期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2015
卷号：112
期号：15
页码：4785-4790
DOI：10.1073/pnas.1419603112
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：SignificanceSleep in fruit flies shares all the essential features of mammalian sleep. Here, by using in vivo calcium imaging, we show for the first time, to our knowledge, that neuronal activity and reactivity decline during sleep and increase during wake simultaneously in many cells of the fly brain. Furthermore, we show that long wake reduces baseline and evoked neural activity and causes neurons to respond inconsistently to stimuli. The latter finding is reminiscent of the phenomenon of "local sleep in wake" described in rats, in which single cortical neurons unpredictably go "offline" during extended wake, leading to performance errors. Thus, these findings open the way to use Drosophila to study the molecular mechanisms underlying the cognitive deficits caused by sleep loss. Sleep in Drosophila shares many features with mammalian sleep, but it remains unknown whether spontaneous and evoked activity of individual neurons change with the sleep/wake cycle in flies as they do in mammals. Here we used calcium imaging to assess how the Kenyon cells in the fly mushroom bodies change their activity and reactivity to stimuli during sleep, wake, and after short or long sleep deprivation. As before, sleep was defined as a period of immobility of >5 min associated with a reduced behavioral response to a stimulus. We found that calcium levels in Kenyon cells decline when flies fall asleep and increase when they wake up. Moreover, calcium transients in response to two different stimuli are larger in awake flies than in sleeping flies. The activity of Kenyon cells is also affected by sleep/wake history: in awake flies, more cells are spontaneously active and responding to stimuli if the last several hours (5-8 h) before imaging were spent awake rather than asleep. By contrast, long wake ([≥]29 h) reduces both baseline and evoked neural activity and decreases the ability of neurons to respond consistently to the same repeated stimulus. The latter finding may underlie some of the negative effects of sleep deprivation on cognitive performance and is consistent with the occurrence of local sleep during wake as described in behaving rats. Thus, calcium imaging uncovers new similarities between fly and mammalian sleep: fly neurons are more active and reactive in wake than in sleep, and their activity tracks sleep/wake history.
