Perrier Jean-François
Dan Med J. 2016 Feb;63(2).
Serotonin is a major neuromodulator in the central nervous system involved in most physiological functions including appetite regulation, sexual arousal, sleep regulation and motor control. The activity of neurons from the raphe spinal tract, which release serotonin on motoneurons, is positively correlated with motor behaviour. During moderate physical activity, serotonin is released from synaptic terminals onto the dendrites and cell bodies of motoneurons. Serotonin increases the excitability of motoneurons and thereby facilitate muscle contraction by acting on several parallel intracellular pathways. By activating 5-HT1A receptors, serotonin inhibits TWIK-related acid-sensitive potassium channels and small conductance calcium-activated potassium channels. In parallel, serotonin binds to 5-HT2 receptors, which promotes the low-threshold L-type Ca(2+) channels. During intense physical activity, more serotonin is released. The reuptake systems saturate and serotonin spills over to reach extrasynaptic 5-HT1A receptors located on the axon initial segment of motoneurons. This in turn induces the inhibition of the Na(+) channels responsible for the initiation of action potentials. Fewer nerve impulses are generated and muscle contraction becomes weaker. By decreasing the gain of motoneurons, serotonin triggers central fatigue.
血清素是中枢神经系统中的一种主要神经调质，参与大多数生理功能，包括食欲调节、性唤起、睡眠调节和运动控制。中缝脊髓束的神经元活动与运动行为呈正相关，该束神经元会向运动神经元释放血清素。在适度的体育活动中，血清素从突触终末释放到运动神经元的树突和细胞体上。血清素通过作用于几条平行的细胞内途径来增加运动神经元的兴奋性，从而促进肌肉收缩。通过激活5-HT1A受体，血清素抑制TWIK相关的酸敏感钾通道和小电导钙激活钾通道。同时，血清素与5-HT2受体结合，促进低阈值L型钙通道。在剧烈的体育活动中，会释放更多的血清素。再摄取系统饱和，血清素溢出，作用于位于运动神经元轴突起始段的突触外5-HT1A受体。这反过来又会抑制负责动作电位起始的钠通道。产生的神经冲动减少，肌肉收缩变弱。通过降低运动神经元的增益，血清素引发中枢性疲劳。
