SBNeC 2010
Resumo:B.092


Poster (Painel)
B.092EFFECT OF THE NMDA INTRAHIPPOCAMPAL INJECTION ON SPATIAL MEMORY AND ON THE EXPRESSION OF AMPA GLUTAMATE RECEPTORS IN RATS
Autores:Helene Aparecida Fachim (FFCLRP-USP - Faculdade de Filosofia, Ciências e Letras de Ribeirão PretoINEC - Instituto de Neurociências de Ribeirão Preto) ; Adriana Colsera Pereira (FFCLRP-USP - Faculdade de Filosofia, Ciências e Letras de Ribeirão PretoINEC - Instituto de Neurociências de Ribeirão Preto) ; Melina Mizusaki Iyomasa (FAMECA-FIPA - Laboratory of Neuroscience, School of Medicine of Catanduva) ; Wagner Ferreira dos Santos (FFCLRP-USP - Faculdade de Filosofia, Ciências e Letras de Ribeirão PretoINEC - Instituto de Neurociências de Ribeirão Preto) ; Maria Luiza Nunes Mamede Rosa (FAMECA-FIPA - Laboratory of Neuroscience, School of Medicine of CatanduvaINEC - Instituto de Neurociências de Ribeirão Preto)

Resumo

OBJECTIVE: There is a complex glutamatergic mechanism underlying the neurotoxicity triggered by the activation of different glutamate receptors on neurons and microglia, contributing to the onset of the inflammatory and neurodegenerative processes. However, this mechanism is not fully known. The aims of this work were to evaluate, in a time course, the changes on spatial memory and on the expression of glutamate AMPA receptors and IL1&beta in hippocampus, arising from neurodegenerative and inflammatory processes induced by NMDA injection. METHODS: Three groups of male Wistar rats (200-250g) were used (n= 6/each). They received a bilateral intrahippocampal (CA1) injection of saline or NMDA (0.2µl, 12mg/Kg). NMDA injected rats were divided in two groups, submitted to Morris Water Maze test for assessment of spatial memory impairment, 2 and 4 weeks after injection, respectively. Animals were deeply anaesthetized, perfused and their brains removed. 30-µm sections were used for immunohistochemistry for GluR1, GluR2 and IL1&beta. Using a light microscope and image analysis, the immunopositive cells (IC) were counted in CA1 (3 sections/rat, bilaterally). Groups were compared by one way ANOVA followed by Newman-Keuls post hoc and the level of significance was set at p<0.05. RESULTS: On the Morris Water Maze NMDA injected groups showed a significant increase (110%) in the latencies to find the platform when compared to control group. This increase persisted during the four days of training (p< 0.05). At the test day, without the platform, NMDA injected animals spent less time (37%) in the target quadrant than the control group (p<0,001) indicating a possible impairment of the capability of spatial memory retention. Even considering a generalized cell death on the hippocampal lesioned area, we found a significant increase in the GluR1-IC (300%) in CA1 for NMDA injected groups compared to control group (p<0,0001). In contrast, GluR2-IC was significantly decreased (33%; p<0,0001). A complete absence of IL1&beta-IC was observed in the CA1 area of the hippocampus in both NMDA injected groups, which is probably due to the fact that the inflammatory mechanism precedes the process of neuronal death. CONCLUSIONS: The spatial memory impairment observed on the Morris Water Maze test demonstrates the efficiency of the lesion induced by NMDA intrahippocampal injection. The increase of the GluR1-IC and the decrease of the GluR2-IC found after NMDA injection may suggest either the involvement of the subunit GluR1 permeable to calcium on the mechanisms of neuronal death triggered by NMDA or an increase in the number of this subunit on the surviving neurons as a compensatory mechanism. Committee on Animal Research and Ethics (CEUA, USP-Ribeirao Preto): 10.1.619.53.3 Financial support: CAPES/PROEX and FAPESP.


Palavras-chave:  AMPA, Glutamate receptors, NMDA, Spatial memory