Effects of hypothermia and gender on survival and behavior after perinatal asphyxia in rats

Previous studies in rats have demonstrated that perinatal asphyxia (PA) produces long-term morphological alterations, particularly affecting hippocampus. neostriatum, and cerebral cortex. These changes were prevented by applying hypothermia during the asphyctic insult. Because these cerebral areas are involved in cognitive and motor functions, the aim of the present study was to determine whether periods of PA during normothermia or hypothermia produces long-term behavioral impairments in rats of both sexes. The cognitive and motor functions were studied using the spatial Morris water maze (MWM) task at 1.5 months, and the open field at 5 months, respectively. The present study revealed that female rats had a higher survival rate than males after PA in normothermic conditions (p < 0.014). and that hypothermia drastically prolonged the time of survival in both sexes (p < 0.001). There were no differences in learning and memory functions between groups or male and female rats when tested with MWM. Rats subjected to hypothermia treatment did not show differences in the MWM compared to controls. A lower locomotor activity in the open field test was only observed in male rats that suffered 15 and 20 min of PA in normothermia (p < 0.05). Hypothermia treatment prevented this hypoactivity. PA in females, even if severe, did not affect the motor activity. The data of both behavioral tests showed differences between sexes, i.e., the female rats learned the MWM task slower, and were more active in the open field. This work lends further support for the hypothesis that hypothermia can prevent mortality as well as long-term sequelae induced by PA.