The Effects of High-Intensity Exercise on Anxiety-Like Behaviors, Fear Extinction, Neurotrophic Factors, and Expression of Apoptosis-Related Factors Induced by Stress in Rat Brain

Background and purpose: Post-traumatic stress disorder (PTSD), a type of psychiatric disorder that occurs after exposure to traumatic events, is associated with anxiety and abnormality in the activity of hypothalamic-pituitary-adrenal axis and cognitive functions. Physical activity can improve symptoms of somatic and neuropsychiatric disorders; however, appropriate exercise intensity and duration are still in question. In the present study, the effects of high-intensity exercise on anxiety-like behaviors, fear extinction, serum insulin-like growth factor (IGF-1), brain-derived neurotrophic factor (BDNF), and expression of apoptosis-related genes were investigated in the prefrontal cortex of the rat PTSD model. Materials and methods: In this experimental study, single prolonged stress (SPS) was used to induce PTSD in adult male Wistar rats. After 10 days, the animals in the exercise groups were subjected to high-intensity treadmill exercise (20 m/min, 5 days/week) for four weeks. Next, anxiety-like behaviors and fear extinction were examined using open field and shuttle box tests, respectively. Thereafter, serum IGF-1 and brain BDNF were measured by ELISA kits; and expression of Bax, Bcl-2, and caspase-3 in the prefrontal cortex were measured by real-time PCR. Results: SPS rats showed increased anxiety and decreased fear extinction, serum IGF-1, and prefrontal BDNF compared to the control animals. In addition, SPS induced apoptosis by an increase in Bax and caspase-3 and a decrease in Bcl-2. High-intensity exercise reduced apoptosis and increased serum IGF-1 significantly (P<0.05). Conclusion: High-intensity exercise decreases anxiety-like behaviors by increasing serum IGF-1 and inhibiting apoptosis in the prefrontal cortex of PTSD rats.