Porkka-Heiskanen T
Institute of Biomedicine, University of Helsinki, Finland.
Ann Med. 1999 Apr;31(2):125-9. doi: 10.3109/07853899908998788.
Sleep propensity increases in the course of wakefulness: the longer the previous wakefulness period is, the longer and deeper (measured as delta power in EEG recordings) is the following sleep. The mechanisms that regulate the need of sleep at the cellular level are largely unknown. The inhibitory neuromodulator, adenosine, is a promising candidate for a sleep-inducing factor: its concentration is higher during wakefulness than during sleep, it accumulates in the brain during prolonged wakefulness, and local perfusions as well as systemic administration of adenosine and its agonists induce sleep and decrease wakefulness. Adenosine receptor antagonists, caffeine and theophylline, are widely used as stimulants of the central nervous system to induce vigilance and increase the time spent awake. Our hypothesis is that adenosine accumulates in the extracellular space of the basal forebrain during wakefulness, increasing the sleep propensity. The increase in extracellular adenosine concentration decreases the activity of the wakefulness-promoting cell groups, especially the cholinergic cells in the basal forebrain. When the activity of the wakefulness-active cells decreases sufficiently sleep is initiated. During sleep the extracellular adenosine concentrations decrease, and thus the inhibition of the wakefulness-active cells also decreases allowing the initiation of a new wakefulness period.
之前清醒的时间越长，随后的睡眠就越长且越深（通过脑电图记录中的δ波功率来衡量）。在细胞水平上调节睡眠需求的机制在很大程度上尚不清楚。抑制性神经调质腺苷是一种有潜力的促眠因子：其浓度在清醒时高于睡眠时，在长时间清醒过程中会在大脑中积累，并且局部灌注以及全身性给予腺苷及其激动剂会诱导睡眠并减少清醒时间。腺苷受体拮抗剂咖啡因和茶碱被广泛用作中枢神经系统兴奋剂以提高警觉性并增加清醒时间。我们的假设是，腺苷在清醒期间会在基底前脑的细胞外空间中积累，从而增加睡眠倾向。细胞外腺苷浓度的增加会降低促进清醒的细胞群的活性，尤其是基底前脑的胆碱能细胞。当促进清醒的细胞的活性充分降低时，睡眠就会开始。在睡眠期间，细胞外腺苷浓度会降低，因此对促进清醒的细胞的抑制也会减弱，从而允许开始新的清醒期。
