No loss of synaptic proteins in the hippocampus of aged, behaviorally impaired rats

The levels of three different synaptic proteins in the hippocampus of young (6 months of age) and aged (26-27 months of age) Long Evans rats were exam ined using quantitative Western blotting. An important feature to this stud y is that prior to the neurobiological analysis, hippocampal unction was de termined by assessing spatial learning ability in the Morris water maze. A subset of the aged rats was impaired on the learning task while the remaini ng aged cohort performed within the range of young rats. The amount of immu noreactivity for synaptophysin, synaptotagmin, and synaptosomal associated protein-25 did not differ between the young and aged rats. In addition, the aged rats with severe cognitive impairment had levels of these synaptic pr oteins that were similar to those of the aged rats with preserved cognitive function. This finding of no change in the levels of synaptic proteins sug gests that substantial synapse loss in the hippocampal formation does not u nderlie cognitive decline in normal aging. (C) 1999 Elsevier Science Inc. A ll rights reserved.