title: Extracellular serotonin levels in the medullary reticular formation during normal sleep and after REM sleep deprivation.
abstract: Rapid eye movement (REM) sleep is hypothesized to result from the activity of REM sleep-generating and REM sleep-inhibiting neurons. The serotoninergic (5-HT) neurons of the dorsal raphe nucleus (DRN) represents one such population of REM-sleep inhibiting neurons since they are silent during REM sleep. Consistent with the decrease in activity of 5-HT neurons, the brain extracellular levels of 5-HT are lower during REM sleep compared to wakefulness. It is not known whether serotonin release is also reduced as a consequence of REM sleep rebound. Using microdialysis sampling coupled to HPLC-ECD, we measured the extracellular levels of 5-HT and its metabolite (5-HIAA) in the medial medullary reticular formation (mMRF) of freely behaving rats during normal sleep, REM sleep deprivation as well as during REM sleep rebound. We found that the levels 5-HT and 5-HIAA were significantly decreased by REM sleep deprivation. The reduction of 5-HT release was maintained during REM sleep rebound but the extracellular level of its main metabolite was increased. In addition, even during REM sleep rebound, 5-HT release during sleep was low compared to wakefulness. Taken together these data support the permissive role of 5-HT neurotransmission for REM sleep expression.
authors.affiliation: Departamento de Fisiología, Facultad de Medicina, Universidad Nacional Autónoma de México, Mexico City, Mexico. carlos_blanco-centurion@hms.harvard.edu
authors.forename: C A
authors.initials: CA
authors.lastname: Blanco-Centurion
authors.forename: R J
authors.initials: RJ
authors.lastname: Salin-Pascual
mesh_terms: D000818:Animals; D005110:Extracellular Space / Q000378:metabolism; D006897:Hydroxyindoleacetic Acid / Q000378:metabolism; D008297:Male; D008526:Medulla Oblongata / Q000378:metabolism*; D017551:Microdialysis; D051381:Rats; D017208:Rats, Wistar; D012154:Reticular Formation / Q000378:metabolism*; D012701:Serotonin / Q000378:metabolism*; D012892:Sleep Deprivation / Q000503:physiopathology*; D012895:Sleep, REM / Q000502:physiology*; D014851:Wakefulness / Q000502:physiology
chemical_list: D012701:Serotonin; D006897:Hydroxyindoleacetic Acid