Multicolor "DiOlistic" labeling of the nervous system using lipophilic dyecombinations

We describe a technique for rapid labeling of a large number of cells in th e nervous system with many different colors. By delivering lipophilic dye-c oated particles to neuronal preparations with a "gene gun," individual neur ons and glia whose membranes are contacted by the particles are quickly lab eled. Using particles that are each coated with different combinations of v arious lipophilic dyes, many cells within a complex neuronal network can be simultaneously labeled with a wide variety of colors. This approach is mos t effective in living material but also labels previously fixed material. I n living material, labeled neurons continue to show normal synaptic respons es and undergo dendritic remodeling. This technique is thus useful for stud ying structural plasticity of neuronal circuits in living preparations. In addition, the Golgi-like labeling of neurons with many different colors pro vides a novel way to study neuronal connectivity.