Behavioral and biochemical dissociation of arousal and homeostatic sleep need influenced by prior wakeful experience in mice

Abstract

Sleep is regulated by homeostatic mechanisms, and the low-frequency power in the electroencephalogram (delta power) during nonrapid eye movement sleep reflects homeostatic sleep need. Additionally, sleep is limited by circadian and environmentally influenced arousal. Little is known, however, about the underlying neural substrates for sleep homeostasis and arousal and about the potential link between them. Here, we subjected C57BL/6 mice to 6 h of sleep deprivation using two different methods: gentle handling and continual cage change. Both groups were deprived of sleep to a similar extent (>99%), and, as expected, the delta power increase during recovery sleep was quantitatively similar in both groups. However, in a multiple sleep latency test, the cage change group showed significantly longer sleep latencies than the gentle handling group, indicating that the cage change group had a higher level of arousal despite the similar sleep loss. To investigate the possible biochemical correlates of these behavioral changes, we screened for arousal-related and sleep needrelated phosphoprotein markers from the diencephalon. We found that the abundance of highly phosphorylated forms of dynamin 1, a presynaptic neuronal protein, was associated with sleep latency in the multiple sleep latency test. In contrast, the abundance of highly phosphorylated forms of N-myc downstream regulated gene 2, a glial protein, was increased in parallel with delta power. The changes of these protein species disappeared after 2 h of recovery sleep. These results suggest that homeostatic sleep need and arousal can be dissociated behaviorally and biochemically and that phosphorylated N-myc downstream regulated gene 2 and dynamin 1 may serve as markers of homeostatic sleep need and arousal, respectively. phosphoproteomics | two-dimensional difference gel electrophoresis S leep-wakefulness is continuously regulated by circadian and homeostatic mechanisms. In addition, multiple factors affect the level of arousal, including emotional, environmental, and physiological influences (1). During non-rapid eye movement (NREM) sleep, the homeostatic sleep need is correlated with the power in the delta wave band (i.e., 1-4 Hz) in the electroencephalogram (EEG). Delta power is augmented in proportion to previous wakefulness time and is dissipated during sleep. These findings imply that homeostatic sleep need is regulated by the durations of prior sleep and wakefulness (2). On the other hand, the level of arousal is inversely related to the likelihood of falling asleep and can be measured in terms of the sleep latency in the multiple sleep latency test (MSLT) (3). Because prolonged waking increases sleep need in addition to lowering the level of arousal, sleep latency often varies inversely with EEG delta power expressed during sleep (3). However, the level of arousal can be affected independently of time spent awake (for example, with stressful or exciting experiences during waking), implying that, under conditions of identical sleep deprivation time, the s...

Entrainment of the mouse circadian clock by sub-acute physical and psychological stress

“…Mild sleep deprivation caused by a cage change34 during ZT4–6 for 3 consecutive days did not shift the phase of peripheral clocks (Figure S7A), indicating that sleep deprivation was not involved in stress-induced circadian entrainment. Stress-induced changes in feeding behaviour and body temperature can also lead to alterations in circadian rhythm353637383940.…”

Call it Worm Sleep

“…The subsequent discovery of Rapid Eye Movement (REM) and non-REM sleep [11] demonstrated that these different sleep states are generated by distinct physiological processes [12]. Experiments using the EEG have also revealed that slow wave activity can serve as a biomarker for sleep need in certain settings [13,14]. …”

The adenosine-mediated, neuronal-glial, homeostatic sleep response

“…Since sleep duration is primarily a function of arousal system activity, it appears that arousal and sleep homeostasis can be dissociated by disrupting the Ado system that links the two (6, 24). On the other hand, different experimental methods of sleep deprivation of the same duration, lead to different levels of arousal with relatively small effect on homeostatic SWA (27). One may, nonetheless speculate that waking activity that especially activates the LC, would elicit a stronger sleep homeostatic response based on the findings that depletion of NE reduces this same response (13).…”

“…The method of sleep deprivation can determine the level of arousal. We have reported that sleep deprivation induced by cage change results in higher arousal than gentle handling (27). The panel of activity-activated gene expression varied in correlation with arousal level as elicited by either cage change or gentle handling.…”