Manipulations during forced wakefulness have differential impact on sleep architecture, EEG power spectrum, and Fos induction

We propose a hypothesis suggesting that the most prominent experiences occu rring during wakefulness activate specific clusters of neurons related to s uch experiences. These neurons could possibly then evoke the release of var ious types of sleep-inducing molecules, thereby causing different patterns of sleep architecture. In this study, we therefore sought to determine whet her manipulations of behavior during wakefulness, such as forced wakefulnes s induced by gentle handling, forced wakefulness associated with a stressfu l condition such as immobilization, or forced wakefulness associated with e xcess intake of palatable food, could result in a variation of Fos immunore activity in selective brain structures and could also result in different s leep and EEG power density patterns. The results showed that the sleep-wake cycle of rats after all the experimental manipulations was different not o nly with respect to the control group but also among themselves. Additional ly, power spectrum analysis showed an increase of 0.25-4.0 Hz in ail experi mental manipulations, whereas the 4.25-8.0 Hz increase occurred only in the situation of forced wakefulness plus stress. The Fos induction showed acti vation of cell clusters in cortical areas and telencephalic centers, in sev eral hypothalamic nuclei, in monoaminergic cell groups, and in brain stem n uclei. The density of Fos-immunoreactive neurons varied in relation to the different paradigms of forced wakefulness. These results suggest that activ ation of cell clusters in the brain are related to the type of manipulation imposed on the rat during wakefulness and that such variation in eel activ ation prior to sleep may be associated with sleep architecture and EEG powe r. (C) 1998 Elsevier Science Inc.