NEURONAL PLASTICITY IN CA1 HIPPOCAMPAL NEURONS AFTER HYPOXIA-ISCHEMIA.

SARACENO, E; CACERES, LG; GUELMAN, LR; KRUSE, MS; VALVERDE, G; MADUREIRA D; GIRALDEZ ALVAREZ, LD; COIRINI, H; CAPANI, F

Buzios, RJ, Brasil

Congreso; Ier Congreso IBRO/LARC De Neurociencias Da América Latina, Caribe E Península Ibérica; 2008

IBRO/LARC

During hypoxia episode, synaptic dysfunction observed has been related with neuronal death, although this mechanism is not fully understood yet. In previous work we have shown modifications in neurons and synapses in the neostriatum of rat subjected to hipoxia. In this work we study the effects of hypoxia-ischemia on the actin cytoskeleton of Hippocampal CA1 post-synaptic densities (PSD) and the actin binding proteins in 30 days olds rats, by combining photooxidation, inmunofluorescent, 3D reconstruction and Western blot. In addition, we test the effects of reduced temperature from 37¨¬c to 15¨¬c on dendritic spines. Staining with phalloidin-alexa 568 followed by confocal microscopy analysis showed an increase of F actin fluorescent staining in the CA1 Hippocampal dendritic spines (Relative fluorescent intensity: control 15.1 ± 3 vs hypoxic animals 33.5 ±6 p < 0.001). Electron microscopy and 3-D reconstruction confirmed these observations showing an increment in the number of F-actin staining spines in CA1 hippocampal excitatory synapses subjected to severe hypoxia (control 2 ± 0.1 vs. hypoxic animals 3.6 ± 0.2 p < 0.001). Western blot revealed ¥â-actin increase in hypoxic animals, consistent with the microscopy data (D.O.R: control: 1.43 ± 0.05 vs. hypoxic animals 2.98 ± 0.41 p < 0.001). Staining with profilin-alexa 488 followed by confocal microscopy analysis showed an increase of pyramidal neurons immunostaining, located in the stratum radiatum (Relative fluorescent intensity: control 20.4 ± 3 vs hypoxic animals 35.9 ± 6 p < 0.005). When hypoxia was induced under hypothermic conditions the changes observed were blocked. These results suggest that the cellular and subcellular alterations in CA1 hippocampal PSDs could be related to F-actin increase probably due to an alteration in profiling dynamic inducing more actin polymerization and changes in the dendritic synaptic cytoarchytecture.