Synthesis and anticonvulsant activity of 1-(2-(8-(benzyloxy)quinolin-2-yl)-1-butyrylcyclopropyl)-3-substituted urea derivatives

H‐Dmt‐D‐Arg‐Phe‐Lys‐NH₂ ([Dmt¹]DALDA) is a synthetic tetrapeptide with extraordinary selectivity for the mu‐opioid receptor and is an extremely potent analgesic. [Dmt¹]DALDA is unusual in the way that the greater part of its analgesic potency appears to be produced by its actions in the spinal cord. Furthermore, [Dmt¹]DALDA inhibits norepinephrine re‐uptake and is a mitochondria‐targeted antioxidant. Such characteristics may make [Dmt¹]DALDA particularly effective against neuropathic pain. The present study was designed to compare the effects of [Dmt¹]DALDA and morphine on thermal hyperalgesia in an experimental neuropathic pain model. Neuropathic pain was induced in rats by surgical ligation of the L5 spinal nerve, and thermal pain thresholds were assessed by latencies of paw withdrawal to radiant heat. The increase in paw withdrawal latency was greater after the administration of [Dmt¹]DALDA than that of morphine in neuropathic rats at doses that were equianalgesic in naïve animals. We conclude that [Dmt¹]DALDA is more effective than morphine against thermal hyperalgesia in this experimental model of neuropathic pain.     

Involvement of glutamate NMDA and AMPA receptors, glial cells and IL-1β in the spinal hyperalgesia evoked by the chemokine CCL2 in mice

We study here the involvement of excitatory amino acid receptors, glial cell activation and IL-1β release in the spinal hyperalgesia evoked by the chemokine CCL2 (MCP-1). Three hours after the intrathecal administration of CCL2 (1-100 ng), mice exhibit dose-dependent thermal hyperalgesia, that was inhibited by the coadministration of the antagonist of chemokine receptor type 2 (CCR2) RS504393 (0.3-3 μg). To assess the involvement of excitatory amino acid receptor sensitisation, CCL2 was coadministered with CPP (0.3-3 ng) and NBQX (25-250 ng), antagonists of NMDA and AMPA receptors, respectively. Both drugs blocked CCL2-evoked hyperalgesia, strongly suggesting that CCL2 evokes in vivo NMDA and AMPA receptor sensitisation, as previously described in electrophysiological studies. Furthermore, this rapid induction of CCL2-mediated hyperalgesia was blocked by the previous acute administration of the microglial inhibitor minocyclin (4.9 μg) or the astroglial inhibitor l-aminoadipate (1.6 μg). Since IL-1β can be released by activated glial cells we tested whether this cytokine could be underlying the spinal sensitisation induced by CCL2. The administration of the type I IL-1 receptor antagonist, IL-1ra (3-30 μg), partially prevented CCL2-evoked hyperalgesia. Finally, to elucidate if IL-1β could produce NMDA and AMPA receptor sensitisation by itself, we performed experiments in which this cytokine was i.t. administered. Thermal hyperalgesia induced by IL-1β (30 pg) was completely prevented by the coadministration of CPP (3 ng) but unaffected by NBQX (250 ng). Globally, our results suggest that spinal CCL2 induces thermal hyperalgesia by sensitising NMDA and AMPA receptors in a process that involves glial activation and IL-1β release.     

Exploring the Pain in Patellofemoral Pain: A Systematic Review and Meta-Analysis Examining Signs of Central Sensitization

BackgroundPatellofemoral pain (PFP) has high recurrence rates and minimal long-term treatment success. Central sensitization refers to dysfunctional pain modulation that occurs when nociceptive neurons become hyperresponsive. Researchers in this area of PFP have been increasingly productive in the past decade.ObjectiveTo determine whether evidence supports manifestations of central sensitization in individuals with PFP.Data SourcesWe searched MeSH terms for quantitative sensory testing (QST) pressure pain thresholds (PPTs), conditioned pain modulation (CPM), temporal summation, sensitization, hyperalgesia, and anterior knee pain or PFP in PubMed, SPORTDiscus, CINAHL, Academic Search Complete, and EBSCOhost.Study SelectionPeer-reviewed studies that were written in English and published between 2005 and 2020 and investigated QST or pain mapping in a sample with PFP were included in this review.Data ExtractionThe initial search yielded 140 articles. After duplicates were removed, 78 abstracts were reviewed. The full text of 21 studies was examined, and we included 15 studies in our evaluation: 6 in the meta-analysis, 4 in the systematic review, and 5 in both the meta-analysis and systematic review.Data SynthesisA random-effects meta-analysis was conducted for 4 QST variables (local PPTs, remote PPTs, CPM, temporal summation). Strong evidence supported lower local and remote PPTs, impaired CPM, and facilitated temporal summation in individuals with PFP compared with pain-free individuals. Evidence for heat and cold pain thresholds was conflicting. Pain mapping demonstrated expanding pain patterns associated with long duration of PFP symptoms.ConclusionsSigns of central sensitization were present in individuals with PFP, indicating altered pain modulation. The etiologic and treatment models of PFP should reflect the current body of evidence regarding central sensitization. Signs of central sensitization should be monitored clinically, and treatments with central effects should be considered as part of a multimodal plan of care.     

骨癌痛模型大鼠脊髓背根神经节P2X3受体的表达变化

目的:观察骨癌痛模型大鼠脊髓背根神经节中P2X3受体及其mRNA的表达变化,初步探讨其可能的意义。方法:60只雌性Wistar大鼠随机分为3组（每组n=20）：空白对照（C）组;骨癌痛模型（CP）组,左胫骨内接种含2×105个Walker-256大鼠乳腺癌细胞的悬液10 μl;假手术（S）组,左侧胫骨骨髓腔内注入等体积的生理盐水。在接种后第4、7、10、14、17、21天进行疼痛行为学测试,在第14、21天各组分别选10只大鼠,取背根神经节,5只行免疫组化染色,另5只抽提RNA行实时PCR,检测背根神经节中P2X3受体及其mRNA的表达。结果:CP组大鼠在胫骨内接种肿瘤后第10天开始出现痛觉过敏,第14~21天最为明显。CP组接种肿瘤后第14、21天患侧背根神经节神经元中P2X3受体免疫阳性细胞率明显增高（P<0.05）,mRNA表达水平显著增高（P<0.05）。结论:骨癌痛模型大鼠存在痛觉敏化,可能与P2X3受体表达增高有关。     

5-HT3 receptors mediate the time-dependent vagal afferent modulation of nociception during chronic food allergen-sensitized visceral hyperalgesia in rats

Abstract  Converging lines of evidence demonstrate a vagally mediated antinociceptive pathway in animals undergoing acute visceral insults, the contribution of this system to visceral pain following chronic noxious stimuli is unknown. 5-HT₃ receptor (5-HT₃Rs) on spinal afferents are crucially involved in nociceptive processing, the role of 5-HT₃Rs on vagal afferents is unclear. The aim of the present study was to determine the contribution of vagal afferents to visceral nociception in rats undergoing chronic luminal allergen stimulation and whether it involves vagal 5-HT₃Rs. Sensitized rats received chicken egg albumin (EA, 1 mg mL⁻¹) in drinking water for 2 weeks (day 1–14). Visceromotor response (VMR) to colorectal distension [colorectal distension (CRD), 60 mmHg] and the levels of mRNA encoding 5-HT₃R (including 3A and 3B subunits) in the nodose ganglia (NG) were evaluated on day 2, 4, 8 and 15. Chronic EA challenge induced gradually increased visceral nociception, with a peak on day 15. Subdiaphragmatic vagotomy or functional deafferentation with capsaicin abolished this time-dependent manner, inducing hyperalgesia from day 2, lasting to day 15. Intraluminal infusion of a 5-HT₃R antagonist (granisetron), whether alone or infused after local mucosa anaesthetic with 1% lidocaine, mimicked the effects of vagotomy. The mRNA levels for 5-HT_3B or 5-HT_3A subunit in the NG showed an opposite time-course to that of visceral pain, which increased from day 2, then decreased gradually to levels lower than those of controls. Our results demonstrate a time-dependent vagal afferent modulation of chronic allergen-sensitized visceral hyperalgesia, which may involve a 5-HT₃R pathway.     

Capsaicin-Induced Glutamate Release Is Implicated in Nociceptive Processing Through Activation of Ionotropic Glutamate Receptors and Group I Metabotropic Glutamate Receptor in Primary Afferent Fibers

Glutamate (Glu) is the major excitatory neurotransmitter in the central nervous system. The role of peripheral Glu and Glu receptors (GluRs) in nociceptive transmission is, however, still unclear. In the present study, we examined Glu levels released in the subcutaneous perfusate of the rat hind instep using a microdialysis catheter and the thermal withdrawal latency using the Plantar Test following injection of drugs associated with GluRs with/without capsaicin into the hindpaw. The injection of capsaicin into the rat hind instep caused an increase of Glu level in the s.c. perfusate. Capsaicin also significantly decreased withdrawal latency to irradiation. These effects of capsaicin were inhibited by pretreatment with capsazepine, a transient receptor potential vanilloid receptor 1 (TRPV1) competitive antagonist. Capsaicin-induced Glu release was also suppressed by combination with each antagonist of ionotropic GluRs (iGluRs: NMDA/AMPA receptors) and group I metabotropic GluR (mGluR), but not group II and group III mGluRs. Furthermore, these GluRs antagonists showed remarkable inhibition against capsaicin-induced thermal hyperalgesia. These results suggest that Glu is released from the peripheral endings of small-diameter afferent fibers by noxious stimulation and then activates peripheral iGluRs and group I mGluR in development and/or maintenance of nociception. Furthermore, the activation of peripheral NMDA/AMPA receptors and group I mGluR may be important in mechanisms whereby capsaicin evokes nociceptive responses.     

Role of peripheral and spinal 5-HT6 receptors according to the rat formalin test

The present study assessed the possible pronociceptive role of peripheral and spinal 5-HT₆ receptors in the formalin test. For this, local peripheral administration of selective 5-HT₆ receptor antagonists N-[3,5-dichloro-2-(methoxy)phenyl]-4-(methoxy)-3-(1-piperazinyl)-benzenesulphonamide (SB-399885) (0.01–1 nmol/paw) and 4-iodo-N-[4-methoxy-3-(4-methyl-1-piperazinyl)phenyl]benzene-sulfonamide hydrochloride (SB-258585) (0.001–0.1 nmol/paw) significantly reduced formalin-induced flinching. Local peripheral serotonin (5-HT) (10–100 nmol/paw) or 5-chloro-2-methyl-3-(1,2,3,6-tetrahydro-4-pyridinyl)-1H-indole hydrochloride (EMD-386088) (0.01–0.1 nmol/paw; a selective 5-HT₆ receptor agonist) augmented 0.5% formalin-induced nociceptive behavior. The local pronociceptive effect of 5-HT (100 nmol/paw) or EMD-386088 (0.1 nmol/paw) was significantly reduced by SB-399885 or SB-258585 (0.1 nmol/paw). In contrast to peripheral administration, intrathecal injection of 5-HT₆ receptor antagonists SB-399885 and SB-258585 (0.1–10 nmol/rat) did not modify 1% formalin-induced nociceptive behavior. Spinal 5-HT (50–200 nmol/rat) significantly reduced formalin-induced flinching behavior during phases 1 and 2. Contrariwise, intrathecal EMD-386088 (0.1–10 nmol/rat) dose-dependently increased flinching during phase 2. The spinal pronociceptive effect of EMD-386088 (1 nmol/rat) was reduced by SB-399885 (1 nmol/rat) and SB-258585 (0.1 nmol/rat). Our results suggest that 5-HT₆ receptors play a pronociceptive role in peripheral as well as spinal sites in the rat formalin test. Thus, 5-HT₆ receptors could be a target to develop analgesic drugs.     

The contributing role of CD14 in toll-like receptor 4 dependent neuropathic pain

We have previously demonstrated that CNS toll-like receptor 4 (TLR4) plays a key role in the development of behavioral hypersensitivity in a rodent model of neuropathic pain, spinal nerve L5 transection (L5Tx). TLR4 is a well-known receptor for lipopolysaccharide (LPS) in innate immune responses. In the current study, we further investigated the role of CD14, an accessory molecule in the LPS-TLR4 signaling pathway, in the development of L5Tx-induced neuropathic pain. CD14 knockout (KO) mice displayed significantly decreased behavioral sensitivity (mechanical allodynia and thermal hyperalgesia) as early as day 1 post-L5Tx, indicating a nociceptive role of CD14. By flow cytometric analyses, we observed significantly elevated microglial surface CD14 expression in the ipsilateral lumbar spinal cord 3 days post-L5Tx, as well as remarkable increases in microglial size (via forward scatter (FSC)) and granularity (via side scatter (SSC)). Further, intrathecal injection of soluble CD14 induced significantly greater mechanical hypersensitivity in wild type (C3H/HeN) mice compared with TLR4-deficient (C3H/HeJ) mice. Together, these data demonstrate that CD14 plays a contributing role in TLR4-dependent nerve injury-induced neuropathic pain.     

鲑鱼降钙素对乳腺癌骨转移大鼠机械痛敏的影响

目的 探讨鲑鱼降钙素对乳腺癌骨转移大鼠机械痛敏的影响.方法 在乳腺癌骨转移癌痛模型成功制备后,各治疗组并分别给予鲑鱼降钙素、鲑鱼降钙素+唑来膦酸、唑来膦酸,用电子yon Frey测痛仪测量各组大鼠的机械缩足阈值(MWT).结果 与空白组相比,大鼠于骨癌痛模型制备后的第8天MWT明显降低(P＜0.05).与对照组相比,各...     

碳酸酐酶抑制剂乙酰唑胺对切口痛大鼠痛行为的影响

目的观察鞘内注射碳酸酐酶抑制剂乙酰唑胺(ACT)对大鼠切口痛行为的影响。方法所有大鼠术前6天鞘内置管,随机分为5组:假手术组、假手术+ACT组、切口痛组、切口痛+ACT低剂量(2.25μg)组、切口痛+ACT高剂量(22.5μg)组,每组16只。按照Brennan法建立切口痛模型。ACT和生理盐水均在术后d 1鞘内给予。分别于术前d1(基础值)、术后d 1(给药前,给药后30、75、120、165、240min)测定大鼠的热缩足潜伏期(TWL)和机械缩足反射阈值(MWT),并予比较。结果切口痛术后d 1(给药前)与基础值相比TWL、MWT均明显降低(P<0.05);鞘内给予高剂量ACT,与给药前相比,给药后30、75、120 min TWL升高(P<0.05),但不影响大鼠的MWT;与切口痛组相比,切口痛+ACT高剂量组在给药后30、75、120 min TWL明显增高(P<0.05)。结论鞘内给予碳酸酐酶抑制剂ACT部分缓解了切口痛大鼠的热痛觉过敏,但是对机械痛觉过敏没有影响,提示碳酸酐酶可能参与了切口痛的热痛敏过程。