Effects of factors inducing diffuse damage to brain tissue on sleep structure in laboratory rats.

Chronic experiments on laboratory rats with implanted electrodes for recording neocortical and hippocampal EEG and cervical muscle electromyogram traces were performed to study the effects of strong treatments inducing diffuse damage to brain tissue on subsequent sleep. Four different experimental models were used: one "chronic" (generalized cerebral ischemia induced by permanent occlusion of one of the common carotid arteries) and three "acute" (hypoxic hypoxia, hypoglycemia, and "penicillin" epilepsy). Sleep recordings were made in freely moving animals either day-round (in the "chronic" model) or daily for 3 h ("acute" models). In all models, traces showed significant increases in the mean total duration of paradoxical sleep, reaching a peak 1-3 days after treatment. The subsequent dynamics depended on the treatment used: in the "acute" models, the duration of paradoxical sleep returned to control levels in 5-6 days, while in the "chronic" model, this occurred at 40-45 days after the beginning of treatment. The sharp increases in the durations of paradoxical sleep after use of strong treatments inducing damage to brain tissue can be regarded as supporting the suggestion that there is an increase in neuronal recovery processes during paradoxical sleep.