The limbic system is part of the central nervous system that is particularly important for emotional response. Several brain structures comprise the limbic system, including the hippocampus, hypothalamus, amygdala, and other neighboring areas. In addition to emotion, the limbic system is highly involved in the formation of memories. Its effects influence the autonomic nervous system and the endocrine system. The limbic system was one of the first systems of the brain to evolve, and as such, can be found in fish, reptiles, and amphibians, as well as mammalian species.

In a double immunofluorescence experiment, this sagittal section of rat brain was fixed, permeabilized, blocked with 10-percent normal goat serum, and then treated with primary mouse antibodies against NF-P (phosphorylated neurofilaments) and rabbit antibodies against GFAP (glial fibrillary acidic protein). The primary targets were then visualized with goat anti-mouse secondary antibodies conjugated to Alexa Fluor 488 and anti-rabbit antibodies conjugated to Alexa Fluor 568. Hoechst 33342 was employed as a nuclear counterstain. 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.