LONG–LASTING BEHAVIORAL IMPACT OF NEONATAL ASPHYCTIC EPISODES IN RAT MALE SUCKLINGS

It is well known that toxic and asphyctic insults in neonatal rat models have produced behavioral changes (in activity, memory and learning). The persistence of these effects longitudinally has not been well documented. 100 male pups from 22 Sprague-Dawley dams were randomly assigned in equal numbers to an asphyctic (7 asphyctic episodes in 4 days in individual vials) and to a control group, at 5 activity testing intervals (7, 14, 21, 30, 50 days of life), where independent groups of 20 animals were placed singlely in a drum actometer to record 10 min (5 trials of 2 min each) of learning activity. In addition, conditioned active avoidance response learning was examined, at 45-50 days of life. ANOVA with repeated measures (where needed) was used for analysis. P < .05 was considered significant. RESULTS: 1) the asphyctic group demonstrated a significant (P < .05) hyperactivity at 21 days of life (compared to control) and then a significant (P < .05) hypoactivity at day 50 of life. There was no difference in activity at 7, 14 or 30 days of life. Intertrial habituation was intact in both groups at all ages. 2) There was no significant difference in active avoidance (number of trials to criterion & escape latency times) learning between asphyctic and controls and in memory testing. These behavioral findings suggest that postnatal asphyctic events in these model may inhibit the cholinergic system and induce early hyperactivity and late (50 days) hypoactivity (possibly) mediated by norepinephrine), but not alter the acquisition of conditioned avoidance responses.