Biocytin injections produce selective neuronal labeling in the rat CNS

Large injections of biocytin into the lateral ventricle or brain resulted in the labeling of particular neuronal subpopulations in the rat CNS. Localization was accomplished using the avidin-biotin-peroxidase technique. In many cases the staining of neurons was totally complete and resembled that obtained with the Golgi technique. Regions containing labeled cells included the olfactory bulb, cerebral cortex, hippocampus, amygdala, striatum, hypothalamus, superior and inferior colliculi, cerebellar cortex, and dorsal horn of the spinal cord. Only particular cell types were labeled in each of these regions. The results of this study suggest that there is selective uptake and/or retention of biocytin, or a biotinylated metabolite of biocytin, by subpopulations of CNS neurons.