Abstract: Rats with selective temporal infarct induced Photochemically was used as an animal model of dementia. The changes of neuratransmitter amino acids in extracellullar fluid in the hippocampus were monitored with microdialysis technique in vivo, and the ultrastructures altered were observed using TEM electromicroscope, also the changes of neurons under the light microscope and the learning and memory ability were determined simultaneously.The results demonstrated that:(1)there were a large amount of releasing of excitatory and inhibitory neurotransmitter amino acids in the hippocampus during temporal ischemia;(2)there were many vesiculae accumulated at the presynapse membrane in the hippocampus at the early period of temporal infarct,then the number of vesiculae reduced and the size of vesicalea became uneven;(3)there was a selective neuron necrosis in hippocampus and neocortex in rats with temporal infarct;(4)there were significant correlations between the releasing of amino acids and selective neuron necrosis and learning and memory disorders. The findings showed that the temporal infarct could induce the selective neuron necrosis in the hippocampus via releasing of neurotransmitter amino acids especially the excitatory amino acids,and the temporal infarct and selective neurons necrosis could result in the learning and memory disorders. The authors believe that inhibiting the release of excitatory amino acids are useful for the treatment of vascular dementia in human beings.

Key words: learning and memory, microdialysis, ultrastracture