Electroencephalogram analysis of non-rapid eye movement sleep in rats.
Sleep states and power spectra of the electroencephalogram were determined for consecutive 4-s epochs during 24 h in rats that had been implanted with electrodes under deep pentobarbital anesthesia. The power spectra in non-rapid eye movement sleep (NREMS) showed marked trends: low-frequency activity (0.75-7.0 Hz) declined progressively throughout the 12-h light period (L) and remained low during most of the 12-h dark period (D); high-frequency activity (10.25-25.0 Hz) rose toward the end of L and reached a maximum at the beginning of D. Within a single NREMS episode (duration 0.5-5.0 min), slow-wave activity (0.75-4.0 Hz) increased progressively to a plateau level. The rise was approximated by a saturating exponential function: although the asymptote level of the function showed a prominent 24-h rhythm, the time constant remained relatively stable (approximately 40 s). After short interruptions of NREMS episodes, slow-wave activity rose more steeply than after long interruptions. The marked 24-h variation of maximum slow-wave activity within NREMS episodes may reflect the level of a homeostatic sleep process.
Trachsel
L
L
Institute of Pharmacology, University of Zürich, Switzerland.
Tobler
I
I
Borbély
A A
AA
D000818:Animals; D003624:Darkness; D004569:Electroencephalography; D008027:Light; D008297:Male; D010507:Periodicity; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012895:Sleep, REM / Q000502:physiology*