Compensatory rebound of body movements during sleep, after asphyxia in neonatal rats.

PURPOSE The usefulness of body movements that occur during sleep when assessing perinatal asphyxia and predicting its long-term consequences is contradictory. This study investigated whether neonatal rats manifest these movements in compensatory rebound after asphyxia, and if these alterations play an important role in its pathogenesis. METHODS Eight neonatal rats (aged 6-48 h) were implanted with small EMG and EKG electrodes and sleep movements were recorded over a 30-minute control period. Recordings were continued during asphyxia caused by the enclosure of the animal in a polyvinyl sheet for 60 minutes, followed by a 30-minute recovery period. RESULTS Heart rate was lowered to bradycardic level during asphyxia causing behavioral agitation and increased waking time during the initial phase (30 minutes). Sleep-related movements were also significantly reduced from 12.5 +/- 0.5 (median +/- SE/2min) to 9.0 +/- 0.44 in the final half of the period (Anova, p<0.05). Movement frequency increased in the recovery period to 15.0 +/- 0.49 (Anova, p<0.05). CONCLUSION These data show that newborn rats present compensatory rebound of body movements during sleep which may help in the diagnosis of asphyxia and other problems related to sleep parameters.