Arousal State-Dependent Alterations in Neural Activity in the Zebra Finch VTA/SNc

Sleep-wake behaviors are important for survival and highly conserved among animal species. A growing body of evidence indicates that the midbrain dopaminergic system is associated with sleep-wake regulation in mammals. Songbirds exhibit mammalian-like sleep structures, and neurons in the midbrain ventral tegmental area (VTA) and substantia nigra pars compacta (SNc) possess physiological properties similar to those in mammals. However, it remains uncertain whether the neurons in the songbird VTA/SNc are associated with sleep-wake regulation. Here, we show that VTA/SNc neurons in zebra finches exhibit arousal state-dependent alterations in spontaneous neural activity. By recording extracellular single-unit activity from anesthetized or freely behaving zebra finches, we found that VTA/SNc neurons exhibited increased firing rates during wakefulness, and the same population of neurons displayed reduced firing rates during anesthesia and slow-wave sleep. These results suggest that the songbird VTA/SNc is associated with the regulation of sleep and wakefulness along with other arousal regulatory systems. These findings raise the possibility that fundamental neural mechanisms of sleep-wake behaviors are evolutionarily conserved between birds and mammals.

睡眠 - 觉醒行为对生存至关重要，并且在动物物种中高度保守。越来越多的证据表明，中脑多巴胺能系统与哺乳动物的睡眠 - 觉醒调节有关。鸣禽表现出类似哺乳动物的睡眠结构，中脑腹侧被盖区（VTA）和黑质致密部（SNc）的神经元具有与哺乳动物相似的生理特性。然而，鸣禽VTA/SNc中的神经元是否与睡眠 - 觉醒调节有关仍不确定。在此，我们表明斑胸草雀的VTA/SNc神经元在自发神经活动中呈现出依赖觉醒状态的变化。通过记录麻醉或自由行为的斑胸草雀的细胞外单单位活动，我们发现VTA/SNc神经元在清醒时放电频率增加，而同一群神经元在麻醉和慢波睡眠期间放电频率降低。这些结果表明，鸣禽的VTA/SNc与睡眠和清醒的调节以及其他觉醒调节系统有关。这些发现增加了一种可能性，即睡眠 - 觉醒行为的基本神经机制在鸟类和哺乳动物之间是进化保守的。