Effects of hypothermia and gender on survival and behavior after perinatalasphyxia in rats

Previous studies in rats have demonstrated that perinatal asphyxia (PA) pro duces long-term morphological alterations, particularly affecting hippocamp us, neostriatum, and cerebral cortex. These changes were prevented by apply ing hypothermia during the asphyctic insult. Because these cerebral areas a re involved in cognitive and motor functions, the aim of the present study was to determine whether periods of PA during normothermia or hypothermia p roduces long-term behavioral impairments in rats of both sexes. The cogniti ve and motor functions were studied using the spatial Morris water maze (MW M) task at 1.5 months, and the open field at 5 months, respectively. The pr esent study revealed that female rats had a higher survival rate than males after PA in normothermic conditions (p < 0.014). and that hypothermia dras tically prolonged the time of survival in both sexes (p < 0.001). There wer e no differences in learning and memory functions between groups or male an d female rats when tested with MWM. Rats subjected to hypothermia treatment did not show differences in the MWM compared to controls. A lower locomoto r activity in the open field test was only observed in male rats that suffe red 15 and 20 min of PA in normothermia (p < 0.05). Hypothermia treatment p revented this hypoactivity. PA in females, even if severe, did not affect t he motor activity. The data of both behavioral tests showed differences bet ween sexes, i.e., the female rats learned the MWM task slower, and were mor e active in the open field. This work lends further support for the hypothe sis that hypothermia can prevent mortality as well as long-term sequelae in duced by PA. (C) 2000 Elsevier Science Inc. All rights reserved.