Ethanol abuse results in a variety of cognitive, behavioral, and medical problems which represent a major public health problem in the United States. The hippocampus is a prominent end-organ target of alcohol toxicity where ethanol-induced alterations in long-term potentiation (LTP) and synaptic plasticity have been well documented. Recent studies have demonstrated a novel pathway for the metabolism of ethanol in hippocampus which results in the formation of fatty acid ethyl esters. The applicant has demonstrated that diminutive concentrations of fatty acid ethyl esters have profound effects on potassium channel function and membrane fusion. Furthermore, they demonstrated that ethanol itself is a potent interfacial activator of the major phospholipase A2 in hippocampus. Since the electrophysiologic properties, synaptic efficiency and stimulus-induced generation of arachidonic acid are each critical components of LTP, these results implicate a novel mechanism contributing to hippocampal dysfunction during ethanol abuse.
In Specific Aim 1, the biochemical and electrophysiologic mechanisms underlying the effects of fatty acid ethyl esters on hippocampal potassium channels will be examined. The domains of the potassium channel which interact with fatty acid ethyl esters will be delineated through construction of a synthetic radiolabeled photoactivatable fatty acid ethyl ester analog in conjunction with deletional and site-directed mutagenesis.
In Specific Aim 2, the biochemical mechanisms underlying ethanol-induced alterations in hippocampal arachidonic acid release, phospholipid composition and phospholipase A2 gene transcription and post-translational processing will be examined utilizing mechanism-based inhibition of phospholipase A2, quantitative electron microscopic autoradiography and electrospray ionization mass spectrometry. Finally, in Specific Aim 3 the effects of fatty acid ethyl esters as modulators of a novel membrane fusion activity in the hippocampus will be determined utilizing microisland cultures of hippocampal cells to examine fatty acid ethyl ester-induced alterations in excitatory and inhibitory post synaptic currents. Collectively, the proposed research represents a multidisciplinary approach designed to dissect the biochemical mechanisms underlying these novel effects of ethanol and ethanol metabolites on hippocampal function.
