Regional alteration of synapsin I in the hippocampal formation of Alzheimer's disease patients.

Synapsin I is a synaptic vesicle-associated protein, participating in synapse formation, regulation of the synthesis of other synaptic vesicle proteins and promotion of neurotransmitter release. The aim of present study was to detect whether regional alteration of synapsin I occurred in the hippocampal formation of Alzheimer's disease (AD) patients. Samples of hippocampus from ten female AD patients and ten non-demented female controls, matched for age and postmortem delay, were investigated immunocytochemically. Using immunofluorescence labeling and laser confocal imaging, we examined the distribution of synapsin I in the CA1 and CA3 subfields of the hippocampus and the dentate gyrus (DG) in AD patients and controls. The results showed that synapsin I was significantly decreased in the stratum radiatum of CA1 subfield and the molecular layer of DG in AD patients. No difference between the two groups in the intensity of synapsin I staining was observed in the stratum pyramidale of CA1, where a number of pretangles stained by Alz-50 were observed in AD patients. These results suggest that there is regional loss of synapsin I in the hippocampal formation of AD patients.