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196 NEUROPATHIC PAIN AND WIND-UP RESPONSES AFTER GRADED SPINAL CORD INJURIES IN THE ADULT RAT
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Posters / European Journal of Pain Supplements 4 (2010) 47–146
195 POTENTIAL MECHANISMS OF COLD HYPERALGESIA INDUCED BY INFRAORBITAL NERVE CONSTRICTION A. Martini1 , J. Chichorro2 , C. Fiuza1 , G. Rae1 . 1 Pharmacology, Universidade Federal de Santa Catarina, Florianopolis, 2 Pharmacology, Universidade Federal do Paran´ a, Curitiba, Brazil Introduction: Transient receptor potential channel TRPA1 is activated by compounds such as mustard oil and icilin, is found in fibers that also express TRPV1 receptors and has been proposed as a sensor of noxious cold. Objective: To assess the role of TRPA1 receptors in cold hyperalgesia in a rat model of trigeminal neuropathic pain. Methods: Naïve male Wistar rats (200–250 g) or rats treated neonatally with capsaicin (50 mg/kg, s.c.) underwent infraorbital nerve constriction (CION) or icilin injection (10 and 30 mg/50 ml, s.c. into the upper lip) and submitted to cold stimulation (Chichorro et al. Pain 2006; 123:64–74). The effects of the selective TRPA1 antagonists HC-030031 (100 mg/kg, i.p.) and AP-18 (10 and 100 mg/50 ml, s.c.) or the TRPM8 antagonist clotrimazole were investigated. Results: Icilin caused dose-dependent cold hyperalgesia and potentiated cold hyperalgesia induced by CION by ~130%, but both CION- and icilin-cold hyperalgesia were abolished by neonatal capsaicin treatment. HC-030031 or AP-18, but not clotrimazole, treatments reduced cold hyperalgesia on day 4 after CION. Conclusions: Capsaicin-sensitive C fibers mediate the cold hyperalgesia triggered by icilin or CION, which is also significantly reduced by TRPA1 selective antagonists. These data suggest that specific blockers of TRPA1 receptors might provide effective therapeutic tools for the management of orofacial cold hyperalgesia. Immunohistochemistry experiments in trigeminal ganglia sections of sham and CION rats are underway to characterize the influence of CION on TRPA1 receptor expression. Financial support: CNPq, CAPES, PRONEX, UFSC 196 NEUROPATHIC PAIN AND WIND-UP RESPONSES AFTER GRADED SPINAL CORD INJURIES IN THE ADULT RAT E. Redondo Castro, E. Udina, E. Verdu, ´ X. Navarro. Cell Biology, Physiology and Immunology, Institute of Neurosciences. Universitat Aut` onoma de Barcelona, Cerdanyola, Spain Introduction: Neuropathic pain (NP) is one of the most devastating consequences of spinal cord injuries. It may appear as hyperalgesia, allodynia and spontaneous pain. Animal models are important tools for the study of mechanisms implicated and of new therapeutic approaches for NP. Objectives: To study the development of NP and spinal circuit facilitation after spinal cord injuries of varying severity in the rat. Methods: Adult female rats received a cord contusion at T8 using the Infinite Horizons Impactor device, applying forces of 100 or 200 kdyn. Mechanical and thermal algesimetry tests and electrophysiological recordings of wind-up responses at the lumbar spinal circuits were performed weekly after injury. Results: Mechanical and thermal nociceptive thresholds were reduced in both lesioned groups compared to intact animals (from 19–20 g to 10–12 g in mechanical tests, and from 12–13 sec to 8–10 sec in thermal tests) during a 2 months follow-up. Electromyographic evaluation showed increased wind-up responses during follow up period (mean increase in intact animals: 2.04; 100 kdyn: 2.56; 200 kdyn: 3.05), indicating central hyperexcitability below the level of injury, especially in injured animals. Conclusions: Signs of NP are frequent after contusive spinal cord injury in adult rats. Lesions of different severity induce similar reduction in pain thresholds to mechanical and heating stimuli, but the wind-up responses increase in relation to the degree of injury, indicating a state of higher hyperexcitability.
197 EFFECT OF THE ARMED SPIDER TOXIN TX3.3 ON NEUROPATHIC PAIN MODELS IN MICE M. Rossato1 , G. Duarte Dalmolin2 , F.K. Rigo2 , M.C. Godoy1 , J. Ferreira1 , M.V. Gomez3 . 1 Universidade Federal de Santa Maria, 2 Universidade Federal de Minas Gerais, Santa Maria, 3 Universidade Federal de Minas Gerais, Belo Horizonte, Brazil Introduction: The w-conotoxin MVIIA from the marine snail Conus magus has been an exceptional lead for drug development in the management of severe and chronic pain. As MVIIA, a peptide toxin extracted from armed spider venom, Tx3.3, blocks calcium channels that regulates spinal pain transmission. Objectives: To evaluate the effect of Tx3.3 in neuropathic pain models in mice, by intrathecal route (i.t) administration. Methods: Male mice were administered with Tx3.3 (30 pmol/site, i.t.). Different group of animals were submitted to diabetic or traumatic neuropathy model. To diabetic neuropathy induction, mice were administered with 200 mg/kg of streptozotocin by intraperitoneal route whereas traumatic neuropathy was induced through the partial sciatic nerve ligation technique. Pain sensitization induced by diabetic and traumatic neuropathy was evaluated 15 and 7 days after its induction, respectively. The mechanical sensitivity was measured through application of Von Frey filaments on mice hind paw plantar surface several times after spinal injection of Tx3.3. Results: Spinal administration of Tx3.3 inhibited neuropathyinduced tactile allodynia in both models. The Tx3.3 anti-allodynic effect was evident 30 minutes after its delivery had a peak effect at 60 minutes and lasting for about 120 minutes post injection, ending after 240 minutes of its administration. However, Tx3.3 was not able to change mice natural mechanical sensitivity. Conclusions: These results showed that Tx3.3 could alleviate the allodynia present in neuropathic states and, therefore, hold significant promise that Tx3.3 can represent a novel therapeutic agent to control neuropathic pain condition. 198 NOVEL BEHAVIORAL MODELS FOR THE ASSESSMENT OF THE EMOTIONAL COMPONENT OF PAIN AND FOR SPONTANEOUS PAIN IN RATS K. Rutten, E. Van der Kam, A. Robens, T. Christoph, T. Tzschentke, J. De Vry. Department of Pharmacology, Gr¨ unenthal, GmbH, Aachen, Germany Introduction: Current preclinical pain models concentrate on the sensory, rather than the emotional, component of pain and measure evoked, as opposed to spontaneous, pain. Objectives: To develop rat models that reliably dissociate: a) The sensory from the emotional component of pain and b) Evoked from spontaneous pain. Methods: Model 1: In order to dissociate the sensory from the emotional component of inflammatory pain (0.5% carrageenan intraplantar), we used a paw pressure test combined with conditioned place aversion and preference (CPP) paradigms, and tested the efficacy of morphine (0.01–10 mg/kg i.p.) in each model. Model 2: In order to dissociate evoked from spontaneous pain, we subjected neuropathic (chronic constriction injury, CCI) and shamoperated animals to a cold plate paradigm combined with a CPP paradigm and tested the efficacy of morphine (1–10 mg/kg i.p.) in each model. Results: Model 1: The minimal effective dose (MED) of morphine for producing anti-hyperalgesic effects was 1 mg/kg, whereas the MED for anti-aversive effects was 0.03 mg/kg, and the MED for producing CPP in carrageenan-treated and sham-treated rats was 10 and 1 mg/kg, respectively. Model 2: The anti-allodynic MED of morphine was 3.16 mg/kg, and the MED for producing CPP in CCI and sham-operated animals was 0.3 and 2.15 mg/kg, respectively.
Posters / European Journal of Pain Supplements 4 (2010) 47–146
195 POTENTIAL MECHANISMS OF COLD HYPERALGESIA INDUCED BY INFRAORBITAL NERVE CONSTRICTION A. Martini1 , J. Chichorro2 , C. Fiuza1 , G. Rae1 . 1 Pharmacology, Universidade Federal de Santa Catarina, Florianopolis, 2 Pharmacology, Universidade Federal do Paran´ a, Curitiba, Brazil Introduction: Transient receptor potential channel TRPA1 is activated by compounds such as mustard oil and icilin, is found in fibers that also express TRPV1 receptors and has been proposed as a sensor of noxious cold. Objective: To assess the role of TRPA1 receptors in cold hyperalgesia in a rat model of trigeminal neuropathic pain. Methods: Naïve male Wistar rats (200–250 g) or rats treated neonatally with capsaicin (50 mg/kg, s.c.) underwent infraorbital nerve constriction (CION) or icilin injection (10 and 30 mg/50 ml, s.c. into the upper lip) and submitted to cold stimulation (Chichorro et al. Pain 2006; 123:64–74). The effects of the selective TRPA1 antagonists HC-030031 (100 mg/kg, i.p.) and AP-18 (10 and 100 mg/50 ml, s.c.) or the TRPM8 antagonist clotrimazole were investigated. Results: Icilin caused dose-dependent cold hyperalgesia and potentiated cold hyperalgesia induced by CION by ~130%, but both CION- and icilin-cold hyperalgesia were abolished by neonatal capsaicin treatment. HC-030031 or AP-18, but not clotrimazole, treatments reduced cold hyperalgesia on day 4 after CION. Conclusions: Capsaicin-sensitive C fibers mediate the cold hyperalgesia triggered by icilin or CION, which is also significantly reduced by TRPA1 selective antagonists. These data suggest that specific blockers of TRPA1 receptors might provide effective therapeutic tools for the management of orofacial cold hyperalgesia. Immunohistochemistry experiments in trigeminal ganglia sections of sham and CION rats are underway to characterize the influence of CION on TRPA1 receptor expression. Financial support: CNPq, CAPES, PRONEX, UFSC 196 NEUROPATHIC PAIN AND WIND-UP RESPONSES AFTER GRADED SPINAL CORD INJURIES IN THE ADULT RAT E. Redondo Castro, E. Udina, E. Verdu, ´ X. Navarro. Cell Biology, Physiology and Immunology, Institute of Neurosciences. Universitat Aut` onoma de Barcelona, Cerdanyola, Spain Introduction: Neuropathic pain (NP) is one of the most devastating consequences of spinal cord injuries. It may appear as hyperalgesia, allodynia and spontaneous pain. Animal models are important tools for the study of mechanisms implicated and of new therapeutic approaches for NP. Objectives: To study the development of NP and spinal circuit facilitation after spinal cord injuries of varying severity in the rat. Methods: Adult female rats received a cord contusion at T8 using the Infinite Horizons Impactor device, applying forces of 100 or 200 kdyn. Mechanical and thermal algesimetry tests and electrophysiological recordings of wind-up responses at the lumbar spinal circuits were performed weekly after injury. Results: Mechanical and thermal nociceptive thresholds were reduced in both lesioned groups compared to intact animals (from 19–20 g to 10–12 g in mechanical tests, and from 12–13 sec to 8–10 sec in thermal tests) during a 2 months follow-up. Electromyographic evaluation showed increased wind-up responses during follow up period (mean increase in intact animals: 2.04; 100 kdyn: 2.56; 200 kdyn: 3.05), indicating central hyperexcitability below the level of injury, especially in injured animals. Conclusions: Signs of NP are frequent after contusive spinal cord injury in adult rats. Lesions of different severity induce similar reduction in pain thresholds to mechanical and heating stimuli, but the wind-up responses increase in relation to the degree of injury, indicating a state of higher hyperexcitability.
197 EFFECT OF THE ARMED SPIDER TOXIN TX3.3 ON NEUROPATHIC PAIN MODELS IN MICE M. Rossato1 , G. Duarte Dalmolin2 , F.K. Rigo2 , M.C. Godoy1 , J. Ferreira1 , M.V. Gomez3 . 1 Universidade Federal de Santa Maria, 2 Universidade Federal de Minas Gerais, Santa Maria, 3 Universidade Federal de Minas Gerais, Belo Horizonte, Brazil Introduction: The w-conotoxin MVIIA from the marine snail Conus magus has been an exceptional lead for drug development in the management of severe and chronic pain. As MVIIA, a peptide toxin extracted from armed spider venom, Tx3.3, blocks calcium channels that regulates spinal pain transmission. Objectives: To evaluate the effect of Tx3.3 in neuropathic pain models in mice, by intrathecal route (i.t) administration. Methods: Male mice were administered with Tx3.3 (30 pmol/site, i.t.). Different group of animals were submitted to diabetic or traumatic neuropathy model. To diabetic neuropathy induction, mice were administered with 200 mg/kg of streptozotocin by intraperitoneal route whereas traumatic neuropathy was induced through the partial sciatic nerve ligation technique. Pain sensitization induced by diabetic and traumatic neuropathy was evaluated 15 and 7 days after its induction, respectively. The mechanical sensitivity was measured through application of Von Frey filaments on mice hind paw plantar surface several times after spinal injection of Tx3.3. Results: Spinal administration of Tx3.3 inhibited neuropathyinduced tactile allodynia in both models. The Tx3.3 anti-allodynic effect was evident 30 minutes after its delivery had a peak effect at 60 minutes and lasting for about 120 minutes post injection, ending after 240 minutes of its administration. However, Tx3.3 was not able to change mice natural mechanical sensitivity. Conclusions: These results showed that Tx3.3 could alleviate the allodynia present in neuropathic states and, therefore, hold significant promise that Tx3.3 can represent a novel therapeutic agent to control neuropathic pain condition. 198 NOVEL BEHAVIORAL MODELS FOR THE ASSESSMENT OF THE EMOTIONAL COMPONENT OF PAIN AND FOR SPONTANEOUS PAIN IN RATS K. Rutten, E. Van der Kam, A. Robens, T. Christoph, T. Tzschentke, J. De Vry. Department of Pharmacology, Gr¨ unenthal, GmbH, Aachen, Germany Introduction: Current preclinical pain models concentrate on the sensory, rather than the emotional, component of pain and measure evoked, as opposed to spontaneous, pain. Objectives: To develop rat models that reliably dissociate: a) The sensory from the emotional component of pain and b) Evoked from spontaneous pain. Methods: Model 1: In order to dissociate the sensory from the emotional component of inflammatory pain (0.5% carrageenan intraplantar), we used a paw pressure test combined with conditioned place aversion and preference (CPP) paradigms, and tested the efficacy of morphine (0.01–10 mg/kg i.p.) in each model. Model 2: In order to dissociate evoked from spontaneous pain, we subjected neuropathic (chronic constriction injury, CCI) and shamoperated animals to a cold plate paradigm combined with a CPP paradigm and tested the efficacy of morphine (1–10 mg/kg i.p.) in each model. Results: Model 1: The minimal effective dose (MED) of morphine for producing anti-hyperalgesic effects was 1 mg/kg, whereas the MED for anti-aversive effects was 0.03 mg/kg, and the MED for producing CPP in carrageenan-treated and sham-treated rats was 10 and 1 mg/kg, respectively. Model 2: The anti-allodynic MED of morphine was 3.16 mg/kg, and the MED for producing CPP in CCI and sham-operated animals was 0.3 and 2.15 mg/kg, respectively.