Hiura Mikio, Sakata Muneyuki, Ishii Kenji, Toyohara Jun, Oda Keiichi, Nariai Tadashi, Ishiwata Kiichi
Hosei University, Faculty of Sports and Health Studies, Tokyo, Japan.
Tokyo Metropolitan Institute of Gerontology, Research Team for Neuroimaging, Tokyo, Japan.
Int J Sports Med. 2017 Jan;38(1):19-26. doi: 10.1055/s-0042-114779. Epub 2017 Jan 10.
The central opioid receptor system likely contributes to the mechanism underlying the changes in affect elicited by exercise. Our aim was to use positron emission tomography (PET) to test whether exercise intensity influences activation of the μ-opioid receptor system in the brain, and whether changes in opioid receptor activation correlate with exercise-induced changes in affect. 7 healthy young male subjects (23±2 years) performed 20-min constant-load cycling exercises at heavy (ExH) and severe-intensity (ExS), and PET was performed using [C]carfentanil as a tracer before and after each exercise. Exercise elicited the μ-opioidergic system activation in the large areas of the limbic system, particularly in the insular cortex, and cerebellum. Of note, deactivation of the μ-opioidergic system in the pituitary gland was identified as a specific finding in ExS, which evoked a distinctive sensation of fatigue. Within these brain areas, μ-opioid receptor activation correlated positively with increased positive affect (R=0.67-0.95) in ExH and negative affect (R=0.63-0.77) in ExS. These findings suggest that central μ-opioidergic neurotransmission evoked by continuous exercise is discriminated by work intensity. Notably, we also observed a possible contribution of the central μ-opioidergic system to the development of the sensation of fatigue during exhaustive exercise.
中枢阿片受体系统可能参与了运动引起的情感变化的潜在机制。我们的目的是使用正电子发射断层扫描（PET）来测试运动强度是否会影响大脑中μ-阿片受体系统的激活，以及阿片受体激活的变化是否与运动引起的情感变化相关。7名健康年轻男性受试者（23±2岁）进行了20分钟的重负荷（ExH）和极强度（ExS）恒定负荷自行车运动，每次运动前后使用[C]卡芬太尼作为示踪剂进行PET检查。运动引起了边缘系统大面积区域，特别是岛叶皮质和小脑的μ-阿片能系统激活。值得注意的是，在ExS中发现垂体腺的μ-阿片能系统失活是一个特定的发现，它引起了独特的疲劳感。在这些脑区中，μ-阿片受体激活与ExH中积极情感增加（R=0.67-0.95）和ExS中消极情感增加（R=0.63-0.77）呈正相关。这些发现表明，持续运动引起的中枢μ-阿片能神经传递因工作强度而异。值得注意的是，我们还观察到中枢μ-阿片能系统可能在力竭运动期间疲劳感的产生中发挥作用。
