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(1) Background: Globally, about 600 million people are afflicted with diabetes, and one of its most prevalent complications is neuropathy, a debilitating condition. At the present time, the exploration of novel therapies for alleviating diabetic-neuropathy-associated pain is genuinely captivating, considering that current therapeutic options are characterized by poor efficacy and significant risk of side effects. In the current research, we evaluated the antihyperalgesic effect the sildenafil (phosphodiesterase-5 inhibitor)–metformin (antihyperglycemic agent) combination and its impact on biochemical markers in alloxan-induced diabetic neuropathy in rats. (2) Methods: This study involved a cohort of 70 diabetic rats and 10 non-diabetic rats. Diabetic neuropathy was induced by a single dose of 130 mg/kg alloxan. The rats were submitted to thermal stimulus test using a hot–cold plate and to tactile stimulus test using von Frey filaments. Moreover, at the end of the experiment, the animals were sacrificed and their brains and livers were collected to investigate the impact of this combination on TNF-α, IL-6, nitrites and thiols levels. (3) Results: The results demonstrated that all sildenafil–metformin combinations decreased the pain sensitivity in the von Frey test, hot plate test and cold plate test. Furthermore, alterations in nitrites and thiols concentrations and pro-inflammatory cytokines (specifically TNF-α and IL-6) were noted following a 15-day regimen of various sildenafil–metformin combinations. (4) Conclusions: The combination of sildenafil and metformin has a synergistic effect on alleviating pain in alloxan-induced diabetic neuropathy rats. Additionally, the combination effectively decreased inflammation, inhibited the rise in NOS activity, and provided protection against glutathione depletion. [ABSTRACT FROM AUTHOR]

Background and objectives: Worldwide, approximately 500 million people suffer from diabetes and at least 50% of these people develop neuropathy. Currently, therapeutic strategies for reducing diabetic neuropathy (DN)-associated pain are limited and have several side effects. The purpose of the study was to evaluate the antihyperalgesic action of different sildenafil (phosphodiesterase-5 inhibitor) and metformin (antihyperglycemic agent) combinations in alloxan-induced DN. Methods: The study included 100 diabetic mice and 20 non-diabetic mice that were subjected to hot and cold stimulus tests. Furthermore, we determined the influence of this combination on TNF-α, IL-6 and nitrites levels in brain and liver tissues. Results: In both the hot-plate and tail withdrawal test, all sildenafil–metformin combinations administered in our study showed a significant increase in pain reaction latencies when compared to the diabetic control group. Furthermore, all combinations decreased blood glucose levels due to the hypoglycemic effect of metformin. Additionally, changes in nitrite levels and pro-inflammatory cytokines (TNF-α and IL-6) were observed after 14 days of treatment with different sildenafil–metformin combinations. Conclusions: The combination of these two substances increased the pain reaction latency of diabetic animals in a dose-dependent manner. Moreover, all sildenafil–metformin combinations significantly reduced the concentration of nitrites in the brain and liver, which are final products formed under the action of iNOS. [ABSTRACT FROM AUTHOR]

Background and objectives: Worldwide, approximately 500 million people suffer from diabetes and at least 50% of these people develop neuropathy. Currently, therapeutic strategies for reducing diabetic neuropathy (DN)-associated pain are limited and have several side effects. The purpose of the study was to evaluate the antihyperalgesic action of different sildenafil (phosphodiesterase-5 inhibitor) and metformin (antihyperglycemic agent) combinations in alloxan-induced DN. Methods: The study included 100 diabetic mice and 20 non-diabetic mice that were subjected to hot and cold stimulus tests. Furthermore, we determined the influence of this combination on TNF-α, IL-6 and nitrites levels in brain and liver tissues. Results: In both the hot-plate and tail withdrawal test, all sildenafil–metformin combinations administered in our study showed a significant increase in pain reaction latencies when compared to the diabetic control group. Furthermore, all combinations decreased blood glucose levels due to the hypoglycemic effect of metformin. Additionally, changes in nitrite levels and pro-inflammatory cytokines (TNF-α and IL-6) were observed after 14 days of treatment with different sildenafil–metformin combinations. Conclusions: The combination of these two substances increased the pain reaction latency of diabetic animals in a dose-dependent manner. Moreover, all sildenafil–metformin combinations significantly reduced the concentration of nitrites in the brain and liver, which are final products formed under the action of iNOS.

Abstract Morin is a flavonoid has been reported with several pharmacological effects such as, antioxidant, anti-inflammatory, anticancer, antidiabetic, etc. However, morin has low solubility in water, which decreases the bioavailability and limits its clinical application. In this way, to improve the pharmaceutical properties, morin was complexed in hydroxypropyl-β-cyclodextrin (HP-β-CD) and its oral bioavailability and anti-inflammatory effects were evaluated. Initially, a phase solubility study was performed, which showed that HP-β-CD would be the better cyclodextrin for the formation of complexes with morin. The morin/HP-β-CD inclusion complex (1:1) was prepared by freeze-drying method. The sample obtained was characterized by DSC, FTIR, PXRD, SEM and 1H NMR techniques, evidencing the formation of morin/HP-β-CD inclusion complex. In addition, complexation efficiency (98.3%) and loading content (17.63%), determined by HPLC demonstrated that morin was efficiently complexed in HP-β-CD. In vitro dissolution study confirmed that morin/HP-β-CD inclusion complex increased the solubility and dissolution rate of morin. The oral bioavailability of the morin/HP-β-CD complex and free morin were evaluated through a pharmacokinetic study in rat plasma. The oral bioavailability of morin complexed with HP-β-CD was increased by 4.20 times compared with the free morin. Hyperalgesia induced by carrageenan and carrageenan-induced pleurisy were carried out in mice to evaluate the antihyperalgesic and anti-inflammatory activities of free morin and inclusion complex. Morin/HP-β-CD inclusion complex showed antihyperalgesic effect in inflammatory pain model and anti-inflammatory effect decreasing leukocyte migration and TNF-α levels at a lower dose than free morin. Therefore, the morin/HP-β-CD inclusion complex improved the solubility, dissolution rate, oral bioavailability, antihyperalgesic and anti-inflammatory effects of morin. In this way, the morin/HP-β-CD inclusion complex exhibits potential for development of new pharmaceutical product for future clinical applications. Highlights • Morin/HP-β-CD complexes have been developed to improve the anti-inflammatory activity. • The FD method showed high efficiency in the formation of inclusion complexes. • Morin inclusion complexes enhanced bioavailability and antihyperalgesic activities. • Morin inclusion complexes also reduced the pro-inflammatory cytokine TNF-α and leukocytes level. [ABSTRACT FROM AUTHOR]

Centhaquin has been shown to produce antinociception in the mouse hot plate and tail flick assays through the opioid, the α 2A and α 2B adrenoceptors. Present study was conducted to determine the effects of centhaquin in a rat model of postoperative pain. Involvement of opioid, and adrenergic receptors was assessed by pretreating rats with antagonists at the opioid (naloxone), α 2 -(atipamezole) or α 2B -(imiloxan) adrenergic receptors. Postoperative pain was induced by hind paw plantar incision in male Sprague Dawley rats. Antihyperalgesic effects were determined by measurement of paw withdrawal latencies and withdrawal force, using dynamic von Frey filaments; attenuation of non-evoked guarding was measured by assigning pain scores to spontaneous behaviors. Rotarod test was used to determine motor impairment. Animals received saline, centhaquin or antagonist plus centhaquin. Centhaquin produced dose-dependent antihyperalgesic effect and attenuation of non-evoked guarding behavior, versus saline treated rats ( P <0.05). Naloxone partially blocked while atipamezole and imiloxan significantly reversed centhaquin's antihyperalgesic effects ( P <0.05). Attenuation of non-evoked guarding behavior was also blocked, but was not statistically significant. Imiloxan produced a greater block compared to atipamezole while naloxone had no significant effect. Rotarod testing indicated that centhaquin did not cause motor impairment. This is the first report demonstrating centhaquin antinociception in the rat postoperative pain model. Opioid, α 2 adrenergic, and particularly α 2B adrenergic receptors are involved in mediating antihyperalgesia while attenuation of nonevoked guarding is mediated by α 2B /α 2 adrenergic receptors. Centhaquin could be an effective non-sedating alternative in treating postoperative pain in ambulatory surgeries. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to establish in healthy volunteers the maximally tolerated multiple dose (MTMD) of the ionotropic glutamate receptor 5 antagonist LY545694 (part A), and to investigate whether that dose had analgesic or antihyperalgesic effects in the brief thermal stimulation (BTS) pain model (Part B). Part A was a double-blind, placebo-controlled study in 3 groups of 10 healthy men. To simulate an extended-release formulation, study drug was administered orally over 6hours (12 equally divided aliquots at 30-minute intervals). Part B was a double-blind, placebo-controlled, double-dummy, 3-way crossover study in 27 healthy men. At each of the 3 study periods, subjects received either LY545694 (MTMD; as determined during part A) as a simulated, twice daily extended-release formulation for 4 doses over 3days, gabapentin (600mg 8hours apart; 6 doses over 3days; positive control), or matching placebo. The BTS model was induced twice with a 1-hour interval on each of the 2 study days, before drug administration and at the time of expected peak analgesia of LY545694. Plasma exposure for LY545694 was approximately linear over the 25- to 75-mg dose range. The MTMD of LY545694 was 25mg twice daily. Areas of secondary hyperalgesia were significantly smaller after administration of LY545694 and gabapentin compared with placebo (P <.0001 and P =.0004, respectively), but there was no difference between areas after administration of gabapentin and LY545694 (P =.400). Neither gabapentin nor LY545694 reduced the painfulness of skin heating during BTS model induction. The most common treatment-emergent adverse event was dizziness. The results of this study suggest that LY545694 should be explored further as a potential treatment for chronic pain involving neuronal sensitization. [Copyright &y& Elsevier]

Abstract: Ethnopharmacological relevance: Achyrocline alata is a locally marketed (Mato Grosso do Sul/ Brazil) herb used in folk medicine as an anti-inflammatory and a sedative. Evaluate the anti-inflammatory properties of Achyrocline alata in both in vivo and in vitro models. Materials and methods: A hydroethanolic extract from inflorescences of Achyrocline alata (HEAa) was characterized by HPLC-DAD and compared to standards (chlorogenic acid; isoquercetrin; quercetin; 4,2׳,4׳-trihydroxy-6׳-methoxychalcone; gnaphalin; 3-O-methyl-quercetin; 3,5-dicaffeoyl-quinic acid and 4,5-dicaffeoyl-quinic acid). The in vivo anti-inflammatory properties of the HEAa (4, 20 and 100mg/kg, per os) were evaluated using the following animal models: carrageenan-induced paw edema in rats, carrageenan-induced vascular permeability and peritonitis in mice and an acetic acid-induced writhing model to test antihyperalgesic activity in mice. In vitro assays were performed to study the effects of the HEAa (0.16, 0.8 and 4mg/ml) on the cell viability, cell spreading and production of NO and H2O2 in stimulated macrophages. Results: The A. alata extract inhibited the development of edema and vascular permeability, reduced polymorphonuclear cell recruitment in the acute peritonitis assay and decreased the amount of writhing induced by acetic acid. The HEAa did not increase NO/H2O2 production, while it did inhibit production when the macrophages were stimulated by LPS or PMA at all tested concentrations. In the presence of HEAa, macrophage spreading did not increase even after stimulation with LPS. Additionally, the HEAa was nontoxic to macrophages at all tested concentrations. Conclusions: The HEAa displayed anti-inflammatory and antihyperalgesic effects, which supports the use of this plant in folk medicine. These effects might be due to the flavonoids and phenylpropanoids derivatives present in the HEAa. [Copyright &y& Elsevier]

Highlights: [•] Synthesis of tetrahydropyrido-pyrimidines. [•] Acute nociceptive assays performed. [•] Chronic constriction injury and partial sciatic nerve ligation models in animals were used. [•] Quantification of ED50 for potential analogs determined. [•] Mechanistic studies on inflammatory mediation, oxidative and nitrosative stress performed. [ABSTRACT FROM AUTHOR]

Chlorogenic acid (CGA) is a natural organic phenolic compound that is found in many plants, fruits and vegetables. CGA has beneficial bioactivities and strong therapeutic effects in inflammatory processes. CGA-rich fractions have analgesic activity but CGA has not been tested previously in neuropathic pain, which results from tissue damage, inflammation or injury of the nervous system. Chronic constrictive nerve injury (CCI) is a peripheral neuropathic pain model which initiates an inflammatory cascade. We aimed to determine possible antihyperalgesic effects of CGA in neuropathic pain. Our study showed for the first time that CGA [50, 100 and 200 mg/kg; intraperitoneally (i.p.)] produced significant dose- and time-dependent antihyperalgesic activity in CCI-induced neuropathic pain. In addition, chronic administration of CGA (100 mg/kg/day; i.p. for 14 days) prevented the development of mechanical hyperalgesia and attenuated CCI-induced histopathological changes. On the other hand, CGA (200 mg/kg) did not affect falling latencies of rats in the rota rod test. Hence, CGA might represent a novel potential therapeutic option for the management of neuropathic pain. [ABSTRACT FROM AUTHOR]

Abstract: We disclose the discovery of a novel series of tetrahydropyrido-pyrazoles that are potent inhibitors of tumour necrosis factor-alpha (TNF-α), nitric oxide and cannabinoid receptor subtype 1 (CB1). We report herein the synthesis and neuropharmacological screening results of the titled compounds in two acute pain and two neuropathic pain models in rodents. Particularly the analogue N-(4-bromophenyl)-3-tert-butyl-5-ethyl-4,5,6,7-tetrahydro-1H-pyrazolo[4,3-c]pyridine-1-carboxamide (8a) exhibited pronounced acute antinociceptive efficacy, also being effective in chronic constriction injury (ED50 = 23.8 mg/kg) and partial sciatic nerve injury (ED50 = 29.0 mg/kg) models with CB1 receptor activity (IC50 = 49.6 nM) and inhibitory effect on TNF-α (86.4% inhibition at 100 mg/kg). These results suggest the importance of the development of this lead as multi-targeted treatment strategy for neuropathic pain. [Copyright &y& Elsevier]

In this work, synthetic integration of substituted semicarbazides and various aliphatic, aryl and heteroaryl acids into 1,2,4-triazol-5-ones was accomplished. Following the assessment of neurotoxicity and peripheral analgesic activity, the compounds were evaluated in two peripheral models of neuropathic pain, the chronic constriction injury and partial sciatic nerve ligation to assess their antihyperalgesic and antiallodynic potential. ED50 studies undertaken for selected compounds exhibiting promising efficacies ( 1c, 3c and 4a) revealed values ranging from 13.21 to 39.85 mg/kg in four behavioral assays of hyperalgesia and allodynia (spontaneous pain, tactile allodynia, cold allodynia, and mechanical hyperalgesia). Mechanistic studies revealed that the compounds suppressed the inflammatory component of the neuropathic pain inhibiting tumor necrosis factor-alpha and preventing oxidative and nitrosative stress. [ABSTRACT FROM AUTHOR]

Abstract: Neuropathic pain is a chronic pain condition that occurs and persists in a heterogeneous group of etiologically different diseases characterized by a primary lesion or dysfunction of the peripheral or central nervous system. Current treatment options do not provide adequate relief for many patients and a significant number of the agents used have dose limiting side effects. During the course of our work on the synthesis and screening of new drugs for the treatment of neuropathic pain, we have identified 5-(4-nitrophenyl)furoic-2-acid hydrazones which showed significant antiallodynic and antihyperalgesic activities in a chronic constriction injury (CCI) model of neuropathic pain in rat. Synthesized compounds thus represent a promising lead for new drug development for the treatment of neuropathic pain. [Copyright &y& Elsevier]

Abstract: A subcutaneous implant of 17β-estradiol or progesterone provides steady-state serum hormone levels from 7 to 24 days after implantation and allows the evaluation of the effects of the replacement with these hormones on phase 1 and phase 2 formalin-induced behaviors in ovariectomized (OVX) rats. Graded doses of 17β-estradiol (5% to 40%) reduce formalin-induced behavior by 35% to 49% during phase 2 but not during phase 1, as measured with an automated formalin apparatus. The maximal response is seen with 20% 17β-estradiol. The antihyperalgesic effect of 20% 17β-estradiol is significant at 8 days after implantation and persists at 21 days. In contrast, graded doses of progesterone have no effect on either phase of formalin. The estrogen receptor antagonist tamoxifen completely prevents the antihyperalgesic effect of the 20% 17β-estradiol implant. Formalin-induced behaviors during phase 2 are significantly less in proestrus females and OVX rats given 20% 17β-estradiol compared with OVX control rats. Also, the formalin-induced increase in serum corticosterone is attenuated in OVX control rats compared with proestrus females and OVX rats given 20% 17β-estradiol. These results indicate that estrogen replacement in OVX rats restores the maximal corticosterone response to tonic pain and, by an estrogen receptor–mediated process, inhibits tonic pain. Perspective: Hormone replacement (HR) therapy remains a widely used modality. We used a pharmacokinetically based rat HR model that results in continuous physiological levels of 17β-estradiol to demonstrate the analgesic (antihyperalgesic) effects of estrogen replacement in an inflammatory pain model (formalin). These results suggest a potentially important consequence of HR therapy. [Copyright &y& Elsevier]

Abstract: Objective: Nociception is the major cause of burn pain and leads to central hyperalgesia. Gabapentin (Gp) is an antihyperalgesic drug that selectively affects central sensitization. We studied the opioid-sparing and analgesic effects of Gp in severely burned patients. Methods: Ten patients (mean total burned body surface area (TBSA), 25%), received 2400mg of oral Gp daily from after burn days 3–24 in addition to standard pain therapy. They were compared to a retrospective matching group. Outcomes were cumulative morphine consumption and mean daily pain scores. Outcomes were recorded during treatment (21 days) and 21 days after treatment. Results: During treatment and post-treatment phases, patients receiving Gp had cumulative morphine consumption and a mean daily pain score significantly lower than controls. Conclusion: Gp use reduced opioid consumption and lowered pain scores that seemed to extend beyond its pharmacologic action probably result from the ability of Gp to prevent central hyperalgesia induced by burns. [Copyright &y& Elsevier]

Central or systemic administration of agonists directed at the μ or δ opiate receptors generally produce a greater degree of analgesia in males than in females. To date, most studies examining sex-based differences in opioid analgesia have used acute noxious stimuli (i.e., tail-flick and hot plate test); thus the potential dimorphic response of centrally acting opiates in the alleviation of persistent inflammatory pain is not well established. In the present study, right hind paw withdrawal latency (PWL) to radiant thermal stimuli was measured in intact male and cycling female Sprague-Dawley rats before and after unilateral hind paw injection of the inflammatory agent complete Freund's adjuvant (CFA). Control animals received intraplantar injection of saline. Twenty four hours after CFA or saline injection, animals received either saline or morphine bisulfate (0.5–15 mg/kg sc). Separate groups of control or inflamed animals were tested on their responsiveness to morphine at 7, 14, and 21 days post-CFA or saline. No sex differences were noted for baseline PWLs, and females displayed slightly less thermal hyperalgesia at 24 h post-CFA. At all morphine doses administered, both the antihyperalgesic effects of morphine in the inflamed animals and the antinociceptive effects of morphine in control animals were significantly greater in males compared with females. Similarly, in males, the antihyperalgesic effects of morphine increased significantly at 7–21 days post-CFA; no significant shift in morphine potency was noted for females. These studies demonstrate sex-based differences in the effects of morphine on thermal hyperalgesia in a model of persistent inflammatory pain. [ABSTRACT FROM AUTHOR]

Abstract: In Sri Lankan folk medicine, the leaves of Crinum bulbispermum Burm. (Family: Amaryllidaceae) are claimed to be useful for earache, which is suggestive of antinociceptive activity. The aim of this study was to examine scientifically the antinociceptive activity of Crinum bulbispermum leaves. One of three doses (1000, 1500 and 3000mg/kg, N =6/group) of aqueous leaf extract (ALE) or 1ml of distilled water (DW) (vehicle) (N =6) was orally administered to male rats and antinociceptive activity was determined using three models of nociception (tail flick, hot plate and formalin tests). In the hot plate test, slight (18–42%) but significant (P &#60;0.05) overall prolongation of reaction time was evident up to 4h. In the hot plate test, reaction time was markedly (84–121%) and significantly increased by the high dose up to 3h. In contrast, in the formalin test, the high and mid doses significantly impaired the number of lickings and time spent on licking at both phases, whilst the lower dose impaired only the time spent on licking at the late phase. Collectively these results suggest that the antinociception is mediated both spinally and supraspinally and is effective against phasic and continuous non-inflammatory/inflammatory pain. Additionally, the ALE had antihyperalgesic activity. The antinociception of the ALE appear to results from opioid mechanisms, sedation and antioxidant activities. Unfortunately, ALE is mild to moderately toxic. [Copyright &y& Elsevier]

The present study aimed to evaluate possible antinociceptive effects of chlorogenic acid in streptozotocin-induced diabetic neuropathic pain in rats. Chlorogenic acid (100 mg/kg) was administered daily for 14 days. Our study showed for the first time that both single and chronic chlorogenic acid treatments produced significant antinociceptive effects in diabetic rats. In contrast, single dose of chlorogenic acid showed no signs of an antinociceptive effect, but chronic treatment exerted antinociceptive potential in nondiabetic rats. Additionally, chronic treatment effectively reduced hyperglycemia that induced by diabetes. In conclusion, chlorogenic acid has beneficial effects for the management of diabetic neuropathic pain. [ABSTRACT FROM AUTHOR]

The Eriobotrya japonica (EJ) is a Chinese medicinal plant that is currently grown in Brazil. E. japonica leaves infusion is traditionally used in the treatment of inflammation; however, there are few scientific studies showing the effects of these properties on joint articular and persistent experimental inflammation. Aim of the study: The present research had objective investigation of the effect of infusion obtained from leaves of E. japonica (EJLE) on acute and persistent experimental articular inflammation. The Swiss mice were treated orally with EJLE and analyzed for acute pleural inflammation (30, 100, and 300 mg/kg), paw edema induced by carrageenan (100 mg/kg), acute knee inflammation induced by zymosan (100 mg/kg), and persistent inflammation induced by Complete Freund's Adjuvant (CFA) (30 and 100 mg/kg). Mechanical hyperalgesia, cold and edema were analyzed. The chromatographic analysis of EJLE revealed the presence of corosolic acid, oleanolic acid, and ursolic acid. EJLE presented anti-inflammatory activity in the pleurisy model, inhibiting leukocyte migration, protein extravasation and nitric oxide production. In the articular inflammation model, EJLE reduced the number of leukocytes in the joint cavity, paw edema and hyperalgesia (4 h after induction). In the persistent inflammation model induced by CFA, the extract reduced paw edema after 11 days of mechanical and cold hyperalgesia on day 6. The EJLE has anti-inflammatory and antihyperalgesic potential in models of acute and persistent experimental articular inflammation, making this infusion a new possibility for complementary treating acute or chronic articular inflammatory diseases. Image 1 [ABSTRACT FROM AUTHOR]

Background: Natural phenolic compounds in medicinal herbs and dietary plants are antioxidants which play therapeutic or preventive roles in different pathological situations, such as oxidative stress and inflammation. One of the most studied phenolic compounds in the last decade is chlorogenic acid (CGA), which is a potent antioxidant found in certain foods and drinks., Objective: This review focuses on the anti-inflammatory and antinociceptive bioactivities of CGA, and the putative mechanisms of action are described. Ethnopharmacological reports related to these bioactivities are also reviewed., Materials and Methods: An electronic literature search was conducted by authors up to October 2019. Original articles were selected., Results: CGA has been shown to reduce inflammation and modulate inflammatory and neuropathic pain in animal models., Conclusion: The consensus of the literature search was that systemic CGA may facilitate pain management via bolstering antioxidant defenses against inflammatory insults., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Background: Chronic pain is treated most commonly with opioid analgesics, anti-inflammatory steroids and nonsteroidal anti-inflammatory drugs., Method: However, these compounds are not uniformly effective and their clinical use is constrained by unwanted side effects. GABAergic neurons are located in spinal nociceptive circuits suggesting that drugs with affinity at these receptors, including benzodiazepine-like drugs, may provide an alternative to opioids for the treatment of pain. However, systemically administered conventional benzodiazepines fail to produce antihyperalgesic effects, likely due to their concurrent sedative properties., Results: Recent evidence suggests that by targeting specific benzodiazepine-sensitive GABAA; receptor subtypes, the sedative properties of benzodiazepines can be circumvented and these compounds may be useful alternatives to opioids for the treatment of chronic pain., Conclusion: The present review provides an overview of the GABAA; receptor subtypes involved in pain transmission as well as implications for the development of analgesic medications., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.)

Neuropathic pain is caused by lesion or inflammation of the nervous system and characterized by the symptoms of allodynia, hyperalgesia and spontaneous pain. SIRT1 (Sir2) is a NAD-dependent deacetylase and is reported to regulate a wide variety of cellular processes including inflammation, aging and lifespan extension. Nevertheless, the role of SIRT1 in neuropathic pain is not fully understood. The present study was intended to detect the effect of intrathecal SRT1720, a SIRT1 agonist, using quantitative real-time PCR and western blot analysis over time in rats following chronic constriction injury (CCI) or sham surgery. In addition, the effect of intrathecal injection of SRT1720 on thermal hyperalgesia and mechanical allodynia was evaluated in CCI rats. It was found that daily intrathecal injection of SRT1720 before and 1, 3, 5, 7 days after CCI surgery produced a transient inhibitory effect on thermal hyperalgesia and mechanical allodynia in CCI rats. In addition, an intrathecal injection of STR1-siRNA before SRT1720 administration reversed the anti-nociceptive effect of SRT1720. Furthermore, intrathecal injection of SRT1720 significantly down-regulated the expression of mammalian target of rapamycin (mROT), NF-κB and inflammatory cytokines, such as IL-6, TNF-α and iNOS mRNA. These data indicate that intrathecal SRT1720 may be an alternative strategy for the treatment of neuropathic pain. Our findings suggest that intrathecal SRT1720, a SIRT1 agonist, exerts antihyperalgesic and antiinflammatory effects on CCI-induced neuropathic pain in rats.