Comparison of hippocampal interleukin-6 immunoreactivity after exhaustive exercise in both exercise-trained and untrained rats.

BACKGROUND/AIM Exhaustive exercise is a strong stress factor and can impact cytokine production in the brain. Interleukin-6 (IL-6) is produced in greater amounts than any other cytokine in response to exercise, and its effects are closely related to both exercise duration and intensity. In this study, we measured the differences between the amount of IL-6 reactivity of the hippocampus after an exhaustive session ofrunning in long-term exercise-trained and untrained rats. MATERIALS AND METHODS The exercise-trained group ran on a treadmill for 12 weeks. Both groups were forced to run until exhaustion. Each group of rats was sacrificed immediately, 1 day, or 3 days after exhaustion and the brains were evaluated for IL-6 immunoreactivity in the hippocampus. RESULTS Hippocampal IL-6 immunoreactivity was absent in controls, mild to severe in untrained rats, and weak to mild in long-term-trained rats. The most prominent increase in IL-6 was observed in the untrained rats sacrificed 1 day after exhaustion. CONCLUSION Exercise to exhaustion resulted in increased IL-6 levels in brain slices in both groups of rats, but long-term exercise training protected the hippocampus from exposure to an extreme increase in IL-6. The immediate effects of these cytokine levels were observed 1 day after exhaustion.