INTRACELLULAR LABELING OF DENTATE GRANULE CELLS IN FIXED TISSUE PERMITS QUANTITATIVE-ANALYSIS OF DENDRITIC MORPHOLOGY

Although cortical neurons in fixed tissue can be labeled by intracellular dye injection, it is not yet known whether the dye diffuses to the most distal tips of the dendrites, or whether all dendritic branches of a neuron are labeled. In this study we addressed these questions by injecting granule neurons from the rat dentate gyrus in fixed, 400-μm-thick hippocampal slices with the fluorescent dye Lucifer yellow and comparing the resultant dendritic morphologies with those of neurons labeled in slices maintained in vitro. Results indicated that each dendritic branch was filled to its most distal tip and that the average number of branches per neuron in the fixed tissue was the same as that seen after in vitro labeling. Thus, intracellular labeling of neurons in fixed tissue permits quantitative studies of dendritic tree structure. © 1990.