Fractionation of human brain by differential and isopycnic equilibration techniques

Fractionation of brain tissue by either differential or isopycnic centrifugation is a useful cytological and biochemical tool to study the intracellular localization of neuronal elements involved in neurotransmission. Several neuroreceptors and uptake sites were found to display a subcellular bimodal distribution in rat brain [10]. However, in the human brain, little is known about the subcellular distribution of neurotransmitter receptors and amine uptake sites. Despite the inevitable post-mortem delay which seems to induce many more morphological changes than modifications of enzymatic [20] or receptor distribution profile [14] from the subcellular fractions, fractionation of human brain areas remains a valid procedure [13] to explore the subcellular localization of neuronal constituents. This paper describes the methods used to separate human brain tissue. As we have previously demonstrated in rat and dog brains [12,14], our results indicate that differential and isopycnic fractionation techniques, used with a large number of markers such as enzymes, receptors and uptake sites, make it possible to separate tissue fractions enriched in nerve endings, dendrites, dendritic spines, plasma membranes or vesicles.