Traditionally neurons have been thought of as the primary cells of the brain, while glia were considered to play solely a supportive role. In recent years, glia, which are about 10 times more abundant in the human brain than neurons, have come to be understood as more important than previously assumed. Though formerly believed to not have synapses and to be unable to release neurotransmitters, research now suggests that as least some glial cells are synaptically linked with other cells and release neurotransmitters in response to certain stimuli. In addition to their role in the transmission of chemical signals, glia structurally and nutritionally support neurons, preserve homeostasis, and comprise the myelin sheaths that form around many nerve cell axons.

A sagittal section of rat brain (shown above) was immunofluorescently labeled for phosphorylated neurofilaments (expressed in neurons) with mouse anti-NF-P antibodies followed by goat anti-mouse secondary antibodies conjugated to Alexa Fluor 488. In addition, glial fibrillary acidic protein (expressed in various astroglia and neural stem cells) was targeted with rabbit anti-GFAP antibodies visualized with goat anti-rabbit secondary antibodies conjugated to Alexa Fluor 568. Cell nuclei were labeled with the popular nuclear counterstain Hoechst 33342. 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.