Aging and atropine effects on spatial navigation in the Morris water task.
A recent animal model that has been particularly useful in the neurobiology of aging has been the age-related decline of spatial information processing capacity in Sprague-Dawley rats measured in the place-learning water task developed by Morris (1981). In the first experiment of the present study, place behavior was examined in young (6 months), old (23-24 months), and very old (28 months) rats of another strain, Long-Evans. As an analogue of aging-related cholinergic dysfunction the effects of atropine sulfate (5-50 mg/kg), an anticholinergic drug that is known to disrupt behavior in this task, also was determined. Place navigation was not impaired in undrugged rats, even those in the oldest age group. Rats treated with atropine showed dose-dependent deficits. In a second experiment, young (4-5 months), old (18-20 months), and very old (28 months) Fischer-344 rats were examined. Place navigation was impaired in the old rats. The very old (28 months) rats could not swim well enough to be tested adequately. Although nonspatial deficits associated with aging may be found across most strains tested, there appear to be very large strain-related differences in spatial processing ability as a function of age.