Modulatory effect of subthalamic nucleus on the development of fatigue during exhausting exercise: an in vivo electrophysiological and microdialysis study in rats.

The purpose of the study was to investigate the modulatory effect of changes of subthalamic nucleus (STN) activity on the development of central fatigue during exhausting exercise, and reveal the possible mechanism that might affect STN activity from the perspective of neurotransmitters. Rats were randomly divided into electrophysiology and microdialysis study groups. For electrophysiological study, electrical activity in sensorimotor cortex and STN were simultaneously recorded before, during and 90min after the exhausting exercise. For microdialysis study, extracellular fluid of STN was continuously collected with a microdialysis probe and glutamate (Glu), gamma-aminobutyric acid (GABA) levels were subsequently detected with high performance liquid chromatography (HPLC). The behavioral studies showed that rats ran well initiatively with the treadmill exercise in the beginning, 45 ± 11.5min later, movement capacity reduced obviously (which was termed as 'early fatigue'). Correspondingly, STN activity increased significantly compared with rest condition (p < 0.05), while, cortex activity decreased significantly (p < 0.05). Subsequently, rats continued their exercise with minor external stimulation till exhaustion. Cortex activity reached the minimum value under exhaustion condition, while STN activity changed insignificantly (p > 0.05). For microdialysis study, the dynamic change of Glu/GABA ratio was consistent with the change of STN activity during the development of 'early fatigue' rather than the development of exhaustion. In conclusion, the present study shows that, the development of the cortex fatigue during exhausting exercise consists of two phases, 'early fatigue' and exhaustion. Our results suggest that, dynamic changes of STN activity are closely relevant to the development of 'early fatigue' rather than exhaustion, and the changes of STN activity during the development of 'early fatigue' might be partly related to the variance of Glu and GABA levels in STN extracellular fluid. Key pointsThe development of the cortex fatigue during exhausting exercise consists of two phases, 'early fatigue' and exhaustion.Dynamic changes of STN activity are closely relevant to the development of 'early fatigue' rather than exhaustion.The changes of STN activity during the development of 'early fatigue' might be partly related to the variance of Glu and GABA levels in STN extracellular fluid.