Influence of basolateral amygdala lesion on the inhibitory effects of propranolol on voluntary exercise- induced enhancement of learning and memory

The beneficial effects of physical activity and exercise on brain functions such as improvement in learning and memory are well documented. In a recent study, we have found that blockade of beta-adrenergic receptors by propranolol attenuates an improvement of learning and memory by exercise. However, the anatomical sites of propranolol actions are not known. The aim of this study was to determine the role of the Basolateral amygdala (BLA) in the inhibitory effects of propranolol on the beneficial effects of exercise on learning and memory. In order to block the beta-adrenergic receptors, male mice were received the beta-antagonist propranolol (10 mg/kg), before each night of five consecutive nights of exercise. The BLA lesion was made by electrolytic lesion (2mA, 2 s). Learning and memory were tested on the Morris water maze task using a two-trials-per-day for five consecutive days. A probe trial was performed two days after the last training day. Our results showed that propranolol reversed the exercise-induced improvement in learning and memory in rat. This effect was not blocked by the BLA lesion. However, lesion of the BLA alone blocked exercise-induced enhancement of learning and memory. These findings indicate beta-adrenergic receptors located outside the BLA may mediate the effects of exercise on learning and memory. Also, the BLA play an important role in the mediating the effects of physical activity on learning and memory.