Homeostatic regulation of sleep: a role for preoptic area neurons.
The median preoptic nucleus (MnPN) and the ventrolateral preoptic area (vlPOA) contain putative sleep-regulatory neurons that exhibit elevated discharge rates during sleep compared with waking. Expression of c-Fos protein immunoreactivity (IR) in GABAergic neurons in the MnPN and the vlPOA is high in spontaneously sleeping rats and in rats undergoing recovery sleep after sleep deprivation. However, it is unclear whether c-Fos-IR in these neurons is evoked by increases in sleep pressure or by increases in sleep amount. We examined c-Fos-IR in MnPN and vlPOA neurons under experimental conditions that dissociated homeostatic sleep pressure, sleep amount, and time of day. Groups of rats with strong diurnal rhythms in sleep-wake organization were killed after (1) spontaneous sleep in the light, (2) spontaneous sleep in the dark, (3) sleep deprivation (SLD) in the light and (4) recovery sleep after SLD in the light. Numbers of GABAergic neurons expressing c-Fos-IR in the MnPN were significantly higher after SLD in the light compared with spontaneous sleep and recovery sleep in the light. In contrast, Fos-IR in vlPOA GABAergic neurons was most prevalent after spontaneous sleep and recovery sleep in the light. No light-dark differences in Fos-IR were observed in the MnPN after SLD in groups of rats with weak or absent diurnal sleep-waking rhythms. Our findings define potential roles for MnPN and vlPOA GABAergic neurons in homeostatic aspects of sleep regulation.
Gvilia
Irma
I
Research Service, Veterans Affairs Greater Los Angeles Healthcare System, North Hills, California 91343, USA. irmagvilia@hotmail.com
Xu
Feng
F
McGinty
Dennis
D
Szymusiak
Ronald
R
D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D002452:Cell Count; D002940:Circadian Rhythm / Q000502:physiology*; D003624:Darkness; D006706:Homeostasis / Q000502:physiology*; D008027:Light; D008297:Male; D009433:Neural Inhibition / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D009474:Neurons / Q000166:cytology / Q000502:physiology*; D010775:Photic Stimulation; D011301:Preoptic Area / Q000166:cytology / Q000502:physiology*; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D012890:Sleep / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism*
D015415:Biomarkers; D016760:Proto-Oncogene Proteins c-fos; D005680:gamma-Aminobutyric Acid