Effects of body weight-supported treadmill training at different speeds on the motor function and depressive behaviors after spinal cord injury in rats

Spinal cord injury (SCI) causes motor dysfunction and depression, which hinders the recovery of motor function. Body weight-supported treadmill training (BWSTT) should be considered an effective method for functional rehabilitation after SCI, as it is an efficacious intervention in healthcare with no side effects. Because exercise exerts different effects on motor function recovery and inhibiting depression after SCI, we aimed to determine the appropriate intensity of BWSTT. In this study, fixed durations, frequencies, and percentages of BWSTT with different speeds of BWSTT (7, 15, and 21 cm/s) were chosen to explore the appropriate intensity, which affected the recovery of motor function and antidepressant effects on SCI rats. Based on our results, BWSTT at 21 cm/s produced the best outcomes for motor function recovery and the spinal cord levels of brain-derived neurotrophic factor (BDNF) and tropomyosin receptor kinase B (TrkB). The antidepressant effects of BWSTT at 15 and 21 cm/s were confirmed based on the increasing sucrose preference, the time spent in the central area and social time, and reduced immobility time. BWSTT at 15 and 21 cm/s improved the modulation of the hypothalamic-pituitary-adrenal axis by decreasing serum corticosterone levels and increasing hippocampal glucocorticoid receptor levels. In addition, higher levels of neurogenesis-related proteins were observed in the hippocampus of the group subjected to BWSTT at 21 cm/s than in the other groups. Thus, BWSTT at 21 cm/s is a potentially favorable treatment that synchronously improves motor function recovery and exerts an antidepressant effect.