This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. We are studying the changes in the actin cytoskeleton after Long Term Potentiation (LTP) in hippocampal area CA1 using a novel technique based in the high affinity of phalloidin for the F-actin followed for photooxidation of diaminobenzidine by eosin and how they could be involved in the protein translocation in the spiny dendrite. At the light microscopic level we detected a decrease of phalloidin staining of F-actin in the striatum radiatum of CA1 in hippocampal slices. Observations using electron microscopy confirmed these results. Mushroom shaped dendritic spines showed a very consistent decrease in F-actin staining after LTP induction suggesting that LTP produces depolymerizaion of F-actin in this particular subtype of spines. Furthermore we observed in cultured hippocampal neurons that the stabilization of F-actin using jasplikanolide an agents that increases the rate of actin polymerization, inhibits the translocation of GFP-CAMKII and the 3kD dextran suggesting that the F-actin polymerization/depolymerization might be involved in the transport of different substances in the dendritic spines. Also we observed a dramatic increment in the number of fillopodias in the neuropil and also in the cytoplasm of the CA1 pyramidal cells. The statistical quantification of the morphological findings is currently under way using 3-D serial reconstructions and electron tomography. A manuscript detailing this work is in preparation.
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