Hippocampal membrane alteration in Alzheimer's disease

The biophysical properties of hippocampal membrane preparations from patients with Alzheimer's disease were examined by fluorescence spectroscopy using the membrane lipid probe 1,6-diphenyl-1,3,5-hexatriene (DPH) and its cationic derivative 1-[4-(trimethylamino)-phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH). Results of these experiments suggest that Alzheimer's disease is associated with a biophysical alteration in superficial regions of brain cell membranes, as reflected by the mobility of TMA-DPH. In contrast, no change in the mobility of DPH, which preferentially localizes to the hydrocarbon core, was observed. Although a trend was observed for TMA-DPH mobility to parallel histopathologic severity in hippocampal specimens, the biophysical changes did not appear to reflect a loss of neuronal membranes relative to glial membranes or the presence of senile plaques or neurofibrillary tangles.