Long term neurological and behavioral effects of graded perinatal asphyxia in the rat.

Perinatal hypoxic-ischemic states can cause irreversible damage to the brain, ranging from minimal brain dysfunction to death. Only few studies have been reported describing neurological, cognitive and behavioral deficits following perinatal asphyxia. We therefore decided to study long term effects of perinatal asphyxia in a well-documented animal model resembling the clinical situation. Caeserean section in rats was performed and the pups, still in the uterus horns, were placed into a water bath at 37 degrees C for periods of 5-20 min; pups were then given to surrogate mothers and examined at three month of age. Examinations consisted of a battery of motor and reflex tests, Morris water maze, multiple T-maze, elevated plus maze and open field studies. No abnormalities were found in rats even with long periods of perinatal asphyxia by neurological examination, in the open field and in mazes. Interestingly, in the elevated plus maze rats with long lasting exposure to hypoxia (15 and 20 min of asphyxia) showed reduced anxiety-related behavior. This finding may be relevant for the explanation of anxiety related disorders in adulthood with a tentative history in the perinatal period.