Changes of melatonin secretion in the neuropathic pain induced sleep disorder model rat.

Chronic pain due to peripheral neuropathy can lead to sleep disorders that significantly worsen the patient's quality of life. Previously, we conducted brain wave measurements in a rat model of neuropathic pain and identified its potential as a model for sleep disorders associated with chronic pain (reported). In this study, we quantified melatonin secretion and assessed its circadian rhythm in a rat model of pain-induced sleep disorder. To create a model of chronic constriction injury (CCI), rats were loosely tied around the sciatic nerve, with approximately 1 mm spacing, 14 days before the experiment. Rats with no ties around the sciatic nerve were used as controls. Electroencephalograms and electromyograms were recorded for 3 days, and the episodes of waking, REM sleep, and non-REM sleep were compared between the groups. The samples for microanalysis were collected every 30 min and used for melatonin analysis. Compared to the control group, the CCI model group exhibited an increase in wake episodes and a decrease in non-REM sleep episodes. Analysis of the area under the curve of melatonin secretion revealed a significant increase in melatonin secretion and a loss of circadian rhythm in the CCI model group. Melatonin secretion markedly increased accompanied by loss of circadian rhythm in a rat model of CCI. Further studies investigating the causal relationship between neuropathic pain and melatonin secretion are warranted.

Effect of sciatic nerve pulsed radiofrequency glial activation levels in spinal dorsal horn in chronic constriction injury rat models and its analgesia effect / 吉林大学学报(医学版)

Objective:To observe the effect of sciatic nerve pulsed radiofrequency (PRF) on the activation levels of microglia cells and astrocytes in spinal dorsal horn in the chronic constriction injury (CCI) rat models, and to explore the relationships between the analgesic mechanism of sciatic nerve PRF and the activation levels of microglia cells and astrocytes in the spinal dorsal horn.Methods:Forty male SD rats were randomly divided into CCI shamoperation+RPF sham group (SS group) , CCI sham-operation+RPF group (SP group) , CCI+RPF sham group (CS group) , CCI+RPF group (CP group) (n=10) .PRF was applied on the sciatic nerve on the 4th day after CCI operation for 120s, with a maximum temperature of 42℃.The mechanical withdrawal thresholds (MWT) and thermal paw withdrawal latencies (TWL) were measured to evaluate mechanical hyperalgesia and thermal hyperalgesia 1dbefore operation (D0) and 1, 3, 5, 7dafter operation (D1, D3, D5, D7) .Western blotting method was used to detect the protein expression levels of ionized calcium binding adapter molecule 1 (Iba-1) and glial fibrillary acidic protein (GFAP) in the ipsilateral spinal dorsal horn of L3-5after pain behavioral test (D7) .Results:Compared with SS group, the rats in CS group after CCI had the significant behavioral changes, such as hallux valgus, lameness, toe bending, and foot raising during walking;MWT and TWL were decreased significantly (P＜0.01) ;the expression levels of Iba-1and GFAP proteins in the ipsilateral spinal dorsal horn were increased significantly (P＜0.05) .Compared with CS group, the behavioral changes of the rats in CP group (D5, D7) such as hallux valgus, lameness, toe bending, and foot raising during walking were alleviated significantly;MWT and TWL were increased significantly (P＜0.01) ;the Iba-1protein expression level in spinal dorsal horn was downregulated significantly (P＜0.05) and the GFAP protein expression level did not change significantly (P＞0.05) .Conclusion:PRF on sciatic nerve can relieve the neuropathic pain (NP) of the CCI rat models;PRF on sciatic nerve can inhibit activation of the microglia cells in the spinal dorsal horn.The analgesic mechanism of PRF on sciatic nerve may be associated with the inhibition of the activation of microglia cells in the spinal dorsal horn.

Effect of sciatic nerve pulsed radiofrequency glial activation levels in spinal dorsal horn in chronic constriction injury rat models and its analgesia effect / 吉林大学学报(医学版)

Objective: To observe the effect of sea tic nerve pulsed radiofrequency (PRF) on the activation levels of microglia cells and astrocytes in spinal dorsal horn in the chronic constriction injury (CCD rat models, and to explore the relationships between the analgesic mechanism of sciatic nerve PRF and the activation levels of microglia cells and astrocytes in the spinal dorsal horn- Methods: Forty male SD rats were randomly divided into CCI shamoperation+RPF sham group (SS group). CC1 sham-operation + RPF group (SP group). CCI+RPF sham group (CS group). CCI+ RPF group (CP group) ( n 10). PRF was applied on the sciatic nerve on the 4th day after CC1 operation for 120 s, with a maximum temperature of 42"C. The mechanical withdrawal thresholds (MWT) and thermal paw withdrawal latencies 0. 05). Conclusion- PRF on sciatic nerve can relieve the neuropathic pain (NT) of the CCI rat models: PRF on saatic nerve can inhibit activation of the microglia cells in the spinal dorsal horn. The analgeac mechanism of PRF on sciatic nerve may be associated with the inhibition of the activation of microglia cells in the spinal dorsal horn.

Mechanisms of the analgesic effect of calcitonin on chronic pain by alteration of receptor or channel expression.

The polypeptide hormone calcitonin is well known clinically for its ability to relieve osteoporotic back pain and neuropathic pain such as spinal canal stenosis, diabetic neuropathy, chemotherapy-induced neuropathy, and complex regional pain syndrome. Because the analgesic effects of calcitonin have a broad range, the underlying mechanisms of pain relief by calcitonin are largely unknown. However, recent studies using several types of chronic pain models combined with various methods have been gradually clarifying the mechanism. Here, we review the mechanisms of the analgesic action of calcitonin on ovariectomy-induced osteoporotic and neuropathic pain. The analgesic action of calcitonin may be mediated by restoration of serotonin receptors that control selective glutamate release from C-afferent fibers in ovariectomized rats and by normalization of sodium channel expression in damaged peripheral nerves. Serotonin receptors are reduced or eliminated by the relatively rapid reduction in estrogen during the postmenopausal period, and damaged nerves exhibit hyperexcitability due to abnormal expression of Na+ channel subtypes. In addition, in chemotherapy-induced peripheral neuropathy, inhibition of signals related to transient receptor potential ankyrin-1 and melastatin-8 is proposed to participate in the anti-allodynic action of calcitonin. Further, an unknown calcitonin-dependent signal appears to be present in peripheral nervous tissues and may be activated by nerve injury, resulting in regulation of the excitability of primary afferents by control of sodium channel transcription in dorsal root ganglion neurons. The calcitonin signal in normal conditions may be non-functional because no target is present, and ovariectomy or nerve injury may induce a target. Moreover, it has been reported that calcitonin reduces serotonin transporter but increases serotonin receptor expression in the thalamus in ovariectomized rats. These data suggest that calcitonin could alleviate lower back pain in patients with osteoporosis or neuropathic pain by the alteration in receptor or channel expression.

A basic bifurcation structure from bursting to spiking of injured nerve fibers in a two-dimensional parameter space.

Two different bifurcation scenarios of firing patterns with decreasing extracellular calcium concentrations were observed in identical sciatic nerve fibers of a chronic constriction injury (CCI) model when the extracellular 4-aminopyridine concentrations were fixed at two different levels. Both processes proceeded from period-1 bursting to period-1 spiking via complex or simple processes. Multiple typical experimental examples manifested dynamics closely matching those simulated in a recently proposed 4-dimensional model to describe the nonlinear dynamics of the CCI model, which included most cases of the bifurcation scenarios. As the extracellular 4-aminopyridine concentrations is increased, the structure of the bifurcation scenario becomes more complex. The results provide a basic framework for identifying the relationships between different neural firing patterns and different bifurcation scenarios and for revealing the complex nonlinear dynamics of neural firing patterns. The potential roles of the basic bifurcation structures in identifying the information process mechanism are discussed.

Pulsed magnetic field enhances therapeutic efficiency of mesenchymal stem cells in chronic neuropathic pain model.

Cell-based or magnetic field therapies as alternative approaches to pain management have been tested in several experimental pain models. The aim of this study therefore was to investigate the actions of the cell-based therapy (adipose tissue derived mesenchymal stem cells; ADMSC) or pulsed magnetic field (PMF) therapy and magneto-cell therapy (combination of ADMSC and PMF) in chronic constriction nerve injury model (CCI). The actions of individual ADMSC (route dependent [systemic or local], time-dependent [a day or a week after surgery]), or PMF and their combination (magneto-cell) therapies on hyperalgesia and allodynia were investigated by using thermal plantar test and a dynamic plantar aesthesiometer, respectively. In addition, various cytokine levels (IL-1ß, IL-6, and IL-10) of rat sciatic nerve after CCI were analyzed. Following the CCI, both latency and threshold significantly decreased. ADMSC or PMF significantly increased latencies and thresholds. The combination of ADMSC with PMF even more significantly increased latency and threshold when compared with ADMSC alone. However, ADMSC-induced decrease in pro-inflammatory or increase in anti-inflammatory cytokines levels were partially prevented by PMF treatments. Present findings may suggest that both cell-based and magnetic therapies can effectively attenuate chronic neuropathic pain symptoms. Combined magneto-cell therapy may also efficiently reverse neuropathic signs. Bioelectromagnetics. 38:255-264, 2017. © 2017 Wiley Periodicals, Inc.

Enhanced Expression of TREK-1 Is Related with Chronic Constriction Injury of Neuropathic Pain Mouse Model in Dorsal Root Ganglion.

Neuropathic pain is a complex state showing increased pain response with dysfunctional inhibitory neurotransmission. The TREK family, one of the two pore domain K⁺ (K2P) channel subgroups were focused among various mechanisms of neuropathic pain. These channels influence neuronal excitability and are thought to be related in mechano/thermosensation. However, only a little is known about the expression and role of TREK-1 and TREK-2, in neuropathic pain. It is performed to know whether TREK-1 and/ or 2 are positively related in dorsal root ganglion (DRG) of a mouse neuropathic pain model, the chronic constriction injury (CCI) model. Following this purpose, Reverse Transcription Polymerase Chain Reaction (RT-PCR) and western blot analyses were performed using mouse DRG of CCI model and compared to the sham surgery group. Immunofluorescence staining of isolectin- B4 (IB4) and TREK were performed. Electrophysiological recordings of single channel currents were analyzed to obtain the information about the channel. Interactions with known TREK activators were tested to confirm the expression. While both TREK-1 and TREK-2 mRNA were significantly overexpressed in DRG of CCI mice, only TREK-1 showed significant increase (~9 fold) in western blot analysis. The TREK-1-like channel recorded in DRG neurons of the CCI mouse showed similar current-voltage relationship and conductance to TREK-1. It was easily activated by low pH solution (pH 6.3), negative pressure, and riluzole. Immunofluorescence images showed the expression of TREK-1 was stronger compared to TREK-2 on IB4 positive neurons. These results suggest that modulation of the TREK-1 channel may have beneficial analgesic effects in neuropathic pain patients.

Enhanced Expression of TREK-1 Is Related with Chronic Constriction Injury of Neuropathic Pain Mouse Model in Dorsal Root Ganglion

Neuropathic pain is a complex state showing increased pain response with dysfunctional inhibitory neurotransmission. The TREK family, one of the two pore domain K+ (K2P) channel subgroups were focused among various mechanisms of neuropathic pain. These channels influence neuronal excitability and are thought to be related in mechano/thermosensation. However, only a little is known about the expression and role of TREK-1 and TREK-2, in neuropathic pain. It is performed to know whether TREK-1 and/or 2 are positively related in dorsal root ganglion (DRG) of a mouse neuropathic pain model, the chronic constriction injury (CCI) model. Following this purpose, Reverse Transcription Polymerase Chain Reaction (RT-PCR) and western blot analyses were performed using mouse DRG of CCI model and compared to the sham surgery group. Immunofluorescence staining of isolectin-B4 (IB4) and TREK were performed. Electrophysiological recordings of single channel currents were analyzed to obtain the information about the channel. Interactions with known TREK activators were tested to confirm the expression. While both TREK-1 and TREK-2 mRNA were significantly overexpressed in DRG of CCI mice, only TREK-1 showed significant increase (~9 fold) in western blot analysis. The TREK-1-like channel recorded in DRG neurons of the CCI mouse showed similar current-voltage relationship and conductance to TREK-1. It was easily activated by low pH solution (pH 6.3), negative pressure, and riluzole. Immunofluorescence images showed the expression of TREK-1 was stronger compared to TREK-2 on IB4 positive neurons. These results suggest that modulation of the TREK-1 channel may have beneficial analgesic effects in neuropathic pain patients.

Comparison of the Effects of Zonisamide, Ethosuximide and Pregabalin in the Chronic Constriction Injury Induced Neuropathic Pain in Rats.

BACKGROUND: Evidence has been generated that various anticonvulsant agents provide relief of several chronic pain syndromes and therefore as an alternative to opioids, nonsteroidal anti-inflammatory, and tricyclic antidepressant drugs in the treatment of neuropathic pain. The results of these studies thus raise the question of whether all anticonvulsant drugs or particular mechanistic classes may be efficacious in the treatment of neuropathic pain syndromes. AIM: The aim was to compare the clinically used anticonvulsant drugs which are differ in their mechanism of action in a chronic pain model, the chronic constriction injury, in order to determine if all anticonvulsants or only particular mechanistic classes of anticonvulsants are analgesic. MATERIALS AND METHODS: The study included zonisamide, ethosuximide and pregabalin. All compounds were anticonvulsant with diverse mechanism of actions. The peripheral neuropathic pain was induced by chronic constriction injury of the sciatic nerve in male Sprague-Dawley rats. Zonisamide (80 and 40 mg/kg), ethosuximide (300 and 100 mg/kg), pregabalin (50 and 20 mg/kg), and saline was administered intraperitoneally in respective groups in a blinded, randomized manner from postoperative day (POD) 7-13. Paw withdrawal duration to spontaneous pain, chemical allodynia and mechanical hyperalgesia and paw withdrawal latency to mechanical allodynia and thermal hyperalgesia were tested before drug administration on POD7 and after administration on POD 7, 9, 11 and 13. RESULTS: The present study suggests that these drugs could provide an effective alternative in the treatment of neuropathic pain. However, zonisamide and pregabalin appears to have suitable efficacy to treat a wide spectrum of neuropathic pain condition. CONCLUSION: The present findings suggest that the inhibition of N-type calcium channels or voltage-gated sodium and T-type calcium channels provides better analgesic potential instead of inhibition of T-type calcium channels alone.

Modulation of cytokine levels in ameliorative effects of pulsed magnetic field on an experimental model of Chronic Constriction Injury.

PURPOSE: Clinical chronic neuropathic pain is often resistant to currently used pharmacotherapeutic applications. A number studies have shown that pulsed magnetic field (PMF) application may ameliorate the pain associated with damages, surgeries or diseases. However, possible potential mechanisms of PMF treatments have not been well documented. This study aimed to assess the therapeutic effects of PMF treatment on a Chronic Constriction Injury model (CCI) which mimics clinical chronic neuropathic pain symptoms. MATERIALS AND METHODS: Effects of PMF treatments or sham PMF (SPMF) were investigated by measuring the latencies, thresholds and cytokine levels (interleukin [IL]-1 beta, IL-6 and IL-10) of sciatic nerve in CCI or sham surgery rats. PMF was treated on CCI rats before (a day after surgery, PMF-AD) and after (a week after surgery, PMF-AW) the development of pain signs. RESULTS: Rats exhibited hyperalgesia and allodynia within one week following surgery, and lasted through the experiment. PMF treatments, but not SPMF, significantly enhanced the latency and threshold. Both anti-hyperalgesic and anti-allodynic actions of PMF-AD were greater than those of PMF-AW treatment. Similarly, PMF-AD had more pronounced effects on the level of pro- and anti-inflammatory cytokines than did PMF-AW. CONCLUSIONS: The present findings may suggest that PMF treatment may reverse the CCI-induced changes in neuropathic pain behaviors by decreasing the production of pro-inflammatory cytokines and increasing the anti-inflammatory cytokine production at the site of injury.

The effects of locally injected triamcinolone on entrapment neuropathy in a rat chronic constriction injury model.

PURPOSE: Patients with idiopathic carpal tunnel syndrome are commonly treated by steroid injections into the carpal tunnel. We administered triamcinolone (Tr) to chronic constriction injury model rats. We hypothesized that Tr administration would have both favorable behavioral effects and quantifiable immunohistological effects on compressed nerves. METHODS: Thirty-six male Wister rats were used. For rats to be treated with Tr, we loosely ligated their right sciatic nerves at 4 sites. Sham rats had their nerves exposed without ligation. On postoperative day 7, we reexposed their ligated nerves, after which we delivered either 0.1 mg of Tr (0.1-mg group), 0.5 mg of Tr (0.5-mg group), or normal saline (saline group) around the nerve fibers at the injured sites. Gait was analyzed, and allodynia was assessed with von Frey hairs, before surgery and on postoperative days 3, 7, 10, 14, and 21. The right sciatic nerve was resected and stained using hematoxylin-eosin, and the fourth and fifth lumbar dorsal root ganglia (DRG) were removed and assessed by immunohistochemistry for calcitonin gene-related peptide (CGRP) and activating transcription factor 3 (ATF3) on postoperative day 21. In addition, interleukin-1ß (IL-1ß) in sciatic nerve was quantified using enzyme-linked immunosorbent assays. RESULTS: Mechanical allodynia was significantly decreased in the 0.5-mg group compared with the saline group. In hematoxylin-eosin sections, the extent of inflammation-induced edema between the nerve fibers and infiltration of inflammatory cells was significantly reduced in the 0.5-mg group compared with the saline group. IL-1ß levels at the sciatic nerve in the 0.5-mg group were significantly lower than those in the saline group. CONCLUSIONS: Tr-treated chronic constriction injury rats exhibited significant alleviation of sensory disturbance, edema, inflammation, and pain-related peptide upregulation. These phenomena suggest the validity of Tr administration as a treatment affecting the nerve itself. TYPE OF STUDY/LEVEL OF EVIDENCE: Therapeutic I.

Hemopressin, an inverse agonist of cannabinoid receptors, inhibits neuropathic pain in rats.

Direct-acting cannabinoid receptor ligands are well known to reduce hyperalgesic responses after nerve injury, although their psychoactive side effects have damped enthusiasm for their therapeutic development. Hemopressin (Hp) is a nonapeptide that selectively binds CB1 cannabinoid receptors (CB1 receptors) and exerts antinociceptive action in inflammatory pain models. We investigated the effect of Hp on neuropathic pain in rats subjected to chronic constriction injury (CCI) of the sciatic nerve, and explored the mechanisms involved. Oral administration of Hp inhibits mechanical hyperalgesia of CCI-rats up to 6h. Hp treatment also decreases Egr-1 immunoreactivity (Egr-1Ir) in the superficial layer of the dorsal horn of the spinal cord of CCI rats. The antinociceptive effect of Hp seems to be independent of inhibitory descending pain pathway since methysergide (5HT1A receptor antagonist) and yohimbine (α-2 adrenergic receptor antagonist) were unable to prevent Hp antinociceptive effect. Hp decreased calcium flux on DRG neurons from CCI rats, similarly to that observed for AM251, a CB1 receptor antagonist. We also investigated the effect of Hp on potassium channels of CCI rats using UCL 1684 (a blocker of Ca(2+)-activated K(+) channels) which reversed Hp-induced antinociception. Furthermore, concomitant administration of URB-584 (FAAH inhibitor) but not JZL-184 (MAGL inhibitor) potentiates antinociceptive effect of Hp in CCI rats indicating an involvement of anadamide on HP-induced antinociception. Together, these data demonstrate that Hp displays antinociception in pain from neuropathic etiology through local effects. The release of anandamide and the opening of peripheral K(+) channels are involved in the antinociceptive effect.