Noradrenergic activity in rat brain during rapid eye movement sleep deprivation and rebound sleep.

Noradrenergic locus ceruleus neurons are most active during waking and least active during rapid eye movement (REM) sleep. We expected REM sleep deprivation (REMSD) to increase norepinephrine utilization and activate the tyrosine hydroxylase (TH) gene critical for norepinephrine production. Male Wistar rats were deprived of REM sleep with the platform method. Rats were decapitated after 8, 24, or 72 h on small (REMSD) or large (control) platforms or after 8 or 24 h of rebound sleep after 72 h of the platform treatment. During the first 24 h, norepinephrine concentration, measured by high-performance liquid chromatography/electrochemical detection, was lower in the neocortex, hippocampus, and posterior hypothalamus in REMSD rats than in large-platform controls. After 72 h of REMSD, TH mRNA, measured by in situ hybridization, was increased in the locus ceruleus and norepinephrine concentrations were increased. Polygraphy showed that small-platform treatment caused effective and selective REMSD. Serum corticosterone measurement by radioimmunoassay indicated that the differences found in norepinephrine and TH mRNA were not due to differences in stress between the treatments. The novel finding of sleep deprivation-specific increase in TH gene expression indicates an important mechanism of adjusting to sleep deprivation.