Effects of beta-adrenoreceptor blockade during chronic exercise on contextual fear conditioning and mRNA for galanin and brain-derived neurotrophic factor.

The authors examined the effects of activity wheel running (AWR) and propranolol on contextual fear conditioning (CFC) and messenger RNA (mRNA) for galanin (GAL) in the locus coeruleus (LC) and brain-derived neurotrophic factor (BDNF) in the hippocampal formation (HF) in rats. Freezing behavior during the testing session of the CFC protocol was elevated in the AWR-placebo group compared to sedentary-placebo and AWR-propranolol groups. AWR increased GAL mRNA in the LC. CFC increased BDNF mRNA in the HF. These results suggest that exercise enhances CFC and that antagonism of the beta-adrenoreceptors attenuates this effect. The exercise-related induction of GAL gene expression in the LC may influence noradrenergic transmission to facilitate CFC.