Blood vessels and tissue space associated with the brain of the rat

Abstract

Tissues from adult Sprague-Dawley rats fixed by perfusion with buffered aldehydes for a combined study of the vascular system of the brain are described in light and electron microscopy. In these preparations lack of shrinkage prevents the formation of perineuronal and perivascular spaces. However, connective tissue stains indicate restricted tissue space along the course of small arteries and veins. In fine structure this space is found within the walls of the vessels. It consists of a tubular extension of tissue space bounded inwardly by the endothelial boundary (basement) membrane and outwardly by the neural boundary membrane. Between these boundaries the formed elements of the media and the adventitia are found. The media consists of a thin layer of smooth muscle cells; each cell being enclosed in its own boundary membrane. The adventitia consists of cells and fibrous elements of the connective tissues which are derived, near the surface of the brain, from the intermingling of pial and vascular leptomeninges. This "neural" portion of the tissue space extends from the depths of the capillary bed (where it is obliterated by the fusion of boundary membranes), along the course of the blood vessels, through the subarachnoid space and into the general tissue space of the body.

Comparison of three rat models of cerebral vasospasm

“…First, there are documented anatomic differences between the cerebral arteries found in rats and those found in humans. For instance, there is a difference in wall structure (17) as well as the abundance of collateral blood flow (20). Also, the lack of mural interadventitial spaces in the rat can make this species more resistant to cerebral arterial constriction.…”

Cytoarchitecture of Periendothelial Cells in Human Cerebral Venous Vessels as Compared with the Scalp Vein. A Scanning Electron Microscopic Study.

“…Previous investigators have mainly studied the intracranial venous vessels by transmission electron microscopy (TEM) (TAKAHASHI, 1968;FREDERICKSON and Low, 1969;ROGGENDORF et al, 1978). According to these studies, intracranial venules up to 20um in diameter are covered with pericytes, while those exceeding 30um in diameter are covered with cells which cannot be classified as pericytes nor as smooth muscle cells.…”

Subarachnoid hemorrhage fails to produce vasculopathy or chronic blood flow changes in rats.

“…An alternative explanation for the lack of vascular changes seen in our study is that rat cerebral blood vessels are somehow more resistant to this insult than the vessels of other species. Previous studies have shown that the structure of rat blood vessels is different from that of humans and other species in that the rat basilar artery does not contain interadventitial spaces, 37 which have been implicated in the development of vasospasm. 38 Our investigations were undertaken in an exhaustive efiFort to document delayed CBF changes after SAH in rats and to reproduce the morphologic changes of vasospasm that have been observed in the clinical setting.…”