Effects of Different Concentrations of Capsaicine on the Chronic Knee Arthritis Pain Model in Mice / 现代生物医学进展

Objective:To observe the therapeutic effect ofcapsaicin at different concentrations on chronic knee arthritis pain model in mice.Methods:Choosing 50 healthy adult male Kunming mice builded chronic knee arthritis pain model by injecting 0.01 mL CFA (Complete Freund's Adjuvant,CFA) into left joint cavity.The model would be succeed in building after 3 weeks.The successful model mice were divided into five groups randomly (n=10):The first experimental group (saline group),the second experimental group (capsaicin excipient group),the third experimental group (0.5 ％ of capsaicin),the fourth experimental group (3 ％ of capsaicin) and the fifth experimental group (8 ％ of capsaicin).All of the mice would be observed the time of withdrawal latencies from the thermal heated surface after administration of one,four and seven hours,and thermal withdrawal time within 60 days after the injection.Results:①The physiological saline group compared with excipient group,the thermal withdrawal time had no statistically significant difference (P＞0.05)after administration of one,four and seven hours,and thermal withdrawal time within 60 days.②The acute pain duration of the third group would disappear after capsaicin injection 7 hours,four hours for the fourth group,and one hour for the fifth group.③The duration of analgesia of the third group,lasted for 18.9± 1.1 days;The analgesia time of the fourth group lasted for 33.7± 1.0 days;The analgesia time of the fifth group lasted for 58.2± 1.2 days.Conclusions:Capsaicin has analgesic effects on chronic knee pain model in mice induced by CFA,and the days of analgesia increases with the concentration of capsaicin.

Expression of Adult and Neonatal Nav1.5 Isoforms in the Dorsal Root Ganglia Neurons of Rats with Spared Nerve Injury / 沈阳医学院学报

Objective:To study the expression of adult and neonatal Nav1.5 isoforms in the dorsal root ganglia (DRG) neurons of rats with spared nerve injury (SNI) . Methods:The expression of adult and neonatal Nav1.5 isoforms in the DRG neurons of rats with SNI was detected by RT-PCR, DNA sequencing, restriction enzyme digestion, immunohistochemistry and immunofluo-rescence methods. The expression of PKC-γwas detected by Western blot. Results:Both adult and neonatal Nav1.5 isoforms were expressed in the DRG neurons, but their expression ratio was approximately 2.5∶1. In SNI rat models, the expression of both adult and neonatal Nav1.5 isoforms decreased by approximately a half in both mRNA and protein levels. In contrast, the expression of PKC-γincreased by approximately one-fold. Conclusions:Both adult and neonatal Nav1.5 isoforms expressed in the DRG neurons of rat,but their expression levels decrease in pain models. The up-regulation of PKC-γmay directly or indirectly down-regulate the expression of Nav1.5 isoforms in SNI rat models,which may further involve in the pathological process of neuropathic pain.

Effect of butorphanol and sufentanil with epidural injections on neurobehavior function in bone cancer pain model rats / 中华行为医学与脑科学杂志

Objective To observe the effect of different doses of butorphanol and sufentanil repeatedly epidural injected on the neurobehavior function in bone cancer model rats.Methods A PE-530 catheter was inserted into the epidural space of all male Sprague-Dawley rats(not mated,weighting 150-180 g) at L1-2 level.Three days after operation,64 rats without any motor dysfunction were randomly divided into eight groups (n=8):sham operated group (group C),normal saline with bone cancer pain group (group N),butorphanol groups(group B 1,B2,B3)and sufentanil groups (group S1,S2,S3).Bone cancer pain model was constructed in group N,B and S when rats in group C were sham operated.Rats in group C and N were epidurally injected NS 30μl each,and rats in group B1,B2 and B3 were respectively epidurally injected butorphanol 25,50,100 μg (all diluted to 30 μl with NS),when rats in group S1,S2 and S3 were respectively cpidurally injected sufentanil 1,2,4 μg (all diluted to 30 μl with NS) on time per day for 10-14 days after modeling.The neurobehavior paw withdrawal threshold (MWT) of the left hind claw was recorded to observe the changes in pain behavior.The neurobehavior function of rats were recorded by BBB (BASSO,BEATTIE and BRESNAHAN) score and the inclined plane test.Results Compared with group C((67.65±9.29) g),the MWT of the model groups obviously decreased before the first time of injection (N (15.23± 2.46) g,B 1 (16.14±2.28) g,B2(15.42±3.22) g,B3(14.35±2.32) g,S1 (15.37±2.11)g,S2(15.22±2.93) g,S3(16.25± 2.36) g) (all P＜0.05)).Compared with group N((16.13±2.37) g),the MWT of group B2,B3 and S3 increased obviously after the first time of injection ((35.12±5.16) g,(35.63± 1.53) g and (34.24±5.93) g) (P＜ 0.05).At the first day of injection,there was no significant difference in the BBB scores and the inclined plane test between the model groups (P＞0.05).At 6 h after the forth injection the inclined plane test and the BBB scores of group B3 were obviously decreased compared with group N ((34.72 ± 4.56) ° and (10.64 ± 1.82) points to (43.15±4.67)° and (14.05±1.78) points (P＜0.05)).Conclusion The results provide evidence that repeatedly epidural injection of butorphanol 50 μg or 100 μg or sufentanil 4 μg can reduce the pain of the rats with bone cancer pain.But repeated epidural injection of butorphanol 100 μg can injure the neurological function.

Systematic analysis of the nociceptive blink reflex: reliability and association with psychological factors / Análise sistemática do reflexo de piscar nociceptivo: confiabilidade e associação com fatores psicológicos

The present study aimed to estimate the reliability of the nociceptive blink reflex (nBR) and to evaluate the possible association between the nBR and various pain-related psychological measures: the Anxiety Sensitivity Index-3 (ASI-3), the Fear of Pain Questionnaire III (FPQ-III), the Pain Vigilance and Awareness Questionnaire (PVAQ), the Somatosensory Amplification Scale (SSAS), the Pain Catastrophizing Scale (PCS) and the Situational Pain Catastrophizing Scale (S-PCS). Twenty-one healthy participants were evaluated in two sessions. The nBR was elicited by a so-called "nociceptive-specific" electrode placed over the entry zone of the right supraorbital (V1R), infraorbital (V2R) and the mental (V3R) nerve and left infraorbital (V2L) nerve. The outcomes were: (a) individual electrical sensory (I0) and pain thresholds (IP); b) root mean square (RMS), area-under-thecurve (AUC) and onset latencies of R2 responses; and c) stimulus-evoked pain on a 0-10 numerical rating scale. The questionnaires ASI-3, FPQ-III, PVAQ, SSAS, PCS and S-PCS were also applied. Intraclass Correlation Coefficients (ICCs) and Kappa statistics were computed as a measure of the reliability (α=5%). Besides, Pearson correlation coefficient was used to associate the average of nBR measurements among all sites and the questionnaires. The significance level was set up after a Bonferroni correction (adjusted α=0.8%). ICCs were fair to excellent in 82% of the psychophysical measures and in 86% of V1R, V2R and V2L nBR parameters, whereas the V3R showed poor reliability in 52%. ICCs for intrarater reliability were fair to excellent in 70% of measurements (V3R showed the lowest values) and in 75% of interrater measurements. All kappa values showed at least fair agreement and the majority of the nBR measures (93%) were considered to have moderate to excellent reliability. There was no correlation for any pair of variables considering the adjusted significance level (p>0.008) and only a single significant correlation considering the standard significance level (p < 0.05), where the pain intensity (NRS) at 50% of IP presented a positive and small to moderate correlation with the PCS (r = 0.43, p = 0.047). The nBR and its associated psychophysical measures can be considered a sufficiently reliable test to assess the trigeminal nociceptive function. On the other hand, it seems not associated with psychological factors in healthy participants.

O presente estudo teve como objetivo estimar a confiabilidade do reflexo de piscar nociceptivo (nBR, sigla em inglês) e avaliar a possível associação entre o nBR e várias medidas psicológicas relacionadas à dor: o Anxiety Sensitivity Index-3 (ASI-3), o Fear of Pain Questionnaire III (FPQ-III), o Pain Vigilance and Awareness Questionnaire (PVAQ), o Somatosensory Amplification Scale (SSAS), o Pain Catastrophizing Scale (PCS) e o Situational Pain Catastrophizing Scale (S-PCS) (siglas e nomes em inglês). Vinte e um participantes saudáveis foram avaliados em 2 sessões. O nBR foi estimulado por meio de um eletrodo "nociceptivo específico" posicionado na zona de entrada do nervo supraorbital direito (V1D, sigla em inglês), infraorbital direito (V2D) e esquerdo (V2E) e mentual direito (V3R). As variáveis analisadas foram: a) limar elétrico sensorial (I0) e doloroso (IP); b) raíz quadrática média (RMS, sigla em inglês), área sobre a curva (AUC, sigla em inglês) e as latências da respostas R2; e c) dor provocada pelo estímulo em uma escala numérica de O a 10. Os questionários ASI-3, FPQ-III, PVAQ, SSAS, PCS e S-PCS também foram aplicados. Coeficiente de Correlação Intraclasse (ICC, sigla em inglês) e estatística Kappa foram calculados como medidas da confiabilidade (α=5%). Além disso, coeficiente de correlação de Pearson foi usado para associar a média do nBR entre todos os sítios de avaliação e os questionários. O nível de significância foi ajustado após correção de Bonferroni (α ajustado=0.8%). ICCs foram razoáveis à excelentes em 82% das medidas psicofísicas e em 86% dos parâmetros do nBR em V1D, V2D e V2E, enquanto que 52% das medidas em V3D apresentaram pobre confiabilidade. ICCs para confiabilidade intra-examinador foram razoáveis à excelente em 70% das medições (V3D apresentou os menores valores) e em 75% das medidas inter-examinadores. Todos os coeficientes Kappa apresentaram pelo menos razoável concordância e a maioria das medidas do nBR (93%) foram consideradas moderadas à excelente em termos de confiabilidade. Não houve correlação para nenhum par de variáveis considerando os valores ajustados de significância (p>0,008) e somente foi constatada uma correlação significante considerando o nível de significância padrão (p<0,005), em que a intensidade de dor em 50% do IP apresentou uma correlação positiva entre pequena e moderada com o PCS. O nBR e suas medidas psicofísicas associadas pode ser considerado um teste com suficiente confiabilidade para avaliar a função nociceptiva trigeminal. Por outro lado, parece que o nBR não está associado com fatores psicológicos em participantes saudáveis.

An improved experimental model for peripheral neuropathy in rats

A modification of the Bennett and Xie chronic constriction injury model of peripheral painful neuropathy was developed in rats. Under tribromoethanol anesthesia, a single ligature with 100% cotton glace thread was placed around the right sciatic nerve proximal to its trifurcation. The change in the hind paw reflex threshold after mechanical stimulation observed with this modified model was compared to the change in threshold observed in rats subjected to the Bennett and Xie or the Kim and Chung spinal ligation models. The mechanical threshold was measured with an automated electronic von Frey apparatus 0, 2, 7, and 14 days after surgery, and this threshold was compared to that measured in sham rats. All injury models produced significant hyperalgesia in the operated hind limb. The modified model produced mean ± SD thresholds in g (19.98 ± 3.08, 14.98 ± 1.86, and 13.80 ± 1.00 at 2, 7, and 14 days after surgery, respectively) similar to those obtained with the spinal ligation model (20.03 ± 1.99, 13.46 ± 2.55, and 12.46 ± 2.38 at 2, 7, and 14 days after surgery, respectively), but less variable when compared to the Bennett and Xie model (21.20 ± 8.06, 18.61 ± 7.69, and 18.76 ± 6.46 at 2, 7, and 14 days after surgery, respectively). The modified method required less surgical skill than the spinal nerve ligation model.

Animal Models for Orofacial Neuropathic Pain / 한양의대학술지

Orofacial neuropathic pain is initiated by extraction of teeth or nerve injury from trauma in the trigeminal nerve that innervates the facial area. In the experiment, orofacial neuropathic pain usually occurred following injury of peripheral trigeminal nerve including infra-orbital nerve, inferior alveolar nerve, or mental nerve. In addition, pathology from trigeminal nerve root or ganglion is involved in orofacial neuropathic pain. This study introduced various animal models that help us study the underlying mechanisms of development or maintenance of orofacial neuropathic pain. One of the most typical symptoms of orofacial neuropathic pain is hypersensitivity to the innocuous mechanical stimuli. Our study presents a novel method to evaluate mechanical allodynia in rats with orofacial neuropathic pain. Recently, accumulate evidence support participation of central glial cells in the development or maintenance of orofacial neuropathic pain. Signaling molecules in glial cells also play an important role in neuropathic pain in the orofacial area.

Effect of intrathecal glycine and related amino acids on the allodynia and hyperalgesic action of strychnine or bicuculline in mice / 대한마취과학회지

BACKGROUND: The intrathecal (IT) administration of glycine or GABAA receptor antagonist result in a touch evoked allodynia through disinhibition in the spinal cord. Glycine is an inhibitory neurotransmitter that appears to be important in sensory processing in the spinal cord. This study was aimed to evaluate the effect of glycine-related amino acids on antagonizing the effects of IT strychnine (STR) or bicuculline (BIC) when each amino acid was administered in combination with STR or BIC. METHODS: A total of 174 male ICR mice were randomized to receive an IT injection of equimolar dose of glycine, betaine, beta-alanine, or taurine in combination with STR or BIC. Agitation in response to innocuous stimulation with a von Frey filament after IT injection was assessed. The pain index in hot-plate test were observed after it injection. The effect of it muscimol in combination with str or bic were also observed. RESULTS: The allodynia induced by STR was relieved by high dose of glycine or betaine. But, allodynia induced by BIC was not relieved by any amino acid. Whereas the STR-induced thermal hyperalgesia was only relieved by high dose of taurine at 120 min after IT injection, the BIC-induced one was relieved by not only high dose of taurine at 120 min but also low dose of glycine or betaine at 60 min after IT injection. The BIC-induced allodynia and thermal hyperalgesia was relieved by IT muscimol. CONCLUSIONS: This study suggests that IT glycine and related amino acids can reduce the allodynic and hyperalgesic action of STR or BIC in mice.

Target-distribution of flurbiprofen axetil in operative incision tissue in incision-induced rats / 临床麻醉学杂志

Objective To study target-distribution of flurbiprofen axetil in operative incision tissue in incision-induced rats. Methods Thirty-two-250 g-weight rats were randomly divided into 4 groups. The incision pain model was established by being operated according to Brennan's method. Two hours after vena caudalis injection, all the rats were anesthetized deeply by pentobarbital sodium-perito injection 100 mg/kg,muscles of both hind paws were dissected, homogenated, centrifuged and supernatant fluids were dissociate. The concentration of flurbiprofen were detected by reversed phase high peformance liquid chromatography(RP-HPLC). Results In these groups of different dosage, the concentration of flurbiprofen in operative incision notably increased compared to that in the non-operative incision, especially in group K16. The concentration of flurbiprofen in operative incision of different dosage increased in dose-dependent manner. The difference of concentration of flurbiprofen in non-operative incisions of K2, K4, K8 was statistically insignificant, but the concentration of flurbiprofen in non-operative incision of K6 increased compared to that of K2, K4 and K8. Conclusion The distribution of flurbiprofen axeti in operative incision was targeted. When rats were injected flurbiprofen axetil at 16 mg/kg by vena caudalis, The concentration of flurbiprofen in the non-operative incision increased notably.

Antihyperalgesic Effects of Ethosuximide and Mibefradil, T-type Voltage Activated Calcium Channel Blockers, in a Rat Model of Postoperative Pain / 대한통증학회지

BACKGROUND: A correlation between a T-type voltage activated calcium channel (VACC) and pain mechanism has not yet been established. The purpose of this study is to find out the effect of ethosuximide and mibefradil, representative selective T-type VACC blockers on postoperative pain using an incisional pain model of rats. METHODS: After performing a plantar incision, rats were stabilized on plastic mesh for 2 hours. Then, the rats were injected with ethosuximide or mibefradil, intraperitoneally and intrathecally. The level of withdrawal threshold to the von Frey filament near the incision site was determined and the dose response curves were obtained. RESULTS: After an intraperitoneal ethosuximide or mibefradil injection, the dose-response curve showed a dose-dependent increase of the threshold in a withdrawal reaction. After an intrathecal injection of ethosuximide, the threshold of a withdrawal reaction to mechanical stimulation increased and the increase was dose-dependent. After an intrathecal injection of mibefradil, no change occurred in either the threshold of a withdrawal reaction to mechanical stimulation or a dose-response curve. CONCLUSIONS: The T-type VACC blockers in a rat model of postoperative pain showed the antihyperalgesic effect. This effect might be due to blockade of T-type VACC, which was distributed in the peripheral nociceptors or at the supraspinal level. Further studies of the effect of T-type VACC on a pain transmission mechanism at the spinal cord level would be needed.

Alteration of Ionic Zinc Distribution in Rat Spinal Ganglion by Inflammatory Pain Stimulus: Autometallography / 대한해부학회지

This study was designed to investigate any correlation between the mechanism of pain development and changes of histochemically reactive zinc contents in the rat spinal ganglion following complete Freund's Adjuvant (CFA) injection, as an inflammatory pain model. Male Sprague-Dawley rats (270~290 g) were used for this study. Surgeries were done under anesthesia using pentobarbital (30 mg/kg). we injected 200 microliter of CFA subcutaneously in the dorsal aspect of one hind paw using a 30- gauge needle and an 1 mL syringe. Semmes-Weinstein monofilaments was used to test for mechanical hyperalgesia. Finally, zinc selenite autometallography (AMG) was done by Danscher's method. The rat suffered from severe painful swelling of the hindpaw 1 day after a CFA inoculation. Changes in pain threshold were significantly changed on 1 day, and lasted during experiment period of 3 weeks after the CFA inoculation. In control group, ganglion cells vary in size from 15 to 100 micrometer. The smaller neurons are strongly stained with AMG, whereas the larger cells are not almostly stained. Each large ganglion cell is surrounded by perineuronal satellite cells, showing apparent AMG stainity. In experiment group, AMG-positive small ganglion cells increased on 1 day after CFA inoculation, and showed a peak in cell number at 3days group, and decreased gradually after 7 days. We found a small number of large-sized ganglion cells with AMG stainity 7 days and 3 weeks after CFA inoculation. Our results indicate that zinc may be involved in pain mechanism in the spinal ganglion level.

Decrease in Zinc Concentration in the Rat Spinal Gray Matter Induced by Peripheral Nerve Ligation, and its Relations with Increased Pain Threshold / 대한해부학회지

This study was designed to investigate any correlation between the mechanism of pain development and changes of histochemically-reactive zinc contents in the rat spinal cords following peripheal nerve ligation. Male Sprague-Dawley rats (270 ~290 g) were used for this study. We ligated a left-sided lumbar spinal nerve with silk under anesthesia using pentobarbital (50 mg/kg). Semmes-Weinstein monofilaments (Stoelting Company, Wood Dale, IL) was used to test for mechanical hyperalgesia. 30 micrometer-thick spinal cord cryosections were stained by automet-allography (Danscher, 1981). The density of zinc was significantly decreased in zinc concentration in the dorsal horn of 4th, 5th and 6th lumbar segments at 5 and 10 days after the spinal nerve ligation. Here, zinc depletion was apparent in superficial gray matter, especially layer III-IV. In addition the nerve ligated rats showed lower pain threshold. This increased pain sensation might be related with lowered vesicular zinc level in the superficial gray matter in the spinal cord. The present findings offer a proposed link between zinc and pain. Our interpretation is that there may be an extension of fine primary afferent fibers into lamina III and possibly lamina IV following peripheral nerve ligation. If further work bears out this conclusion, this would provide a possible explanation for the chronic pain states that sometimes follow peripheral nerve damage.

Changes of dopamine-beta-hydroxylase and activator protein-2? expression in spinal cord of formalin-induced rat pain model / 第三军医大学学报

Objective To investigate the changes of dopamine-?-hydroxylase(DBH) and activator protein 2-?(AP-2?) expression in spinal cord under the condition of stress or pain stimulation,so as to explore the mechanism for changes of noradrenergic(NA) neurons in the spinal cord of rat pain model.Methods Immunohistochemical staining,double immunofluorescent staining,Western blotting and computing-image analysis system were used to detect the changes of DBH/AP-2? expression in the spinal cord of formalin-induced rat pain model.Results A small number of DBH-positive neurons were sparsely distributed in the ventral horn of the normal spinal cord,while in the formalin-treated group,much more darkly-stained DBH-positive neurons appeared primarily in the ventral horn,intermediate zone,and the dorsal horn,which reached the highest level on day 3 after formalin-injection.The grey value and number of DBH-positive neurons on day 7 after injection began to decrease,but still higher than that in the control group.Compared with control group,the number of noradrenergic neurons in spinal cord of formalin-treated rat was increased significantly,which was also confirmed by Western blotting.Double immunofluorescent staining showed that DBH and AP-2? co-existed in the cells of the spinal cord.The changes of AP-2? expression were similarly to that of DBH in the spinal cord of rat pain model.Conclusion Our results indicated that some non-noradrenergic neurons with different chemical properties might convert into noradrenergic neurons under pain stimulation;noradrenaline may be involved in the formalin-induced pain and behavior regulation;As one of transcription factors,AP-2? may promote the DBH synthesis.

Neuropathic Pain Model Induced by Electrical Injury of Sciatic Nerve in Rats

OBJECTIVE: The purpose of this study was to develop a new neuropathic pain model in rat. METHOD: Twenty Sprague-Dawley adult male rats, 10 for control and 10 for experimental, were anesthetized and their sciatic nerves were exposed. In an experimental group, exposed nerve was injured with 10 volts electrical current for 10 seconds. The mechanical and thermal allodynia and pain behavior were evaluated in pre-electrical injury and post-injury 1, 2, 3 days, 1, 2, 3, 4, 6 and 8 weeks. The mechanical allodynia was evaluated by the frequency of response to 5 stimulations of von Frey hairs (4.31 and 4.56) and the thermal allodynia was tested by withdrawal latency to stimulation with radiant heat. Spontaneous pain behavior (paw shaking, paw elevation) was observed for 5 minutes in the cage. RESULTS: The experimental group exhibited significantly higher withdrawal frequency to mechanical stimulation: from post-injury 3 days to 6 weeks for von Frey hair 4.31 and from 2 days to 4 weeks for von Frey hair 4.56 (p<0.05). There was no difference between two groups in withdrawal latency to radiant heat stimulation. The experimental group showed spontaneous pain behavior but control group did not. In electron microscopic finding, prominent myelin destruction and axonal sprouting were observed in experimental group. CONCLUSION: These results suggest that a new neuropathic pain model can be made by 10 volts electrical injury for 10 seconds to rat sciatic nerve.

Effects of Intrathecal Magnesium Sulphate in a Rat Model of Postoperative Pain / 대한마취과학회지

BACKGROUND: The mechanical hyperalgesia that follows peripheral tissue injury results from peripheral and central sensitization. Central sensitization is initiated and maintained by windup that can be prevented by N-methyl-D-aspartate (NMDA) antagonists. NMDA antagonists, therefore, have the potential to prevent and treat pain, although clinical uses are limited because of their side effects. This study was designed to evaluate the analgesic action of intrathecal (IT) magnesium sulphate in a rat model of postoperative pain and investigate the analgesic mechanism of magnesium. METHODS: Forty-two Sprague-Dawley rats (300 +/- 20 g) were prepared with a chronic IT catheter. Under brief enflurane anesthesia, a 1-cm incision including skin, muscle and fascia was made in the plantar aspect of the hind paw and closed. Normal saline, magnesium (30, 100, 300, 600 microgram), NMDA 50 ng or NMDA 50 ng with magnesium 300 microgram was administered via the IT catheter after recovery. Response frequency, using Von Frey filaments, cumulative pain scores and motor deficits were assessed. RESULTS: The mechanical hyperalgesia and nonevoked pain behaviors decreased significantly at 1 h or 1 h and 3 h after IT injection of magnesium 100 microgram or 300 microgram compared to the saline group without profound motor deficits in a rat model of postoperative pain. However, the rats administered with magnesium 600 microgram were lethargic due to severe motor weakness. Effective duration of magnesium decreased significantly in the group of NMDA 50 ng with magnesium 300 microgram compared to that of magnesium 300 microgram administered alone, but the initial effects were similar between the two groups. CONCLUSIONS: We conclude that IT magnesium sulphate can modulate nociceptive processing after tissue injury and the analgesic mechanism of magnesium is involved in NMDA receptors. Magnesium,therefore, may offer a therapeutic agent for postoperative pain and may be an agent that prevents postoperative pain from changing to persistent pathological pain.

Development of Neuropathic Pain Model with 1% Phenol Injection in Rat Sciatic Nerve

OBJECTIVE: The purpose of this study is to develop a new neuropathic pain model in the rat. METHOD: Each male adult rat was anesthetized and the sciatic nerve was exposed. Each exposed nerve was injected with 0.03 cc of 1% phenol solution. Normal saline 0.03 cc was injected to the placebo group. Rats were tested for the presence of mechanical allodynia by von Frey hair. Spontaneous pain behavior (paw shaking, paw elevation) was examined for 5 minutes in the cage. RESULTS: Phenol injected group developed allodynia after the second post-injection day for up to 1 month. Allodynia was also observed in the contralateral legs of phenol injected group. The control group did not develop allodynia. Spontaneous pain behavior was not observed in either group. CONCLUSION: Neuropathic pain model was developed by 1% phenol solution injection to the rat sciatic nerve. This study suggests an easier method for making the neuropathic pain model.