Behavioral changes in ACTH-(1-24)-induced excessive grooming in aging rats

Age-related behavioral changes are commonly associated with impaired cognitive functioning. As a result an abundance of neuropsychological tools have been developed to study learning and memory in man and animal. The combined use of ethological methods and the extensively studied measures of excessive grooming behavior in rats provides an excellent tool to study non-cognitive behavioral changes. In the present study, a sequential analysis was applied to the different grooming elements. Aged rats showed a loss in the sequential organization of their grooming behavior, which led to a decrease in the display of tail sniffing. Interestingly, the reduced display of an element which appears latest in the ontogeny of grooming is reminiscent of the Jacksonian principle of behavioral degeneration. Seemingly, this principle is not necessarily confined to learning paradigms, but may be extended to other behavioral systems as well.