Aging affects cognition and hippocampal ultrastructure in male Wistar rats.

It is now well established that aging is associated with emotional and cognitive changes. Although the basis of such changes is not fully understood, ultrastructural alterations in key brain areas are likely contributing factors. Recently, we reported that aging-related anxiety in male Wistar rats is associated with ultrastructural changes in the central nucleus of amygdala, an area that plays important role in emotional regulation. In this study, we evaluated the cognitive performance of adolescent, adult, and aged male Wistar rats in multi-branch maze (MBM) as well as in Morris water maze (MWM). We also performed ultrastructural analysis of the CA1 region of the hippocampus, an area intimately involved in cognitive function. The behavioral data indicate significant impairments in few indices of cognitive functions in both tests in aged rats compared to the other two age groups. Concomitantly, a total number of presynaptic vesicles as well as vesicles in the resting pool were significantly lower, whereas postsynaptic mitochondrial area was significantly higher in aged rats compared to the other age groups. No significant differences in presynaptic terminal area or postsynaptic mitochondrial number were detected between the three age groups. These results indicate that selective ultrastructural changes in specific hippocampal region may accompany cognitive decline in aging rats.