The vulnerable period of perinatal hypoxia with regard to dopamine release and behaviour in adult rats.

The relations between a perinatal exposure schedule and the outcome of dopamine (DA) release from striatum slices on the one hand and behaviour on the other, were studied in order to identify the vulnerable period. A mild chronic postnatal hypoxia (2nd-10th day of life) induces long-term effects on the DA release rate (FER) from striatum slices. A 10 h daily exposure to hypoxia for 5 days (2nd-6th day of life) induces the same long-term effects. Adult rats exposed to hypoxia (pO2 8.6 kPa) for 16 h respond with a drastic decrease of FER of DA. Exposure to early postnatal hypoxia prevented this drastic decrease of FER of DA when adult rats were again exposed to hypoxia. 3 ten h periods of hypoxia within the first 10 days of life were enough to the long lasting effects. Prenatal hypoxia as well as hypoxia during the adolescent period did not show any long-term effects on the dopaminergic system. Alterations in behaviour (decreased learning capacity as well as decreased reaction to stimuli after prolonged stress in adulthood) were found after 3-9 days of hypoxia between the 2nd and 10th day of life.