RESUMO
Opioid analgesics remain the mainstay for managing intractable chronic pain, but their use is limited by detrimental side effects such as analgesic tolerance and hyperalgesia. Calcium-dependent synaptic plasticity is a key determinant in opiates tolerance and hyperalgesia. However, the exact substrates for this calcium-dependent synaptic plasticity in mediating these maladaptive processes are largely unknown. Canonical transient receptor potential 1, 4, and 5 (TRPC1, 4, 5) proteins assemble into heteromultimeric nonselective cation channels with high Ca2+ permeability and influence various neuronal functions. However, whether and how TRPC1/4/5 channels contribute to the development of opiates tolerance and hyperalgesia remains elusive. Here, we show that TRPC1/4/5 channels contribute to the generation of morphine tolerance and hyperalgesia. Chronic morphine exposure leads to upregulation of TRPC1/4/5 channels in the spinal cord. Spinally expressed TRPC1, TPRC4, and TRPC5 are required for chronic morphine-induced synaptic long-term potentiation (LTP) as well as remodeling of synaptic spines in the dorsal horn, thereby orchestrating functional and structural plasticity during the course of morphine-induced hyperalgesia and tolerance. These effects are attributed to TRPC1/4/5-mediated Ca2+ elevation in the spinal dorsal horn induced by chronic morphine treatment. This study identifies TRPC1/4/5 channels as a promising novel target to prevent the unwanted morphine tolerance and hyperalgesia.
Assuntos
Hiperalgesia/induzido quimicamente , Hiperalgesia/metabolismo , Morfina/farmacologia , Plasticidade Neuronal/fisiologia , Medula Espinal/metabolismo , Canais de Cátion TRPC/metabolismo , Analgésicos/farmacologia , Analgésicos Opioides/farmacologia , Animais , Tolerância a Medicamentos/fisiologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Plasticidade Neuronal/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Medula Espinal/efeitos dos fármacos , Corno Dorsal da Medula Espinal/efeitos dos fármacos , Corno Dorsal da Medula Espinal/metabolismoRESUMO
Cervical radiculopathic pain is a very common symptom that may occur with cervical spondylosis. Mechanical allodynia is often associated with cervical radiculopathic pain and is inadequately treated with current therapies. However, the precise mechanisms underlying cervical radiculopathic pain-associated mechanical allodynia have remained elusive. Compelling evidence from animal models suggests a role of large-diameter dorsal root ganglion neurons and plasticity of spinal circuitry attached with Aß fibers in mediating neuropathic pain. Whether cervical radiculopathic pain condition induces plastic changes of large-diameter dorsal root ganglion neurons and what mechanisms underlie these changes are yet to be known. With combination of patch-clamp recording, immunohistochemical staining, as well as behavioral surveys, we demonstrated that upon chronic compression of C7/8 dorsal root ganglions, large-diameter cervical dorsal root ganglion neurons exhibited frequent spontaneous firing together with hyperexcitability. Quantitative analysis of hyperpolarization-activated cation current ( Ih) revealed that Ih was greatly upregulated in large dorsal root ganglion neurons from cervical radiculopathic pain rats. This increased Ih was supported by the enhanced expression of hyperpolarization-activated, cyclic nucleotide-modulated channels subunit 3 in large dorsal root ganglion neurons. Blockade of Ih with selective antagonist, ZD7288 was able to eliminate the mechanical allodynia associated with cervical radiculopathic pain. This study sheds new light on the functional plasticity of a specific subset of large-diameter dorsal root ganglion neurons and reveals a novel mechanism that could underlie the mechanical allodynia associated with cervical radiculopathy.
Assuntos
Gânglios Espinais/citologia , Gânglios Espinais/metabolismo , Neuralgia/etiologia , Neuralgia/metabolismo , Neurônios/citologia , Neurônios/metabolismo , Radiculopatia/etiologia , Radiculopatia/metabolismo , Animais , Dor Crônica/etiologia , Dor Crônica/metabolismo , Dor Crônica/patologia , Masculino , Potenciais da Membrana/fisiologia , Neuralgia/patologia , Neurônios Aferentes/citologia , Neurônios Aferentes/metabolismo , Radiculopatia/patologia , Ratos , Ratos Sprague-DawleyRESUMO
Postsynaptic NMDARs at spinal synapses are required for postsynaptic long-term potentiation and chronic pain. However, how presynaptic NMDARs (PreNMDARs) in spinal nociceptor terminals control presynaptic plasticity and pain hypersensitivity has remained unclear. Here we report that PreNMDARs in spinal nociceptor terminals modulate synaptic transmission in a nociceptive tone-dependent manner. PreNMDARs depresses presynaptic transmission in basal state, while paradoxically causing presynaptic potentiation upon injury. This state-dependent modulation is dependent on Ca2+ influx via PreNMDARs. Small conductance Ca2+-activated K+ (SK) channels are responsible for PreNMDARs-mediated synaptic depression. Rather, tissue inflammation induces PreNMDARs-PKG-I-dependent BDNF secretion from spinal nociceptor terminals, leading to SK channels downregulation, which in turn converts presynaptic depression to potentiation. Our findings shed light on the state-dependent characteristics of PreNMDARs in spinal nociceptor terminals on modulating nociceptive transmission and revealed a mechanism underlying state-dependent transition. Moreover, we identify PreNMDARs in spinal nociceptor terminals as key constituents of activity-dependent pain sensitization.
Assuntos
Dor Crônica/fisiopatologia , Nociceptores/metabolismo , Terminações Pré-Sinápticas/metabolismo , Receptores de N-Metil-D-Aspartato/metabolismo , Animais , Fator Neurotrófico Derivado do Encéfalo/genética , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Cálcio/metabolismo , Dor Crônica/genética , Dor Crônica/metabolismo , Proteína Quinase Dependente de GMP Cíclico Tipo I/genética , Proteína Quinase Dependente de GMP Cíclico Tipo I/metabolismo , Gânglios Espinais/citologia , Gânglios Espinais/fisiologia , Inflamação , Potenciação de Longa Duração , Depressão Sináptica de Longo Prazo , Camundongos , Camundongos Transgênicos , Substância Cinzenta Periaquedutal/citologia , Substância Cinzenta Periaquedutal/fisiologia , Canais de Potássio Cálcio-Ativados/genética , Canais de Potássio Cálcio-Ativados/metabolismo , Receptores de N-Metil-D-Aspartato/genética , Transmissão SinápticaRESUMO
The role of capsaicin-sensitive primary afferent fibers in rat pain-related behaviors and paw edema induced by scorpion Buthus martensi Karch (BmK) venom was investigated in this study. It was found that functional depletion of capsaicin-sensitive primary afferent fibers with a single systemic injection of resiniferatoxin (RTX) dramatically decreased spontaneous nociceptive behaviors, prevented the development of primary mechanical and thermal hyperalgesia as well as mirror-image mechanical hyperalgesia. RTX treatment significantly attenuated BmK venom-induced c-Fos expression in all laminaes of bilateral L4-L5 lumbar spinal cord, especially in superficial laminaes. Moreover, RTX treatment markedly reduced the early paw edema induced by BmK venom. Thus, the results indicate that capsaicin-sensitive primary afferent fibers play a critical role in various pain-related behaviors and paw edema induced by BmK venom in rats.
Assuntos
Capsaicina/metabolismo , Edema/fisiopatologia , Neurônios Aferentes/fisiologia , Nociceptores/fisiologia , Dor/fisiopatologia , Venenos de Escorpião/efeitos adversos , Animais , Diterpenos/farmacologia , Membro Posterior , Hiperalgesia/fisiopatologia , Imuno-Histoquímica , Neurônios Aferentes/efeitos dos fármacos , Limiar da Dor , Proteínas Proto-Oncogênicas c-fos/biossíntese , Ratos , Ratos Sprague-Dawley , Medula Espinal/metabolismoRESUMO
AIM OF THE STUDY: Asian scorpion Buthus martensi Karsch (BmK) is widely used to treat neurological symptoms, especially chronic pain, in traditional Chinese medicine for thousands of years. BmK AS, a polypeptide from BmK venom, could produce peripheral potent anti-nociceptive effects in rats. In the present study, spinal anti-nociceptive effects of BmK AS were investigated in rat formalin test. MATERIALS AND METHODS: Spinal anti-nociceptive activity of BmK AS was studied using formalin test in rats. BmK AS in doses of 0.02, 0.1 and 0.5 microg was administered intrathecally before formalin injection 10 min. The suppression by intrathecal injection of BmK AS on formalin-induced spontaneous nociceptive behaviors and spinal c-Fos expression were investigated. RESULTS: Intrathecal injection of BmK AS markedly reduced formalin-evoked biphasic spontaneous nociceptive behaviors in a dose-dependent manner. Formalin-induced c-Fos expression could be dose-dependently inhibited by BmK AS in superficial (I-II), the nucleus proprius (III and IV) and deep (V-VI) dorsal horn laminae, but not in the ventral gray laminae (VII-X) of lumbar spinal cord. The suppression by BmK AS on c-Fos expression in superficial laminaes was much stronger than that in deep laminaes. CONCLUSION: The present study demonstrates that BmK AS is capable of producing remarkable anti-nociceptive effects not only in periphery but also in spinal cord.
Assuntos
Analgésicos/farmacologia , Medição da Dor/efeitos dos fármacos , Peptídeos/farmacologia , Venenos de Escorpião/química , Animais , Relação Dose-Resposta a Droga , Formaldeído , Expressão Gênica/efeitos dos fármacos , Genes fos/efeitos dos fármacos , Imuno-Histoquímica , Injeções Espinhais , Masculino , Peptídeos/administração & dosagem , Peptídeos/química , Ratos , Ratos Sprague-Dawley , Venenos de Escorpião/administração & dosagem , Venenos de Escorpião/farmacologiaRESUMO
In the present study, it was investigated whether the degranulation of mast cells and histamine release were involved in rat pain-related behaviors and edema induced by the venom of scorpion Buthus martensi Karch (BmK) or not. It was found that the obvious degranulation of mast cells could be triggered in rat hindpaw skin by BmK venom. The chronic degranulation of mast cells using compound 48/80 relieved the spontaneous nociceptive responses, the primary thermal and bilateral mechanical hyperalgesia and the rat paw edema, as well as partially reduced c-Fos expression in superficial layers (laminae I-II) of bilateral spinal cord induced by BmK venom. In addition, individual peripheral co-administration of either 100 nmol chlorpheniramine or 100 nmol pyrilamine (histamine H(1) receptor antagonist) or 500 nmol cimetidine (histamine H(2) receptor antagonist) and BmK venom suppressed the spontaneous nociceptive responses, partially the primary thermal and bilateral mechanical hyperalgesia and rat paw edema induced by BmK venom. Thus, these results suggest that the peripheral cellular incidents of mast cells degranulation and histamine release are involved in BmK venom-induced pain-related behaviors and inflammation.
Assuntos
Edema , Antagonistas dos Receptores Histamínicos/farmacologia , Liberação de Histamina/efeitos dos fármacos , Mastócitos/efeitos dos fármacos , Dor , Venenos de Escorpião , Escorpiões/química , Animais , Clorfeniramina/farmacologia , Cimetidina/farmacologia , Relação Dose-Resposta a Droga , Edema/induzido quimicamente , Edema/patologia , Liberação de Histamina/fisiologia , Hiperalgesia/induzido quimicamente , Hiperalgesia/patologia , Inflamação/induzido quimicamente , Inflamação/patologia , Mastócitos/metabolismo , Mastócitos/patologia , Dor/induzido quimicamente , Dor/patologia , Proteínas Proto-Oncogênicas c-fos/genética , Proteínas Proto-Oncogênicas c-fos/metabolismo , Pirilamina/farmacologia , Ratos , Ratos Sprague-Dawley , Medula Espinal/metabolismo , Fatores de TempoRESUMO
The central anti-nociception of BmK IT2, a sodium channel modulator from scorpion Buthus martensi Karsh (BmK) was investigated in this study. It was found that the formalin-induced rat spontaneous flinches and spinal c-Fos expression could be significantly suppressed by intrathecal BmK IT2 pre- or post-formalin injection in a dose-dependent manner. The time course of inhibitory effect exerted by intrathecal BmK IT2 on spontaneous flinches was longer in the pre-treatment group than in post-treatment group. This was consistent with the stronger suppression on spinal c-Fos expression exerted by intrathecal BmK IT2 pre-treatment. In addition, the suppression by intrathecal BmK IT2 on formalin-induced c-Fos expression in superficial laminae was more significant than that in deeper laminae. These results indicate that BmK IT2 can induce central anti-nociceptive response and might thus be a valuable molecular tool for the understanding of pain mechanisms.
Assuntos
Comportamento Animal/efeitos dos fármacos , Medição da Dor , Dor/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Venenos de Escorpião , Medula Espinal/metabolismo , Animais , Relação Dose-Resposta a Droga , Injeções Espinhais , Masculino , Distribuição Aleatória , Ratos , Ratos Sprague-Dawley , Venenos de Escorpião/administração & dosagem , Venenos de Escorpião/farmacologia , Canais de Sódio/metabolismo , Medula Espinal/citologia , Toxinas Biológicas/administração & dosagem , Toxinas Biológicas/farmacologiaRESUMO
The present study investigated the involvement of spinal glutamate receptors in the induction and maintenance of the pain-related behaviors induced by the venom of scorpion Buthus martensi Karsch (BmK). (5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5-10-imine hydrogen maleate (MK-801; 40nmol; a non-competitive NMDA receptor antagonist), 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 40nmol; a non-NMDA receptor antagonist), dl-amino-3-phosphonopropionic acid (dl-AP3; 100nmol; a group I metabotropic glutamate receptor antagonist) and 4-aminopyrrolidine-2,4-dicarboxylate (APDC; 100nmol; a group II metabotropic glutamate receptor agonist) were employed. On intrathecal injection of glutamate receptor antagonists/agonist before BmK venom administration by 10min, BmK venom-induced spontaneous nociceptive responses could be suppressed by all tested agents. Primary thermal hyperalgesia could be inhibited by MK-801 and dl-AP3, while bilateral mechanical hyperalgesia could be inhibited by CNQX and dl-AP3 and contralateral mechanical hyperalgesia could be inhibited by APDC. On intrathecal injection of glutamate receptor antagonists/agonist after BmK venom injection by 4.5h, primary thermal hyperalgesia could be partially reversed by all tested agents, while bilateral mechanical hyperalgesia could only be inhibited by APDC. The results suggest that the role of spinal glutamate receptors may be different on the various manifestations of BmK venom-induced pain-related behaviors.
Assuntos
Antagonistas de Aminoácidos Excitatórios/administração & dosagem , Dor/tratamento farmacológico , Receptores de Glutamato/fisiologia , Venenos de Escorpião/toxicidade , 6-Ciano-7-nitroquinoxalina-2,3-diona/administração & dosagem , Alanina/administração & dosagem , Alanina/análogos & derivados , Animais , Maleato de Dizocilpina/administração & dosagem , Injeções Espinhais , Masculino , Prolina/administração & dosagem , Prolina/análogos & derivados , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/fisiologiaRESUMO
In the present study, BmK alphaIV, a novel modulator of sodium channels, was cloned from venomous glands of the Chinese scorpion (Buthus martensi Karsch) and expressed successfully in Escherichia coli. The BmK alphaIV gene is composed of two exons separated by a 503 bp intron. The mature polypeptide contains 66 amino acids. BmK alphaIV has potent toxicity in mice and cockroaches. Surface-plasmon-resonance analysis found that BmK alphaIV could bind to both rat cerebrocortical synaptosomes and cockroach neuronal membranes, and shared similar binding sites on sodium channels with classical AaH II (alpha-mammal neurotoxin from the scorpion Androctonus australis Hector), BmK AS (beta-like neurotoxin), BmK IT2 (the depressant insect-selective neurotoxin) and BmK abT (transitional neurotoxin), but not with BmK I (alpha-like neurotoxin). Two-electrode voltage clamp recordings on rNav1.2 channels expressed in Xenopus laevis oocytes revealed that BmK alphaIV increased the peak amplitude and prolonged the inactivation phase of Na+ currents. The structural and pharmacological properties compared with those of other scorpion alpha-toxins suggests that BmK alphaIV represents a novel subgroup or functional hybrid of alpha-toxins and might be an evolutionary intermediate neurotoxin for alpha-toxins.
Assuntos
Neurotoxinas/farmacologia , Venenos de Escorpião/metabolismo , Bloqueadores dos Canais de Sódio/farmacologia , Sequência de Aminoácidos , Animais , Sequência de Bases , Membrana Celular/efeitos dos fármacos , Dicroísmo Circular , Clonagem Molecular , Baratas/citologia , Baratas/efeitos dos fármacos , Evolução Molecular , Feminino , Genes , Vetores Genéticos/genética , Transporte de Íons/efeitos dos fármacos , Dose Letal Mediana , Masculino , Camundongos , Dados de Sequência Molecular , Canal de Sódio Disparado por Voltagem NAV1.2 , Proteínas do Tecido Nervoso/efeitos dos fármacos , Neurônios/efeitos dos fármacos , Neurotoxinas/química , Neurotoxinas/classificação , Neurotoxinas/genética , Neurotoxinas/toxicidade , Oócitos , Ratos , Ratos Sprague-Dawley , Proteínas Recombinantes de Fusão/biossíntese , Proteínas Recombinantes de Fusão/isolamento & purificação , Proteínas Recombinantes de Fusão/farmacologia , Venenos de Escorpião/química , Venenos de Escorpião/classificação , Venenos de Escorpião/genética , Venenos de Escorpião/farmacologia , Escorpiões/química , Escorpiões/genética , Convulsões/induzido quimicamente , Alinhamento de Sequência , Sódio/metabolismo , Bloqueadores dos Canais de Sódio/toxicidade , Canais de Sódio/efeitos dos fármacos , Espasmo/induzido quimicamente , Espectrometria de Massas por Ionização e Dessorção a Laser Assistida por Matriz , Sinaptossomos/efeitos dos fármacos , Xenopus laevisRESUMO
In the present study, we investigated the anti-nociceptive effect and the underlying mechanism of BmK AS, an active peptide purified from scorpion Buthus martensi Karsch. The results showed that BmK AS can significantly relieve formalin-induced two-phase spontaneous flinching response and carrageenan-induced mechanical hyperalgesia. Using the whole-cell patch-clamp recording, exposure of acutely isolated sensory neurons to 500 nM BmK AS produced a one-fold decrease in the number of action potentials (APs) evoked by a ramp of depolarizing current. To investigate the mechanism of action of BmK AS, isolated membrane current and Ca2+ influx on rat primary sensory neurons were examined. BmK AS produced insignificant effect on voltage-dependent I(K) and KCl or caffeine-induced Ca2+ influx, but caused remarkable suppressive effect on tetrodotoxin-resistant (TTX-R) and tetrodotoxin-sensitive (TTX-S) I(Na). Further experiments showed that BmK AS reduced the peak TTX-R and TTX-S Na+ conductance in a dose-dependent manner, prompted the voltage-dependent activation, and caused a negative shift of the steady-state inactivation of TTX-R and TTX-S I(Na). Thus, the present results indicate the anti-nociceptive response of BmK AS may be ascribed to its specific modulation of voltage-gated Na+ channels of sensory neurons.
Assuntos
Analgésicos/farmacologia , Ativação do Canal Iônico/efeitos dos fármacos , Neurônios Aferentes/efeitos dos fármacos , Peptídeos/farmacologia , Venenos de Escorpião/farmacologia , Bloqueadores dos Canais de Sódio/farmacologia , Potenciais de Ação/efeitos dos fármacos , Animais , Formaldeído/metabolismo , Formaldeído/farmacologia , Masculino , Neurônios Aferentes/citologia , Neurônios Aferentes/fisiologia , Medição da Dor , Ratos , Ratos Sprague-Dawley , Canal de Liberação de Cálcio do Receptor de Rianodina/efeitos dos fármacos , Canal de Liberação de Cálcio do Receptor de Rianodina/metabolismo , Escorpiões , Canais de Sódio/metabolismo , Tetrodotoxina/metabolismo , Fatores de TempoRESUMO
The developmental and pharmacological characteristics of pain responses induced by the experimental scorpion BmK (Buthus martensi Karsch) sting were detailed in this study. Following the unilateral intraplantar injection of BmK venom into rat hind paw, it was found: 1) BmK venom induced an edematogenic response, spontaneous pain and pain hypersensitivity in a dose-dependent manner; 2) the paw edema and flare were induced rapidly and restricted at the injected paw for about 24-48 h; 3) the monophasic tonic spontaneous pain manifested as continuous paw flinching and lifting/licking of the injected paw and lasted for more than 2 h; 4) the detectable thermal hypersensitivity to radiant heat stimuli was just at the injected side for about 72-96 h; 5) the mechanical hypersensitivity to von Frey filaments was evoked surprisingly to be the bilateral and mirror-like for about 2-3 weeks; 6) morphine, indomethacin and bupivacaine could suppress BmK venom-induced pain responses with different intensity and time courses. The results indicated that the experimental BmK sting could evoke the prolonged paw inflammation, tonic spontaneous behaviors, unilateral thermal and bilateral mechanical hypersensitivity. The distinct time development of pain responses induced by experimental BmK sting might be involved in different nervous and/or tissue mechanisms. The experimental BmK sting test thus may be an available tissue injury-induced tonic inflammatory pain model for understanding the mechanisms underlying clinical spontaneous pain, thermal and mirror-imaged bilateral mechanical pain hypersensitivity.
Assuntos
Medição da Dor , Dor/fisiopatologia , Venenos de Escorpião/toxicidade , Escorpiões/química , Analgésicos Opioides/farmacologia , Anestésicos Locais/farmacologia , Animais , Anti-Inflamatórios não Esteroides/farmacologia , Bupivacaína/farmacologia , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Edema/induzido quimicamente , Edema/patologia , Edema/prevenção & controle , Hiperalgesia/induzido quimicamente , Hiperalgesia/fisiopatologia , Hiperalgesia/prevenção & controle , Indometacina/farmacologia , Morfina/farmacologia , Dor/induzido quimicamente , Dor/prevenção & controle , Medição da Dor/métodos , Limiar da Dor/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Pele/efeitos dos fármacos , Pele/patologia , Fatores de TempoRESUMO
The aim of this study was to assess the cell-type and distribution of highly activated neurons in rat spinal cord underlying nociceptive responses induced by scorpion BmK venom using Fos immunohistochemistry. BmK venom was intraplantarly injected into one hind paw of a conscious rat. Fos-like immunoreactive neurons were found to predominantly distribute at L4-5 segments in the rat spinal cord after BmK venom application. c-Fos labeling was most dense in the medial half portion of laminae I-II, moderately dense in laminae V-VI and less dense in laminae III-IV, VII-X. c-Fos labeling could be detected at 0.5 h, reached the peak at 2 h, decreased steeply from 4 h and then almost disappeared at 24 h. Ten to fifty micrograms of BmK venom was deemed to be a sufficient dosage to evoke c-Fos expression. On the other hand, c-Fos expression induced by BmK venom could be suppressed partially by systemic morphine in a dose-dependent manner. The results suggest that the different extent of activities of neuronal subpopulation in the spinal cord involved in nociceptive transmission manifesting as c-Fos expression, were mainly correlated with mechanisms underlying the generation, maintenance and/or modulation of spontaneous pain and hyperalgesia evoked by BmK venom.
Assuntos
Vias Aferentes/efeitos dos fármacos , Nociceptores/efeitos dos fármacos , Dor/induzido quimicamente , Células do Corno Posterior/efeitos dos fármacos , Venenos de Escorpião/antagonistas & inibidores , Vias Aferentes/fisiologia , Analgésicos Opioides/farmacologia , Animais , Relação Dose-Resposta a Droga , Imuno-Histoquímica , Injeções Subcutâneas , Vértebras Lombares , Masculino , Morfina/farmacologia , Nociceptores/fisiologia , Dor/metabolismo , Dor/fisiopatologia , Células do Corno Posterior/metabolismo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Sprague-Dawley , Pele/efeitos dos fármacos , Pele/inervação , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/fisiologiaRESUMO
In the present communication, we determined the dynamic release of amino acid transmitters from spinal dorsal horn induced by scorpion Buthus martensi Karsch (BmK) venom and a neurotoxin (BmK I). The results found that glutamate and aspartate release could be evoked significantly within the initial 30 min with the applied doses of either 0.05 and 0.01 mg BmK venom or 0.01 and 0.002 mg BmK I. However, gamma-aminobutyric acid (GABA) release could be largely evoked during the second 30 min by the venom, but not by BmK I. The result suggested that nociceptive afferent fibers could be activated to induce excitatory amino acid release from spinal dorsal horn by nociceptive factors such as BmK I, but the delayed release of GABA might be attributed to the modulating role of some antinociceptive components in the venom.
Assuntos
Neurotransmissores/metabolismo , Nociceptores/efeitos dos fármacos , Nociceptores/metabolismo , Células do Corno Posterior/metabolismo , Venenos de Escorpião/farmacologia , Animais , Ácido Aspártico/metabolismo , Ácido Glutâmico/metabolismo , Masculino , Microdiálise , Dor/induzido quimicamente , Dor/metabolismo , Ratos , Ratos Sprague-Dawley , Ácido gama-Aminobutírico/metabolismoRESUMO
The integrated mechanisms of dynamic signaling of sodium channels involved in clinical pain are still not yet clear. In this study, a new rat inflammatory pain model was developed by using the unilateral intraplantar injection of BmK I, a receptor site 3-specific modulator of sodium channels from the venom of scorpion Buthus martensi Karsch (BmK). It was found that BmK I could induce several kinds of inflammatory pain-related behaviors including spontaneous pain companied with unique episodic paroxysms, primary thermal hypersensitivity, and mirror-image mechanical hypersensitivity with different time course of development, which could be suppressed by morphine, indomethacin, or bupivacaine to a different extent. The dramatic attenuation by pretreatment with resiniferatoxin (RTX), an ultrapotent analog of capsaicin, on BmK I-induced pain-related behaviors, paw edema, and spinal L4-L5 c-Fos expression demonstrated that capsaicin-sensitive primary afferent neurons played important roles in pain induced by BmK I. Furthermore, the electrophysiological recordings showed that BmK I persistently increased whole-cell and tetrodotoxin-resistant (TTX-R) peak sodium currents and significantly delayed the inactivation phase of whole-cell sodium currents but could not enhance capsaicin-evoked inward currents, in acute isolated small dorsal root ganglion neurons of rat. The results strongly suggested that the dynamic modulation of BmK I on sodium channels located in peripheral primary afferent neurons, especially in capsaicin-sensitive neurons, mediated pain sensation. Thus, BmK I may be a valuable pharmacological tool to understand the sodium channel-involved pain mechanisms.
Assuntos
Comportamento Animal/fisiologia , Inflamação/psicologia , Dor/psicologia , Venenos de Escorpião/farmacologia , Bloqueadores dos Canais de Sódio/farmacologia , Analgésicos Opioides/farmacologia , Anestésicos Locais/farmacologia , Animais , Anti-Inflamatórios não Esteroides/farmacologia , Bupivacaína/farmacologia , Capsaicina/farmacologia , Gânglios Espinais/citologia , Gânglios Espinais/efeitos dos fármacos , Indometacina/farmacologia , Inflamação/complicações , Masculino , Morfina/farmacologia , Neurônios/efeitos dos fármacos , Dor/etiologia , Medição da Dor/efeitos dos fármacos , Técnicas de Patch-Clamp , Fenótipo , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
The present study investigated whether spinal astrocyte and microglia were activated in Buthus martensi Karch (BmK) venom-induced rat pain-related behaviors. The results showed that glial fibrillary acidic protein (GFAP) immunoreactivity indicative astrocyte activation in bilateral spinal cord started to increase by day 3, peaked at day 7 and gradually reversed at day 14 following intraplantar injection of BmK venom. Western blotting analysis confirmed GFAP expression was up-regulated by BmK venom. In contrast, bilateral spinal increase of OX-42 immunoreactivity indicative of microglial activation began at 4h peaked at day 1 and gradually reversed by days 3 to 7 after the administration of BmK venom. Pretreatment with either intrathecal injection of fluorocitrate or intraperitonial injection of minocycline, and two glial activation inhibitors, suppressed the spontaneous nociceptive responses, and prevented the primary thermal and bilateral mechanical hyperalgesia induced by BmK venom. The post-treatment with fluorocitrate or minocycline could not affect the mechanical hyperalgesia. Moreover, minocycline partially inhibited BmK venom-induced spinal c-Fos expression but lack of effects on BmK venom-induced paw edema. Taken together, the current study demonstrated that spinal astrocyte and microglial activation may contribute to BmK venom-induced rat pain-related behaviors. Thus, spinal glia may represent novel targets for effective treatment of pain syndrome associated with scorpion envenomation.
Assuntos
Astrócitos/fisiologia , Microglia/fisiologia , Nociceptores/efeitos dos fármacos , Dor/fisiopatologia , Venenos de Escorpião/toxicidade , Medula Espinal/citologia , Analgésicos não Narcóticos/administração & dosagem , Analgésicos não Narcóticos/metabolismo , Analgésicos não Narcóticos/uso terapêutico , Animais , Astrócitos/efeitos dos fármacos , Astrócitos/metabolismo , Comportamento Animal/efeitos dos fármacos , Biomarcadores/metabolismo , Citratos/administração & dosagem , Citratos/uso terapêutico , Esquema de Medicação , Edema/induzido quimicamente , Proteína Glial Fibrilar Ácida/metabolismo , Hiperalgesia/induzido quimicamente , Hiperalgesia/tratamento farmacológico , Antígeno de Macrófago 1/metabolismo , Masculino , Microglia/efeitos dos fármacos , Microglia/metabolismo , Minociclina/administração & dosagem , Minociclina/metabolismo , Minociclina/uso terapêutico , Especificidade de Órgãos , Dor/induzido quimicamente , Dor/tratamento farmacológico , Medição da Dor , Proteínas Proto-Oncogênicas c-fos/metabolismo , Ratos , Ratos Sprague-Dawley , Picadas de Escorpião/tratamento farmacológico , Venenos de Escorpião/administração & dosagem , Escorpiões , Medula Espinal/metabolismo , Medula Espinal/patologia , Fatores de TempoRESUMO
In the present study, using the single fiber recording technique, we found that BmK I, the main toxic component in scorpion Buthus martensi Karsch (BmK) venom, induced dramatic increase in excitability of rapidly adapting (RA) and type I slowly adapting (SAI) low threshold mechanical A fibers of rat. Five micrograms BmK I (691 nmol, in 10 microl saline) administrated to the receptive fields induced spontaneous activity in 80% of RA and SAI fibers, increased the response to 10 g-10 s stimulation at about 20 times and altered the firing pattern to burst mode with maximal NS (number of spikes in burst) averaging from all fibers studied as many as 59. The increase in the excitability of RA and SAI fibers did not recover completely in 2h. Our finding suggests that the gigantic abnormal activity in low threshold mechanical A fibers is involved in BmK scorpion sting pain, and the experimental model of BmK scorpion sting pain can be used to study A-fiber related central pathway which is important for relief of refractory neuropathic pain likewise.
Assuntos
Potenciais de Ação/efeitos dos fármacos , Fibras Nervosas Mielinizadas/efeitos dos fármacos , Venenos de Escorpião/farmacologia , Animais , Eletrofisiologia , Masculino , Condução Nervosa/efeitos dos fármacos , Ratos , Ratos Sprague-Dawley , Processamento de Sinais Assistido por Computador , Fatores de TempoRESUMO
This study showed that rat unilateral intracerebroventricular injection of BmK alphaIV, a sodium channel modulator derived from scorpion Buthus martensi Karsch, induced clusters of spikes, epileptic discharges and convulsion-related behavioral changes. BmK alphaIV potently promoted the release of endogenous glutamate from rat cerebrocortical synaptosomes. In vitro examination of the effect of BmK alphaIV on intrasynaptosomal free calcium concentration [Ca(2+)](i) and sodium concentration [Na(+)](i) revealed that BmK alphaIV-evoked glutamate release from synaptosomes was associated with an increase in Ca(2+) and Na(+) influx. Moreover, BmK alphaIV-mediated glutamate release and ion influx was completely blocked by tetrodotoxin, a blocker of sodium channel. Together, these results suggest that the induction of BmK alphaIV-evoked epileptic seizures may be involved in the modulation of BmK alphaIV on tetrodotoxin-sensitive sodium channels located on the nerve terminal, which subsequently enhances the Ca(2+) influx to cause an increase of glutamate release. These findings may provide some insight regarding the mechanism of neuronal action of BmK alphaIV in the central nervous system for understanding epileptogenesis involved in sodium channels.
Assuntos
Epilepsia/fisiopatologia , Venenos de Escorpião/toxicidade , Canais de Sódio/fisiologia , Animais , Cálcio/química , Cálcio/metabolismo , Córtex Cerebral/efeitos dos fármacos , Córtex Cerebral/metabolismo , Relação Dose-Resposta a Droga , Eletroencefalografia/efeitos dos fármacos , Eletrofisiologia , Epilepsia/induzido quimicamente , Fluorometria/métodos , Ácido Glutâmico/metabolismo , Injeções Intraventriculares , Masculino , Cloreto de Potássio/toxicidade , Ratos , Ratos Sprague-Dawley , Venenos de Escorpião/administração & dosagem , Sódio/química , Sódio/metabolismo , Bloqueadores dos Canais de Sódio/toxicidade , Sinaptossomos/efeitos dos fármacos , Sinaptossomos/metabolismo , Tetrodotoxina/toxicidade , Fatores de TempoRESUMO
The binding of BmK IT2 to insect and mammal sodium channels was investigated by surface plasmon resonance technique. The results showed that BmK IT2 could bind not only to cockroach neuronal membranes but also to rat cerebrocortical and hippocampal synaptosomes with distinct affinity. The binding of BmK IT2 could be competed significantly by BmK AS and BmK abT, but not by AaH II, BmK I and veratridine. Furthermore, BmK alphaIV could partially inhibit the binding of BmK IT2 to rat cerebrocortical synaptosomes and cockroach neuronal membranes, but not to rat hippocampal synaptosomes. These results suggested that BmK IT2 had diverse binding properties on the mammal and insect sodium channels.
Assuntos
Baratas/metabolismo , Peptídeos/metabolismo , Venenos de Escorpião/metabolismo , Canais de Sódio/metabolismo , Ressonância de Plasmônio de Superfície , Animais , Ligação Competitiva/efeitos dos fármacos , Membrana Celular/efeitos dos fármacos , Membrana Celular/metabolismo , Membrana Celular/fisiologia , Córtex Cerebral/citologia , Hipocampo/citologia , Cinética , Masculino , Neurônios/citologia , Peptídeos/química , Peptídeos/farmacologia , Ratos , Ratos Sprague-Dawley , Venenos de Escorpião/farmacologia , Canais de Sódio/efeitos dos fármacos , Canais de Sódio/fisiologia , Sinaptossomos/efeitos dos fármacos , Sinaptossomos/metabolismoRESUMO
In the present study, the susceptibility to rat epileptic seizures induced by the intrahippocampal administration of BmK I, a modulator of sodium channels purified from the venom of Chinese scorpion, has been investigated. The results showed that the strong epileptic behaviors and discharges in the hippocampus were evoked by BmK I dose-dependently. The hippocampal c-Fos expression displayed two peak waves in a specific spatio-temporal pattern elicited by BmK I. The whole cell patch clamp recordings showed that the inactivation of sodium currents in rat cultured hippocampal neurons was prolonged significantly by BmK I, and restored partially after washing. These results indicated that the rat hippocampus is a susceptible target for the proconvulsant effects of BmK I, and the induction of epileptic seizures may be ascribed to the modulation of BmK I on the inactivation of voltage-gated sodium channels distributing in the rat hippocampal neurons.
Assuntos
Convulsivantes , Venenos de Escorpião/toxicidade , Convulsões/induzido quimicamente , Bloqueadores dos Canais de Sódio/toxicidade , Animais , Comportamento Animal/efeitos dos fármacos , Células Cultivadas , Relação Dose-Resposta a Droga , Eletroencefalografia/efeitos dos fármacos , Expressão Gênica/efeitos dos fármacos , Genes fos/efeitos dos fármacos , Hipocampo/efeitos dos fármacos , Hipocampo/metabolismo , Imuno-Histoquímica , Potenciais da Membrana/efeitos dos fármacos , Microinjeções , Neurônios/efeitos dos fármacos , Neurônios/metabolismo , Técnicas de Patch-Clamp , Ratos , Ratos Sprague-Dawley , Venenos de Escorpião/administração & dosagem , Bloqueadores dos Canais de Sódio/administração & dosagem , Canais de Sódio/efeitos dos fármacos , Canais de Sódio/metabolismo , Técnicas EstereotáxicasRESUMO
In this paper, the central neuronal activities elicited by BmK I, a specific voltage-gated Na+ channel modulator, were examined by monitoring the c-Fos expression pattern of rat spinal cord. c-Fos protein in laminae I-II, V-VI, and VII-X could be detected at 0.5 h, increased steadily at 1 h, reached a peak at 2 h, and then decreased rapidly from 4 to 24 h after Bmk I was subcutaneously injected into the rat hind paw. However, c-Fos expression in laminae III-IV was activated to a peak at 0.5 h and then declined gradually from 0.5 to 24 h. Furthermore, c-Fos expression could be induced by BmK I in a dose-dependent manner. In addition, the increase of c-Fos expression in laminae I-II, V-VI, and VII-X induced by BmK I, and not in laminae III-IV, could be partially inhibited by systemic morphine in a dose-dependent manner. The results suggested that peripheral administration of BmK I could evoke a profound change of spinal neuronal activities manifested as specific patterns of c-Fos expression, which may be partially attributed to the selective modulation of BmK I on voltage-gated Na+ channels located in peripheral nociceptors.