RESUMO
Spontaneous neuronal activity in dorsal cochlear nucleus (DCN) may be involved in the physiological processes underlying salicylate-induced tinnitus. As a neuronal activity marker, immediate-early gene (IEG) expression, especially activity-dependent cytoskeletal protein (Arc/Arg3.1) and the early growth response gene-1 (Egr-1), appears to be highly correlated with sensory-evoked neuronal activity. However, their relationships with tinnitus induced by salicylate have rarely been reported in the DCN. In this study, we assessed the effect of acute and chronic salicylate treatment on the expression of N-methyl D-aspartate receptor subunit 2B (NR2B), Arg3.1, and Egr-1. We also observed ultrastructural alterations in the DCN synapses in an animal model of tinnitus. Levels of mRNA and protein expression of NR2B and Arg3.1 were increased in rats that were chronically administered salicylate (200 mg/kg, twice daily for 3, 7, or 14 days). These levels returned to baseline 14 days after cessation of treatment. However, no significant changes were observed in Egr-1 gene expression in any groups. Furthermore, rats subjected to long-term salicylate administration showed more presynaptic vesicles, thicker and longer postsynaptic densities, and increased synaptic interface curvature. Alterations of Arg3.1 and NR2B may be responsible for the changes in the synaptic ultrastructure. These changes confirm that salicylate can cause neural plasticity changes at the DCN level.
Assuntos
Núcleo Coclear/metabolismo , Regulação da Expressão Gênica , Genes Precoces/genética , RNA Mensageiro/genética , Zumbido/genética , Animais , Núcleo Coclear/ultraestrutura , Modelos Animais de Doenças , Imuno-Histoquímica , Masculino , Microscopia Eletrônica de Transmissão , Ratos , Ratos Sprague-Dawley , Reação em Cadeia da Polimerase em Tempo Real , Salicilato de Sódio/toxicidade , Sinapses/genética , Sinapses/metabolismo , Zumbido/induzido quimicamente , Zumbido/metabolismoRESUMO
Aspirin (salicylate), as a common drug that is frequently used for long-term treatment in a clinical setting, has the potential to cause reversible tinnitus. However, few reports have examined the inflammatory cytokines expression and alteration of synaptic ultrastructure in the cochlear nucleus (CN) in a rat model of tinnitus. The tinnitus-like behavior of rats were detected by the gap prepulse inhibition of acoustic startle (GPIAS) paradigm. We investigated the expression levels of the tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), N-methyl D-aspartate receptor subunit 2A (NR2A) mRNA and protein in the CN and compared synapses ultrastructure in the CN of tinnitus rats with normal ones. GPIAS showed that rats with long-term administration of salicylate were experiencing tinnitus, and the mRNA and protein expression levels of TNF-α and NR2A were up-regulated in chronic treatment groups, and they returned to baseline 14 days after cessation of treatment. Furthermore, compared to normal rats, repetitive salicylate-treated rats showed a greater number of presynaptic vesicles, thicker and longer postsynaptic densities, increased synaptic interface curvature. These data revealed that chronic salicylate administration markedly, but reversibly, induces tinnitus possibly via augmentation of the expression of TNF-α and NR2A and cause changes in synaptic ultrastructure in the CN. Long-term administration of salicylate causes neural plasticity changes at the CN level.
Assuntos
Núcleo Coclear/metabolismo , Mediadores da Inflamação/metabolismo , Ácido Salicílico , Sinapses/metabolismo , Zumbido/induzido quimicamente , Animais , Comportamento Animal , Núcleo Coclear/imunologia , Núcleo Coclear/ultraestrutura , Modelos Animais de Doenças , Regulação da Expressão Gênica , Interleucina-6/genética , Interleucina-6/metabolismo , Masculino , Plasticidade Neuronal , RNA Mensageiro/metabolismo , Ratos , Ratos Sprague-Dawley , Receptores de N-Metil-D-Aspartato/genética , Receptores de N-Metil-D-Aspartato/metabolismo , Reflexo de Sobressalto , Sinapses/imunologia , Sinapses/ultraestrutura , Fatores de Tempo , Zumbido/genética , Zumbido/imunologia , Zumbido/patologia , Zumbido/psicologia , Fator de Necrose Tumoral alfa/genética , Fator de Necrose Tumoral alfa/metabolismoRESUMO
OBJECTIVE: To study the mechanism of electrophysiologic changes caused by different type of sodium salicylate injection. METHODS: Decapitated three group rats ( acute injected, chronic injected and normal rats ) separately, dissected the temporal bones to collect cochlea, and the otic capsules were removed. Then the cochlear materials from each groups were pooled and homogenized respectively, extracted the total RNA, obtained cDNA from purified total RNA by reversed transcription, cDNA were transcripted to cRNA probes in vitro. Hybridized the cRNA probes with tester chip to evaluate the quality of probes, if good, hybridized the probes with real chip. Obtained three gene expression profiles of different groups of cochlea Analyzed the differentially expressed genes among three groups by SOM. Analogized the SOM result to electrophysiologic changes. Then analyzed the genes in clusters of analog results by Gene Ontology. Then the genes in clusters of analog results were analyzed by Gene Ontology. Hsp27 was chosen to validate the result of gene chip using real time quantitative reverse transcription PCR ( RTQ RT-PCR). RESULTS: The probes was good, and the chip hybridization results was credible. We obtained 6 clusters genes by SOM analysis, in which we choose cluster 3 and cluster 4 as candidate cluster. There were 46 genes in cluster 3 and 30 genes in cluster 4 employing GO analysis, which involved in cell communication, cell motility, metabolism, immune response and nerve ensheathment, et al. The result of RTQ RT-PCR showed high concordance with that of gene chip. CONCLUSION: It's a new method to study the mechanism of electrophysiologic changes caused by sodium salicylate by gene chip and SOM analysis.