A promising and widely studied example of vertebrate synaptic plasticity is long-term potentiation (LTP), the persistent synaptic enhancement seen following a brief period of intense synaptic activity. The cellular and molecular mechanisms underlying LTP may elucidate several physiological and pathological processes, including learning, memory, developmental synapse specificity, pain, neuronal death, epilepsy and dementia. The cellular signaling responsible for generating LTP has been studied extensively. A molecule thought to play an important role in LTP is the Ca++/calmodulin-dependent protein kinase II (CaMKII). In this project I will test the hypothesis that an increase in postsynaptic CaMKII activity is sufficient to produce LTP.
The specific aim of this project is to test this hypothesis by answering the following: 1. Does acute expression of a constitutively active CaMKII enzyme in postsynaptic neurons mimic and occlude LTP? i.e. does it enhance transmission and use up the LTP process? 2. Does acute expression of the wild type CamKII enzyme in postsynaptic cells rescue LTP in slices prepared from mice in which CaMKII has been genetically """"""""knocked out""""""""? These questions will be addressed using a novel viral infection technique that allows acute expression of a gene of interest in targeted regions of hippocampal slices. Extensive data shows the efficacy of this technique and preliminary data indicates that expression of a constitutively active CaMKII in postsynaptic hippocampal slice neurons enhances synaptic transmission and prevents more LTP. The proposed experiments will combine this new method with modern electrophysiological assays of synaptic transmission. The broad long-term objectives of my laboratory are to delineate the biochemical and biophysical mechanisms underlying activity-dependent synaptic plasticity in the CNS. This project will serve as a foundation by identifying a central piece in the puzzle of LTP. More generally we will continue to develop a methodology applicable to a large range of signal transduction problems in the CNS. Furthermore, it is not unreasonable that such viral strategies will soon be used in gene therapy for CNS pathologies. It will be important to continue to develop these experimental systems, to test the effect of viral infection and recombinant expression on synaptic transmission and plasticity. Acute expression of recombinant products in the hippocampal slice offers many advantages since numerous physiological and pathological processes have been carefully studied in this preparation.
