Exercise Physiology Laboratory, Department of Physical Education, School of Physical Education, Physiotherapy and Occupational Therapy, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
Scand J Med Sci Sports. 2013 Feb;23(1):46-56. doi: 10.1111/j.1600-0838.2011.01350.x. Epub 2011 Jun 15.
We investigated brain mechanisms modulating fatigue during prolonged physical exercise in cold environments. In a first set of studies, each rat was subjected to three running trials in different ambient temperatures (T(a)). At 8 °C and 15 °C, core body temperature (T(core)) decreased and increased, respectively, whereas at 12 °C, the T(core) did not change throughout the exercise. In another set of experiments, rats were randomly assigned to receive bilateral 0.2 μL injections of 2.5 × 10(-2) M methylatropine or 0.15 M NaCl solution into the ventromedial hypothalamic nuclei (VMH). Immediately after the injections, treadmill exercise was started. Each animal was subjected to two experimental trials at one of the following T(a) : 5 °C, 12 °C or 15 °C. Muscarinic blockade of the VMH reduced the time to fatigue (TF) in cold environments by 35-37%. In all T(a) studied, methylatropine-treated rats did not present alterations in T(core) and tail skin temperature compared with controls. These results indicate that, below the zone of thermoneutrality, muscarinic blockade of the VMH decreases the TF, independent of changes in T(core). In conclusion, our data suggest that VMH muscarinic transmission modulates physical performance, even when the effects of thermoregulatory adjustments on fatigue are minimal.
我们研究了在寒冷环境中长时间体力活动时调节疲劳的大脑机制。在一系列研究中，每组大鼠在不同的环境温度（T(a)）下进行三次跑步试验。在 8°C 和 15°C 时，核心体温（T(core)）分别降低和升高，而在 12°C 时，T(core)在整个运动过程中没有变化。在另一组实验中，大鼠被随机分配到接受双侧脑室腹内侧核（VMH）的 0.2 μL 2.5×10(-2) M 甲基阿托品或 0.15 M NaCl 溶液注射。注射后立即开始跑步机运动。每只动物在以下 T(a)之一进行两次实验：5°C、12°C 或 15°C。VMH 的毒蕈碱阻断减少了寒冷环境中的疲劳时间（TF）35-37%。在所有研究的 T(a)中，与对照组相比，甲基阿托品处理的大鼠在 T(core)和尾巴皮肤温度方面没有变化。这些结果表明，在体温中性区以下，VMH 的毒蕈碱阻断独立于 T(core)的变化而减少 TF。总之，我们的数据表明，VMH 的毒蕈碱传递调节体力活动，即使在热调节对疲劳的影响最小的情况下也是如此。
