Two different basic types of cells compose the brain: neurons and glia. Neurons are nerve cells that are specialized to transmit and receive nervous impulses over long distances. One or more branching dendrites and a single axon help facilitate this transmission by linking neurons to other neurons, sensory cells, and muscle cells. The site where neuron communication occurs, that is where the axon of one cell meets a dendrite, axon, or body of another cell, is called a synapse. Each synapse consists of a presynaptic end that contains neurotransmitters and various organelles separated from a postsynaptic end with receptor sites for neurotransmitters by a small gap termed the synaptic cleft.

A rat brain sagittal section was immunofluorescently labeled for phosphorylated neurofilaments with mouse anti-NF-P monoclonal antibodies followed by goat anti-mouse secondary antibodies conjugated to Alexa Fluor 488. In addition, glial fibrillary acidic protein was targeted in the tissue section with rabbit anti-GFAP antibodies visualized with goat anti-rabbit secondaries conjugated to Alexa Fluor 568. A dsDNA probe, Hoechst 33342, was used to counterstain cell nuclei. Images were recorded in grayscale with a 12-bit digital camera coupled to a Nikon Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.