The time-dependent effects of physical exercise on fear memory reconsolidation and extinction in male rats

Aversive memories can enter a labile state during reactivation, allowing its content to be modified. Molecular changes induced by distinct interventions such as physical exercise can either facilitate or impair the strength of the original memory. However, the effect of the physical exercise performed at distinct time-points around memory reactivation remains poorly understood. Here we investigated how a single treadmill exercise bout delivered at different moments before or after a 5, 15 or 30-min reactivation session influences the reconsolidation and extinction of contextual fear conditioned memory in rats. Our results indicate that physical exercise of low-intensity 24 h and 10 min before the reactivation impairs reconsolidation and facilitates extinction. However, when the exercise protocol is performed immediately after the reactivation session, it facilitates reconsolidation and impairs extinction memory. Our results suggest that the specific time-point in which the physical exercise is performed plays an essential role in the reconsolidation and extinction outcome in fear conditioned animals.