Previous studies have demonstrated that perinatal asphyxia (PA) produces long-term morphological alterations, particularly affecting striatum and cortex and that this changes as well survival after PA could be prevented and improved respectively by the application of hypothermia. Since the neostriatum and cerebral cortex are areas involved in motor and cognitive functions, the aim of this study was to determine whether PA affects the behaviour of rats after different periods of PA and severe PA induced in hypothermic conditions. Sex differences were compared in all the groups studied.

The behaviour of the rats was automatically registered with a computerized system (Ethovision) using to study cognitive functions the Morris's water maze test at 1,5 and 6 months and to study motor functions the open field at 5 months. Results showed motor hypoactivity only in male rats that suffered severe PA (>20 min PA at 37°C). The application of hypothermia during insult prevented hypoactivity in this particular group. No alterations in learning and memory activities were detected in any group of male and female rats studied. Even severe PA in female rats caused no motor alterations. Our data showed sex differences in the resistance to perinatal asphixia not only in survival but also in motor behaviour when studied with the open field test. The present findings lend further support for the hypothesis that hypothermia can prevent long-term sequelae of PA. Future research on the mechanisms by which female rats have more resistance to PA could be useful to find strategies to prevent brain damage.