Fine structure of the area postrema of the rabbit brain

Summary The area postrema of the rabbit, which was perfused with glutaraldehyde and postfixed in osmium tetroxide, was observed under the electron microscope. This area showed neuronal and neuroglial structures similar to those of ordinary cerebral tissue, except for rich blood capillaries, which were surrounded by conspicuous perivascular spaces. Parenchymal cells included a moderate number of small neurons and large numbers of specific astrocyte-like cells. The neuropil consisted of a small number of thin myelinated and many non-myelinated nerve fibers of varying calibers, axo-dendritic synapses, and neuroglial cell processes, leaving no spaces between them. The axons and synaptic terminals contained moderate amounts of granular vesicles, which were similar in size to those found in the hypothalamus and were supposed to contain catecholamine. Glycogen paticles were demonstrated mainly in the cytoplasm of the astrocyte-like cells.