14 research outputs found

    Experimental model to study intervertebral disc herniation

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    OBJETIVO: Apresentar um modelo experimental de hérnia de disco e sua validação para estudo da hiperalgesia mecânica e térmica produzidas pelo contato do núcleo pulposo (NP) com as estruturas nervosas envolvidas nessa afecção. MÉTODOS: Foram utilizados ratos Wistar, sendo o NP autólogo retirado da região sacrococcígea e depositado sobre a dura-máter, raiz nervosa ou gânglios das raízes dorsais L4, L5 ou L6. Os experimentos foram divididos em quatro etapas: 1ª) determinação da estrutura nervosa mais sensível ao contato com o NP; 2ª) identificação do melhor nível lombar para a indução da hiperalgesia; 3ª) determinação da ausência de lesão motora; e 4ª) determinação da influência do procedimento cirúrgico no desenvolvimento do processo inflamatório. A hiperalgesia foi avaliada nos testes de von Frey eletrônico e de Hargreaves e a função motora, pelo teste de rota-rod. RESULTADOS: O NP induziu hiperalgesia de maior intensidade na pata quando em contato com o gânglio da raiz dorsal (GRD) do que em contato com a dura-máter ou a raiz nervosa. Quando em contato com o GRD-L5, o NP induziu hiperalgesia ainda maior que a induzida pelo contato com os GRDs L4 e L6. Não foram observadas lesão motora e influência do processo inflamatório cirúrgico sobre a hiperalgesia. CONCLUSÃO: O GRD é a estrutura mais sensível aos componentes do NP para a produção da hiperalgesia, sendo o quinto nível lombar o que apresentou maior alteração nas sensibilidades mecânica e térmica avaliadas na pata dos animais, de acordo com os métodos utilizados.OBJECTIVE:The purpose of this study is to present an experimental model of disc herniation and to validate such model to study mechanic and thermal hyperalgesia produced by the contact of the nucleus pulposus (NP) with nerve structures involved in this condition. METHODS: The authors used Wistar rats, the autologous NP being removed from the sacrococcygeal region and deposited on the dura mater, nerve root, or L4, L5, or L6 dorsal root ganglia. The experiments were divided into four steps: 1) determining the nerve structure that is the most sensitive to the contact with NP; 2) identifying the best lumbar level to induce hyperalgesia; 3) determining absence of a motor lesion; and 4) determining the impact of the surgical procedure upon the inflammatory process. Hyperalgesia was evaluated by the von Frey electronic test and the Hargreaves test, and the motor function was evaluated by the rota-rod test. RESULTS: NP induced higher intensity hyperalgesia in the paw when it was in contact with the dorsal root ganglion (GRD) than when it was in contact with the dura mater or the nerve root. Contact with GRD-L5, led NP to induce even higher hyperalgesia than that induced in the contact with L4 and L6 GRDs. No motor lesion and impact of the surgical inflammatory process on hyperalgesia were observed. CONCLUSION: GRD is the structure that is most sensitive to NP components to produce hyperalgesia, the fifth lumbar level being that showed the greatest change in the mechanic and thermal sensitivities evaluated in the paws of the animals, under the methods used

    Estresse e resposta imune primaria em ratos com lesão septal

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    Orientador : Gilberto D'Assunção FernandesDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de BiologiaResumo: O efeito da lesão septal e estresse na resposta imune primária e no eixo hipotálamo-hipófise-adrenal foi investigado em ratos imunizados com hemácias de carneiro. Ratos machos da linhagem Wistar, com idade entre 2 a 3 meses, foram submetidos à aspiração bilateral dos núcleos septais com auxílio de um aparelho estereotáxico. O procedimento de estresse utilizado foi a contenção noturna por 12 horas. Amostras de sangue foram coletadas para a determinação dos níveis séricos de corticosterona e imunoglobulinas, ao longo dos 15 dias que sucederam a imunização. Os resultados mostraram que a lesão septal diminui o aparecimento de imunoglobulinas 2-mercaptoetanol-resistentes (Ig G) na circulação, altera a dinâmica das imunoglobulinas 2-mercaptoetanol-sensíveis (Ig M), nos primeiros dias após a imunização, e induz uma resposta hiperreativa do eixo hipotálamo-hipófise-adrenal, nos animais imunizados, independente do estresse aplicado. ...Observação: O resumo, na íntegra, poderá ser visualizado no texto completo da tese digitalAbstract: The effects of septal lesion and stress on the primary immune response and hypothalamic-pituitary-adrenal axis were investigated in rats immunized with sheep red blood cells. Male Wistar rats were set up on a stereotaxic instrument and their septal nucleus were bilaterally aspirated. The stress procedure used was the restraint for 12 hour during the dark period. Blood samples were collected for determination of corticosterone levels and serum immunoglobulins,during 15 days after immunization. The results had shown that the septal lesion decreases the level of 2-mercaptoethanol-resistant immunoglobulins (Ig G) in the blood stream, modifies the dynamics of 2-mercaptoethanol-sensitive immunoglobulins (Ig M) until the third day after immunization and induces hiperreactivity of hipotalamic-pituitary-adrenal axis associated with the immune response, independently of the applied stress. ...Note: The complete abstract is available with the full electronic digital thesis or dissertationsMestradoFisiologiaMestre em Ciências Biológica

    Peripheral Mechanisms Underlying The Essential Role Of P2x7 Receptors In The Development Of Inflammatory Hyperalgesia.

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    Activation of P2X7 receptors by endogenous ATP contributes to the development of inflammatory hyperalgesia. Given the clinical importance of mechanical hyperalgesia in inflammatory states, we hypothesized that the activation of the P2X7 receptor by endogenous ATP contributes to carrageenan-induced mechanical hyperalgesia, and that this contribution is mediated by an indirect sensitization of the primary afferent nociceptors. Co-administration of the selective P2X7 receptor antagonist, A-438079, or the P2X7 receptor antagonist, oATP, with carrageenan blocked the mechanical hyperalgesia induced by carrageenan and significantly reduced the increased concentration of TNF-alpha, IL-6 and CINC-1, but not of IL-1beta induced by carrageenan in the subcutaneous tissue of the rat's hind paw. We concluded that the activation of P2X7 receptors by endogenous ATP is essential to the development of the mechanical hyperalgesia induced by carrageenan in the subcutaneous tissue. It is suggested that this essential role of P2X7 receptors in the development of carrageenan-induced mechanical hyperalgesia is mediated by an indirect sensitization of the primary afferent nociceptors dependent on the previous release of TNF-alpha, IL-6 and CINC-1, but not of IL-1beta.64455-6

    The Functional Role Of Ascending Nociceptive Control In Defensive Behavior.

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    Ascending nociceptive control is a novel spino-striato-rostral ventral medulla pain modulation pathway that mediates heterosegmental pain-induced analgesia, i.e., noxious stimulus-induced antinociception. In this study, we used the dorsal immobility response in rats as a model of the defensive responses. We demonstrated that the activation of ascending nociceptive control by peripheral noxious stimulation and spinal AMPA and mGluR1 receptor blockade significantly potentiated the duration of the dorsal immobility response in rats via an opioid-dependent mechanism in the nucleus accumbens. These results demonstrated the functional role of ascending nociceptive control in the modulation of defensive responses and spinal glutamatergic receptors in the dorsal immobility response. The immobility response is an antipredator behavior that reflects the underlying state of fear, and ascending nociceptive control may modulate fear.146424-

    Avaliação da hiperalgesia e alterações histológicas do gânglio da raiz dorsal induzidas pelo núcleo pulposo Evaluation of hyperalgesia and histological changes of dorsal root ganglion induced by nucleus pulposus

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    OBJETIVO: Avaliar a hiperalgesia e as alterações histológicas induzidas pelo contato do gânglio da raiz dorsal com o núcleo pulposo. MÉTODOS: Foram utilizados 20 ratos Wistar, divididos em dois grupos experimentais. Em um dos grupos um fragmento do NP autólogo retirado da região sacrococcígea foi colocado sobre os gânglios da raiz dorsal de L5, e no outro grupo (controle) um fragmento de tecido adiposo foi colocado sobre o gânglio da raiz dorsal de L5. A hiperalgesia mecânica e térmica foi avaliada no terceiro dia, na primeira, terceira, quinta e sétima semanas de pós-operatório. O gânglio da raiz dorsal de L5 foi retirado na primeira, terceira, quinta e sétima semanas de pós-operatório para estudo histológico por meio da coloração com HE e estudo histoquímico (marcação específica para iNOS). RESULTADOS: Foi observada hiperalgesia térmica e mecânica de maior intensidade no grupo de animais em que o NP foi colocado em contato com o GRD, e nesse grupo o estudo histológico evidenciou alterações dos tecidos do gânglio da raiz dorsal, caracterizadas por processo inflamatório e degeneração axonal. As alterações histopatológicas dos tecidos do gânglio da raiz dorsal apresentaram intensidade crescente com o aumento do período de observação, apresentando correlação com a manutenção da hiperalgesia observada na avaliação comportamental. A imunohistoquímica com marcação específica para iNOS demonstrou, no grupo de animais em que o núcleo pulposo foi colocado em contato com o gânglio da raiz dorsal, aumento da expressão dessa enzima nos núcleos das células inflamatórias (células da glia) ao redor dos neurônios. CONCLUSÃO: O contato do núcleo pulposo com o gânglio da raiz dorsal de L5 induziu a hiperalgesia mecânica e térmica e provocou alterações histológicas dos componentes do gânglio da raiz dorsal. As alterações foram caracterizadas por processo inflamatório e degenerativo das estruturas do gânglio da raiz dorsal e apresentaram aumento da intensidade nos períodos mais longos de observação.<br>OBJECTIVE: To evaluate hyperalgesia and histological changes of dorsal root ganglia induced by nucleus pulposus (NP) contact. METHODS: Twenty Wistar rats were used, divided into two experimental groups. In one of the groups, a fragment of the autologous NP was removed from the sacroccocigeal region and deposited on the L5 dorsal root ganglia. In the control group, the NP was removed from the sacrococcygeal region, L5 dorsal root ganglia were exposed and covered by a piece of adipous fat tissue. Hyperalgesia was evaluated by the von Frey electronic test and Hargreaves test, and histological changes of the dorsal root ganglia by HE staining and immunohistochemistry using iNOS. The evaluation of hyperalgesia and histological changes of the dorsal root ganglia were performed on the third postoperative day and after 1, 3, 5, and 7 weeks. RESULTS: NP induced higher intensity mechanical and thermal hyperalgesia. Dorsal root ganglia in contact with nucleus pulposus presented histological changes and the intensity of these changes were proportional to the length of time in contact. The expression of iNOS was higher in the glial cells in contact with the nucleus pulposus. CONCLUSION: The contact of nucleus pulposus with dorsal root ganglia induced histological changes and mechanical and thermal hyperalgesia. These changes were more intense after longer period of evaluation

    Tratamento farmacológico da hiperalgesia experimentalmente induzida pelo núcleo pulposo Pharmacologic treatment of hyperalgesia experimentally induced by nucleus pulposus

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    OBJETIVO: Avaliar o efeito de drogas anti-inflamatórias (dexametasona, indometacina, atenolol, indometacina e atenolol) e analgésica (morfina) sobre a hiperalgesia experimentalmente induzida pelo núcleo pulposo em contato com o gânglio da raiz dorsal de L5. MÉTODOS: Trinta ratos Wistar machos com peso de 220 a 250g foram utilizados no estudo. A indução da hiperalgesia foi realizada por meio do contato de fragmento de núcleo pulposo retirado da região sacrococcígea e colocado sobre o gânglio da raiz dorsal de L5. Os 30 animais foram divididos em grupos experimentais de acordo com a droga utilizada. As drogas foram administradas durante duas semanas a partir da realização do procedimento cirúrgico para a indução da hiperalgesia. A hiperalgesia mecânica e térmica foram avaliadas por meio do teste da pressão constante da pata, von Frey eletrônico e Hargraves por um período de sete semanas. RESULTADOS: A maior redução da hiperalgesia foi observada no grupo de animais tratados pela morfina, seguido pela dexametasona, indometacina e atenolol. A redução da hiperalgesia foi observada após a interrupção da administração das drogas, com exceção do grupo de animais tratados com morfina, nos quais ocorreu aumento da hiperalgesia após a interrupção do tratamento. CONCLUSÕES: A hiperalgesia induzida pelo contato do núcleo pulposo com o gânglio da raiz dorsal pode ser reduzida com a administração de anti-inflamatórios e analgésicos, tendo sido observado a maior redução da hiperalgesia com a administração da morfina e dexametasona.<br>OBJECTIVE: To evaluate the effect of antiinflammatory (dexamethasone, indomethacin, atenolol, indomethacin and atenolol) and analgesic drugs (morphine) on hyperalgesia experimentally induced by nucleus pulposus (NP) contact with the L5- dorsal root ganglion (DRG). METHODS: Thirty male Wistar rats with weights ranging from 220 to 250 g were used in the study. The hyperalgesia was induced by contact of a fragment of NP removed from the sacrococcygeal region and placed on the dorsal root ganglion of L5. The 30 animals were divided into experimental groups according to the drug administered. The drugs were administered during the two weeks after the surgical procedure to induce hyperalgesia. Mechanical and thermal hyperalgesia was evaluated by the paw pressure test, von Frey electronic test, and the Hargraves test, for a period of seven weeks. RESULTS: The greatest reduction of hyperalgesia was observed in animals treated by morphine and dexamethasone, followed by dexamethasone, indomethacin, and atenolol. The reduction of hyperalgesia was observed after drug administration ceased, except for animals treated with morphine, in which there was an increased hyperalgesia after cessation of treatment. CONCLUSION: Hyperalgesia induced by NP contact with L5-DRG can be reduced by administration of antiinflammatory and analgesic drugs, but there was a greater reduction observed with the administration of dexamethasone and indometaci

    P2x3 And P2x2/3 Receptors Mediate Mechanical Hyperalgesia Induced By Bradykinin, But Not By Pro-inflammatory Cytokines, Pge₂ Or Dopamine.

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    Activation of peripheral P2X3 and P2X2/3 receptors by endogenous ATP is essential to the development of inflammatory hyperalgesia. We have previously demonstrated that this essential role of P2X3 and P2X2/3 receptors in the development of mechanical hyperalgesia induced by the inflammatory agent carrageenan is mediated by an indirect sensitization of the primary afferent nociceptors dependent on the previous release of tumor necrosis factor alpha (TNF-α) and by a direct sensitization of the primary afferent nociceptors. Therefore, in this study we asked whether activation of P2X3 and P2X2/3 receptors contribute to the mechanical hyperalgesia induced by the inflammatory mediators involved in carrageenan-induced mechanical hyperalgesia, such as bradykinin, tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), interleukin-6 (IL-6), chemokine-induced chemoattractant-1 (CINC-1), prostaglandin E₂ (PGE₂) and dopamine. Co-administration of the non-selective P2X3 receptor antagonist TNP-ATP or the selective P2X3 and P2X2/3 receptor antagonist A-317491 with bradykinin, but not with TNF-α, IL-1β, IL-6, CINC-1, PGE₂ or dopamine, prevented in a dose-dependent manner the mechanical hyperalgesia. We also verified whether the activation of P2X3 and P2X2/3 receptors by endogenous ATP contributes to bradykinin-induced mechanical hyperalgesia via neutrophil migration and/or cytokine release. Co-administration of TNP-ATP or A-317491 did not affect either neutrophil migration or the increased concentration of TNF-α, IL-1β, IL-6 and CINC-1 induced by bradykinin. These findings demonstrate that the activation of P2X3 and P2X2/3 receptors by endogenous ATP mediates bradykinin-induced mechanical hyperalgesia by a mechanism that does not depend on neutrophil migration or cytokines release.649177-8

    Evidence for the involvement of endogenous ATP and P2x receptors in TMJ pain

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    Evidence is accumulating which supports a role for ATP in the initiation of pain by acting on P2X receptors expressed on nociceptive afferent nerve terminals. To investigate whether these receptors play a role in temporomandibular (TMJ) pain, we studied the presence of functional P2X receptors in rat TMJ by examining the nociceptive behavioral response to the application of the selective P2X receptor agonist alpha,beta-methylene ATP (alpha,beta-meATP) into the TMJ region of rat. The involvement of endogenous ATP in the development of TMJ inflammatory hyperalgesia was also determined by evaluating the effect of the general P2 receptor antagonist pyridoxal-phosphate-6-azophenyl-2',4'-disulphonic acid (PPADS) on carrageenan-induced TMJ inflammatory hyperalgesia. Application of alpha,beta-meATP into the TMJ region of rats produced significant nociceptive responses that were significantly reduced by the co-application of lidocaine N-ethyl bromide quaternary salt, QX-314, (2%) or of the P2 receptor antagonist PPADS. Co-application of PPADS with carrageenan into the TMJ significantly reduced inflammatory hyperalgesia. The results indicate that functional P2X receptors are present in the TMJ and suggest that endogenous ATP may play a role in TMJ inflammatory pain mechanisms possibly by acting primarily in these receptors.Evidence is accumulating which supports a role for ATP in the initiation of pain by acting on P2X receptors expressed on nociceptive afferent nerve terminals. To investigate whether these receptors play a role in temporomandibular (TMJ) pain, we studied the presence of functional P2X receptors in rat TMJ by examining the nociceptive behavioral response to the application of the selective P2X receptor agonist α,β‐methylene ATP (α,β‐meATP) into the TMJ region of rat. The involvement of endogenous ATP in the development of TMJ inflammatory hyperalgesia was also determined by evaluating the effect of the general P2 receptor antagonist pyridoxal‐phosphate‐6‐azophenyl‐2′,4′‐disulphonic acid (PPADS) on carrageenan‐induced TMJ inflammatory hyperalgesia. Application of α,β‐meATP into the TMJ region of rats produced significant nociceptive responses that were significantly reduced by the co‐application of lidocaine N‐ethyl bromide quaternary salt, QX‐314, (2%) or of the P2 receptor antagonist PPADS. Co‐application of PPADS with carrageenan into the TMJ significantly reduced inflammatory hyperalgesia. The results indicate that functional P2X receptors are present in the TMJ and suggest that endogenous ATP may play a role in TMJ inflammatory pain mechanisms possibly by acting primarily in these receptors91879

    Local kappa opioid receptor activation decreases temporomandibular joint inflammation

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    In an attempt to decrease central side effects associated with the use of opioids, some strategies have been developed by targeting peripheral opioid receptors. In this context, kappa receptors are of major interest, since, in contrast to other opioid receptors, their activation is not associated with potent peripheral side effects. We have recently demonstrated that local activation of kappa opioid receptors significantly decreases formalin-induced temporomandibular joint nociception; however, whether it also decreases temporomandibular joint inflammation is not known. To address this issue, we evaluated if a specific kappa opioid receptor agonist, U50,488 (trans-(1S,2S)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl] benzeneacetamide hydrochloride hydrate), administered into the temporomandibular joint decreases formalin-induced plasma extravasation and neutrophil migration. Ipsilateral, but not contralateral, administration of U50,488 into the temporomandibular joint blocked formalin-induced plasma extravasation and neutrophil migration in a dose-dependent manner. This anti-inflammatory effect was reversed by the ipsilateral, but not contralateral, administration of the kappa opioid receptor antagonist nor-BNI (nor-binaltorphimine dihydrochloride). This study demonstrates that local activation of kappa opioid receptors decreases two important parameters of temporomandibular joint inflammation, that is, plasma extravasation and neutrophil migration, in a dose-dependent and antagonist-reversible manner. This anti-inflammatory effect taken together with the potent antinociceptive effect, suggests that drugs targeting peripheral kappa opioid receptors are promising for the treatment of inflammatory temporomandibular joint pain and probably, other articular pain conditions with an inflammatory basis.In an attempt to decrease central side effects associated with the use of opioids, some strategies have been developed by targeting peripheral opioid receptors. In this context, kappa receptors are of major interest, since, in contrast to other opioid receptors, their activationis not associated with potent peripheral side effects. We have recently demonstrated that local activation of kappa opioid receptors significantly decreases formalin-induced temporomandibular joint nociception; however, whether it also decreases temporomandibular jointinflammation is not known. To address this issue, we evaluated if a specific kappa opioid receptor agonist, U50,488 (trans-(1S,2S)-3,4-dichloro-N-methyl-N-[2-(1-pyrrolidinyl)cyclohexyl] benzeneacetamide hydrochloride hydrate), administered into the temporomandibular jointdecreases formalin-induced plasma extravasation and neutrophil migration. Ipsilateral, but not contralateral, administration of U50,488 into the temporomandibular joint blocked formalin-induced plasma extravasation and neutrophil migration in a dose-dependent manner. This anti-inflammatory effect was reversed by the ipsilateral, but not contralateral, administration of the kappa opioid receptor antagonist nor-BNI (nor-binaltorphimine dihydrochloride). This study demonstrates that local activation of kappa opioid receptors decreases two important parameters of temporomandibular joint inflammation, that is, plasma extravasation and neutrophil migration, in a dose-dependent and antagonist-reversible manner. This anti-inflammatory effect taken together with the potent antinociceptive effect, suggests that drugs targeting peripheral kappa opioid receptors are promising for the treatment of inflammatory temporomandibular joint pain and probably, other articular pain conditions with an inflammatory basis35137137

    Peripheral sympathetic component of the temporomandibular joint inflammatory pain in rats

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    The aim of this study was to further validate our carrageenan-induced temporomandibular joint (TMJ) inflammatory hyperalgesia model in rats by showing that administration of indomethacin before the initiation of inflammation would diminish the TMJ hyperalgesia. Using this model, we investigated whether norepinephrine and local beta-adrenoceptors contribute to the development of inflammatory TMJ hyperalgesia. Carrageenan-induced TMJ hyperalgesia was assessed by measuring the behavioral nociceptive responses, such as rubbing the orofacial region and flinching the head, induced by the injection of a low dose of 5-hydroxytryptamine into the TMJ sensitized 1 h before by a TMJ injection of carrageenan. Blockade of prostaglandin synthesis by indomethacin prior to initiation of inflammation by carrageenan significantly attenuated the TMJ hyperalgesia. The guanethidine depletion of norepinephrine or the blockade of beta(2)but not the blockade of the beta(1)-adrenoceptor by the selective adrenoceptor antagonists ICI 118.55 and atenolol, respectively, significantly reduced carrageenan-induced TMJ hyperalgesia. In the present study, we further validated our carrageenan-induced TMJ hyperalgesia model to study the mechanisms involved in inflammatory TMJ hyperalgesia and to test the analgesic effect of different types of peripheral analgesics. We also demonstrated that norepinephrine released at the site of injury contributes to the development of the inflammatory TMJ hyperalgesia by the activation of beta(2)-adrenoceptors. The findings that local sympathomimetic amines contribute to the inflammatory TMJ hyperalgesia by activating beta(2)-adrenoceptors may be relevant to clinical TMJ inflammatory pain states less sensitive to nonsteroidal anti-inflammatory drugs.The aim of this study was to further validate our carrageenan-induced temporomandibular joint (TMJ) inflammatory hyperalgesia model in rats by showing that administration of indomethacin before the initiation of inflammation would diminish the TMJ hyperalgesia. Using this model, we investigated whether norepinephrine and local β-adrenoceptorscontribute to the development of inflammatory TMJ hyperalgesia. Carrageenan-induced TMJ hyperalgesia was assessed by measuring the behavioral nociceptive responses, such as rubbing the orofacial region and flinching the head, induced by the injection of a low dose of 5-hydroxytryptamine into the TMJ sensitized 1 h before by a TMJ injection of carrageenan. Blockade of prostaglandin synthesis by indomethacin prior to initiation of inflammation by carrageenan significantly attenuated the TMJ hyperalgesia. The guanethidine depletion of norepinephrine or the blockade of β2but not the blockade of the β1-adrenoceptor by the selective adrenoceptor antagonists ICI 118.55 and atenolol, respectively, significantly reduced carrageenan-induced TMJ hyperalgesia. In the present study, we further validated our carrageenan-induced TMJ hyperalgesia model to study the mechanisms involved in inflammatory TMJ hyperalgesia and to test the analgesic effect of different types of peripheral analgesics. We also demonstrated that norepinephrine released at the site of injury contributes to the development of the inflammatory TMJ hyperalgesia by the activation of β2-adrenoceptors71292993
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