Areal and laminar variations in the vascularity of the visual, auditory, and entorhinal cortices of the developing rat brain

Understanding of place-specific cortical cerebrovascular changes after insult and injury depends on the detailed knowledge of the areal and laminar variations in cortical vascularity. The present study examines comparatively the developmental changes of the total vascular density and the density of capillaries and medium- and large-sized vessels in the primary visual cortex (Oc1), the primary auditory cortex (Te1), and the lateral entorhinal cortex (EntL) of the developing rat brain. Vascular networks in the three cortical areas were marked after transcardial perfusion of India ink and quantified with an image analysis system. Parameters examined exhibited (i) peculiar developmental time course within individual cortical layers and (ii) area- and age-dependent variations. Angioarchitecture in Te1 layers was stabilized earlier than that in Oc1 layers and the period of postnatal development of the vascularity of neocortical sensory areas Oc1 and Te1 appeared to be more protracted compared to that of the phylogenetically older entorhinal cortex. By the end of the first postnatal month, vascular densities in the three cortical areas established a dorsoventral gradient (Oc1 > Te1 > EntL). Finally, in all areas, layer IV was the first layer to obtain adult values of capillary density.