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 during birth in the rat results in long-term alterations in CNS function. Morphologic studies have indicated that the hippocampus is particularly vulnerable to perinatal anoxia. Thus, the present study tested adult rats, which had undergone acute birth asphyxia, for their performance in spatial learning and memory tasks associated with the hippocampus. Rat fetuses on the day of birth were submitted to an acute period of complete asphyxia by submersion of the isolated uterus into a water bath for 5-20 min before delivery of the pups. Control animals were either 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 deficit in acquisition of spatial learning, measured as latency to find a hidden platform in the Morris water maze. However, at 4 mo of age, separate groups of rats, which had undergone 10, 15, or 20 min of birth asphyxia, showed a deficit in initial acquisition of the spatial learning task compared with vaginally born controls, whereas the 5-min group performed similarly to controls. After overtraining, there was no difference among groups on short-term (1 wk) retention of the spatial navigation 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 undergone 15 min of birth asphyxia weighed less than did vaginally born animals, but showed no deficit in swimming ability, spontaneous alternation in a T maze, or other sensorimotor indices.(ABSTRACT TRUNCATED AT 250 WORDS)