Development of the blood vessels and extracellular spaces during postnatal maturation of rat cerebral cortex

Abstract

A s part of a larger study of the development of postnatal rat cerebral cortex, this report deals with the maturation of the cortex as a tissue from birth to twenty-one days of age. The changes in the numerical density of cells and blood vessels and the thickness of the cortex at successive ages were followed on light micrographs, and both were related to the ultrastructural observations on routine electron microscopic preparations. The maturation of the cortex is divided into two periods: The first ten days during which the growth to adult dimensions occurs and few patent blood vessels but large extracellular spaces are to be found, and the second ten days in which the majority of the vessels develop patent lumina, the perivascular sheath of astrocyte end-feet develops, and the large extracellular spaces disappear concomitant with the maturation of the neuropil.The blood vessels appear to develop during the first ten days as solid cords of mesodermal elements which form a network of primordial vessels with thick walls and slit-like lumina containing a flocculent material. The formation of a blood filled, patent lumen apparently occurs synchronously over a brief period of time for the majority of the vessels during the early part of the second ten-day period. The basal lamina is ill-defined initially but takes on mature appearance parallel with the development of the pcrivascular glial sheath.The volume of the extracellular space was found to be largest during the phase of rapid growth of axons and dendrites when few patent vessels exist. The disappearance of these large extracellular spaces during maturation of the blood vessels and neuropil is discussed i n terms of the possible artifactitious nature of these spaces in both immature and mature cortex.

Pepsin pretreatment allows collagen IV immunostaining of blood vessels in adult mouse brain

“…Indeed one of the major structural differences between immature and mature vessels in brain is the large perivascular spaces present in immature vessels that separate the outer glial basal lamina and the inner vascular one (Caley and Maxwell, 1970;Szabo and Kalman, 2004). In the rat, after about P10 the glial and vascular basal laminae fuse and the extravascular spaces are largely eliminated.…”

Carnosine-related dipeptides in the mammalian brain

“…Within this context it is worth noting that the SEL, as a remnant of the primitive subventricular zone, retains several embryonic features, among which there is the tendency of the cells to shrink during fixation, leaving enlarged extracellular spaces (Jankovski and Sotelo, 1996;Lois et al, 1996;Peretto et al, 1997). It is accepted that extracellular spaces are wider in the embryonic versus the mature nervous tissue; for example, during the postnatal maturation of the rat cerebral cortex, the extracellular space was found to diminish dramatically during the first three postnatal weeks of age (Bondareff and Pysh, 1968;Caley and Maxwell, 1970). Moreover, the existence of chain migration in the SEL, involving large amounts of neuroblasts which advance at a speed three to six times faster in comparison to that observed during CNS development (see Wichterle et al, 1997), likely implies rapid and striking variations in the extracellular spaces.…”

Substrate Utilization and Brain Development

“…In the rat, the decline continues post natally and adult rates are reached at between 10 and 15 days of age (Ferguson and Woodbury, 1969). Junctional complexes between endothelial cells can be seen even in primitive capillaries of the devel oping brain (Donahue and Pappas, 1961;Caley and Maxwell, 1970). The physical barrier separating blood and brain is, therefore, an early phenomenon among developmental changes.…”