Effects of age and anxiety on learning and memory.

ABSTRACT

This study aims to investigate the effects of age and anxiety on behavior, learning and memory in rats. Before and after the anxiety and learning tests, locomotor activity, exploratory activity and autonomic functions of the rats were tested in open field area. At the beginning and at the end of behavior tests, urines were collected so as to determine 5-hydroxyindolaceticacid (5-HIAA) levels. Following these tests, rats were anesthetized and their serum corticosteron (CORT) levels were analyzed. After anxiety, except for defecation, all parameters in open field such as line crossing, rearing, sitting and number of grooming were decreased in both young and aged animals. 5-Hydroxyindolaceticacid levels were decreased and serum CORT levels were increased, it is supported that especially the aged rats were much more affected from anxiety compared to the young ones. Elevated T-maze results show that emotional learning did not change while conditioned performance was tested in the closed arm and unconditioned performance was tested in the open arm. Nevertheless, it is observed that aging leaded to extensions in avoidance responses and thus caused difficulty in learning. In water maze test, rats showed higher performance in reaching the platform in repetitive trials; this demonstrates that they have learned by environmental cues. Experimental group had not better performance in reaching the platform according to control group, so this supports that anxiety affects spatial learning. As a conclusion, it could be stated that especially in aged rats, anxiety that is created by elevated T-maze and cat odor and supported with 5-hydroxyindoleacetic acid and serum corticosterone, causes difficulty in emotional and spatial learning.