Choroidal bodies: a new structure in the fourth ventricular choroid plexus of the rat and mouse.

Histologic study of the caudal end of the fourth ventricular choroid plexus of the rat and mouse revealed 1-4 small, discrete collections of cells that differed from the surrounding choroidal epithelial cells in appearance. They did not occur in other parts of the choroid plexuses. These choroidal bodies were not affected by a chemical toxin that caused hydropic degeneration of all the epithelial cells in the choroid plexuses. The function, if any, of the choroidal bodies is unknown. They were present in all rats that were studied by serial sections.