The Effect of Different Crowding Duration and Age on Spatial Learning in Rats in the Morris Water Maze

Abstract This work compared the effect of different periods of rat housing in crowded conditions on their spatial learning in the Morris water maze. Experiments were carried out on 65 adult male Wistar rats. In crowded conditions (18 individuals per standard cage), the rats were kept starting from 3 months of age until the end of the experiments, while control rats were housed in standard conditions (5 individuals per cage). Training in the Morris water maze was conducted at 4, 8, and 20 months of age, focusing on the manifestations of both long-term and working memory. Young (4-month-old) rats kept in crowded conditions learned to find the hidden underwater platform better than control rats, as manifested in a shorter distance swum to the platform. In middle and old age, crowded and standard rats did not differ in spatial learning. Learning with working memory deteriorated in old age regardless of housing conditions. The swimming speed in rats kept in crowded conditions was lower in all age groups.