RESUMO
BACKGROUND: Peripheral diabetic neuropathy can be painful and its symptoms include hyperalgesia, allodynia and spontaneous pain. Hydrogen sulfide (H2S) is involved in diabetes-induced hyperalgesia and allodynia. However, the molecular target through which H2S induces hyperalgesia in diabetic animals is unclear. The aim of this study was to determine the possible involvement of transient receptor potential (TRP) channels in H2S-induced hyperalgesia in diabetic rats. RESULTS: Streptozotocin (STZ) injection produced hyperglycemia in rats. Intraplantar injection of NaHS (an exogenous donor of H2S, 3-100 µg/paw) induced hyperalgesia, in a time-dependent manner, in formalin-treated diabetic rats. NaHS-induced hyperalgesia was partially prevented by local intraplantar injection of capsazepine (0.3-3 µg/paw), HC-030031 (100-316 µg/paw) and SKF-96365 (10-30 µg/paw) blockers, at 21 days post-STZ injection. At the doses used, these blockers did not modify formalin-induced nociception. Moreover, capsazepine (0.3-30 µg/paw), HC-030031 (100-1000 µg/paw) and SKF-96365 (10-100 µg/paw) reduced formalin-induced nociception in diabetic rats. Contralateral injection of the highest doses used did not modify formalin-induced flinching behavior. Hyperglycemia, at 21 days, also increased protein expression of cystathionine-ß-synthase enzyme (CBS) and TRPC6, but not TRPA1 nor TRPV1, channels in dorsal root ganglia (DRG). Repeated injection of NaHS enhanced CBS and TRPC6 expression, but hydroxylamine (HA) prevented the STZ-induced increase of CBS protein. In addition, daily administration of SKF-96365 diminished TRPC6 protein expression, whereas NaHS partially prevented the decrease of SKF-96365-induced TRPC6 expression. Concordantly, daily intraplantar injection of NaHS enhanced, and HA prevented STZ-induced intraepidermal fiber loss, respectively. CBS was expressed in small- and medium-sized cells of DRG and co-localized with TRPV1, TRPA1 and TRPC6 in IB4-positive neurons. CONCLUSIONS: Our data suggest that H2S leads to hyperalgesia in diabetic rats through activation of TRPV1, TRPA1 and TRPC channels and, subsequent intraepidermal fibers loss. CBS enzyme inhibitors or TRP-channel blockers could be useful for treatment of painful diabetic neuropathy.
Assuntos
Diabetes Mellitus Experimental/metabolismo , Sulfeto de Hidrogênio/metabolismo , Hiperalgesia/metabolismo , Canais de Potencial de Receptor Transitório/metabolismo , Acetanilidas/farmacologia , Analgésicos/farmacologia , Animais , Capsaicina/análogos & derivados , Capsaicina/farmacologia , Cistationina beta-Sintase/metabolismo , Diabetes Mellitus Experimental/tratamento farmacológico , Diabetes Mellitus Experimental/patologia , Feminino , Formaldeído , Hidroxilamina/farmacologia , Hiperalgesia/tratamento farmacológico , Hiperalgesia/patologia , Imidazóis/farmacologia , Nociceptividade/efeitos dos fármacos , Nociceptividade/fisiologia , Purinas/farmacologia , Ratos Wistar , Pele/inervação , Pele/metabolismo , Raízes Nervosas Espinhais/efeitos dos fármacos , Raízes Nervosas Espinhais/metabolismo , Raízes Nervosas Espinhais/patologia , SulfitosRESUMO
BACKGROUND: Ventral root avulsion is an experimental model of proximal axonal injury at the central/peripheral nervous system interface that results in paralysis and poor clinical outcome after restorative surgery. Root reimplantation may decrease neuronal degeneration in such cases. We describe the use of a snake venom-derived fibrin sealant during surgical reconnection of avulsed roots at the spinal cord surface. The present work investigates the effects of this fibrin sealant on functional recovery, neuronal survival, synaptic plasticity, and glial reaction in the spinal motoneuron microenvironment after ventral root reimplantation. METHODOLOGY/PRINCIPAL FINDINGS: Female Lewis rats (7 weeks old) were subjected to VRA and root replantation. The animals were divided into two groups: 1) avulsion only and 2) replanted roots with fibrin sealant derived from snake venom. Post-surgical motor performance was evaluated using the CatWalk system twice a week for 12 weeks. The rats were sacrificed 12 weeks after surgery, and their lumbar intumescences were processed for motoneuron counting and immunohistochemistry (GFAP, Iba-1 and synaptophysin antisera). Array based qRT-PCR was used to evaluate gene regulation of several neurotrophic factors and receptors as well as inflammatory related molecules. The results indicated that the root reimplantation with fibrin sealant enhanced motor recovery, preserved the synaptic covering of the motoneurons and improved neuronal survival. The replanted group did not show significant changes in microglial response compared to VRA-only. However, the astroglial reaction was significantly reduced in this group. CONCLUSIONS/SIGNIFICANCE: In conclusion, the present data suggest that the repair of avulsed roots with snake venom fibrin glue at the exact point of detachment results in neuroprotection and preservation of the synaptic network at the microenvironment of the lesioned motoneurons. Also such procedure reduced the astroglial reaction and increased mRNA levels to neurotrophins and anti-inflammatory cytokines that may in turn, contribute to improving recovery of motor function.
Assuntos
Adesivo Tecidual de Fibrina/farmacologia , Neurônios Motores/patologia , Regeneração Nervosa/efeitos dos fármacos , Radiculopatia/fisiopatologia , Recuperação de Função Fisiológica/efeitos dos fármacos , Raízes Nervosas Espinhais/patologia , Sinapses/patologia , Animais , Proteínas de Ligação ao Cálcio/metabolismo , Regulação para Baixo/efeitos dos fármacos , Feminino , Adesivo Tecidual de Fibrina/uso terapêutico , Proteína Glial Fibrilar Ácida/metabolismo , Proteínas dos Microfilamentos/metabolismo , Neurônios Motores/efeitos dos fármacos , Fatores de Crescimento Neural/biossíntese , Neuroglia/efeitos dos fármacos , Neuroglia/metabolismo , Neuroglia/patologia , Fármacos Neuroprotetores/farmacologia , Pressão , Implantação de Prótese , Radiculopatia/tratamento farmacológico , Ratos , Ratos Endogâmicos Lew , Venenos de Serpentes/química , Medula Espinal/efeitos dos fármacos , Medula Espinal/patologia , Medula Espinal/fisiopatologia , Raízes Nervosas Espinhais/efeitos dos fármacos , Raízes Nervosas Espinhais/fisiopatologia , Sinapses/efeitos dos fármacos , Sinaptofisina/metabolismo , Regulação para Cima/efeitos dos fármacos , Cicatrização/efeitos dos fármacosRESUMO
G-CSF is a glycoprotein commonly used to treat neutropenia. Recent studies have shown that the G-CSF receptor (G-CSF-R) is expressed by neurons in the central nervous system (CNS), and neuroprotective effects of G-CSF have been observed. In this study, the influence of G-CSF treatment on the glial reactivity and synaptic plasticity of spinal motoneurons in rats subjected to ventral root avulsion (VRA) was investigated. Lewis rats (7 weeks old) were subjected to unilateral VRA and divided into two groups: G-CSF and placebo treated. The drug treated animals were injected subcutaneously with 200 µg/kg/day of G-CSF for 5 days post lesion. The placebo group received saline buffer. After 2 weeks, both groups were sacrificed and their lumbar intumescences processed for transmission electron microscopy (TEM), motoneuron counting, and immunohistochemistry with antibodies against GFAP, Iba-1, and synaptophysin. Furthermore, in vitro analysis was carried out, using newborn cortical derived astrocytes. The results indicated increased neuronal survival in the G-CSF treated group coupled with synaptic preservation. TEM analyses revealed an improved preservation of the synaptic covering in treated animals. Additionally, the drug treated group showed an increase in astroglial reactivity both in vivo and in vitro. The astrocytes also presented an increased cell proliferation rate when compared with the controls after 3 days of culturing. In conclusion, the present results suggest that G-CSF has an influence on the stability of presynaptic terminals in the spinal cord as well as on the astroglial reaction, indicating a possible neuroprotective action.
Assuntos
Fator Estimulador de Colônias de Granulócitos/fisiologia , Neurônios Motores/efeitos dos fármacos , Fármacos Neuroprotetores/uso terapêutico , Rizotomia , Raízes Nervosas Espinhais/efeitos dos fármacos , Animais , Animais Recém-Nascidos , Astrócitos/efeitos dos fármacos , Astrócitos/patologia , Astrócitos/fisiologia , Modelos Animais de Doenças , Feminino , Neurônios Motores/patologia , Neurônios Motores/fisiologia , Terminações Pré-Sinápticas/efeitos dos fármacos , Terminações Pré-Sinápticas/patologia , Terminações Pré-Sinápticas/fisiologia , Cultura Primária de Células , Ratos , Ratos Endogâmicos Lew , Rizotomia/efeitos adversos , Medula Espinal/efeitos dos fármacos , Medula Espinal/patologia , Medula Espinal/fisiopatologia , Raízes Nervosas Espinhais/patologia , Raízes Nervosas Espinhais/fisiologiaAssuntos
Herpes Zoster/tratamento farmacológico , Radiculopatia/tratamento farmacológico , Esteroides/uso terapêutico , Causalidade , Transtornos Neurológicos da Marcha/tratamento farmacológico , Transtornos Neurológicos da Marcha/etiologia , Transtornos Neurológicos da Marcha/fisiopatologia , Humanos , Doença Iatrogênica/prevenção & controle , Imunossupressores/efeitos adversos , Injeções Epidurais , Radiculopatia/virologia , Raízes Nervosas Espinhais/efeitos dos fármacos , Raízes Nervosas Espinhais/fisiopatologia , Esteroides/administração & dosagem , Esteroides/efeitos adversosRESUMO
Recent results implicate a new original mechanism involving oxytocin (OT), as a mediator via descending fibers of the paraventricular hypothalamic nucleus (PVN), in antinociception and analgesia. In rats electrical stimulation of the PVN or topical application of OT selectively inhibits A-delta and C fiber responses in superficial dorsal horn neurons, and this inhibition is reversed by a selective OT antagonist. However, little is known about the mechanisms and the spinal elements participating in this phenomenon. Here we show that topical application of bicuculline blocks the effects produced by PVN electrical stimulation or OT application. PVN electrical stimulation also activates a subpopulation of neurons in lamina II. These PVN-On cells are responsible for the amplification of local GABAergic inhibition. This result reinforces the suggestion that a supraspinal descending control of pain processing uses a specific neuronal pathway in the spinal cord in order to produce antinociception involving a GABAergic interneuron. Moreover, the topical administration of naloxone or a mu-opiate receptor antagonist beta-funaltrexamine only partially blocks the inhibitory effects produced by OT application or PVN electrical stimulation. Thus, this OT mechanism only involves opiate participation to a minor extent. The OT-specific, endogenous descending pathway represents an interesting mechanism to resolve chronic pain problems in special the neuropathic pain.
Assuntos
Hipotálamo/metabolismo , Neurônios/metabolismo , Nociceptores/metabolismo , Ocitocina/metabolismo , Medula Espinal/metabolismo , Raízes Nervosas Espinhais/metabolismo , Animais , Bicuculina/farmacologia , Vias Eferentes/citologia , Vias Eferentes/metabolismo , Estimulação Elétrica , Antagonistas GABAérgicos/farmacologia , Hipotálamo/citologia , Antagonistas de Entorpecentes/farmacologia , Fibras Nervosas Mielinizadas/efeitos dos fármacos , Fibras Nervosas Mielinizadas/metabolismo , Fibras Nervosas Mielinizadas/ultraestrutura , Fibras Nervosas Amielínicas/efeitos dos fármacos , Fibras Nervosas Amielínicas/metabolismo , Fibras Nervosas Amielínicas/ultraestrutura , Inibição Neural/efeitos dos fármacos , Inibição Neural/fisiologia , Neurônios/citologia , Nociceptores/citologia , Nociceptores/efeitos dos fármacos , Peptídeos Opioides/metabolismo , Ocitocina/farmacologia , Dor/metabolismo , Dor/fisiopatologia , Células do Corno Posterior/citologia , Células do Corno Posterior/efeitos dos fármacos , Células do Corno Posterior/metabolismo , Ratos , Ratos Wistar , Medula Espinal/citologia , Medula Espinal/efeitos dos fármacos , Raízes Nervosas Espinhais/citologia , Raízes Nervosas Espinhais/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Transmissão Sináptica/fisiologia , Ácido gama-Aminobutírico/metabolismoRESUMO
In the somatosensory system, the flow of sensory information is regulated at early stages by presynaptic inhibition. Recent findings have shown that the mechanisms generating the primary afferent depolarization (PAD) associated with presynaptic inhibition are complex, with some components mediated by a non-spiking mechanism. How sensory inputs carried by neighbouring afferent fibres interact to regulate the generation of PAD, and thus presynaptic inhibition, is poorly known. Here, we investigated the interaction between neighbouring primary afferents for the generation of PAD in an in vitro preparation of the turtle spinal cord. To monitor PAD we recorded the dorsal root potential (DRP), while the simultaneous cord dorsum potential (CDP) was recorded to assess the population postsynaptic response. We found that the DRP and the CDP evoked by a primary afferent test stimulus was greatly reduced by a conditioning activation of neighbouring primary afferents. This depression had early and late components, mediated in part by GABAA and GABAB receptors, since they were reduced by bicuculline and SCH 50911 respectively. However, with the selective stimulation of C and Adelta fibres in the presence of TTX, the early and late depression of the DRP was replaced by facilitation of the GABAergic and glutamatergic components of the TTX-resistant DRP. Our findings suggest a subtle lateral excitatory interaction between primary afferents for the generation of PAD mediated by a non-spiking mechanism that may contribute to shaping of information transmitted by C and Adelta fibres in a spatially confined scale in analogy with the retina and olfactory bulb.
Assuntos
Potenciais de Ação/fisiologia , Inibição Neural/fisiologia , Neurônios Aferentes/metabolismo , Medula Espinal/metabolismo , Raízes Nervosas Espinhais/metabolismo , Transmissão Sináptica/fisiologia , Potenciais de Ação/efeitos dos fármacos , Vias Aferentes/efeitos dos fármacos , Vias Aferentes/metabolismo , Animais , Potenciais Pós-Sinápticos Excitadores/efeitos dos fármacos , Potenciais Pós-Sinápticos Excitadores/fisiologia , Antagonistas GABAérgicos/farmacologia , Ácido Glutâmico/metabolismo , Fibras Nervosas Mielinizadas/efeitos dos fármacos , Fibras Nervosas Mielinizadas/metabolismo , Fibras Nervosas Amielínicas/efeitos dos fármacos , Fibras Nervosas Amielínicas/metabolismo , Inibição Neural/efeitos dos fármacos , Neurônios Aferentes/efeitos dos fármacos , Terminações Pré-Sinápticas/efeitos dos fármacos , Terminações Pré-Sinápticas/metabolismo , Receptores de GABA/efeitos dos fármacos , Receptores de GABA/metabolismo , Reflexo/efeitos dos fármacos , Reflexo/fisiologia , Bloqueadores dos Canais de Sódio/farmacologia , Medula Espinal/anatomia & histologia , Raízes Nervosas Espinhais/efeitos dos fármacos , Transmissão Sináptica/efeitos dos fármacos , Tartarugas , Ácido gama-Aminobutírico/metabolismoRESUMO
Intrathecal injection of phenol (ITP) has been used to control intractable pain and spasticity. Direct caustic nerve damage has been postulated as the mechanism of analgesia. Sensation is commonly recovered, suggesting that a spontaneous regeneration process takes place. There is, however, a lack of mechanistic information on ITP therapy. To define morphologically the neurolysis and regeneration phenomena produced by ITP, anesthetized rats were subjected to laminectomy at L5; 5 microl of 22% phenol in saline solution or vehicle (control) was injected. Light and electron microscopy studies of nerve roots were performed at 2, 14, and 60 days after injection. Rats given ITP showed at the early stage a variable amount of roots with signs of infarction characterized by loss of axon-myelin units and thrombosis of intra-root vessels. At 14 days, abundance of macrophages removing debris, open vessels, and nerve sprouts was identified in damaged roots. At this time, non-myelinating glial fibrillary acidic protein-positive Schwann cells were observed in both damaged and apparently undamaged roots. At 60 days, abundance of 2',3'-cyclic nucleotide 3'-phosphodiesterase-positive Schwann cells myelinating newly formed axons was observed in damaged roots. Control rats did not show signs of neural or vascular pathology. Attempting to prevent thrombosis, another group of rats received heparin before ITP; these anti-coagulated rats developed radicular thrombosis, neurolysis, and hemorrhage. In conclusion, neurolysis produced by ITP is associated with acute ischemia (not prevented by heparin) and is followed by vascular, nerve, and myelin regeneration. Our results help understand the lack of efficacy of and some complications by ITP clinical therapy.
Assuntos
Analgésicos/administração & dosagem , Injeções Espinhais , Degeneração Neural/induzido quimicamente , Regeneração Nervosa/efeitos dos fármacos , Fenol/administração & dosagem , Raízes Nervosas Espinhais/efeitos dos fármacos , Animais , Isquemia/etiologia , Masculino , Degeneração Neural/patologia , Ratos , Raízes Nervosas Espinhais/irrigação sanguínea , Raízes Nervosas Espinhais/patologiaRESUMO
1, The mechanisms underlying the dorsal root potential (DRP) were studied in transverse slices of turtle spinal cord. DRPs were evoked by stimulating one filament in a dorsal root and were recorded from another such filament. 2. The DRP evoked at supramaximal stimulus intensity was reduced but not eliminated after blockade of GABAA receptors. The remaining component was eliminated by blocking NMDA and AMPA receptors. 3. The DRP was reduced but not eliminated after blockade of AMPA receptors. The early component of the remaining DRP was dependent on GABAA receptors and the residual component on NMDA receptors. 4. The DRP was reduced but not eliminated by TTX. GABAA, NMDA and AMPA receptors contributed to the generation of the TTX-insensitive DRP. The early component of the DRP in the presence of TTX depended on GABAA receptor activation, and the late component mainly on the activation of NMDA receptors. 5. Our results show that part of the DRP is generated by a TTX-resistant, probably non-spiking micro-circuit with separate components mediated by GABA and glutamate.
Assuntos
Potenciais Evocados/fisiologia , Rede Nervosa/efeitos dos fármacos , Medula Espinal/metabolismo , Raízes Nervosas Espinhais/metabolismo , Tetrodotoxina/farmacologia , 6-Ciano-7-nitroquinoxalina-2,3-diona/farmacologia , Animais , Bicuculina/farmacologia , Potenciais Evocados/efeitos dos fármacos , Antagonistas de Aminoácidos Excitatórios/farmacologia , Antagonistas GABAérgicos/farmacologia , Antagonistas de Receptores de GABA-A , Técnicas In Vitro , Rede Nervosa/citologia , Rede Nervosa/metabolismo , Tempo de Reação/efeitos dos fármacos , Receptores de AMPA/antagonistas & inibidores , Receptores de N-Metil-D-Aspartato/antagonistas & inibidores , Medula Espinal/citologia , Medula Espinal/efeitos dos fármacos , Raízes Nervosas Espinhais/citologia , Raízes Nervosas Espinhais/efeitos dos fármacos , TartarugasRESUMO
After ventral root avulsion, a large percentage of the wounded spinal motoneurons die within 2 weeks. Neuronal death is preceded by a series of morphological and physiological changes probably as a result of both apoptotic and necrotic mechanisms. Associated with neuronal death, inflammation develops in the wounded area, resulting in additional neuronal loss as well as the degeneration of fibers from different tracts of the ventral and lateral funiculi. In the present study we tested the neuroprotective and local anti-inflammatory effects of monosialoganglioside (GM-1) after an initial 150 mg/kg body weight dose, followed by the daily administration of 100 mg/kg body weight for 2 weeks. The results showed a statistically significant enhancement of surviving motoneurons which showed good morphological preservation. Also, GM-1 treatment reduced by less then a half, the number of degenerating fibers into the ventral and lateral funiculi. Taken together, our results indicate that the administration of GM-1 in high doses during the critical period of motoneuron death after avulsion is neuroprotective, and diminishes local inflammation.