H2S Alleviates Neuropathic Pain in Mice by Nrf2 Signaling Pathway Activation.

Objective To evaluate the relationship between hydrogen sulfide (H2S) and P2X3 receptors in dorsal root ganglions (DRGs) of rats with neuropathic pain (NP). Methods Thirty-six healthy male Sprague-Dawley rats, aged 4-6 weeks, weighing 180-200 g, in which IT catheters were successfully implanted, were divided into 3 groups (n=12 each) using a random number table method: sham operation group (group S), group NP and endogenous H2S synthase(cystathionine beta-syntheses[CBS])inhibitor animooxyacetic acid(AOAA)group (group A). NP was induced by chronic constriction injury (CCI) to the sciatic nerve at 3 days after IT catheters were successfully implanted.AOAA (10 μg/kg) 10 μl and normal saline 10 μl were intrathecally injected once a day for 14 consecutive days starting from 1 day after CCI in group A, and normal saline 20 μl was intrathecally injected instead in S and NP groups.At 1 day before CCI and 1, 3, 7, 10 and 14 days after CCI, the thermal paw withdrawal latency (TWL) and mechanical paw withdrawal threshold (MWT) were measured at 30 min after intrathecal injection.The animals were sacrificed at 7 and 14 days after CCI, and ipsilateral DRGs of the lumbar segment (L4-6) were removed for detection of the expression of CBS and P2X3 receptors by Western blot. Results Compared with group S, the TWL was significantly shortened, MWT was decreased, and the expression of CBS and P2X3 receptors in DRGs was up-regulated at each time point after CCI in group NP (P<0.05). Compared with group NP, the TWL was significantly prolonged, the MWT was increased, and the expression of CBS and P2X3 receptors in DRGs was down-regulated at each time point after CCI in group A (P<0.05). Conclusion H2S in DRGs can up-regulate the expression of P2X3 receptors, which may be involved in the pathophysiological mechanism of NP in rats. Key words: Neuralgia; Ganglia, spinal; Receptors, purinergic P3; Hydrogen sulfide

Objective To evaluate the effect of intrathecal ropivacaine on spinal histone deacetylase 1 (HDAC1) and HDAC2 expression in the rats with neuropathic pain (NP). Methods Thirty adult male Sprague-Dawley rats, weighing 220-250 g, in which intrathecal catheters were successfully placed, were randomly divided into 3 groups (n=10 each) using a random number table: sham operation group (group S), group NP, and NP + ropivacaine group (group R). NP was induced by chronic constriction injury (CCI) in anesthetized rats.Sciatic nerve was exposed and 4 loose ligatures were placed on the left sciatic nerve at 1 mm intervals with 4-0 chromic catgut.Starting from 7th day after CCI, 0.25% ropivacaine 20 μl was injected intrathecally in group R, while the equal volume of normal saline was given instead of ropivacaine in S and CCI groups once a day for 7 consecutive days.At 1 day before CCI (T0), and 3, 7, 10, 14, 17 and 21 days after CCI (T1-6), the mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured.After the pain threshold was measured at T4, 3 rats from each group were sacrificed, and their lumbar enlargements were harvested for determination of the expression of HDAC1 and HDAC2 by Western blot. Results Compared with group S, the MWT was significantly decreased, and the TWL was shortened at T2-6, and the expression of HDAC1 and HDAC2 was up-regulated at T4 in NP and R groups (P<0.05). Compared with group NP, the MWT was significantly increased at T4, and the TWL was prolonged at T3, 4, and the expression of HDAC1 and HDAC2 was down-regulated at T4 in group R (P<0.05). Conclusion The mechanism by which intrathecal ropivacaine alleviates NP may be related to inhibited up-regulation of spinal HDAC1 and HDAC2 expression in rats. Key words: Histone deacetylases; Spinal cord; Amides; Injection, spinal; Neuralgia

Neuropathic pain (NP) is a common clinical chronic pain with very complex mechanisms. This study explored the function of activated Wnt signaling pathway in NP. A rat model of chronic constriction injury (CCI) was established. Different doses of IWP-2, a Wnt signal inhibitor, were intrathecally injected to observe the behavior indicators at different time-points, including the pain induced by mechanical stimulation and thermal stimulation. The mRNA and protein levels of Wnt-3a, Frizzled 4 and β-catenin in lumbar (L) 4–6 dorsal root ganglion (DRG) of rats in each group, as well as synaptic plasticity-related molecules in DRG region of rats were detected by RT-PCR and western blotting, respectively. Compared with Sham group and Naive group, paw withdrawal thermal latency and paw withdrawal mechanical threshold were significantly decreased after CCI, while synaptic plasticity was increased (P<0.05). Besides, activation of Wnt/β-catenin signaling pathway was observed in rats with CCI. We found that intrathecal injection of IWP-2 effectively relieved the pain behavior and reduced the synaptic plasticity in rats with neuropathic pain after CCI, suggesting that the inactivated Wnt/β-catenin signaling pathway might be the major mechanism responsible for this effect. Our data demonstrated that intrathecal injection of IWP-2 ameliorated neuropathic pain in CCI rats by inhibiting the Wnt/β-catenin pathway.

In the present study, we investigated the antinociceptive effect of herpes simplex virus type 1 (HSV-1) amplicon vector-mediated human proenkephalin (hPPE) on chronic constriction injury (CCI)-induced neuropathic pain in rats. Male Sprague-Dawley rats were intrathecally administered normal saline (NS), pHSVIRES-lacZ (SHZ) or recombinant HSV-1 amplicon vector pHSVIRES-hPPE-lacZ (SHPZ), respectively. Once a week for 5 weeks after the intrathecal (i.t.) administration, the expression levels of hPPE mRNA and leu‑enkephalin (L-EK) were determined. The paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) were measured before CCI (baseline) on day 3 and once a week for 5 weeks after i.t. administration. The results showed that the PWMT and PWTL in the SHPZ group were significantly increased compared to the thresholds before i.t. administration. The antinociceptive effect of SHPZ reached its peak 3 weeks after i.t. administration and was maintained for 5 weeks. In the rats administered vehicle or SHZ, there were no significant differences between the PWMT or PWTL and the thresholds before i.t. administration. These results indicate that a single i.t. administration of HSV-1 amplicon vector-mediated hPPE attenuated CCI-induced hypersensitivity in rats.

Dexmedetomidine attenuates neuropathic pain in chronic constriction injury by suppressing NR2B, NF-κB, and iNOS activation

This study investigates the mechanism of the TRPV1 channel in neuropathic pain (NP), focusing on the c/EBPβ/Uchl3/TRPV1 axis and mitochondrial dynamics. Using male rats chronic constriction injury (CCI) model and an LPS-induced dorsal root ganglion (DRG) cell model, we measured paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL), assessed expression changes of related molecules via Real-time quantitative reverse transcription PCR (RT-qPCR) and Western blot, observed mitochondrial fission via transmission electron microscopy (TEM) and Tomm20 immunofluorescence, evaluated mitochondrial function via JC-1 and MitoSOX, and examined neuronal excitability via calcium imaging. Co-immunoprecipitation (Co-IP) confirmed Uchl3-TRPV1 binding, and ubiquitination assay combined with Cycloheximide (CHX) chase and proteasome inhibition assays demonstrated that Uchl3 inhibits TRPV1 degradation via deubiquitination. Luciferase and Chromatin immunoprecipitation (ChIP) assays verified c/EBPβ as a transcriptional activator of Uchl3. Results showed that TRPV1 activation promoted mitochondrial fission, dysfunction, and neuronal excitability, driving NP. Uchl3 stabilized TRPV1 by removing its ubiquitination, altering mitochondrial dynamics. c/EBPβ transcriptionally upregulated Uchl3, forming a regulatory cascade. Intrathecal si-c/EBPβ in CCI rats downregulated c/EBPβ, Uchl3, and TRPV1, restored mitochondrial homeostasis, and alleviated pain behavior. In conclusion, the c/EBPβ/Uchl3/TRPV1 pathway regulates NP through mitochondrial dynamics in male rats, presenting a novel therapeutic target for NP treatment.

Neuropathic pain (NP) is caused by damage to or disease of the somatosensory nervous system, but its mechanism is still not fully understood. In this study, DEAD-box helicase 54 (DDX54) was targeted, and its regulatory role was explored in a chronic constriction injury (CCI) rat model. Microglia and HMC3 cells were stimulated with LPS. The interaction between DDX54 and myeloid differentiation factor-88 adapter protein (MYD88) was verified. A CCI of sciatic nerve model in rats was established. Behavioral testing was performed before and after the CCI. The expressions of IL-1β, TNF-α, and IL-6 were upregulated, and those of DDX54, MYD88, NF-κB, and NOD-like receptor 3 (NLRP3) were upregulated in microglia and HMC3 cells after LPS induction. DDX54 knockdown in microglia and HMC3 cells inhibited IL-1β, TNF-α, and IL-6 expressions and downregulated the protein levels of MYD88, p-NF-κB p65 (p-p65), and NLRP3. DDX54 overexpression promoted the stability of MYD88 mRNA. DDX54 binds to the MYD88-3'-untranslated region (UTR). DDX54 interference in rats could alleviate the decrease of paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) induced by CCI, inhibit Iba1 expression, and reduce inflammatory factors as well as MYD88 and NF-κB expressions. DDX54 promotes the activation of NF-κB/NLRP3 signaling by regulating MYD88 mRNA stability, thereby affecting inflammatory response and NP progression in CCI rats.NEW & NOTEWORTHY The role of DDX54 protein in LPS-induced microglia and a chronic constriction injury (CCI) rat model was investigated for the first time. DDX54 interference can inhibit microglial activation and reduce the secretion of inflammatory factors. The interaction between DDX54 protein and MYD88 mRNA was explored for the first time. DDX54 promotes NF-κB/NLRP3 signaling activation by regulating MYD88 transcription in a CCI rat model.

To observe the effects of MMP-9 (matrix metalloproteases-9) on the mechanical allodynia and thermal hyperalgesia and the expression of CX3CL1 (CX3C chemokine ligand 1) protein in the spinal dorsal root ganglion (DRG) in rats with chronic sciatic nerve constriction injury (CCI). A total of 84 male SD rats were randomly divided into seven groups, namely the normal group , the sham operation group , the model group , the CCI + MMP-9 group, the CCI + TIMP-1 group , the CCI + siRNA group, and the CCI + MM-siRNA group. The CCI model was prepared 5 days after implantation of intrathecal catheter. The rat paw mechanical withdrawal threshold (PWMT) and paw thermal withdrawal latency (PWTL) were measured 1 day before CCI surgery and 1, 2, 3 and 5 days after CCI respectively. Western blot (WB) was used to detect the expressions of the MMP-9 and the CX3CL1 protein in the L5 DRG of the spinal cord 1 day after CCI operation. (I) Behavioral assessment of hyperalgesia: compared with the Sham group, the PWMT and PWTL of the CCI group were significantly reduced at each time point after CCI surgery; compared with the CCI group, the PWMT and PWTL of the CCI + MMP-9 group decreased 1 day after CCI; for the PWMT and PWTL of the CCI + TIMP-1 group and CCI + siRNA group, PWMT and PWTL increased 1 day after CCI; (II) The expressions of MMP-9 and CX3CL1 protein in the DRG of the spinal cord: compared with Sham group, the expressions of MMP-9 and CX3CL1 protein in the DRG of the CCI group increased significantly 1 day after CCI surgery; compared with the CCI group, the expressions increased in the CCI + MMP-9 group 1 day after CCI . However, the expressions of MMP-9 and CX3CL1 in the CCI + TIMP-1 group and CCI + siRNA group were reduced on the first postoperative day. The mechanism of MMP-9 participating in the early phase of neuropathic pain (NP) in CCI rats is related to the upregulation of CX3CL1.

Objective To evaluate the effects of curcumin on the activity of NR2B and NR1 in the spinal dorsal horn in a rat model of diabetic neuropathic pain (DNP).Methods Diabetes mellitus was induced by high-sucrose and high-fat diet and intraperitoneal streptozotocin 35 mg/kg,then confirmed by fasting blood glucose level ≥ 16.7 mmol/L 3 days later in male Sprague-Dawley rats.DNP was confirmed by the mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) measured on day 14 after streptozotocin administration ＜ 80％ of the baseline value.The rats were then randomly divided into 3 groups (n =27 each) using a random number table:DNP,DNP+ curcumin group (group DCur)and DNP + solvent control group (group DSC).Curcumin 100 mg· kg-1 · d-1 and corn oil 4 ml· kg-1 · d-1 were injected intraperitoneally for 14 consecutive days starting from 14 days after administration of streptozotocin in DCur and DSC groups,respectively.Another 27 normal male Sprague-Dawley rats served as control group (group C) and were fed with normal forage.At 3,7 and 14 days after curcumin injection,MWT and TWL were measured and the lumbar segments (L4-6) of the spinal cord were removed.The expression of pTyr1472-NR2B and pSer896-NR1 in the spinal dorsal horn was determined by immunohistochemistry and Western blot.Results Compared with group C,MWT was significantly decreased,TWL was shortened,and the expression of pTyr1472-NR2B was up-regulated at each time point in group DNP.Compared with group DNP,MWT was significantly increased,and TWL was prolonged at 7 days after curcumin injection,and the expression of pTyr1472-NR2B was down-regulated at 3 days after curcumin injection in group DCur.There was no significant difference in each parameter between DNP and DSC groups,and in the expression of pSer896-NR1 between the four groups.Conclusion The mechanism by which curcumin mitigates neuropathic pain in type 2 diabetic rats may be related to inhibition of up-regulation of pTyr1472-NR2B expression,while unrelated to pSer896-NR1 expression in the spinal dorsal horn. Key words: Curcumin; Diabetes mellitus, type 2; Neuralgia; Spinal cord; pTyr1472-NR2B; pSer896-NR1

Objective To evaluate the changes in the expression of isolectin B4 (IB4) and calcium gene-related peptide (CGRP) in neurons in dorsal root ganglion (DRG) of rats with neuropathic pain (NP). Methods Forty healthy male Sprague-Dawley rats, weighing 250-280 g, were divided into 2 groups (n=20 each) using a random number table method: solvent group (group S) and group NP.NP was induced by intraperitoneally injecting resiniferatoxin 210 μg/kg, and the solvent of resiniferatoxin was intraperitoneally injected in group S. The mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured in 5 rats selected before establishing the model and at 1, 3, 7 and 42 days after establishing the model.Five rats were sacrificed at 1, 3, 7 and 42 days after establishing the model, and the L4-6 segments of the DRGs were removed to determine the expression of CGRP and IB4 in neurons using immunofluorescence. Results Compared with the baseline before establishing the model, the MWT was significantly decreased at 3, 7 and 42 days after establishing the model, and the TWL was prolonged at 1, 3, 7 and 42 days after establishing the model in group NP (P<0.05). Compared with group S, the MWT was significantly decreased at 3, 7 and 42 days after establishing the model, the TWL was prolonged at 1, 3, 7 and 42 days after establishing the model, and the expression of IB4 and CGRP in neurons in DRGs was down-regulated at 1, 3, 7 and 42 days after establishing the model in group NP (P<0.05). Conclusion Down-regulated expression of IB4 expression in neurons in DRGs may be involved in the development and maintenance of mechanical hypersensitivity to pain, and down-regulated expression of CGRP may be involved in the development and maintenance of thermal analgesia in rats with NP. Key words: Neuralgia; Ganglia, spinal; Plant lectins; Calcitonin gene-related peptide

To explore the role of P2X4 receptor in opioid-induced hyperalgesia (OIH). Methods: A total of 30 Sprague-Dawley (SD) male rats were randomly divided into 5 groups: a saline (N0) group, a remifentanil at 0.5 μg/(kg.min) (R1) group, a remifentanil at 1.0 μg/(kg.min) (R2) group, a remifentanil at 1.5 μg/(kg.min) (R3) group, and a remifentanil at 5.0 μg/(kg.min) (R4) group. The paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) were measured at follow time points to optimize the dosages: the day before treatment (T1), 30 min after tail intravenous catheterization (T2), and 30 min (T3), 1 h (T4), 2 h (T5), 24 h (T6) after withdrawal from remifentanil. Then, the rats were randomly divided into 2 groups: a saline group (N group), a remifentanil at 1.0 μg/(kg.min) group (R group). The PWMT and PWTL were measured at follow time points: T1, T2, and T4. The lumbar enlargement of spine was selected at 1 h after withdrawal from remifentanil, and the expression of P2X4 receptor mRNA and protein was examined in OIH. Additional male rats were selected and randomly divided into 2 groups: a plantar incision surgery followed by saline treatment group (I+N group), a plantar incision surgery followed by remifentanil treatment group (I+R group). The PWMT and PWTL were measured at follow time points: T1, T2, T3, T4, T5, T6, 48 h (T7) and 72 h (T8) after withdrawal from remifentanil. The lumbar enlargement of spine was selected at 1 h after withdrawal from remifentanil, the expression of P2X4 receptor mRNA and protein was examined by PCR and Western blotting, and the microglial activation in spine 1 h after withdrawal from remifentanil were assessed by immunofluorescence. Results: The pain thresholds including PWMT and PWTL in different groups were as follows: R4 group<R3 group<R2 group<R1 group at T3 and T5 (all P<0.05). At T4, the PWMT and PWTL in the R4 group were lower than those in the R2 group, while in the R4 group they were lower than those in the R3 group (both P<0.05). Meanwhile, the PWMT and PWTL in the R2 group, the R3 group and the R4 group at T4 were lower than those in the other time points (all P<0.05). Compared with the N group, the rats in the R group had a lower PWMT and PWTL at T4 (both P<0.05), but there was no significant difference in P2X4 receptor protein and mRNA expression in the lumbar enlargement of spine between the R group and the N group. Compared with the I+N group, the pain threshold including PWMT and PWTL at T4, T5, and T6 in the I+R group was significantly decreased (all P<0.05). Meanwhile, compared with the I+N group, the expressions of P2X4 receptor mRNA and protein in rat spinal cord in the I+R group were significantly up-regulated, and the microglia was activated (all P<0.05). Conclusion: Remifentanil pumped via tail intravenous can result in the hyperalgesia, but the spinal P2X4 receptor might be not relevant to remifentanil-induced hyperalgesia. Remifentanil incision pain can cause significant hyperalgesia in rats, and the spinal P2X4 receptors and microglial activation is involved in the remifentanil-induced postoperative hyperalgesia.

Objective To study the effects of intrathecal injection of dopamine D2 receptor agonist quinpirole on expression of glial cell line-derived neurotrophic factor in the spinal cord in rats with chronic constrictive injury (CCI) and explore its possible mechanism of mediating antinociception.Methods In this study,models were established CCI in male Sprague-Dawley rats.The experiment was performed as 2 parts.In part one,30 CCI rats were randomly divided into 5 groups (n=6):CCI+saline (group NS),CCI+quinpirole 0.1 μg (group Q0.1),CCI+quinpirole 1 μg (group Q1),CCI+quinpirole 5 μg (group Q5),CCI+quinpirole 10μg (group Q 10).The drugs were injected intrathecally on day 7 after CCI,respectively.Paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) were measured before and at 0.5,1,2,4,8 h and 16 h after intrathecal injection.In part two 54 CCI rats were randomly divided into 3 groups (group Q5,Q10 and NS,n=18).Group Q5 and Q10 were sacrificed at 0.5,1,2,4,8,16 h after intrathecal quinpirole 5,10 μg on day 7 after CCI.Group NS,a single intrathecal injection of saline 10 μl.Group M,another 6 normal rats as model control group.Another 6 normal rats as control group C.The expression of glial cell linederived neurotrophic fact (GDNF) in the spinal cord was determined by Western blot.Results Part one:compared with group NS,the PWMT and PWTL of group Q0.1 at each time point after injection had no statistically significant difference (P＞0.05).The PWMT and PWTL of 2 h of group Q1 [(4.3±1.5) g,(13.2±1.6) s].1,2,4 h of group Q5 [(4.7±1.6),(5.3±1.6),(4.7±2.1) g,(14.0±1.7),(15.2±1.5),(13.4±1.6) s] and Q10 [(6.0±1.3),(7.3±1.0),(5.3±2.1) g,(15.3±1.8),(17.5±1.2),(14.9±1.7) s] after drug administration were significantly promoted (P＜0.05).Part two:compared with group C,the expression of GDNF was significantly increased in group M (0.95±0.09)(P＜0.05).Compared with group M and NS,group Q5 [(1.47±0.12),(1.24±0.05)] and Q10[(1.63±0.08),(1.27±0.06)] significantly increased the expression of GDNF (P＜0.05),and it can last until 4 h after injection at least.Conclusions Intrathecal injection of quinpirole can significantly increase the level of GDNF expression in the spinal cord.At the same time,the pain behavior was improved.The upregulation of GNDF expression is involved in the modulation of dopamine D2 receptor agonist on neuropathic pain. Key words: Neuropathic pain; Dopamine agonist; Spinal; Glial cell line-derived neurotrophic fact; Intrathecal injection

Objective To investigate the effect of curcumin on the apoptosis in spinal cord and dorsal root ganglion neurons in a rat model of diabetic neuropathic pain (DNP) . Methods One hundred and eight male SD rats weighing 200-230 g were randomly divided into 4 groups ( n = 27 each): control group (group C), DNP group, solvent control group (group SC) and curcumin group (group Cur) . Diabetes was induced with intraperitoneal streptozocin 70 mg/kg. Successful induction of diabetes was defined as blood glucose ＞ 16.7 mmol/L. Curcumin and com oil 100 mg/kg (23 mg/ml) were given intraperitoneally once a day for 14 consecutive days starting from 14 days after administration of streptozocin in Cur and SC groups respectively. Mechanical paw withdrawal threshold (MWT) and thermal paw withdrawal latency (TWL) were measured 2 d before and 14 d after streptozocin injection and 3, 7 and 14 d after curcumin injection. The pain threshold measured at 14 d after administration of streptozocin decreased by more than 15% of the baseline in all the rats. The expression of caspase-3 and Bcl-2 in spinal cord and dorsal root ganglion was determined at 3, 7 and 14 d after curcumin injection by immuno-histochemistry and Western blot, and the neuronal apoptosis rate was determined by TUNEL. Results Compared with group C, MWT and Bcl-2 expression were significantly decreased, TWL was significantly shortened, the neurona lapoptosis rate and caspase-3 expression were significantly increased in DNP, SC and Cur groups ( P ＜ 0.05).Compared with group DNP, MWT and Bcl-2 expression were significantly increased, TWL was significantly prolonged, the neuronal apoptosis rate and caspase-3 expression were significantly decreased in Cur group ( P ＜0.05) . There was no significant difference in the parameters mentioned above between DNP and SC groups ( P ＞0.05). Conclusion Curcumin can attenuate DNP by inhibiting the apoptosis in spinal dorsal hom and dorsal root ganglion neurons in rats, and the inhibition of caspase-3 expression and increase in Bcl-2 expression are involved in the mechanism. Key words: Curcumin; Diabetic mellitus; Neuralgia; Apoptosis; Spinal cord; Ganglia,spinal

Background/Objectives: Fructose-1,6-bisphosphate (FBP) is an intermediate product of the glycolytic pathway with analgesic effect in acute inflammatory pain model via the production of adenosine. However, whether FBP is active in neuropathic pain is unknown. Therefore, we reason that it would be suitable to investigate the analgesic effect and mechanism of action of FBP in a model of chronic constriction injury (CCI) of sciatic nerve-induced neuropathic pain in mice. Methods: After CCI induction, mice received FBP, adenosine, A1 and/or A2A receptor antagonists, and/or inhibitors of the nitric oxide (NO)/cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG)/ATP sensitive K channels (KATP) signaling pathway. Results: FBP (up to 85%) and adenosine (up to 84%) inhibited the mechanical hyperalgesia (electronic aesthesiometer) induced by CCI with similar profiles. FBP analgesia was dependent on adenosine because adenosine A1 and A2A receptors antagonists diminished FPB activity (100% and 79%, respectively). FBP analgesia was also dependent on activating the NO/cGMP/PKG/KATP signaling pathway. Furthermore, FBP treatment increased the production of NO in cultured dorsal root ganglia (DRG) neurons (100% increase), whereas neuronal nitric oxide synthase (nNOS) inhibition decreased (up to 70%) the analgesic effect of FBP. We also observed that FBP reduced the calcium levels of transient receptor potential ankyrin 1 (TRPA1)+ DRG neurons (85%) and paw-flinching triggered by TRPA1 activation (38%). Conclusions: FBP reduced neuropathic pain by reducing DRG neuron activation. The mechanisms involved the activation of adenosine A1 and A2A receptors to trigger the analgesic NO/cGMP/PKG/KATP signaling pathway and reducing TRPA1+ DRG neuron activity.

Characterization of nociceptive responses to bee venom-induced inflammation in neonatal rats