Influence of Age-related Changes on Freezing Behavior in the Cat-freezing Test Apparatus.

Abstract:
Freezing has been shown to be one of the most frequently expressed fear-related behaviors in rats. The objective of this study was to investigate whether the age of the rat could influence fear-related behavior and to study the habituation of cat-exposure induced fear in rats of two different age groups with simultaneous assessment of their freezing responses. Male hooded PVG rats were divided into two age groups; young(1-2 months-old) and adult(5-6 months-old). Statistical interference of data concerning the two different age was estimated by the turkey test. The data shows that the age of rats highly influenced the results of the subjects exposed to the cat-freezing test apparatus. The young age group demonstrated lower levels of freezing in comparison to the adult age group which demonstrated higher levels of freezing (p<0.05). The opposite were observed when the locomotor activities were compared. The changes in behavior might be due to deficits in brain maturity for the young rats. The results of the present study highlight the importance of age in behavioral experimentation. It may also highlight the problems of methodology in that increasing age should be taken into consideration in repeated administration studies where animals are kept over a few months. It would be of great interest to correlate these results with possible neurochemical changes.