Intrathecal transplantation of neuroblastoma cells decreases heat hyperalgesia and cold allodynia in a rat model of neuropathic pain

Intrathecal grafting of cells as biological pumps to deliver monoamines, endorphins, and/or trophic factors, has been shown to be effective in treating chronic pain both in experimental animals and in clinical trials. We have tested whether intrathecal implantation of neuroblastoma cells reduces heat hyperalgesia and cold allodynia in a rat model of neuropathic pain induced by chronic constriction injury (CCI) of the sciatic nerve. Behavioral tests and cerebrospinal fluid (CSF) collection were performed before CCI, 1 week later (after which, vehicle or NB69 cells were intrathecally injected) and at 4, 7, and 14 days post-injection. Both CSF sampling and injection of the cells were performed by direct lumbar puncture. Intrathecal grafting of 4 x 10(6) NB69 neuroblastoma cells reduced to basal levels the nociceptive response to heat in nerve-injured hindpaws, while the response of control limbs remained unchanged. Similarly, the allodynic response to cold elicited by acetone evaporation decreased in the animals implanted with NB69 cells. An increase in the concentrations of dopamine and serotonin metabolites of around 150% was observed in the CSF of animals that received grafts of NB69 cells. These data suggest that the monoamines released by NB69 cells in the intrathecal space produce analgesia to neuropathic pain in rats.     

VEGF and its receptor-2 involved in neuropathic pain transmission mediated by P2X2/3 receptor of primary sensory neurons

The pathogenesis of neuropathic pain is complex. P2X_2/3 receptor plays a crucial role in nociception transduction of chronic pain. VEGF inhibitors are effective for pain relief. The present study investigated the effects of VEGF and VEGF receptor-2 (VEGFR2) on the pain transmission in neuropathic pain states that mediated by P2X_2/3 receptor in primary sensory neurons. Chronic constriction injury (CCI) model was used as neuropathic pain model. Sprague-Dawley rats had been randomly divided into sham group, CCI group and CCI rats treated with anti-rVEGF antibody group. Mechanical withdrawal threshold and thermal withdrawal latency were measured. Expressions of VEGF, VEGFR2 and P2X_2/3 in L4-6 dorsal root ganglia (DRG) were detected by immunohistochemistry, RT-PCR and western blot analysis. The mechanical withdrawal threshold and thermal withdrawal latency in CCI group were lower than those in sham group and CCI rats treated with anti-rVEGF antibody group (p < 0.05), while VEGF, VEGFR2 and P2X_2/3 receptors’ expressions of L4-6 DRG in CCI group were higher than those in the other two groups (p < 0.05). The expressions of VEGF, VEGFR2 and P2X_2/3 in L4-6 DRG of CCI rats treated with anti-rVEGF antibody group were decreased compared with those in CCI group (p < 0.05). The results show that VEGF and VEGFR2 are involved in the pathogenesis of neuropathic pain and VEGF primarily potentiates pain responses mediated by P2X_2/3 receptor on DRG neurons. Anti-rVEGF treatment in CCI rats may alleviate chronic neuropathic pain by decreasing the expressions of VEGFR2 and P2X_2/3 receptors on DRG neurons to inhibit the transmission of neuropathic pain signaling.     

Effects of morphine on mechanical allodynia in a rat model of central neuropathic pain

We examined whether morphine reduced the behavioral signs of neuropathic pain below level induced by T13 spinal hemisection in rats. In order to examine the effect of morphine on the mechanical allodynia, morphine alone, morphine with naloxone and saline were administered intraperitoneally and intrathecally and behavioral tests were conducted. In systemic injection, mechanical allodynia was reduced only when a higher concentration of morphine (5 mg/kg) was used. Intrathecally injected morphine (0.5, 1, 2, 5 microg) reduced mechanical allodynia dose-dependently. It is suggested that systemic morphine has limited effect on mechanical allodynia but direct spinal administration of morphine is more effective in controlling central pain following spinal cord injury.     

Intrathecal delivery of farnesyl thiosalicylic acid and GW 5074 attenuates hyperalgesia and allodynia in chronic constriction injury-induced neuropathic pain in rats

The role of mitogen-activated protein kinase (MAPK) family has been well defined in neuropathic pain. Ras and c-Raf constitute an important part of MAP kinase family as Ras/Raf/MEK/ERK2 signaling cascade. The present study was designed to investigate the analgesic potential of farnesyl thiosalicylic acid, a novel Ras inhibitor, and GW 5074, a selective c-Raf1 inhibitor, in chronic constriction-induced injury (CCI)-induced peripheral neuropathic pain. Neuropathic pain was induced by placing four loose ligatures around the sciatic nerve. The development of pain was assessed on 14th day in terms of cold allodynia; mechanical hyperalgesia and mechanical allodynia by performing acetone test, pinprick and Von Frey tests, respectively. Farnesyl thiosalicylic acid (2.5, 5 and 10 μg) and GW 5074 (1, 2 and 4 μg) were injected intrathecally on 14th day following nerve ligature to assess their analgesic potential in CCI model. Nerve ligature-induced CCI produced significant neuropathic pain manifestations in terms of cold and mechanical allodynia, and mechanical hyperalgesia. Single intrathecal administration of farnesyl thiosalicylic acid (5 and 10 μg) as well as GW 5074 (2 and 4 μg) significantly attenuated CCI-induced hyperalgesia and allodynia. The analgesic effects of farnesyl thiosalicylic acid and GW 5074 in CCI model suggests that pharmacological inhibition of Ras and c-Raf-1 signaling may be potentially useful for managing neuropathic pain.     

Down-regulation of GFRalpha-1 expression by antisense oligodeoxynucleotide attenuates electroacupuncture analgesia on heat hyperalgesia in a rat model of neuropathic pain

Glial cell line-derived neurotrophic factor (GDNF) has been proved to play an important role in the modulation of nociceptive transmission especially during neuropathic pain. It was reported that electroacupuncture (EA) had potent analgesic effect on neuropathic pain and our previous studies indicated that EA could activate endogenous GDNF signaling system (GDNF and its receptor GFRalpha-1) in dorsal root ganglions (DRGs) of neuropathic pain rats. In order to investigate whether GDNF signaling system was involved in EA analgesia on neuropathic pain, which was induced by chronic constriction injury (CCI) of the sciatic nerve in rats, antisense oligodeoxynucleotide (ODN) specifically against GFRalpha-1 was used in the present study to result in down-regulation of GFRalpha-1 expression. The results showed that: (1) cumulative EA had potent analgesic effect on neuropathic pain in rats; (2) the expression of GFRalpha-1 in DRGs was down-regulated by intrathecal delivery of antisense ODN, but not by normal saline (NS) or mismatch ODN; (3) EA analgesia was significantly attenuated by antisense ODN treatment. The present study demonstrated that endogenous GDNF signaling system was involved in EA analgesia on neuropathic pain in rats, which would deepen our realization of the mechanism of EA analgesia.     

Effect of tetramethylpyrazine on primary afferent transmission mediated by P2X3 receptor in neuropathic pain states

Neuropathic pain is the most difficult type of pain to treat. The P2X₃ receptors play a crucial role in facilitating pain transmission at peripheral and spinal sites. The present research investigated the effects of tetramethylpyrazine (TMP) on the primary afferent transmission induced by P2X₃ receptor in neuropathic pain states. Chronic constriction injury (CCI) model was adopted. Sprague–Dawley male rats (n = 30) had been randomly divided into normal saline (sham + NS) group (I), TMP group (II), sham group (III), CCI + TMP group (IV), and CCI group (V). Mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured and P2X₃ immunoreactivity in L4/L5 dorsal root ganglion (DRG) and spinal cord was detected by immunohistochemistry. The mechanical withdrawal threshold and thermal withdrawal latency in group V were lower than those in groups I–III or IV (p < 0.05), while P2X₃ receptor expression of L4/L5 DRG and spinal cord in group V was higher than those in groups I–III (p < 0.01) or group IV (p < 0.05). The mechanical withdrawal threshold, thermal withdrawal latency and P2X₃ immunoreactivity of L4/L5 DRG and spinal cord in group IV showed no significant difference compared with those in groups I, II or III (p > 0.05). The amplitudes of the currents in group V (CCI) were much larger than those obtained in other groups after application of same concentration adenosine 5′-triphosphate disodium (ATP) (p < 0.01). α,β-Methylene-ATP (α,β-meATP)-activated currents in DRG neurons of CCI rats were more obvious than those obtained in other group rats (p < 0.01). The results showed that TMP may inhibit the primary afferent transmission of neuropathic pain induced by P2X₃ receptor.     

Chronic dizocilpine or apomorphine and development of neuropathy in two rat models I: behavioral effects and role of nucleus accumbens

Dopaminergic and glutamatergic inputs converge on nucleus accumbens (NAC) and affect the neuropathic pain. We tested the effects of daily systemic administration of dizocilpine (MK-801), a N-methyl-d-Aspartate (NMDA) noncompetitive receptor antagonist, or apomorphine (APO), a dopamine (DA) D1 and D2 receptor agonist, on neuropathic manifestations in the chronic constriction injury (CCI) and the spared nerve injury (SNI) models of mononeuropathy in rats. Six groups of rats were subjected to CCI or SNI neuropathy and 5–7 days later received daily intraperitoneal (ip) injections of saline, MK-801, or APO for two weeks. Tests for nociception and motor behaviors were performed at regular intervals. Tactile and cold allodynia were assessed using von Frey hairs or acetone drops, respectively. Heat hyperalgesia was assessed by the paw withdrawal test. Tests were performed before administering the daily injections. Another four groups of rats were subjected to SNI surgery, and then had their NAC (contralateral to the lesioned paw) perfused for two weeks with MK-801, saline, APO + ascorbic acid, or ascorbic acid alone using mini-osmotic pumps. Behavioral manifestations were assessed as above. Systemic daily injections of MK-801 and APO markedly attenuated the neuropathic manifestations in the CCI and SNI models with a minimal effect on cold allodynia. The same results were seen in the SNI model with chronic perfusion of NAC. Our results suggest that daily systemic administration of DA agonists and NMDA antagonists can attenuate neuropathic pain manifestations and that the NAC is involved in the modulation of neuropathic-like behaviors.     

Blockade of IL-18 signaling diminished neuropathic pain and enhanced the efficacy of morphine and buprenorphine

Currently, the low efficacy of antinociceptive drugs for the treatment of neuropathic pain is a major therapeutic problem. Here, we show the potential role of interleukin (IL)-18 signaling in this phenomenon. IL-18 is an important molecule that performs various crucial functions, including the alteration of nociceptive transmission in response to neuropathic pain. We have studied the changes in the mRNA and protein levels (qRT-PCR and Western blot analysis, respectively) of IL-18, IL-18-binding protein (IL-18BP) and the IL-18 receptor (IL-18R) over time in rats following chronic constriction injury (CCI) of the sciatic nerve. Our study demonstrated that the spinal levels of IL-18BP were slightly downregulated at days 7 and 14 in the rats subjected to CCI. In contrast, the IL-18 and IL-18R mRNA expression and protein levels were elevated in the ipsilateral spinal cord on days 2, 7 and 14. Moreover, in rats exposed to a single intrathecal administration of IL-18BP (50 and 100 ng) 7 or 14 days following CCI, symptoms of neuropathic pain were attenuated, and the analgesia pursuant to morphine and buprenorphine (0.5 and 2.5 μg) was enhanced. In summary, the restoration of the analgesic activity of morphine and buprenorphine via the blockade of IL-18 signaling suggests that increased IL-18 pathway may account for the decreased analgesic efficacy of opioids for neuropathic pain.     

Enhanced 3,5-dihydroxyphenylglycine-induced sustained nociceptive behaviors in rats with neuropathy or chronic inflammation

Sustained nociceptive behaviors (SNBs) are an important but under-studied component of chronic pain conditions. The group I metabotropic glutamate receptor (mGluR) agonist (R,S)-3,5-dihydroxyphenylglycine (DHPG) produces SNBs when injected intrathecally, and group I mGluR antagonists are effective at reducing symptoms of neuropathic and inflammatory pain. The present experiments examined whether rats with sciatic nerve injury or persistent inflammation exhibit greater SNBs following intrathecal DHPG compared with control animals. SNBs were observed following intrathecal injection of DHPG (25 nmol) between the L4 and L5 vertebrae. We used a behavioral observation scoring system that allowed for assessment of specific behaviors in the hind paws. When DHPG was injected intrathecally in rats with chronic constriction injury (CCI) of the sciatic nerve, they showed increased paw stamping behavior compared to DHPG-injected sham controls. Rats treated with complete Freund's adjuvant (CFA)-induced inflammation failed to demonstrate a significant increase in paw stamping behavior. However, both CCI and CFA rats showed increased paw licking and biting of the neuropathic/inflamed hind paw after intrathecal DHPG injection. These results provide evidence for behaviorally relevant contributions of group I mGluRs to SNBs in models of neuropathic and inflammatory pain.     

Investigating the possible pain attenuating mechanisms of pregabalin in chronic constriction injury-induced neuropathic pain in rats

Abstract

Aim of the study: The current study was aimed to investigate the neuropathic pain attenuating mechanism of pregabalin using chronic constriction injury (CCI) model in rats.

Material and Methods: The sciatic nerve was ligated by placing four loose ligatures around it to induce neuropathic pain. The pain development in terms of cold allodynia, mechanical hyperalgesia, and heat hyperalgesia was assessed on the 7th and 14th day after surgery, using acetone drop, pinprick, and hot plate tests. On the 14th day after the injury, pain parameters were assessed 30?minutes after administration of pregabalin (30?mg/kg) and sodium nitroprusside (5?mg/kg) in CCI-subjected rats.

Results: CCI led to induction of neuropathic pain, which was more prominent on 14th day in comparison to 7th day. A single administration of pregabalin and sodium nitroprusside on 14th day, markedly reduced pain parameters and increased serum nitrite levels. Pretreatment with L-NAME abolished neuropathic pain attenuating effects of pregabalin suggesting that pregabalin may increase the levels of nitric oxide to mitigate neuropathic pain. Pretreatment with naloxone significantly abrogated pain attenuating effects of pregabalin and sodium nitroprusside in CCI-subjected rats suggesting that pregabalin and nitric oxide-mediated analgesic action are mediated through release of endogenous opioids. Moreover, naloxone failed to modulate pregabalin-induced increase in nitric oxide levels suggesting that the opioid system does not control the nitric oxide levels, and opioids may be downstream modulators of nitric oxide.

Conclusion: Pregabalin may increase the release of nitric oxide, which may increase the release of endogenous opioids to attenuate neuropathic pain in CCI subjected rats.     

Effects of anti-rVEGF on the expression of VEGF receptor-2 and P2X(2/3) receptors of the spinal dorsal horn in neuropathic pain rats

Neuropathic pain is caused by the peripheral or central nervous system structure damage or dysfunction. VEGF is involved in nociception and inflammation. VEGF may target VEGF receptor-2 (VEGFR-2) on the surface of neurons. P2X(2/3) receptors play a crucial role in facilitating pain transmission at the spinal sites. Chronic constriction injury (CCI) rats were used as neuropathic pain model. Sprague-Dawley male rats were randomly divided into sham group, anti-recombinant VEGF antibody group with phosphate-buffer saline (anti-rVEGF+PBS group), CCI rats treated with phosphate-buffer saline group (CCI+PBS group) and CCI rats treated with anti-recombinant VEGF antibody group (CCI+anti-rVEGF group). The expressions of VEGFR-2, P2X(2) and P2X(3) protein in spinal dorsal horn (SDH) were detected by immunohistochemistry, double-label immunofluorescence and western blotting. The protein levels of VEGFR-2, P2X(2) and P2X(3) in L4/5 SDH of CCI+PBS group were higher than those in sham group. VEGFR-2 and P2X(2) or P2X(3) receptors were co-expressed in the cytoplasm and surface membranes of SDH. Anti-rVEGF treatment in CCI rats reduced the expression of VEGFR-2 and P2X(2/3) receptors in L4/5 SDH compared with those in CCI+PBS group. Therefore, VEGF may activate VEGFR-2 to participate the process of neuropathic pain. Anti-rVEGF treatment in CCI rats reduced the expression of VEGFR-2 and inhibited the transmission of neuropathic pain in L4/5 SDH via decreasing the expression of P2X(2/3). There is a cross-potentiation between VEGFR-2 and P2X(2/3) receptors in neuropathic pain state.     

C-FOS ANTISENSE OLIGODEOXYNUCLEOTIDE OFFSETS BEHAVIORAL NOCICEPTIVE RESPONSES AND BOTH UP-REGULATIONS OF C-FOS PROTEIN AND DYNORPHIN A (1-8) IN DORSAL HORN: A STUDY USING THE FORMALIN TEST IN RATS

The formalin test was used to elicit acute and chronic pain in rats, and antisense oligodeoxynucleotide (AS-ODN) was used as a tool to modulate the expression of nociceptive behavioral and neurochemical responses. AS-ODN complementary to c-Fos mRNA was administered intrathecally (i.t.) 4 h before formalin injection in the experimental group. Normal saline or reverse AS-ODN was pre-administered i.t. at the same time in two control groups (saline and reverse AS-ODN). The results showed that the acute phase of nociceptive behavior showed no change by AS-ODN administration, whereas the tonic phase of nociceptive licking and biting behavior was significantly suppressed by AS-ODN as compared with the saline or the reverse AS-ODN group, respectively (p < .05 and p < .01). At the same time, both Fos-like immunoreactive (FLI) neurons and density of dynorphin-like immunoreactivities (DLI) were decreased significantly (p < .05 and p < .01) in the AS-ODN group as compared with that in two control groups. The results indicate that the long-lasting nociceptive responses elicited by sustained noxious inputs are based on the up-regulation of c-Fos gene expression, which in turn induces the upregulation of Dyn A production. It is proposed that intensified Dyn A production in the dorsal horn may be pivotal for the appearance of chronic pain.     

Transcranial direct current stimulation combined with exercise modulates the inflammatory profile and hyperalgesic response in rats subjected to a neuropathic pain model: Long-term effects

BackgroundBehavioral alterations, like mechanical and thermal hyperalgesia, and modulation of biomarkers in the peripheral and central nervous systems (CNS) are markers of chronic pain. Transcranial direct current stimulation (tDCS) with exercise is a promising therapy for pain due to its neuromodulatory capacity.ObjectiveTo assess the individual effects of tDCS, exercise, and the two combined on the nociceptive response and BDNF, IL-1β, and IL-4 levels in the CNS structures of rats in a chronic pain model.MethodsFor 8 consecutive days after the establishment of chronic neuropathic pain by inducing a constriction injury to the sciatic nerve (CCI), the rats received tDCS, exercise, or both treatments combined (20 min/day). The hyperalgesic response was assessed by von Frey and hot plate tests at baseline, 7, and 14 days after CCI surgery and immediately, 24 h, and 7 days after the end of treatment. The BDNF, IL-1β, and IL-4 levels were assessed in the cerebral cortex, brainstem, and spinal cord by enzyme-linked immunosorbent assay at 48 h and 7 days after the end of treatment.ResultsThe CCI model triggered marked mechanical and thermal hyperalgesia. However, bimodal tDCS, aerobic exercise, and the two combined relieved nociceptive behavior for up to 7 days following treatment completion.ConclusionsBimodal tDCS, aerobic exercise, or both treatments combined promoted analgesic effects for neuropathic pain. Such effects were reflected by cytokine modulation throughout the spinal cord-brainstem-cerebral cortex axis.     

Effect of emodin on neuropathic pain transmission mediated by P2X2/3 receptor of primary sensory neurons

Neuropathic pain is the most difficult type of pain to cure. The P2X_2/3 receptors play a crucial role in facilitating the transmission of pain at neuropathic pain states. Emodin is a natural anthraquinone in rhubarb. The present research investigated the effects of emodin on the pain transmission in neuropathic pain states that was mediated by P2X_2/3 receptor in primary sensory neurons. Chronic constriction injury (CCI) model was used as neuropathic pain model. Emodin was dissolved in 0.5% sodium carboxymethyl cellulose (CMC) as vehicle. Sprague-Dawley male rats had been randomly divided into Sham + vehicle group, CCI + emodin group, and CCI + vehicle group. Mechanical withdrawal threshold and thermal withdrawal latency were measured. P2X_2/3 expression in L4/L5 dorsal root ganglion (DRG) was detected by immunohistochemistry, in situ hybridization (ISH) and RT-PCR. The mechanical withdrawal threshold and thermal withdrawal latency in CCI + vehicle group were lower than those in Sham + vehicle group and CCI + emodin group (p < 0.05), while P2X₂ and P2X₃ receptor expression of L4/L5 DRG in CCI + vehicle group was higher than those in the other two groups (p < 0.05). The co-local staining of P2X₂ and P2X₃ in the DRG of CCI group appeared to be more intense than that in the DRG of the other two groups with double-label fluorescence immunohistochemistry. The results showed that the application of emodin alleviated the hyperalgesia of CCI rats and significantly decreased the P2X_2/3 expression of L4/L5 DRG in CCI + emodin group compared with that in CCI + vehicle group (p < 0.05). The data of ISH and RT-PCR in P2X₂ and P2X₃ mRNA expression suggest that the pharmacologic mechanism of emodin is involved in the nucleic acid level. The results showed that emodin can inhibit the transmission of neuropathic pain mediated by P2X_2/3 receptor of primary sensory neurons to alleviate chronic neuropathic pain.     

Does Fibromyalgia Affect the Outcomes of Spinal Cord Stimulation: An 11-Year,Multicenter, Retrospective Matched Cohort Study

BackgroundFibromyalgia is a prevalent disorder manifesting with widespread musculoskeletal pain and central sensitization, as well as fatigue, sleep issues, psychologic distress, and poor quality of life. Patients with fibromyalgia also may be diagnosed with other painful conditions amenable to treatment with spinal cord stimulation (SCS), although it is unclear how these patients respond to SCS compared with patients without fibromyalgia.Materials and MethodsWe performed an 11-year, multicenter, retrospective matched cohort study comparing SCS-treated patients with fibromyalgia and those without fibromyalgia. The primary outcome was comparison in mean calculated percentage pain relief between cohorts at six months after SCS implantation. Secondary outcomes included comparison of patient satisfaction between six and 12 months after SCS implantation, and percentage of patients reporting opioid intake and neuropathic medication intake at six months and 12 months after SCS implantation. Adjusted regression analysis was performed to make comparisons while adjusting for age, sex, body mass index, Charlson comorbidity index, preoperative opioid intake, and preoperative neuropathic medication intake.ResultsOf 90 patients with fibromyalgia who underwent SCS trial, 18 patients (20%) failed their SCS trial and did not proceed toward implantation. Sixty-eight patients with fibromyalgia were matched to 141 patients in the control cohort based on age, sex, Charlson comorbidity index, and the American Society of Anesthesiologists physical status score. At six months after SCS implantation, there was no statistical difference in calculated percentage change in pain intensity between the fibromyalgia cohort (46.6 ± 29.0) and the control cohort (50.9 ± 32.8; β, ?18.4; 95% CI, ?44.3 to 7.6; p = 0.157). At baseline, a greater percentage of patients in the fibromyalgia cohort reported preoperative opioid intake (51.5% vs 22.7%, p < 0.001) and preoperative neuropathic medication intake (67.6% vs 15.6%, p < 0.001). However, there was no difference between cohorts in the percentage of patients taking opioid or neuropathic medications at six months and 12 months after SCS implantation. Similarly, there was no difference between cohorts in the percentage of patients reporting satisfaction between six and 12 months.ConclusionPatients with fibromyalgia who received a diagnosis approved for treatment with SCS may expect similar post–SCS-implantation pain relief, overall satisfaction, and analgesic use rate to those of patients without fibromyalgia.     

Intrathecal treatment with dextrorphan or ketamine potently reduces pain-related behaviors in a rat model of peripheral mononeuropathy

The therapeutic effects of dextrorphan and ketamine, two non-competitive N-methyl-d-aspartate (NMDA) receptor antagonists, on neuropathic pain-related behaviors were examined in rats with peripheral mononeuropathy induced by loose ligation of the common sciatic nerve (chronic constrictive injury, CCI). Four daily intrathecal treatments (beginning 1 h after nerve ligation) with dextrorphan or ketamine (12.5–100 nmol) reliably attenuated hyperalgesia to radiant heat and spontaneous pain-related behaviors in CCI rats. Thermal hyperalgesia also was reduced in CCI rats receiving a single intrathecal treatment with either dextrorphan or ketamine (50 and 100 nmol for each compound) on day 3 after nerve ligation when thermal hyperalgesia was well developed. Since both dextrorphan and ketamine are currently utilized in other clinical applications, the results suggest a new therapeutic utility of these ‘old’ compounds in treatment of neuropathic pain syndromes resulting from peripheral nerve injury.     

鞘内注射LXM-10对神经病理性疼痛大鼠Fos蛋白和P2X3受体表达的影响

目的 研究鞘内注射新型镇痛药LXM-10（2,4-dimethyl-9-β-phenylethyl-3-oxo-6,9-diazaspiro[5,5]undecane chloride,2,4-乙烷基-9-β-苯乙酸-3-oxo-6,9-二氮杂螺环-[5,5]十二烷基盐酸盐,LXM-10）对神经病理性疼痛（neuropathic pain,NPP）大鼠脊髓背角和背根神经节Fos蛋白和P2X3受体表达的影响。方法 选取SD大鼠108只,随机分为假手术组（S组）、对照组（C组）和药物组（L组）,对照组和药物组制备坐骨神经慢性压迫模型（chronic constriction injury of the sciatic nerve,CCI-SN）。假手术组、药物组和对照组根据给药时间不同分为3个亚组（n=12只）,药物组和对照组分别在CCI-SN造模成功后1、5、12d开始向蛛网膜下腔注射生理盐水10μl,连续3d,分别设为C3组、C7组、C14组,或向蛛网膜下腔注射LXM-10 6μg/kg,连续3d,分别设为L3组、L7组、L14组;假手术组仅在相应时间点向鞘内注射生理盐水,设为S3组、S7组、S14组。连续注射3d后于末次给药后2h处死动物,取腰膨大脊髓节段和腰4～6背根神经节分别进行免疫组化实验检测Fos蛋白和P2X3受体的表达情况。结果 对照组各时间点Fos蛋白随着时间延长表达增强,Fos蛋白主要表达于脊髓背角。药物组在各时间点脊髓背角Fos蛋白免疫反应阳性（Fos-like immunoreactivity,F-LI）细胞均较相应时间点对照组明显减少（（L3组 vs C3组,P =0.003;L7组 vs C7组,P =0.023;L14组 vs C14组,P =0.005）。背根神经节中Fos蛋白变化趋势同脊髓背角（L3组 vs C3组,P =0.002;L7组 vs C7组,P =0.003;L14组 vsC14组,P =0.002）。P2X3在CCI-SN造模成功后3～14d,表达逐渐升高,主要在背根神经节表达。在脊髓背角药物组各时间点P2X3阳性细胞表达均较对照组对应时间点降低（L3组 vs C3组,P =0.043;L7组 vs C7组,P =0.008;L14组 vs C14组,P=0.005）。在背根神经节鞘内给药后,各时间点P2X3阳性细胞表达明显减少（L3组 vs C3组,P =0.034;L7组 vs C7组,P =0.001;L14组 vs C14组,P =0.003）。结论 对于NPP大鼠,CCI-SN后脊髓背角和背根神经节中Fos蛋白和P2X3受体表达均明显增强。LXM-10鞘内给药可明显降低二者表达。     

Microinjection of HSV-1 Amplicon Vector-Mediated Human Proenkephalin into the Periaqueductal Grey Attenuates Neuropathic Pain in Rats

ABSTRACT We investigated the antinociceptive effect of microinjection of HSV-1 amplicon vector-mediated human proenkephalin (hPPE) into the ventral periaqueductal grey (PAG) on neuropathic pain in rats. Male Sprague-Dawley rats with chronic constriction injury (CCI)-induced neuropathic pain were microinjected into the ventral PAG with normal saline (NS), pHSVIRES-lacZ (SHZ), or HSV-1 amplicon vector pHSVIRES-hPPE-lacZ (SHPZ), respectively. Pain thresholds in the SHPZ-treated rats were significantly higher at day 3, then reached peak at day 14 and lasted until day 35 after PAG administration, and these effects were reversed by naloxone. In contrast, NS or SHZ-treated rats did not significantly affect pain thresholds. These results demonstrated that microinjection of HSV-1 amplicon vector-mediated hPPE into the ventral PAG attenuates neuropathic pain in rats.     

Differential effects of intrathecally administered N- and P-type voltage-sensitive calcium channel blockers upon two models of experimental mononeuropathy in the rat

We investigated the effects of intrathecally administered N-type and P-type voltage-sensitive calcium channel (VSCC) blockers on the level of thermal hyperalgesia in two neuropathic pain models: the chronic constriction injury (CCI) model and the partial sciatic nerve injury (PSNI) model. N-type, but not P-type, VSCC blockers attenuated the level of thermal hyperalgesia induced by CCI in a dose-dependent manner. In the PSNI model, both N-type and P-type VSCC blockers had no effect on thermal hyperalgesia. This suggests that some types of neuropathic pain may be treatable with N-type VSCC blockers.     

Effects of electroacupuncture on orphanin FQ immunoreactivity and preproorphanin FQ mRNA in nucleus of raphe magnus in the neuropathic pain rats

Orphanin FQ (OFQ) is an endogenous ligand for opioid receptor-like-1 (ORL1) receptor. Previous studies have shown that both OFQ immunoreactivity and preproorphanin FQ (ppOFQ) mRNA expression could be observed in the brain regions involved in pain modulation, e.g., nucleus of raphe magnus (NRM), dorsal raphe nucleus (DRN), and ventrolateral periaqueductal gray (vlPAG). It was reported that electroacupuncture (EA) has analgesic effect on neuropathic pain, and the analgesic effect was mediated by the endogenous opioid peptides. In the present study, we investigated the effects of EA on the changes of OFQ in the neuropathic pain rats. In the sciatic nerve chronic constriction injury (CCI) model, we investigated the changes of ppOFQ mRNA and OFQ immunoreactivity in NRM after EA by in situ hybridization (ISH) and immunohistochemistry methods, respectively. Then, the ppOFQ mRNA-positive and OFQ immunoreactive cells were counted under a computerized image analysis system. The results showed that expression of ppOFQ mRNA decreased and OFQ immunoreactivity increased after EA treatment in the neuropathic pain rats. These results indicated that EA modulated OFQ synthesis and OFQ peptide level in NRM of the neuropathic pain rats.