[Cerebral blood flow and cerebrovascular reactivity in the early postnatal ontogeny of rats].

The development of cortical cerebral blood flow (CBF) and cerebrovascular reactivity (CVR) were studied in Wistar rats during early postnatal ontogenesis, in groups aged 2-5, 6-8, 9-11, 12-15, 16-18 and 19-25 days. CBF was measured polarographically using inhaled hydrogen clearance method, with platinum electrodes inserted into parietal cortex. At the mentioned age periods, CBF and its percentage of adult level averaged as 38 (21%), 81 (45%), 142 (78%), 85 (47%), 110 (61%), and 118 (65%) ml/100 g/min, respectively. Hence, during the early postnatal ontogenesis CBF increased gradually, however, it did not reach the adult level up to the end of the first month. CBF peak at 9-11 days period is suggested as a result of sharp rise of the brain vessels growth. CVR was assessed as the percentage of CBF increase after standardized 5% CO2 inhalation test. At the above age periods, CVR was found to bi 26, 33, 36, 41, 44 and 31% respectively, and was similar to adult rat CVR of 36%. The conclusion was drawn that regulatory mechanisms of adequate responses of brain vasculature to chemical metabolic factors are well developed already at the very beginning of postnatal life.