Distribution of Fluoro-Gold (FG) in the central nervous system of the rat following its injection into the cerebello-medullary cistern.

Fluoro-Gold (FG) injected into the cerebello-medullary cistern (CMC) is accumulated in several nuclei and neurons of the brain. These structures include: taenia tecta, some fusiform perikarya in the diagonal band of Broca, pyramidal cells in the fifth layer of the cerebral cortex, paraventricular nuclei, zona incerta, medial habenular nuclei, red nuclei, dorsal tegmental nuclei, median raphe nucleus, nuclei pontis, cochlear and vestibular nuclei and some Purkinje cells in the most lateral segment of the cerebellar cortex. The supraoptic nucleus and the median eminence are free of FG. Many nuclei in the myelencephalon and large groups of neurons in the dorsal, intermediate and anterior horns of the spinal cord are also labeled with FG, but exact identification of these cell groups needs further experimentation. Our findings indicate that FG can be picked up from the subarachnoid space into many cell groups of the brain and spinal cord. It is concluded that possible leaking of FG into the subarachnoid space following its injection into the central nervous system has to be taken into account whenever FG is used in tract tracing experiments.