Enhanced passive avoidance retention following posttrain serotonergic receptor antagonist administration in...

The experiments examined the ability of posttrain administration of serotonergic receptor antagonists to attenuate the age-related deficits in avoidance retention normally exhibited by middle-aged (12 months) and aged (22 months) rats. Ketanserin (0, 1.0, 10.0 mg/kg) produced a significant dose-dependent increase in test step-through latencies in both age groups. The suppression of responding did not appear to be due to generalized learned aversion as nonshocked rats, injected with the highest dose of ketanserin, did not exhibit similar elevations in test latencies. In order to determine whether the ketanserin-induced effect could be generalized to other serotonergic antagonists, middle-aged and aged animals were injected with a single dose of mianserin (10.0 mg/kg). This antagonist also significantly increased step-through latencies in both age groups, while not affecting the performance of nonshocked animals. The results provide additional evidence for a role of the serotonergic nervous system in memory, and may have important implications in the development of effective treatment strategies for geriatric-related cognitive disorders.