-Dawley adult male rats submitted to cortical impact contusion. Effects of etifoxine treatment on neuronal survival and apoptosis were also assessed by immune stains in the perilesional area. Etifoxine induced a significant reduction in the lesion volume compared to nontreated animals in a dose-dependent fashion with a similar effect on neurological outcome at four weeks that correlated with enhanced neuron survival and reduced apoptotic activity. These results are consistent with the neuroprotective effect of etifoxine in TBI that may justify further translational research.

Contralateral C7 transfer combined with acellular nerve allografts seeded with differentiated adipose stem cells for repairing upper brachial plexus injury in rats

Nerve grafting has always been necessary when the contralateral C7 nerve root is transferred to treat brachial plexus injury. Acellular nerve allograft is a promising alternative for the treatment of nerve defects, and results were improved by grafts laden with differentiated adipose stem cells. However, use of these tissue-engineered nerve grafts has not been reported for the treatment of brachial plexus injury. The aim of the present study was to evaluate the outcome of acellular nerve allografts seeded with differentiated adipose stem cells to improve nerve regeneration in a rat model in which the contralateral C7 nerve was transferred to repair an upper brachial plexus injury. Differentiated adipose stem cells were obtained from Sprague-Dawley rats and transdifferentiated into a Schwann cell-like phenotype. Acellular nerve allografts were prepared from 15-mm bilateral sections of rat sciatic nerves. Rats were randomly divided into three groups: acellular nerve allograft, acellular nerve allograft + differentiated adipose stem cells, and autograft. The upper brachial plexus injury model was established by traction applied away from the intervertebral foramen with micro-hemostat forceps. Acellular nerve allografts with or without seeded cells were used to bridge the gap between the contralateral C7 nerve root and C5–6 nerve. Histological staining, electrophysiology, and neurological function tests were used to evaluate the effect of nerve repair 16 weeks after surgery. Results showed that the onset of discernible functional recovery occurred earlier in the autograft group first, followed by the acellular nerve allograft + differentiated adipose stem cells group, and then the acellular nerve allograft group; moreover, there was a significant difference between autograft and acellular nerve allograft groups. Compared with the acellular nerve allograft group, compound muscle action potential, motor conduction velocity, positivity for neurofilament and S100, diameter of regenerating axons, myelin sheath thickness, and density of myelinated fibers were remarkably increased in autograft and acellular nerve allograft + differentiated adipose stem cells groups. These findings confirm that acellular nerve allografts seeded with differentiated adipose stem cells effectively promoted nerve repair after brachial plexus injuries, and the effect was better than that of acellular nerve repair alone. This study was approved by the Animal Ethics Committee of the First Affiliated Hospital of Sun Yat-sen University of China (approval No. 2016-150) in June 2016.

Nerve Repair Using Decellularized Nerve Grafts in Rat Models. A Review of the Literature

Peripheral nerve regeneration after severe traumatic nerve injury is a relevant clinical problem. Several different strategies have been investigated to solve the problem of bridging the nerve gap. Among these, the use of decellularized nerve grafts has been proposed as an alternative to auto/isografts, which represent the current gold standard in the treatment of severe nerve injury. This study reports the results of a systematic review of the literature published between January 2007 and October 2017. The aim was to quantitatively analyze the effectiveness of decellularized nerve grafts in rat experimental models. The review included 33 studies in which eight different decellularization protocols were described. The decellularized nerve grafts were reported to be immunologically safe and able to support both functional and morphological regeneration after nerve injury. Chemical protocols were found to be superior to physical protocols. However, further research is needed to optimize preparation protocols, including recellularization, improve their effectiveness, and substitute the current gold standard, especially in the repair of long nerve defects.

Noncellular Modification of Acellular Nerve Allografts for Peripheral Nerve Reconstruction: A Systematic Critical Review of the Animal Literature

BACKGROUND

Acellular nerve allografts (ANAs) have been established as promising alternatives to autologous nerve grafts, which represent the reference standard. Our research group recently performed a systematic review of reported cell-based-enriching methods for recellularization of ANAs. Recellularization results in consistent improvement of peripheral neuroregeneration compared with plain ANAs. We systematically reviewed the effects on nerve regeneration when ANA enrichment was obtained through biological, chemical, and physical modification instead of cells.

METHODS

The PubMed, ScienceDirect, Medline, and Scopus databases were searched for reports of noncellular modification of ANAs, reported from January 2007 to December 2017. The inclusion criteria were English language, noncellular enrichment of ANAs in peripheral nerve regeneration, an in vivo study design, and postgrafting neuroregenerative outcomes assessment. The exclusion criteria were the central nervous system as the site of ANA application, nerve conduits, xenografts, case series, case reports, and reviews.

RESULTS

Only animal studies were found to be eligible. We included 16 studies, which were analyzed regarding the animal model, decellularization method, graft-enriching mode, and neuroregenerative tests performed.

CONCLUSIONS

Noncellular-based stimulation of ANAs demonstrated positive effects on recovery of nerve function compared with nerve grafting compared with plain ANAs. The neuroregenerative effect of autografting still appeared superior to ANAs, even with noncellular enrichment of ANAs. However, we found that in a few studies, modified ANAs closely approached or even outperformed autografts. Future research should include more preclinical investigations of this promising tool and clinical translation to increase the level of evidence available in the challenging field of peripheral nerve reconstruction.

Anxiolytics targeting GABAA receptors: Insights on etifoxine

OBJECTIVES

Anxiety and adjustment disorders are among the most prevalent mental health conditions. This review focuses on γ-aminobutyric acid receptor type A (GABA_AR)-mediated anxiolysis, describing the action of both endogenous and exogenous modulators of GABA_AR. Future directions and innovative strategies to alleviate anxiety symptoms are discussed, with a particular emphasis on etifoxine.

METHODS

We used available data from the recent literature to update the mode of action of anxiolytics. We focussed our search on anxiolytics acting at GABA_ARs, as well as on the pharmacological properties of formerly and currently prescribed anxiolytics.

RESULTS

Considering the adverse effects of current treatments aimed at increasing inhibitory controls, optimisation of existing pharmacotherapies is of crucial importance. Among the alternative compounds targeting the GABAergic system, translocator protein (TSPO) ligands, such as etifoxine (EFX), which promote endogenous neurosteroidogenesis, are emerging as promising candidates for anxiety relief. In several papers comparing the efficacy of benzodiazepines and EFX, EFX showed interesting properties with limited side effects. Indeed, neurosteroids are potent GABA_AR modulators with highly underrated anxiolytic properties.

CONCLUSIONS

Novel therapeutic strategies have been emerging following the recognition of neurosteroids as potent anxiolytics. Featured at the top of the list for well-tolerated anxiety relief, TSPO ligands such as etifoxine appear promising.

Miconazole enhances nerve regeneration and functional recovery after sciatic nerve crush injury

INTRODUCTION

Improving axonal outgrowth and remyelination is crucial for peripheral nerve regeneration. Miconazole appears to enhance remyelination in the central nervous system. In this study we assess the effect of miconazole on axonal regeneration using a sciatic nerve crush injury model in rats.

METHODS

Fifty Sprague-Dawley rats were divided into control and miconazole groups. Nerve regeneration and myelination were determined using histological and electrophysiological assessment. Evaluation of sensory and motor recovery was performed using the pinprick assay and sciatic functional index. The Cell Counting Kit-8 assay and Western blotting were used to assess the proliferation and neurotrophic expression of RSC 96 Schwann cells.

RESULTS

Miconazole promoted axonal regrowth, increased myelinated nerve fibers, improved sensory recovery and walking behavior, enhanced stimulated amplitude and nerve conduction velocity, and elevated proliferation and neurotrophic expression of RSC 96 Schwann cells.

DISCUSSION

Miconazole was beneficial for nerve regeneration and functional recovery after peripheral nerve injury. Muscle Nerve 57: 821-828, 2018.

Various changes in cryopreserved acellular nerve allografts at -80°C

The experimental design evaluated histological, mechanical, and biological properties of allogeneic decellularized nerves after cryopreservation in a multi-angle, multi-directional manner to provide evidence for long-term preservation. Acellular nerve allografts from human and rats were cryopreserved in a cryoprotectant (10% fetal bovine serum, 10% dimethyl sulfoxide, and 5% sucrose in RPMI1640 medium) at −80°C for 1 year, followed by thawing at 40°C or 37°C for 8 minutes. The breaking force of acellular nerve allografts was measured using a tensile test. Cell survival was determined using L-929 cell suspensions. Acellular nerve allografts were transplanted into a rat model with loss of a 15-mm segment of the left sciatic nerve. Immunohistochemistry staining was used to measure neurofilament 200 expression. Hematoxylin-eosin staining was utilized to detect relative muscle area in gastrocnemius muscle. Electron microscopy was applied to observe changes in allograft ultrastructure. There was no obvious change in morphological appearance or ultrastructure, breaking force, or cytotoxicity of human acellular nerve allografts after cryopreservation at −80°C. Moreover, there was no remarkable change in neurofilament 200 expression, myelin sheath thickness, or muscle atrophy when fresh or cryopreserved rat acellular nerve allografts were applied to repair nerve injury in rats. These results suggest that cryopreservation can greatly extend the storage duration of acellular nerve tissue allografts without concomitant alteration of the physiochemical and biological properties of the engineered tissue to be used for transplantation.

Differential effects of the 18-kDa translocator protein (TSPO) ligand etifoxine on steroidogenesis in rat brain, plasma and steroidogenic glands: Pharmacodynamic studies

Etifoxine is indicated in humans for treating anxiety. In rodents, besides its anxiolytic-like properties, it has recently shown neuroprotective and neuroregenerative activities. It acts by enhancing GABA_A receptor function and by stimulating acute steroid biosynthesis via the activation of the 18-kDa translocator protein. However, the regulatory action of etifoxine on steroid production is not well characterized. In this work, we performed dose-response, acute and chronic time-course experiments on the effects of intraperitoneal injections of etifoxine on steroid levels in adult male rat brain and plasma analyzed by gas chromatography-mass spectrometry. Concentrations of pregnenolone, progesterone and its 5α-reduced metabolites were significantly increased in both tissues in response to 25 and 50mg/kg of etifoxine, as compared with vehicle controls, and reached maximal values at 0.5-1h post-injection. Daily injections of etifoxine (50mg/kg, 15days) kept them increased at day 15. Comparisons between steroidogenic tissues revealed that 1h after 50mg/kg of etifoxine treatment, levels of pregnenolone, progesterone and corticosterone were highest in adrenal glands and markedly increased together with their reduced metabolites. They were also increased by etifoxine in brain and plasma, but not in testis except for corticosterone and its metabolites. In contrast, testosterone level was significantly decreased in testis while with its 5α-reduced metabolites, it was unchanged in brain. Results demonstrate that the modulation of steroid concentrations by etifoxine is dependent on the type of steroid and on the steroidogenic organ. They further suggest that adrenal steroids upregulated by etifoxine make an important contribution to the steroids present in brain. This work provides a precise and complete view of steroids regulated by etifoxine that could be useful in therapeutic research.

Tissue-engineered rhesus monkey nerve grafts for the repair of long ulnar nerve defects: similar outcomes to autologous nerve grafts

Acellular nerve allografts can help preserve normal nerve structure and extracellular matrix composition. These allografts have low immunogenicity and are more readily available than autologous nerves for the repair of long-segment peripheral nerve defects. In this study, we repaired a 40-mm ulnar nerve defect in rhesus monkeys with tissue-engineered peripheral nerve, and compared the outcome with that of autograft. The graft was prepared using a chemical extract from adult rhesus monkeys and seeded with allogeneic Schwann cells. Pathomorphology, electromyogram and immunohistochemistry findings revealed the absence of palmar erosion or ulcers, and that the morphology and elasticity of the hypothenar eminence were normal 5 months postoperatively. There were no significant differences in the mean peak compound muscle action potential, the mean nerve conduction velocity, or the number of neurofilaments between the experimental and control groups. However, outcome was significantly better in the experimental group than in the blank group. These findings suggest that chemically extracted allogeneic nerve seeded with autologous Schwann cells can repair 40-mm ulnar nerve defects in the rhesus monkey. The outcomes are similar to those obtained with autologous nerve graft.

Therapeutic actions of translocator protein (18 kDa) ligands in experimental models of psychiatric disorders and neurodegenerative diseases

Translocator protein (TSPO) is an 18kDa protein located at contact sites between the outer and the inner mitochondrial membrane. Numerous studies have associated TSPO with the translocation of cholesterol across the aqueous mitochondrial intermembrane space and the regulation of steroidogenesis, as well as with the control of some other mitochondrial functions, such as mitochondrial respiration, mitochondrial permeability transition pore opening, apoptosis and cell proliferation. In the brain, changes in TSPO expression occur in several neuropathological conditions including neurodegenerative diseases and psychiatric disorders. Furthermore, TSPO ligands have been shown to promote neuroprotection in animal models of brain pathology. At least in some cases, the mechanisms of neuroprotection are associated with modifications in brain steroidogenesis. In addition, regulation of neuroinflammation seems to be a common mechanism in the neuroprotective actions of TSPO ligands in different animal models of brain pathology.

Neuroactive steroids and the peripheral nervous system: An update

In the present review we summarize observations to date supporting the concept that neuroactive steroids are synthesized in the peripheral nervous system, regulate the physiology of peripheral nerves and exert notable neuroprotective actions. Indeed, neuroactive steroids have been recently proposed as therapies for different types of peripheral neuropathy, like for instance those occurring during aging, chemotherapy, physical injury and diabetes. Moreover, pharmacological tools able to increase the synthesis of neuroactive steroids might represent new interesting therapeutic strategy to be applied in case of peripheral neuropathy.

Nerve defect repair by differentiated adipose-derived stem cells and chondroitinase ABC-treated acellular nerves

OBJECTIVE

To evaluate the effects of differentiated adipose-derived stem cells (dADSC) and chondroitinase ABC (ChABC)-treated acellular nerves (ACN) in building artificial nerves and repairing nerve defects.

METHODS

ADSC were isolated from the adipose tissue of Wistar rats, induced to differentiate into Schwann-like cells, and implanted into ChABC-treated ACN to repair a 15-mm sciatic nerve defect in Sprague-Dawley rats (the experimental group, group D). The control groups were an autologous nerve transplantation group (group E); ACN (group A), ChABC-treated ACN graft group (group B), and dADSC + ACN (group C). Twelve weeks after surgery, electromyography recordings, tricep surae muscle wet weight recovery rate, and axon counts were measured to evaluate the repair of peripheral nerve defects.

RESULTS

The nerve conduction velocity, compound muscle action potentials, tricep surae muscle wet weight recovery rate, and myelinated axon counts in the ChABC-ACN/dADSC group were significantly higher than in the other groups (P < 0.05), which were all lower than the autologous group (P < 0.05).

CONCLUSIONS

The combination of ChABC-treated ACN and dADSC exhibited a synergistic effect in promoting nerve regeneration, and could be an alternative for effective tissue-engineered nerves.

Cartilage Oligomeric Matrix Protein Angiopoeitin-1 Provides Benefits During Nerve Regeneration In Vivo and In Vitro

Our group pioneered the study of nerve regeneration in China and has successfully developed human "acellular nerve grafts (ACNGs)". However, our clinical studies revealed that the effects of ACNGs for long and large nerve defects are far from satisfactory. To improve the efficacy of ACNGs, we combined Cartilage oligomeric matrix protein angiopoietin-1 (COMP-Ang1) with ACNGs in rat sciatic nerve injury models and observed the outcomes via angiographic, morphological, and functional analyses. Co-cultures of endothelial cells (ECs) and dorsal root ganglion neurons (DRGs) were also used to characterize the relationship between neovascularization and nerve regeneration. The results showed significant improvements in early neovascularization, nerve regeneration, and functional outcomes in vivo in the ACNG + COMP-Ang1 group. In vitro, neurite length, and density as well as the expression levels of neurofilament 68 (NF68) and phosphorylated-Tie-2 (p-Tie-2) significantly increased when ECs were co-cultured with DRGs using COMP-Ang1. p-Tie-2 expression dramatically decreased after treatment with a Tie-2 kinase inhibitor (S157701), which consequently decreased the level of NF68. COMP-Ang1 can be concluded to promote early neovascularization followed by brisk nerve regeneration, and the mechanism of this regeneration may involve the modulation of the p-Tie-2 and Tie-2 receptors on ECs. These findings demonstrate that ACNGs can be modified using COMP-Ang1 to improve their efficacy in repairing peripheral nerve defects in clinical trials.

Etifoxine for pain patients with anxiety

Etifoxine (etafenoxine, Stresam®) is a non-benzodiazepine anxiolytic with an anticonvulsant effect. It was developed in the 1960s for anxiety disorders and is currently being studied for its ability to promote peripheral nerve healing and to treat chemotherapy-induced pain. In addition to being mediated by GABA_Aα2 receptors like benzodiazepines, etifoxine appears to produce anxiolytic effects directly by binding to β2 or β3 subunits of the GABA_A receptor complex. It also modulates GABA_A receptors indirectly via stimulation of neurosteroid production after etifoxine binds to the 18 kDa translocator protein (TSPO) of the outer mitochondrial membrane in the central and peripheral nervous systems, previously known as the peripheral benzodiazepine receptor (PBR). Therefore, the effects of etifoxine are not completely reversed by the benzodiazepine antagonist flumazenil. Etifoxine is used for various emotional and bodily reactions followed by anxiety. It is contraindicated in situations such as shock, severely impaired liver or kidney function, and severe respiratory failure. The average dosage is 150 mg per day for no more than 12 weeks. The most common adverse effect is drowsiness at the initial stage. It does not usually cause any withdrawal syndromes. In conclusion, etifoxine shows less adverse effects of anterograde amnesia, sedation, impaired psychomotor performance, and withdrawal syndromes than those of benzodiazepines. It potentiates GABA_A receptor-function by a direct allosteric effect and by an indirect mechanism involving the activation of TSPO. It seems promising that non-benzodiazepine anxiolytics including etifoxine will replenish shortcomings of benzodiazepines and selective serotonin reuptake inhibitors according to animated studies related to TSPO.

Characterization of the fast GABAergic inhibitory action of etifoxine during spinal nociceptive processing in male rats

Etifoxine (EFX) is a non-benzodiazepine anxiolytic which potentiate GABAA receptor (GABAAR) function directly or indirectly via the production of 3α-reduced neurosteroids. The later effect is now recognized to account for the long-term reduction of pain symptoms in various neuropathic and inflammatory pain models. In the present study, we characterized the acute antinociceptive properties of EFX during spinal pain processing in naive and monoarthritic rats using in vivo electrophysiology. The topical application of EFX on lumbar spinal cord segment, at concentrations higher than 30 μM, reduced the excitability of wide dynamic range neurons receiving non-nociceptive and nociceptive inputs. Windup discharge resulting from the repetitive stimulation of the peripheral receptive field, and recognized as a short-term plastic process seen in central nociceptive sensitization, was significantly inhibited by EFX at these concentrations. In good agreement, mechanical nociceptive thresholds were also significantly increased following an acute intrathecal injection of EFX. The acute modulatory properties of EFX on spinal pain processing were never seen in the simultaneous presence of bicuculline. This result further confirmed EFX antinociception to result from the potentiation of spinal GABAA receptor function.

Ginkgo biloba extract (EGb 761) promotes peripheral nerve regeneration and neovascularization after acellular nerve allografts in a rat model

This study aimed to investigate whether or not ginkgo biloba extract (EGb 761) enhances peripheral nerve regeneration and vascularization after repair using acellular nerve allografts (ANA). Seventy-two Sprague-Dawley rats were randomly divided into three experimental groups: a unilateral 15-mm sciatic nerve defect was created and repaired with an autologous graft (autograft group); the same defect was repaired with an 18 mm ANA with an i.p. injection of normal saline for 10 days (saline group); and in the final group, the same defect was repaired with an 18 mm ANA with an i.p. injection of EGb 761 for 10 days (EGb 761 group). Axon outgrowth and vascularization were evaluated by immunocytochemistry 14 days post-implantation. The expression of genes associated with angiogenesis was analyzed by real-time polymerase chain reaction (PCR) seven days post-implantation. Compared with the saline group, rats in the EGb 761 group significantly increased the number of myelinated fibers and the average diameter of the nerves within the graft. There is no significant difference between the EGb 761 group and the autograft group. The expression of CD34 and NF200 was significantly higher in the EGb 761 group than in the saline group. Additionally, EGb 761 treatment increased the expression of several angiogenesis-related genes, including Vegf, SOX18, Prom 1, and IL-6. In conclusion, ANA repair with EGb 761 treatment demonstrates effects on peripheral nerve regeneration and vascularization that are equal to those of autologous graft repair, and that are superior to ANA repair alone.