A Pusher and a Clip Applied to Hind Paws Under Isoflurane Sedation to Evaluate Neuropathic Pain in a CCI Model

: Rodent behavior assessments have been developed to evaluate pain. However, their fidgety activity and reactivity to human contact make it hard to activate animals in a consistent manner and get uniform and trustworthy responses. The present study was performed on prairie voles (aged 8 weeks). Sham (7 male prairie voles) and chronic constriction injury (CCI) (8 male prairie voles) rodents were investigated before surgery and four and seven days later. Each animal was assessed for nociceptive behavior. Pressure and mechanical threshold tests were conducted by the application of three different pushers to the center of hind paws and arterial clips to the toes while sedated with isoflurane. The CCI affected right lower extremity prominently increased nociceptive behavior scores four and seven days after the experiment, and the CCI affected right hind paw prominently decreased pressure and mechanical threshold tests four and seven days after the experiment . The pressure and mechanical thresholds were relevant to the scorings of nociceptive behavior in CCI model animals.

Potamogeton perfoliatus L. Extract Attenuates Neuroinflammation and Neuropathic Pain in Sciatic Nerve Chronic Constriction Injury-Induced Peripheral Neuropathy in Rats

Sciatic nerve injury is often associated with neuropathic pain and neuroinflammation in the central and peripheral nervous systems. In our previous work, Potamogeton perfoliatus L. displayed anti-inflammatory, antipyretic and analgesic properties, predominantly via the inhibition of COX-2 enzyme and attenuation of oxidative stress. Herein, we extended our investigations to study the effects of the plant’s extract on pain-related behaviors, oxidative stress, apoptosis markers, GFAP, CD68 and neuro-inflammation in sciatic nerve chronic constriction injury (CCI) rat model. The levels of the pro-inflammatory marker proteins in sciatic nerve and brainstem were measured with ELISA 14 days after CCI induction. Pretreatment with the extract significantly attenuated mechanical and cold allodynia and heat hyperalgesia with better potential than the reference drug, pregabalin. In addition, CCI lead to the overexpression of prostaglandin E2 (PGE2), inducible nitric oxide synthase (iNOS), tumor necrosis alpha (TNFα), nuclear factor κB (NF-κB), cyclooxygenase-2 (COX-2), 5-lipoxygenase (5-LOX), and NADPH oxidase-1 (NOX-1) and decreased the catalase level in sciatic nerve and brainstem. The observed neuro-inflammatory changes were accompanied with glial cells activation (increased GFAP and CD68 positive cells), apoptosis (increased Bax) and structural changes in both brainstem and sciatic nerve. The studied extract attenuated the CCI-induced neuro-inflammatory changes, oxidative stress, and apoptosis while it induced the expression of Bcl-2 and catalase in a dose dependent manner. It also decreased the brainstem expression of CD68 and GFAP indicating a possible neuroprotection effect. Taking together, P. perfoliatus may be considered as a novel therapy for neuropathic pain patients after performing the required clinical trials.

Selected Thiadiazine-Thione Derivatives Attenuate Neuroinflammation in Chronic Constriction Injury Induced Neuropathy

Neuropathic pain refers to a lesion or disease of peripheral and/or central somatosensory neurons and is an important body response to actual or potential nerve damage. We investigated the therapeutic potential of two thiadiazine-thione [TDT] derivatives, 2-(5-propyl-6-thioxo-1, 3, 5-thiadiazinan-3-yl) acetic acid [TDT1] and 2-(5-propyl-2-thioxo-1, 3, 5-thiadiazinan-3-yl) acetic acid [TDT2] against CCI (chronic constriction injury)-induced neuroinflammation and neuropathic pain. Mice were used for assessment of acute toxicity of TDT derivatives and no major toxic/bizarre responses were observed. Anti-inflammatory activity was assessed using the carrageenan test, and both TDT1 and TDT2 significantly reduced carrageenan-induced inflammation. We also used rats for the induction of CCI and performed allodynia and hyperalgesia-related behavioral tests followed by biochemical and morphological analysis using RT-qPCR, immunoblotting, immunohistochemistry and immunofluorescence. Our findings revealed that CCI induced clear-cut allodynia and hyperalgesia which was reversed by TDT1 and TDT2. To determine the function of TDT1 and TDT2 in glia-mediated neuroinflammation, Iba1 mRNA and protein levels were measured in spinal cord tissue sections from various experimental groups. Interestingly, TDT1 and TDT2 substantially reduced the mRNA expression and protein level of Iba1, implying that TDT1 and TDT2 may mitigate CCI-induced astrogliosis. In silico molecular docking studies predicted that both compounds had an effective binding affinity for TNF-α and COX-2. The compounds interactions with the proteins were dominated by both hydrogen bonding and van der Waals interactions. Overall, these results suggest that TDT1 and TDT2 exert their neuroprotective and analgesic potentials by ameliorating CCI-induced allodynia, hyperalgesia, neuroinflammation and neuronal degeneration in a dose-dependent manner.

EFFICACY OF P-COUMARIC ACID IN CHRONIC CONSTRICTION INJURY INDUCED NEUROPATHIC PAIN IN RATS

The present research work has been designed to evaluate the effect of p-coumaric acid in chronic constriction injury (CCI) of sciatic nerve induced neuropathic pain in rats. In addition, biochemical tests such as thiobarbituric acid reactive substances (TBARS), reduced glutathione (GSH) and total protein were performed in sciatic nerve tissue sample. The neuropathic pain has been effi ciently and successfully induced in rat by the performance of CCI. The battery of behavioural test showed the development of neuropathic pain as an index of rising the paw and tail thermal and mechanical pain sensitivity. The treatment of p-coumaric acid at dose 50 and 100 mg kg-1 , p.o. for 15 consecutive days have been shown to produce signifi cant ameliorative effect on CCI of sciatic nerve induced neuropathic pain sensitivity. In addition, CCI of sciatic nerve also induces the oxidative stress in nervous system by rising TBARS, decrease GSH and proteins levels in sciatic nerve tissue and these effects are reversed via administration of p-coumaric acid and statistically equivalent to standard drug. Hence, it may be concluded that, p-coumaric acid can be useful in the management of neuropathic pain symptoms.

Evaluating the Effects of Probiotic Supplementation on Neuropathic Pain and Oxidative Stress Factors in an Animal Model of Chronic Constriction Injury of the Sciatic Nerve

Background: Neuropathic pain is a common and painful somatosensory nervous system disease, and its treatment remains a medical challenge. Evidence demonstrates that gut microbiota alters in neuropathic pain and, therefore, improvement of the gut flora may affect the disease. The present study aimed to evaluate the antinociceptive effect of probiotics in neuropathic pain and oxidative biomarkers' responsiveness to the probiotic treatment. Methods: Using chronic constriction injury (CCI) of the rats' sciatic nerve, neuropathic pain was induced. Investigating the analgesic effect of the probiotics mixture, 40 male rats were randomly assigned to 4 groups (n=10 for each): Sham-operated (SM), and CCI model rats have orally received 1 ml saline (CS), or 100 mg/kg Gabapentin (CG) or 1 ml probiotics mixture (CP) Lactobacillus plantarum, Lactobacillus delbrueckii, Lactobacillus acidophilus, Lactobacillus rhamnosus, and Bifidobacterium bifidum (109 CFU of each) daily. Using behavioral tests, the pain was assessed on days 1, 4, 7, 14, and 21 of the study. Finally, the biochemical evaluation of sciatic nerve tissue was done. Results: Probiotics decreased cold and mechanic allodynia and thermal hyperalgesia. Reducing lipid peroxidation level and increasing total antioxidant capacity, SOD, and GPx activity was also significant in the probiotics group. Conclusions: These findings suggest that probiotics have analgesic effects on the chronic constriction injury (CCI) model of neuropathic pain via increasing antioxidant capacity of the rats' sciatic nerve.