Sleep homeostasis in suprachiasmatic nuclei-lesioned rats: effects of sleep deprivation and triazolam administration.

The electroencephalogram (EEG) and electromyogram of rats with lesions in the suprachiasmatic nuclei (SCNx) were recorded during two series of 24-h baseline, 6-h sleep deprivation (SD), and 24-h recovery. At recovery onset, rats were injected i.p. with vehicle (VEH) control solution or 0.4 mg/kg triazolam (TRZ) in a balanced crossover design. Consecutive 10-s epochs were scored for vigilance states and EEG power spectra were computed. Arousal states were uniformly distributed during 24-h baseline (wake 47% of recording time, non-rapid-eye movement sleep (nonREMS) 47%, REMS 7%), and EEG spectra (0-25 Hz) were devoid of significant trends. State-specific EEG power spectra profiles in SCNx rats were similar to those of intact animals reported previously. However, EEG delta power (0.5-3.5 Hz) of nonREMS was markedly lower in SCNx rats. Recovery from 6-h SD was characterised by a short-lasting reduction of REMS, and a long-lasting increase of nonREMS time at the cost of wakefulness. EEG delta power rebounded during the first 8 h in recovery, and fell below baseline level after 12 h in recovery. During 0-2 h TRZ recovery, rats spent more time in nonREMS with higher EEG slow wave activity as compared to the corresponding VEH recovery period. EEG slow wave activity fell below baseline levels 10 h after TRZ injection and termination of SD. We conclude that major features of homeostatic sleep EEG regulation are present in SCNx rats.(ABSTRACT TRUNCATED AT 250 WORDS)