Patterns of capillaries in developing cerebral and cerebellar cortices of rats.

Patterns of capillaries in cerebral and cerebellar cortices were studied in developing rats. In cerebral cortex, the ventricular zone is well vascularized throughout the developmental period. The cell dense cortical plate is poorly vascularized, with capillary branches appearing in individual layers as they emerge from the cortical plate. In cerebellar cortex, the external granular layer appears devoid of capillary branches. Capillary branching appears first in the Purkinje and granule cell layers and later in the molecular layer. These results indicate: (1) an inside-out pattern of development of capillaries in both cortices, and (2) marked differences in vascularization of the proliferative zones for cerebral and cerebellar cortical neurons.