Sleep deprivation and c‐fos expression in the rat brain

This study examined the effects of sleep deprivation on the expression of the immediate early gene c‐fos in the brain with both in situ hybridization and immunocytochemistry. Rats were manually sleep‐derived for 3 h, 6 h, 12 h, and 24 h starting at light onset (08.00 hours), and for 12 h starting at dark onset (20.00 hours). c‐Fos expression was found to be higher in sleep‐deprived rats with respect to control animals in several brain areas. The increase was evident both in terms of c‐fos mRNA and Fos protein, although with a different time course. Among the areas that showed a consistent induction of c‐fos were many cortical regions, the medial preoptic area and the posterior hypothalamic area, some thalamic nuclei, and several nuclei of the dorsal pontine tegmentum. The pattern of c‐fos expression after sleep deprivation was very similar to that observed after comparable periods of spontaneous wakefulness (Pompeiano et al. 1994). In general, the increase in c‐fos expression was not simply proportional to the amount of previous wakefulness. In many areas, the highest levels of c‐fos were seen after 3 h of sleep deprivation. These observations are discussed with respect to the homeostatic regulation of sleep and to the functional consequences of wakefulness in specific brain areas.