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247 THE INFLUENCE OF BRUSHING FORCE AND STROKING VELOCITY ON DYNAMIC MECHANICAL ALLODYNIA IN PATIENTS WITH PERIPHERAL NEUROPATHY
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Poster Sessions / European Journal of Pain 13 (2009) S55–S285
This substance regulates various systems including excitatory glutamatergic nervous system activation of the N-methyl-Daspartate (NMDA) receptor related to nitric oxide (NO) production. Hyperalgesia caused by peripheral tissue damage is involved in glutamate-related neuronal plasticity of the spinal cord. However, its mechanism of action still is unknown. Therefore, we determined the analgesic effect of agmatine in relation to modification of glutamate-related neuronalplasticity using a rat inflammatory pain model. Methods: SD rats implanted with an intrathecal catheter were subjected to formalin-induced hyperalgesia. Pain behavior was assessed by counting spontaneous flinches per min after formalin injection into paws under halothane anesthesia. The rats were separated into six groups as follows, (1) Non-treated (saline, it. inj.); (2) Agmatine (30 ug, it. inj.); (3) MK-801 (15 ug, it. inj.); (4) AVS (OH radical scavenger, 100 ug, it. inj); (5) Agmatine + MK-801; (6) Agmatine + AVS. Results: Rats showed biphasic pain behavior – the sum of the first (0–5 min) is 14/min and the sum of the second (20–60 min) is 147/min. All drugs diminished the sum of the second phase 32–68% compared with non-treated animals but did not affect the first phase. An additive effect of agmatine was obtained with MK801 but not with AVS. Conclusion: We suggest that the synergistic analgesia effect of agmatine may involve the inhibition of NMDA receptor(s) related to NO production, and that agmatine acts on multiple sites of glutamatergic neuronal activation in developing hyperalgesia. 245 ROLE OF SIGMA-1 RECEPTORS IN COLD ALLODYNIA INDUCED BY PACLITAXEL ´ 1 , J.M. Entrena1 *, E.J. Cobos1 , R. GonzalezF.R. Nieto1 , C.M. Cendan 1 2 Cano , D. Zamanillo , J.M. Baeyens1 . 1 Department of Pharmacology, Biomedical Research Centre and Institute of Neuroscience. University of Granada, Granada, Spain; 2 Laboratorios Esteve, Barcelona, Spain Paclitaxel is a widely-used antineoplastic drug that frequently produces neuropathic pain. There are no well-established treatments to counteract it. We developed an experimental model of this neuropathy in mice [Nieto et al., Pain 137:520–31, (2008)] which permits to test new treatments. Sigma-1 receptor antagonists are efficient in several pain models; however, it is unknown whether they can modify paclitaxel-induced pain. Paclitaxel 2 mg/kg was administered i.p., once per day during five consecutive days, to wild type (WT) and sigma-1 receptor knockout (KO) mice. Cold allodynia was tested previously to paclitaxel administration and after antineoplastic treatment, every 3–4 days during 2–4 weeks. Cold allodynia was assayed by touching the plantar skin of the hind paws with an acetone drop and duration of paw licking/biting was measured. WT mice treated with paclitaxel (but not with its solvent) developed cold allodynia. However, sigma-1 receptor KO mice did not develop paclitaxel-induced cold allodynia. Interestingly, s.c. administration of BD-1063 (selective sigma-1 antagonist), 30 min before each paclitaxel dose in WT mice, inhibited the development of cold-allodynia. The day of maximum expression of cold allodynia in WT mice (day 10 post-treatment), acute BD-1063 administration (8–64 mg/kg, s.c.) dose-dependently inhibited the expression of paclitaxel-induced allodynia, whereas saline was inactive. These results suggest that sigma-1 receptors are involved in paclitaxel-induced neuropathic pain and sigma-1 receptor antagonists might have therapeutic value for its prevention and/or treatment. Mice were handled in accordance with the European Communities Council Directive (86/609/ECC). Supported partially by Junta-Andaluc´ıa, Laboratorios Esteve, MECFPU and project SAF2006–06122
246 RESPONSE TO NOCIVE MECHANICAL STIMULATION OF THE RAT SKIN-SAPHENOUS NERVE PREPARATION AFTER TREATMENT WITH ANTINEOPLASTIC DRUGS N.A. Paniagua de Veizaga *, R. Giron ´ Moreno, M.I. Mart´ın Fontelles. Universidad Rey Juan Carlos, Alcorc´ on, Spain Our purpose is to test the effect of two antineoplastic drugs (paclitaxel and cisplatinum), that can induce peripheral neuropathies, in the rat skin-saphenous nerve preparation under nocive mechanical stimulation conditions. In a previous study, using this in vitro preparation (Reeh, 1986), we evaluated the response of single primary afferent Admechanoreceptors, isolated from control tissues (naïve rats) and from tissues obtained from rats chronically treated with cisplatin or paclitaxel to innocuous mechanical stimulation. A force-controlled electromechanical stimulator was perpendicularly placed on the most sensitive spot of the skinny receptive field of the unit, and a ramp-pressure stimulation protocol was applied (increasing stimulus with a speed of 8 mN/s from 0 to 96 mN). Units from tissues treated with the antineoplastics, in comparison to control units, expressed an enhanced response, characterized by decreased mechanical thresholds and significant enhancement in the total number of spikes elicited per stimulus. In the present study, the response to longer pressure-ramps, reaching to the nocive stimulus of 200 mN was tested after treatment with the antineoplastics and compared with those obtained in control tissues. Ussing this protocol, of our results show that up to about 72 mN, there is a declining of the discharge rate in cisplatin and paclitaxel groups, whereas the response of control fibers becomes significantly increased and irregular and differences between control and antineoplastic treated groups is smaller. More work is required to understand mechanisms that underlie these interesting differences between responses induced by innocuous and nocive stimulation. Supported by SAF2006–13391-CO3–01 247 THE INFLUENCE OF BRUSHING FORCE AND STROKING VELOCITY ON DYNAMIC MECHANICAL ALLODYNIA IN PATIENTS WITH PERIPHERAL NEUROPATHY M. Samuelsson1 *, A.S. Leffler1 , B. Johansson2 , P. Hansson1 . 1 Clinical Pain Research, Dep of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden; 2 Somedic Sales AB, H¨ orby, Sweden Brush-evoked allodynia in patients with peripheral neuropathy has been demonstrated to be a partially graded phenomenon since increased brushing length and number of strokes significantly increased brush-evoked pain intensity. In this study the influence of stroking velocity and brushing force on dynamic mechanical allodynia was examined. In accordance with Helsinki Declaration, 16 patients with peripheral neuropathy were recruited. Brush-evoked allodynia was induced by lightly stroking 60 mm of the skin twice with a 16 mm brush while varying stroking velocity (10, 20, 30 mm/s) and brushing force (10, 20, 40 g). Intensity and duration of allodynia was recorded using a computerized visual analogue scale. The total brush-evoked pain intensity, including aftersensation was calculated as the area under the curve. Following each stimulus, the patients selected pain descriptors from a validated instrument. Increased total brush-evoked pain intensity was demonstrated with lower stroking velocity (comparing 10 mm/s with 20 or 30 mm/s (P < 0.001), respectively, and 20 mm/s with 30 mm/s (P < 0.01)) and higher brushing force (comparing 10 g with 40 g (P < 0.05)). There was no difference in the frequency of aftersensation when altering brushing force or stroking velocity. The most commonly used sensory-discriminative descriptors were sore, aching and pressing and for the affective descriptors troublesome and annoying.
Poster Sessions / European Journal of Pain 13 (2009) S55–S285
A significant relationship between the total brush-evoked pain intensity and stroking velocity as well as brushing force was found. Together with previously accumulated data this substantiates the usefulness of the method in longitudinal studies. 248 DEVELOPMENT OF QUANTITATIVE MECHANICAL SENSORY TESTING APPROACHES FOR PAIN ASSESSMENT IN PIGS D. Sandercock1 *, I. Gibson1 , H. Brash2 , M. Scott3 , A. Nolan1 . 1 University of Glasgow, Division of Cell Sciences, Faculty of Veterinary Medicine, Glasgow, United Kingdom; 2 University of Edinburgh, Department of Hepatology, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom; 3 University of Glasgow, Department of Statistics, Glasgow, United Kingdom Background and Aims: Obtaining accurate and repeatable measurements of sensory thresholds in freely behaving animals presents a considerable challenge. The aim of these studies was to develop methods of quantitative sensory testing (QST) in juvenile pigs and evaluate two models of acute inflammatory pain. Methods: Two QST approaches were developed to detect allodynia and hyperalgesia; (1) von Frey filaments for mechanical force threshold testing around the tail root, and (2) noxious mechanical stimulation of the plantar surface of the foot pad. Assessment protocols were developed in three groups of 8 juvenile pigs (7–9 weeks). Pigs were habituated to the investigators, apparatus and procedures before testing. Response thresholds and behaviours were measured before, and up to 24 h after inflamogen injection. Inflamation was induced by injection of capsaicin (10–100 mg) or carrageenan (3%) into the tail root or hind foot pad. Data analysed using GLM repeated measures ANOVA. Results: Inflamogen injection significantly (p < 0.05) reduced mechanical force thresholds in both tests and behavioural signs of mechanical allodynia and hyperalgesia were observed (tail flicking and foot withdrawal). Maximum reductions in force thresholds were measured 30 min after capsaicin and 4 h after carrageenan injection. Conclusions: Quantification of thresholds using the two approaches reported provides reliable data. Capsaicin and carrageenan induced inflammation and hypersensitivity was measurable in pigs, and its onset and duration was consistent with laboratory species. These approaches will be used in future studies to investigate the effects of neonatal tail-docking on nociceptive processing in pigs. Supported by BBSRC 249 THE THERAPEUTIC EFFECT OF EPIDURALLY-ADMINSTERED LIPO-PROSTAGLANDIN E1 IN A RAT SPINAL STENOSIS MODEL S.Y. Park1 *, Y.C. Kim2 , S.S. Choi3 , S.E. Kim4 . 1 Department of Anesthesiology and Pain Medicine, Jeju National University Hospital, Jeju, South Korea; 2 Department of Anesthesiology and Pain Medicine, Seoul National University Hospital, Seoul, South Korea; 3 Department of Anesthesiology and Pain Medicine, Korea University Hospital, Seoul, South Korea Background: Lipo-Prostaglandin E1(Lipo-PGE1) has vasodilating and platelet aggregation-inhibition characteristics and has been used as a treatment for blood flow dysfunction disease. Based on mechanisms of lumbar spinal stenosis, including veno congestion, neuro-ischemia and mechanical compression, we aimed to study whether epidural Lipo-PGE1 injection has any therapeutic effect on hyperalgesia in a rat foraminal stenosis model. Methods: In this study, 40 male Sprague-Dawley rats were divided into EP (n = 15), NS (n = 15), control (n = 10) groups. A small stainless steel rod was inserted into L5-L6 intervertebral foramen to develop intervertebral foraminal stenosis and chronic DRG compression. In the EP group, 0.15 mg/kg of Lipo-PGE1 were injected epidurally via epidural catheter for 10 days, from the 3rd day after the operation. In the NS group, Saline were injected epidurally via epidural catheter for 10 days, from the 3rd day after the operation.
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Behavioral test for mechanical and thermal hyperalgesia was performed for 3 weeks. Microscopic analysis performed 3 days later at the end of Behavioral test. Results: From the 10th day after Lipo-PGE1 injection, EP group showed significant recovery of mechanical threshold, and this effect was maintained for 3 weeks. No significant difference in the thermal hyperalgesia were observed between three groups. Microscopic analysis showed much less chromatolysis in EP group compared to NS, Control group. 250 ANANDAMIDE CAUSES ANALGESIA IN NEUROPATHIC RATS BY ACTIVATING SPINAL TRPV1 RECEPTORS K. Starowicz1 *, W. Makuch1 , M. Osikowicz1 , S. Petrosino2 , F. Guadagno2 , V. Di Marzo2 , B. Przewlocka1 . 1 Dept. of Pain Pharmacology, Institute of Pharmacology Polish Academy of Sciences, Cracow, Poland; 2 Endocannabinoid Research Group, Istituto di Chimica Biomolecolare CNR, Pozzuoli (NA), Italy Background and Aims: Latest reports suggest a role for anandamide (AEA) as an endovanilloid substance. However, no data exist on the potential role of spinal TRPV1 activation by AEA in neuropathic pain models. Methods: Rats chronically implanted with intrathecal (i.t.) catheters underwent sciatic nerve ligation (CCI model), and mechanical allodynia and thermal hyperalgesia were measured. Seven days after CCI we tested the effect of AEA (5, 50, 100 mg; i.t.); or the inhibitor of AEA enzymatic hydrolysis, URB597; we evaluated the involvement of TRPV1 or cannabinoid CB1 receptors by blocking these receptors with I-RTX or AM251, respectively; and determined the levels of AEA in the spinal cord of CCI rats. All experiments were carried out according to IASP rules (Pain 16, 1983). Results: AEA displayed dose-depended antiallodynic and antihyperalgesic action. The analgesic effect of AEA was abolished by pretreatment with I-RTX but not AM251. Depending on the administered dose, URB597 (100–200 mg/rat) reduced thermal and tactile nociception via CB1 or TRPV1 receptors as demonstrated by the attenuation of its effects by pretreatment with the respective antagonists. URB597 dose-dependently enhanced spinal AEA levels. Conclusions: We suggest that i.t. AEA reduces neuropathic pain by acting as an endovanilloid, possibly by activating/desensitizing TRPV1 receptors co-localized with CB1 receptors in the superficial lamina of the spinal cord. When endogenously up-regulated with URB597, AEA exerts analgesia via both receptors. AEA- and TRPV1-based therapies might be useful to treat pathogenesis in neuropathic pain after peripheral nerve injury. Supported by 0152/B/2008/35, FNP and EEA Financial Mechanism. 251 EFFECTS OF MEMANTINE, DEXTROMETHORPHAN AND MORPHINE ON CARRAGEENAN-INDUCED INFLAMMATION AND PAIN SENSITIVITY IN MICE P.L. Tao *, C.F. Yao, E.Y.K. Huang. Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan Memantine, dextromethorphan (DM) have been reported to have anti-inflammatory effect. In this study, we evaluated the effects of single drug or combination drug treatments of memantine, dextromethorphan and morphine on the carrageenan (Cg) induced inflammation and inflammatory hypernociception in the mouse hind paw. Drugs (s.c.) were given at 0, 1, 2, 3 hours after Cg (100 mg / 10 ml, i.pl.). The effect of different treatments on Cginduced mechanical hyperalgesia was determined by Von Frey test at 30, 90, 150, 210 min and edema was determined at 60, 120, 180, 240 min after Cg (i.pl.). Mice were sacrificed after all the tests and the injected paws were taken for determination of pro-inflammatory substances (TNF-a and IL-1b). Our results showed that combination use of morphine and memantine may have better
Poster Sessions / European Journal of Pain 13 (2009) S55–S285
This substance regulates various systems including excitatory glutamatergic nervous system activation of the N-methyl-Daspartate (NMDA) receptor related to nitric oxide (NO) production. Hyperalgesia caused by peripheral tissue damage is involved in glutamate-related neuronal plasticity of the spinal cord. However, its mechanism of action still is unknown. Therefore, we determined the analgesic effect of agmatine in relation to modification of glutamate-related neuronalplasticity using a rat inflammatory pain model. Methods: SD rats implanted with an intrathecal catheter were subjected to formalin-induced hyperalgesia. Pain behavior was assessed by counting spontaneous flinches per min after formalin injection into paws under halothane anesthesia. The rats were separated into six groups as follows, (1) Non-treated (saline, it. inj.); (2) Agmatine (30 ug, it. inj.); (3) MK-801 (15 ug, it. inj.); (4) AVS (OH radical scavenger, 100 ug, it. inj); (5) Agmatine + MK-801; (6) Agmatine + AVS. Results: Rats showed biphasic pain behavior – the sum of the first (0–5 min) is 14/min and the sum of the second (20–60 min) is 147/min. All drugs diminished the sum of the second phase 32–68% compared with non-treated animals but did not affect the first phase. An additive effect of agmatine was obtained with MK801 but not with AVS. Conclusion: We suggest that the synergistic analgesia effect of agmatine may involve the inhibition of NMDA receptor(s) related to NO production, and that agmatine acts on multiple sites of glutamatergic neuronal activation in developing hyperalgesia. 245 ROLE OF SIGMA-1 RECEPTORS IN COLD ALLODYNIA INDUCED BY PACLITAXEL ´ 1 , J.M. Entrena1 *, E.J. Cobos1 , R. GonzalezF.R. Nieto1 , C.M. Cendan 1 2 Cano , D. Zamanillo , J.M. Baeyens1 . 1 Department of Pharmacology, Biomedical Research Centre and Institute of Neuroscience. University of Granada, Granada, Spain; 2 Laboratorios Esteve, Barcelona, Spain Paclitaxel is a widely-used antineoplastic drug that frequently produces neuropathic pain. There are no well-established treatments to counteract it. We developed an experimental model of this neuropathy in mice [Nieto et al., Pain 137:520–31, (2008)] which permits to test new treatments. Sigma-1 receptor antagonists are efficient in several pain models; however, it is unknown whether they can modify paclitaxel-induced pain. Paclitaxel 2 mg/kg was administered i.p., once per day during five consecutive days, to wild type (WT) and sigma-1 receptor knockout (KO) mice. Cold allodynia was tested previously to paclitaxel administration and after antineoplastic treatment, every 3–4 days during 2–4 weeks. Cold allodynia was assayed by touching the plantar skin of the hind paws with an acetone drop and duration of paw licking/biting was measured. WT mice treated with paclitaxel (but not with its solvent) developed cold allodynia. However, sigma-1 receptor KO mice did not develop paclitaxel-induced cold allodynia. Interestingly, s.c. administration of BD-1063 (selective sigma-1 antagonist), 30 min before each paclitaxel dose in WT mice, inhibited the development of cold-allodynia. The day of maximum expression of cold allodynia in WT mice (day 10 post-treatment), acute BD-1063 administration (8–64 mg/kg, s.c.) dose-dependently inhibited the expression of paclitaxel-induced allodynia, whereas saline was inactive. These results suggest that sigma-1 receptors are involved in paclitaxel-induced neuropathic pain and sigma-1 receptor antagonists might have therapeutic value for its prevention and/or treatment. Mice were handled in accordance with the European Communities Council Directive (86/609/ECC). Supported partially by Junta-Andaluc´ıa, Laboratorios Esteve, MECFPU and project SAF2006–06122
246 RESPONSE TO NOCIVE MECHANICAL STIMULATION OF THE RAT SKIN-SAPHENOUS NERVE PREPARATION AFTER TREATMENT WITH ANTINEOPLASTIC DRUGS N.A. Paniagua de Veizaga *, R. Giron ´ Moreno, M.I. Mart´ın Fontelles. Universidad Rey Juan Carlos, Alcorc´ on, Spain Our purpose is to test the effect of two antineoplastic drugs (paclitaxel and cisplatinum), that can induce peripheral neuropathies, in the rat skin-saphenous nerve preparation under nocive mechanical stimulation conditions. In a previous study, using this in vitro preparation (Reeh, 1986), we evaluated the response of single primary afferent Admechanoreceptors, isolated from control tissues (naïve rats) and from tissues obtained from rats chronically treated with cisplatin or paclitaxel to innocuous mechanical stimulation. A force-controlled electromechanical stimulator was perpendicularly placed on the most sensitive spot of the skinny receptive field of the unit, and a ramp-pressure stimulation protocol was applied (increasing stimulus with a speed of 8 mN/s from 0 to 96 mN). Units from tissues treated with the antineoplastics, in comparison to control units, expressed an enhanced response, characterized by decreased mechanical thresholds and significant enhancement in the total number of spikes elicited per stimulus. In the present study, the response to longer pressure-ramps, reaching to the nocive stimulus of 200 mN was tested after treatment with the antineoplastics and compared with those obtained in control tissues. Ussing this protocol, of our results show that up to about 72 mN, there is a declining of the discharge rate in cisplatin and paclitaxel groups, whereas the response of control fibers becomes significantly increased and irregular and differences between control and antineoplastic treated groups is smaller. More work is required to understand mechanisms that underlie these interesting differences between responses induced by innocuous and nocive stimulation. Supported by SAF2006–13391-CO3–01 247 THE INFLUENCE OF BRUSHING FORCE AND STROKING VELOCITY ON DYNAMIC MECHANICAL ALLODYNIA IN PATIENTS WITH PERIPHERAL NEUROPATHY M. Samuelsson1 *, A.S. Leffler1 , B. Johansson2 , P. Hansson1 . 1 Clinical Pain Research, Dep of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden; 2 Somedic Sales AB, H¨ orby, Sweden Brush-evoked allodynia in patients with peripheral neuropathy has been demonstrated to be a partially graded phenomenon since increased brushing length and number of strokes significantly increased brush-evoked pain intensity. In this study the influence of stroking velocity and brushing force on dynamic mechanical allodynia was examined. In accordance with Helsinki Declaration, 16 patients with peripheral neuropathy were recruited. Brush-evoked allodynia was induced by lightly stroking 60 mm of the skin twice with a 16 mm brush while varying stroking velocity (10, 20, 30 mm/s) and brushing force (10, 20, 40 g). Intensity and duration of allodynia was recorded using a computerized visual analogue scale. The total brush-evoked pain intensity, including aftersensation was calculated as the area under the curve. Following each stimulus, the patients selected pain descriptors from a validated instrument. Increased total brush-evoked pain intensity was demonstrated with lower stroking velocity (comparing 10 mm/s with 20 or 30 mm/s (P < 0.001), respectively, and 20 mm/s with 30 mm/s (P < 0.01)) and higher brushing force (comparing 10 g with 40 g (P < 0.05)). There was no difference in the frequency of aftersensation when altering brushing force or stroking velocity. The most commonly used sensory-discriminative descriptors were sore, aching and pressing and for the affective descriptors troublesome and annoying.
Poster Sessions / European Journal of Pain 13 (2009) S55–S285
A significant relationship between the total brush-evoked pain intensity and stroking velocity as well as brushing force was found. Together with previously accumulated data this substantiates the usefulness of the method in longitudinal studies. 248 DEVELOPMENT OF QUANTITATIVE MECHANICAL SENSORY TESTING APPROACHES FOR PAIN ASSESSMENT IN PIGS D. Sandercock1 *, I. Gibson1 , H. Brash2 , M. Scott3 , A. Nolan1 . 1 University of Glasgow, Division of Cell Sciences, Faculty of Veterinary Medicine, Glasgow, United Kingdom; 2 University of Edinburgh, Department of Hepatology, Royal Infirmary of Edinburgh, Edinburgh, United Kingdom; 3 University of Glasgow, Department of Statistics, Glasgow, United Kingdom Background and Aims: Obtaining accurate and repeatable measurements of sensory thresholds in freely behaving animals presents a considerable challenge. The aim of these studies was to develop methods of quantitative sensory testing (QST) in juvenile pigs and evaluate two models of acute inflammatory pain. Methods: Two QST approaches were developed to detect allodynia and hyperalgesia; (1) von Frey filaments for mechanical force threshold testing around the tail root, and (2) noxious mechanical stimulation of the plantar surface of the foot pad. Assessment protocols were developed in three groups of 8 juvenile pigs (7–9 weeks). Pigs were habituated to the investigators, apparatus and procedures before testing. Response thresholds and behaviours were measured before, and up to 24 h after inflamogen injection. Inflamation was induced by injection of capsaicin (10–100 mg) or carrageenan (3%) into the tail root or hind foot pad. Data analysed using GLM repeated measures ANOVA. Results: Inflamogen injection significantly (p < 0.05) reduced mechanical force thresholds in both tests and behavioural signs of mechanical allodynia and hyperalgesia were observed (tail flicking and foot withdrawal). Maximum reductions in force thresholds were measured 30 min after capsaicin and 4 h after carrageenan injection. Conclusions: Quantification of thresholds using the two approaches reported provides reliable data. Capsaicin and carrageenan induced inflammation and hypersensitivity was measurable in pigs, and its onset and duration was consistent with laboratory species. These approaches will be used in future studies to investigate the effects of neonatal tail-docking on nociceptive processing in pigs. Supported by BBSRC 249 THE THERAPEUTIC EFFECT OF EPIDURALLY-ADMINSTERED LIPO-PROSTAGLANDIN E1 IN A RAT SPINAL STENOSIS MODEL S.Y. Park1 *, Y.C. Kim2 , S.S. Choi3 , S.E. Kim4 . 1 Department of Anesthesiology and Pain Medicine, Jeju National University Hospital, Jeju, South Korea; 2 Department of Anesthesiology and Pain Medicine, Seoul National University Hospital, Seoul, South Korea; 3 Department of Anesthesiology and Pain Medicine, Korea University Hospital, Seoul, South Korea Background: Lipo-Prostaglandin E1(Lipo-PGE1) has vasodilating and platelet aggregation-inhibition characteristics and has been used as a treatment for blood flow dysfunction disease. Based on mechanisms of lumbar spinal stenosis, including veno congestion, neuro-ischemia and mechanical compression, we aimed to study whether epidural Lipo-PGE1 injection has any therapeutic effect on hyperalgesia in a rat foraminal stenosis model. Methods: In this study, 40 male Sprague-Dawley rats were divided into EP (n = 15), NS (n = 15), control (n = 10) groups. A small stainless steel rod was inserted into L5-L6 intervertebral foramen to develop intervertebral foraminal stenosis and chronic DRG compression. In the EP group, 0.15 mg/kg of Lipo-PGE1 were injected epidurally via epidural catheter for 10 days, from the 3rd day after the operation. In the NS group, Saline were injected epidurally via epidural catheter for 10 days, from the 3rd day after the operation.
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Behavioral test for mechanical and thermal hyperalgesia was performed for 3 weeks. Microscopic analysis performed 3 days later at the end of Behavioral test. Results: From the 10th day after Lipo-PGE1 injection, EP group showed significant recovery of mechanical threshold, and this effect was maintained for 3 weeks. No significant difference in the thermal hyperalgesia were observed between three groups. Microscopic analysis showed much less chromatolysis in EP group compared to NS, Control group. 250 ANANDAMIDE CAUSES ANALGESIA IN NEUROPATHIC RATS BY ACTIVATING SPINAL TRPV1 RECEPTORS K. Starowicz1 *, W. Makuch1 , M. Osikowicz1 , S. Petrosino2 , F. Guadagno2 , V. Di Marzo2 , B. Przewlocka1 . 1 Dept. of Pain Pharmacology, Institute of Pharmacology Polish Academy of Sciences, Cracow, Poland; 2 Endocannabinoid Research Group, Istituto di Chimica Biomolecolare CNR, Pozzuoli (NA), Italy Background and Aims: Latest reports suggest a role for anandamide (AEA) as an endovanilloid substance. However, no data exist on the potential role of spinal TRPV1 activation by AEA in neuropathic pain models. Methods: Rats chronically implanted with intrathecal (i.t.) catheters underwent sciatic nerve ligation (CCI model), and mechanical allodynia and thermal hyperalgesia were measured. Seven days after CCI we tested the effect of AEA (5, 50, 100 mg; i.t.); or the inhibitor of AEA enzymatic hydrolysis, URB597; we evaluated the involvement of TRPV1 or cannabinoid CB1 receptors by blocking these receptors with I-RTX or AM251, respectively; and determined the levels of AEA in the spinal cord of CCI rats. All experiments were carried out according to IASP rules (Pain 16, 1983). Results: AEA displayed dose-depended antiallodynic and antihyperalgesic action. The analgesic effect of AEA was abolished by pretreatment with I-RTX but not AM251. Depending on the administered dose, URB597 (100–200 mg/rat) reduced thermal and tactile nociception via CB1 or TRPV1 receptors as demonstrated by the attenuation of its effects by pretreatment with the respective antagonists. URB597 dose-dependently enhanced spinal AEA levels. Conclusions: We suggest that i.t. AEA reduces neuropathic pain by acting as an endovanilloid, possibly by activating/desensitizing TRPV1 receptors co-localized with CB1 receptors in the superficial lamina of the spinal cord. When endogenously up-regulated with URB597, AEA exerts analgesia via both receptors. AEA- and TRPV1-based therapies might be useful to treat pathogenesis in neuropathic pain after peripheral nerve injury. Supported by 0152/B/2008/35, FNP and EEA Financial Mechanism. 251 EFFECTS OF MEMANTINE, DEXTROMETHORPHAN AND MORPHINE ON CARRAGEENAN-INDUCED INFLAMMATION AND PAIN SENSITIVITY IN MICE P.L. Tao *, C.F. Yao, E.Y.K. Huang. Department of Pharmacology, National Defense Medical Center, Taipei, Taiwan Memantine, dextromethorphan (DM) have been reported to have anti-inflammatory effect. In this study, we evaluated the effects of single drug or combination drug treatments of memantine, dextromethorphan and morphine on the carrageenan (Cg) induced inflammation and inflammatory hypernociception in the mouse hind paw. Drugs (s.c.) were given at 0, 1, 2, 3 hours after Cg (100 mg / 10 ml, i.pl.). The effect of different treatments on Cginduced mechanical hyperalgesia was determined by Von Frey test at 30, 90, 150, 210 min and edema was determined at 60, 120, 180, 240 min after Cg (i.pl.). Mice were sacrificed after all the tests and the injected paws were taken for determination of pro-inflammatory substances (TNF-a and IL-1b). Our results showed that combination use of morphine and memantine may have better