Newborn XXXX blood-brain barrier is selectively permeable and differs substantially from the adult.

@entity2656 @entity4343 @entity1522 @entity3042 @entity2642 @entity95 @entity5536 @entity1877 @entity369 @entity413
Examination of blood-brain barrier (BBB) function by the intracarotid injection technique has been utilized in studies of newborn (6-30 h) and adult @entity95 . The exclusion of @entity2656 (mol. wt. 182), dextran (mol. wt. 60,000-90,000), and @entity4343 -bound EDTA indicate that the newborn BBB has restrictive properties similar to the adult. At birth, saturable, carrier-mediated transport mechanisms are present, regulating the entry of @entity413 , @entity1522 , organic acids, @entity3042 , @entity2642 , and @entity1877 . No difference in brain uptake of @entity413 was observed between adult and newborn, but considerably higher uptake rates for @entity369 , @entity1877 , and @entity5536 were seen in the newborn. In contrast to suggestions of an immature barrier in young animals, these studies indicate that a sophisticated, selective BBB is operative at birth. Furthermore, the specific selectivity and dramatic increases seen for certain metabolites imply a vital function in the newborn for these carrier systems.
