Specific immediate early gene expression induced by high doses of salicylate in the cochlear nucleus and inferior colliculus of the rat / Expressão específica de genes precoces imediatos induzida por doses elevadas de salicilato no núcleo coclear e colículo inferior de rato

Abstract Introduction: Salicylate at high doses induces tinnitus in humans and experimental animals. However, the mechanisms and loci of action of salicylate in inducing tinnitus are still not well known. The expression of Immediate Early Genes (IEG) is traditionally associated with long-term neuronal modifications but it is still not clear how and where IEGs are activated in animal models of tinnitus. Objectives: Here we investigated the expression of c-fos and Egr-1, two IEGs, in the Dorsal Cochlear Nucleus (DCN), the Inferior Colliculus (IC), and the Posterior Ventral Cochlear Nucleus (pVCN) of rats. Methods: Rats were treated with doses known to induce tinnitus in rats (300 mg/kg i.p. daily, for 3 days), and c-fos and Egr-1 protein expressions were analyzed using western blot and immunocytochemistry. Results: After administration of salicylate, c-fos protein expression increased significantly in the DCN, pVCN and IC when assayed by western blot. Immunohistochemistry staining showed a more intense labeling of c-fos in the DCN, pVCN and IC and a significant increase in c-fos positive nuclei in the pVCN and IC. We did not detect increased Egr-1 expression in any of these areas. Conclusion: Our data show that a high dose of salicylate activates neurons in the DCN, pVCN and IC. The expression of these genes by high doses of salicylate strongly suggests that plastic changes in these areas are involved in the genesis of tinnitus.

Resumo Introdução: Salicilato em doses elevadas induz zumbido nos seres humanos e em animais experimentais. No entanto, os mecanismos e loci de ação do salicilato na indução de zumbido ainda não são bem conhecidos. A expressão dos genes precoces imediatos (GPIs) está tradicionalmente associada a alterações neuronais em longo prazo, mas ainda não está claro como e onde os GPIs são ativados em modelos animais de zumbido. Objetivos: No presente estudo investigamos a expressão de c-fos e Egr-1, dois GPIs, no núcleo coclear dorsal (NCD), colículo inferior (CI) e núcleo coclear ventral posterior (NCVp) de ratos. Métodos: Os ratos foram tratados com doses que, conhecidamente, induzem zumbido em ratos (300 mg/kg IP/dia, por três dias) e as expressões das proteínas c-fos e Egr-1 foram analisadas por meio de Western blot e imunoistoquímica. Resultados: Após a administração de salicilato, a expressão da proteína c-fos aumentou significativamente no NCD, NCVp e CI, quando analisados por Western blot. A coloração imunoistoquímica mostrou uma marcação mais intensa de c-fos no NCD, NCVp e CI e um aumento significativo de núcleos positivos de c-fos no NCVp e CI. Não detectamos aumento da expressão de Egr-1 em qualquer dessas áreas. Conclusão: Nossos dados mostram que uma dose alta de salicilato ativa neurônios no NCD, NCVp e CI. A expressão desses genes por doses altas de salicilato sugere que as alterações plásticas nessas áreas estão envolvidas na gênese do zumbido.

The Expression of GAP-43 in Cochlear Nucleus and Inferior Colliculus after Unilateral Cochlear Damage in Rats / 听力学及言语疾病杂志

Objective To study the changes of the expression of growth associated protein -43(GAP 43) in cochlear nucleus and the inferior colliculus (IC) in rats after unilateral cochlear damage at different time points after surgery ,and explore the remodeling and repair process of synapse in brainstem auditory center of rats after auditory deprivation .Methods Thirty rats were randomly divided into six groups :the 3 ,7 ,15 ,30 ,60 days group (with u-nilateral cochlea damage) and the control group (without cochlea damage) with 5 rats in each group .The immuno-histochemical SP method was used to detect the expression of GAP -43 in cochlear nucleus and inferior colliculus at different time points after cochlea damaged in the control group .Results After the unilateral cochlear ear was dam-aged at 3 ,7 ,15 days ,GAP -43 in operation side cochlear nucleus were expressed and the expression level signifi-cantly increased compared with normal control group .After 30 days postoperatively ,GAP - 43 expression level decreased ,but it was still higher than normal control group .After 60 days postoperatively ,GAP - 43 expression level was slightly higher than that of normal control group .After 3 days postoperatively ,GAP - 43 expression level was higher than normal control group .After 7 ,15 days postoperatively ,expression levels were increased .After 30 , 60 days postoperatively ,the expressions gradually decreased ,but still higher than the normal control group .Conclusion After unilateral cochlea damaged ,GAP - 43 was expressed an obvious dynamic change process in cochlear nucleus and infe-rior colliculus .It may reflect the axonal regeneration and synaptic plasticity after hearing loss in brainstem auditory neurons .

GluR2 expression in developing rat cochlear nucleus and relationship with development of synapse / 上海第二医科大学学报

Objective To investigate the trend of developmental expression of GluR2,subtype of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid(AMPA) receptor and synaptophysin(SYP) in the rat cochlear nucleus(CN) in different developmental stages,and explore the association of GluR2 expression with the development of synapse. Methods SD rats of 2,3,4,6,8 and 10 weeks old were selected,the expression of GluR2 and SYP in CN was detected with immunofluorescence histochemical method,and the association of them was explored. Results GluR2 expression was observed in all the neurons of CN in each postnatal groups.The expression was relatively weaker in the second and third week,became denser in the fourth week,reached the peak in the sixth week and then sharply decreased to the weakest in the tenth week.The expression of GluR2 was denser at granular cell layer,while weaker at molecular layer and multipolar cell layer in the dorsal CN.SYP expression was detected in all the neurons of CN in each postnatal groups.The expression was weakest in the second week,significantly denser in the fourth week,reached the peak in the sixth week,was then sharply decreased and stably maintained. Conclusion The expressions of GluR2 and SYP in the postnatal rat CN exhit an equally age-dependent tendency.The expression of GluR2 in the CN may be associated with the the maturation and function development of the CN.The different expression and distribution of GluR2 and SYP in the rat CN of different developmental stages may be involved in the development and plasticity of auditory center.

The Expression of GluR2/3 in Cochlear Nucleus of Different Age SD Rat / 听力学及言语疾病杂志

Objective To investigate the expression of ?-amino-3-hydroxy-5-methyl-4-isoxazole-propionic acid(AMPA) receptor subunit proteins GluR2/3 in the postnatal rat cochlear nucleus(CN), and the relationship with the auditory brainstem response(ABR).Methods The thresholds of ABR of different age SD rats were recorded respectively,and the expression of GluR2/3 in CN was detected with FITC-immunocytochemistry.Results ①P1w SD rats did not show ABR wave, and there was no significant difference in the ABR threshold among P4w,P9w and P15w SD rats. ②GluR2/3 was expressed in all sorts of neurons of CN of every postnatal groups, the expression of P4w rats was denser than that of P1w, P9w and P15w rats. The immunostaining of P4w rats was located at the cell membrance, while P9w and P15w rats in the endochylema majoritily. Conclusion The different expression and distribution of GluR2/3 in different age rat CN may be involved in the development of auditory centre.