[The neural basis of learning and memory declines in aged rats].

The synapses, AChE fibers, synaptophysin (SYP), parvalbumin (PV)-containing neurons, synaptosomal Ca2+ concentration and membrane fluidity were studied quantitatively in the brain tissues of young and aged memory-nonimpaired and aged memory-impaired rats according to their memory abilities in the Morris water maze. The results indicated that statistically significant decreases were found in SYP content, the density of synapses, AChE fibers, PV positive neurons and synaptosomal membrane fluidity while an increase was found in [Ca2+]i of neocortex and hippocampal formation in the aged memory-impaired rats as compared with the young and aged memory-nonimpaired rats. But there were no significant differences of these indexes between the young rats and the aged memory-nonimpaired ones. The study suggested that the abnormality of these indexes was closely correlated with the decline of learning and memory in aged rats.