EFFECTS OF A PERIOD OF ASPHYXIA DURING BIRTH ON SPATIAL-LEARNING IN THE RAT

The present study aimed to test whether an acute period of asphyxia du ring birth in the rat results in long-term alterations in CNS function . Morphologic studies have indicated that the hippocampus is particula rly vulnerable to perinatal anoxia. Thus, the present study tested adu lt rats, which had undergone acute birth asphyxia, for their performan ce in spatial learning and memory tasks associated with the hippocampu s. Rat fetuses on the day of birth were submitted to an acute period o f complete asphyxia by submersion of the isolated uterus into a water bath for 5-20 min before delivery of the pups. Control animals were ei ther born vaginally or delivered by rapid cesarean section. At 1.5 mo of age, rats that had undergone 15 min of birth asphyxia showed no def icit in acquisition of spatial learning, measured as latency to find a hidden platform in the Morris water maze. However, at 4 mo of age, se parate groups of rats, which had undergone 10, 15, spatial learning ta sk compared with vaginally born controls, whereas the 5-min group perf ormed similarly to controls. After overtraining, there was no differen ce among groups on short-term (1 wk) retention of the spatial navigati on task; however, asphytic animals tested at 1.5 mo and retested at 4 mo showed a slight deficit in retention on retest. Animals that had un dergone 15 min of birth asphyxia weighed less than did vaginally born animals, but showed no deficit in swimming ability, spontaneous altern ation in a T maze, or other sensorimotor indices. Our results show tha t a brief period of asphyxia during a cesarean birth can produce subtl e deficits in spatial learning that become evident only in adulthood.