Three-dimensional architecture of cerebral microvessels with a scanning electron microscope: a cerebrovascular casting method for fetal and adult rats.

Vascular casting for scanning electron microscopic studies on microvascular architecture is in common use for various visceral organs in the field of anatomy. However, only a few studies have been performed on the brain using the previously reported casting method, and no detailed descriptions deal with suitable methodology for producing brain vascular casts. Our casting method, introduced here, for the CNS from the fetal to the adult stage involves the following modifications: (1) Perfusion fixation of the brain is carried out before injecting the plastic resin for casting into the cerebral blood vessels; (2) digestion of nervous tissue is accomplished with a sodium hydroxide and sodium hypochlorite solution; and (3) vascular casts are dried by a freeze-drying method, while the nondigested brain slices opposite the casts can be investigated with light microscopy and transmission electron microscopy. This modified casting method enables one to represent the microvascular system of the rat brain three-dimensionally from embryonal day 17 onward. It is hoped that this method will prove to be a useful tool in morphological vascular research on the nervous system.