Anti-allodynic efficacy of NMDA antagonist peptide and noradrenaline alone and in combination in rodent neuropathic pain model

Background: The present experiment was conducted to identify the cooperative effect of serine histogranin (SHG) and noradrenaline in alleviating peripheral neuropathic pain. Methods: Chronic constriction injury of the right sciatic nerve was used to induce chronic neuropathic pain. For drug delivery, a PE10 tube was inserted into the subarachnoid space. Acetone drops and a 44°C water bath were used to evaluate the cold and heat allodynia, respectively. Placing and grasping reflexes were used to assess the locomotor system. Results: SHG at 0.5 and 1 μg significantly (P < 0.05) decreased the thermal allodynia. The cold allodynia was also significantly reduced by intrathecal injections of 0.5 (P < 0.05) and 1 μg (P < 0.001) of SHG. 1 μg of noradrenaline, but not 0.5 μg, significantly alleviated the cold (P < 0.01) and thermal (P < 0.05) allodynia. The ameliorating effect of noradrenaline or SHG disappeared when the two compounds were administrated in equal concentrations. A significant difference (P < 0.01 in the acetone and P < 0.05 in the heat) was observed in the groups under equal doses of the two compounds, with a lower effectiveness of the combination therapy. Conclusions: Our findings suggest that the simultaneous administrations of noradrenaline and SHG do not result in synergistic analgesia, and combination therapy may not be a good approach to the treatment of chronic neuropathic pain syndrome. © The Korean Pain Society, 2015

Antinociceptive effect of ascorbic acid and involvement of nitric oxide in a chronic pain model

Objectives: Ascorbate which is presented in high concentration in nervous system, inhibit nitric oxide synthase enzyme (NOS). We investigated the involvement of NO pathway in the analgesic effects of ascorbic acid (AA) in CCI model of neuropathic rats. Methods: In this experimental study, neuropathic pain is induced by 4 loose ligature around sciatic nerve on left paw of male rats using 4/0 chromic gut (CCI model). Ascorbic acid (1, 5 or 10 mg/kg) or saline was injected intraperituneally two weeks after CCI. Heat and mechanical hyperalgesia and mechanical allodynia were investigated 15 and 30 min after injection. To investigate the involvement of NO on antinociceptive effect of AA on the second week after CCI, 30 min after injection of saline or AA, animals received intraperitunealy injection of L-arginin (500 mg/kg), or L-NAME (20mg/kg) and were tested 20 min after on. Results: Acute injection of 5 and 10 mg/kg but not 1 mg/kg of AA increased pain threshold in the second week after CCI. Injection of 5 mg/kg AA inhibited the nociceptive effect of L-arginin and potentiates the antinociceptive effect of L-NAME and pain threshold was significantly different in these two groups comparing the animals which received normal saline instead of AA. Conclusion: Injection of AA increase pain threshold after nerve injury. Antinociceptive effect of ascorbic acid is dose dependant and that seems to be mediated at least partially via NO pathway

The Effect of Bone Marrow-Derived Mesenchymal Stem Cell Transplantation on Allodynia and Hyperalgesia in Neuropathic Animals: A Systematic Review with Meta-Analysis

Stem cell transplantation has been considered a possible therapeutic method for neuropathic pain. However, no quantitative data synthesis of stem cell therapy for neuropathic pain exists. Therefore, the present systematic review and meta-analysis assessed the efficacy of bone marrow mesenchymal stem cell (BMMSC) transplantation on alleviating pain symptoms in animal models of neuropathic pain. In the present meta-analysis, controlled animal studies assessing the effect of administrating BMMSC on neuropathic pain were included through an extensive literature search of online databases. After collecting data, effect sizes were computed and the standardized mean difference (SMD) with 95 confidence interval (CI) was entered in all analyses. Random-effects models were used for data analysis. Sensitivity and subgroup analyses were performed to investigate expected or measured heterogeneity. Finally, 14 study were included. The analyses showed that BMMSC transplantation lead to significant improvement on allodynia (SMD = 2.06; 95 CI, 1.09 to 3.03; I2 = 99.7; P &lt; .001). The type of neuropathy (P =036), time between injury and intervention (P =02), and the number of transplanted cells (P = 023) influence the improvement of allodynia after BMMSC transplantation. BMMSC transplantation has no effect on hyperalgesia (SMD =3; 95 CI, -1.09 to 1.68; I2 = 100; P &lt;001) unless it occurs during the first 4 days after injury (P =02). The present systematic review with meta-analysis suggests that BMMSC transplantation improves allodynia but does not have any significant effect on hyperalgesia unless it is given during the first 4 days after injury. © 2015 American Society for Blood and Marrow Transplantation

NMDA antagonist peptide supplementation enhances pain alleviation by adrenal medullary transplants

Spinal transplantation of adrenal medullary chromaffin cells has been shown to decrease pain responses in several animal models. Improved potency may be possible by engineering cells to produce greater levels of naturally derived analgesics. As an initial screen for potential candidates, adrenal medullary transplants were evaluated in combination with exogenously administered neuropeptides in rodent pain models. Histogranin is a 15-amino acid peptide that exhibits NMDA receptor antagonist activity. The stable derivative Ser 1histogranin (SHG) can attenuate pain symptoms in some animal models. The formalin model for neurogenic inflammatory pain and the chronic constriction injury (CCI) model for neuropathic pain were used to evaluate the combined effects of chromaffin cell transplantation and intrathecal (IT) SHG injections. Animals were implanted with either adrenal medullary or control striated muscle tissue in the spinal subarachnoid space. For evaluation of formalin responses, animals were pretreated with SHG (0.5, 1.0, 3.0 μg) followed by an intraplantar injection of formalin, and flinching responses were quantified. Pretreatment with SHG had no significant effect on flinching behavior in control animals at lower doses, with incomplete attenuation only at the highest dose. In contrast, 0.5 μg SHG significantly reduced flinching responses in animals with adrenal medullary transplants, and 1.0 μg nearly completely eliminated flinching in these animals in the tonic phase. For evaluation of effects on neuropathic pain, animals received transplants 1 week following CCI, and were tested for thermal and mechanical hyperalgesia and cold allodynia before and following SHG treatment. The addition of low doses of SHG nearly completely eliminated neuropathic pain symptoms in adrenal medullary transplanted animals, while in control transplanted animals only thermal hyperalgesia was attenuated, at the highest dose of SHG. These results suggest that SHG can augment adrenal medullary transplants, and the combination may result in improved effectiveness and range in the treatment of chronic pain syndromes. Copyright © 2005 Cognizant Comm. Corp

Viral vectors encoding endomorphins and serine histogranin attenuate neuropathic pain symptoms after spinal cord injury in rats

Background: The treatment of spinal cord injury (SCI)-induced neuropathic pain presents a challenging healthcare problem. The lack of available robust pharmacological treatments underscores the need for novel therapeutic methods and approaches. Due to the complex character of neuropathic pain following SCI, therapies targeting multiple mechanisms may be a better choice for obtaining sufficient long-term pain relief. Previous studies in our lab showed analgesic effects using combinations of an NMDA antagonist peptide Ser1histogranin (SHG), and the mu-opioid peptides endomorphins (EMs), in several pain models. As an alternative to drug therapy, this study evaluated the analgesic potential of these peptides when delivered via gene therapy. Results: Lentiviruses encoding SHG and EM-1 and EM-2 were intraspinally injected, either singly or in combination, into rats with clip compression SCI 2weeks following injury. Treated animals showed significant reduction in mechanical and thermal hypersensitivity, compared to control groups injected with GFP vector only. The antinociceptive effects of individually injected components were modest, but the combination of EMs and SHG produced robust and sustained antinociception. The onset of the analgesic effects was observed between 1-5 weeks post-injection and sustained without decrement for at least 7weeks. No adverse effects on locomotor function were observed. The involvement of SHG and EMs in the observed antinociception was confirmed by pharmacologic inhibition using intrathecal injection of either the opioid antagonist naloxone or an anti-SHG antibody. Immunohistochemical analysis showed the presence of SHG and EMs in the spinal cord of treated animals, and immunodot-blot analysis of CSF confirmed the presence of these peptides in injected animals. In a separate group of rats, delayed injection of viral vectors was performed in order to mimic a more likely clinical scenario. Comparable and sustained antinociceptive effects were observed in these animals using the SHG-EMs combination vectors compared to the group with early intervention. Conclusions: Findings from this study support the potential for direct gene therapy to provide a robust and sustained alleviation of chronic neuropathic pain following SCI. The combination strategy utilizing potent mu-opioid peptides with a naturally-derived NMDA antagonist may produce additive or synergistic analgesic effects without the tolerance development for long-term management of persistent pain. © 2015 Nasirinezhad et al

Effect of intrathecal transplantation of adrenal medullary tissue on the sciatic nerve regeneration following chronic constriction injury in the rat

Introduction: It has been demonstrated that the adrenal medullary transplants into the spinal subarachnoid space can alleviate neuropathic pain behaviors. The aim of the present study was to test the possibility that histological changes of the sciatic nerve in a neuropathic model as well as sensory dysfunction are repaired by adrenal medullary transplantation. Material and Methods: Left sciatic nerve was ligated in three groups of rats by 4 loose ligatures (CCI). After one week of nerve constriction, rats of first group were implanted with adrenal medullary tissue (CCI + adrenal medulla) and rats of the second group with striated muscle at the level of L1-L2 (CCI + muscle). The third group received only left ligature (CCI) and in the fourth group the sciatic nerve was exposed and then muscle and skin sutured (sham). Behavioral assessment was evaluated before surgery and 2, 4, 7, 10, 14, 21, 28, 42, and 56 days after the onset of experiment. According to behavioral results, 4 rats in each group were anesthetized and then the distal part of sciatic nerve were isolated and prepared for histological quantitative investigation of nerve regeneration. Results: The results showed that CCI was accompanied with hyperalgesia and morphological changes in the distal part of sciatic nerve. In animals with adrenal medullary transplantation, not only hyperalgesia was markedly reduced or even eliminated, but also the number of myelinated fibers in the distal segment of nerve increased to nearly normal. Conclusions: Our findings showed that the implantation of adrenal medullary tissue might have caused regeneration of ligated nerves as well as alleviation of pain behavior

Minocycline mitigation of tremor syndrome and defect of cognitive and balance induced by harmaline

Introduction: Minocycline has anti-inflammatory, anti-apoptotic, and anti-oxidant effects. Preclinical data suggest that minocycline could be beneficial for treating common neurological disorders, including Parkinson disease and multiple sclerosis. Methods: In this study, the effects of minocycline on harmaline-induced motor and cognitive impairments were studied in male Wistar rats. The rats were divided into four groups of ten animals each. Harmaline was used for the induction of Essential Tremor (ET). Minocycline (90 mg/kg, IP) was administered 30 minutes before the saline or harmaline. Tremor intensity, spontaneous locomotor activity, passive avoidance memory, anxiety-related behaviors, and motor function were assessed in the rats. Results: The results showed that minocycline could recover tremor intensity and step width but failed to recuperate the motor balance. The memory impairments observed in harmalinetreated rats were somewhat reversed by administration of minocycline. The cerebellum and inferior olive nucleus were studied for neuronal degeneration using histochemistry and transmission electron microscopy techniques. Harmaline caused ultrastructural changes and neuronal cell loss in inferior olive and cerebellar Purkinje cells. Minocycline exhibited neuroprotective changes on cerebellar Purkinje cells and inferior olivary neurons. Conclusion: These results open new therapeutic perspectives for motor and memory impairments in ET. However, further studies are needed to clarify the exact mechanisms. © 2021 Iran University of Medical Sciences. All rights reserved

Simultaneous intrathecal injection of muscimol and endomorphin-1 alleviates neuropathic pain in rat model of spinal cord injury

Introduction: Due to side effects of medications used for chronic pain, combination therapy seems to be an appropriate solution for alleviation of chronic pain and reducing the side effects. The role of inhibitory GABA system is well proven in reducing neuropathic pain. Also, special attention has been focused on endogenous morphine (endomorphins) in reducing chronic pain originates from damage to the nervous system. The purpose of this study is to investigate the analgesic effect of simultaneous administration of GABA agonist and endomorphin-1 on neuropathic pain in rat model of spinal cord injury (SCI). The role of oxidative stress, NR1 subunits of NMDA receptors, and α2 subunits of GABA receptors in the spinal cord has also been investigated. Methods: Spinal cord at level of T6�T8 was compressed. Three weeks after spinal cord injury, muscimol and endomorphin-1 were injected (intrathecally once a day for 7 days) individually or in combination. Mechanical and cold allodynia, thermal and mechanical hyperalgesia were evaluated before injection and 15 and 60 min after injection. At the end of behavioral experiments, histological and biochemical evaluations were done on prepared spinal cord samples. Results: Isobologram results showed that combination therapy significantly increased the pain threshold comparing to injection of endomorphin-1 (EM) or muscimol alone. Histological studies indicated the increased expression of α2 subunits of GABA receptors, and NR1 subunits of NMDA receptors in the spinal cord. The combination therapy also increased the glutathione (GSH) and superoxide dismutase (SOD) level and decreased the malondialdehyde (MDA) levels in the spinal cord. Conclusion: Simultaneous administration of muscimol and endomorphine-1 could be a new candidate for alleviation of pain resulting from spinal cord injury. © 2020 The Authors. Brain and Behavior published by Wiley Periodicals, Inc

The effect of preconditioning with high-intensity training on tissue levels of G-CSF, its receptor and C-kit after an acute myocardial infarction in male rats

Background: Exercise training is known as a practical way to increase cardioprotection against stress, and it seems that stem cell recruitment is one of its mechanisms. The purpose of the present study was to investigate the effect of preconditioning with High-intensity interval training (HIIT) on tissue levels of G-CSF, its receptor and C-Kit following acute myocardial infarction in male rats. Methods: Twenty Male Wistar rats were randomly divided into 4 groups of control, MI, HIIT, and HIIT+MI. Training groups performed 2 weeks of high intensity interval training in 4 sections. The first section consisted training in 3 days and 2 sessions in each day (4 � 2 min with 35-40 m/min and 3 � 2 min with 25-30 m/min between high intervals. The second part included 2 days of training (4 � 2 min with 40 to 45 m/min and 3 � 2 min with 28 to 32 m /min). The third part was performed in 3 days with one more repetition. The fourth section consisted 2 days of training and with one more repetition compared to section 3. For induction of myocardial infarction, subcutaneous injection of isoprenaline was used. CK, total CK, LDH, and troponin T were measured in serum and G-CSF, G-CSFR and C-Kit proteins were measured by the Western Blot method in the heart tissue. Results: The results of this study showed that enzymes of CK, total CK, LDH, troponin T had a significant increase in both MI and HIIT+MI groups compared to the other two groups (P < 0.001) and these indices in the MI group were significantly higher than the HIIT+MI group. Also, the results demonstrated that G-CSF, G-CSFR and C-Kit protein expression in the heart tissue significantly increased after MI. As well as, 2 weeks of HIIT training significantly increased G-CSF and C-kit in the training group compared to the control group, but the training caused that these proteins does not increase in HIIT+MI group as much as MI group. Conclusions: Along with other protective pathways, high intensity interval training can increase cardioprotection and decrease heart injuries through the increase in G-CSF, G-CSFR and C-kit level. © 2020 The Author(s)