EFFECTS OF NEONATAL FOCAL CEREBRAL HYPOXIA-ISCHEMIA ON SLEEP-WAKING PATTERN, ECOG POWER SPECTRA AND LOCOMOTOR-ACTIVITY IN THE ADULT-RAT

The aim of this study was to determine the influence of neonatal focal cerebral hypoxia-ischemia (HI) on sleep-waking pattern, electrocortic ogram (ECoG) power spectra and locomotor activity (LA) in adult Wistar rats. Seven-day old pups were subjected to permanent unilateral ligat ion of the common carotid artery and transient hypoxia (8% O-2). At 10 weeks of age, the extent of brain damages was evaluated by magnetic r esonance imaging (MRI) and homogenous injured animals were selected be fore chronic implantation of radiotelemetry device. Using a single ECo G recording channel method, waking (W), paradoxical sleep (PS) and slo w wave sleep (SWS) were continuously recorded for 72 h and they were s emi-automatically analyzed off-line. We observed that neonatal HI trig gers a cascade of events leading, in adult rats, tl, brain dysfunction characterized by an increase in SWS (55.0 vs. 40.2% in sham-operated rats, p < 0.05) and a marked decrease in W phases duration (43.4 vs. 5 1.5%, p < 0.05) while PS was almost suppressed in HI rats (1.6 vs. 8.3 %, p < 0.05). In addition, power spectral analysis of ECoG revealed si gnificant (p < 0.05) alteration in PS power density with a shift of th e dominant frequency peak (5.0 to 7.5 Hz for HI and sham-operated rats , respectively). During the light period, we found that HI induced a p ronounced reduction of LA (-30%, p < 0.05). These results indicate tha t Wistar rats exposed to a neonatal unilateral cerebral HI present sig nificant ECoG activity, sleep-waking pattern and behavioral disturbanc es when adults. However, it remains to establish whether such alterati ons can be prevented by neuroprotective agents. (C) 1998 Elsevier Scie nce B.V. All rights reserved.