The effects of acute voluntary wheel running on recovery of function following medial frontal cortical contusions in rats

Purpose: Traumatic brain injury (TBI) produces significant deficits in executive function, sensory-motor function, and on spatial learning tasks. We wish to study if recovery from TBI can be benefited by voluntary exercise. Methods: A variation of the stop-signal reaction time (SSRT) task was employed to measure rats ability to obtain maximum reinforcers in a complex behavioral task. A 2x2 (lesion x treatment) experimental design was constructed with 31 weight restricted male Long-Evans rats which received either bilateral cortical contusions to the medial frontal cortex or sham preparations following the acquisition of the SSRT task (matched based on pre-surgical performance). Following surgery, rats were randomly assigned to either an environment with free access to running wheels or traditional single housing without running wheels. Results: Rats receiving a bilateral TBI performed significantly worse than sham operated rats on a complex task. Contrary to our original hypothesis, acute exercise following injury exacerbated the deficits in the complex task that did not return to levels of the injured rats without access to running wheels until post-TBI day 13. Conclusion: We found a significant interaction between severe bilateral TBI and the introduction of voluntary exercise immediately post-injury. In this paradigm, voluntary wheel running exacerbated the TBI-induced deficit, rather than reducing it.