EFFECTS OF DIETARY RESTRICTION ON MOTOR LEARNING AND CEREBELLAR NORADRENERGIC DYSFUNCTION IN AGED F344 RATS

Fisher 344 rats were fed either ad libitum or with a diet containing a 40% reduction of calories beginning at 4 months of age. At 14 months and 22 months male rats were tested for their ability to learn a complex motor skill. At both ages the diet restricted rats reached criterion of performing 10 successful crosses in 10 min at an earlier time than ad libitum fed controls. At 22 months of age the diet restricted rats showed improved acquisition of running times for the task. Male rats at 14 and 22 months and female rats at 24 months were examined electrophysiologically for the ability of isoproterenol to augment the action of GABA in the cerebellum when both substances were applied iontophoretically from an extracellular multibarreled glass electrode. In all 3 age and sex groups there was an improvement in the beta-adrenergic receptor modulation of GABA responses in the dietary restricted vs. ad libitum rats. However, no difference was observed between dietary restricted and ad libitum rats when the number and affinity of cerebellar beta-adrenergic receptors was assessed with I-125-iodopindolol binding. Overall, there was a significant improvement in cerebellar noradrenergic function in the dietary restricted rats and this was accompanied by an improvement in motor learning.