Located in the core of the brain stem is a collection of nerve fibers known as the reticular formation. This neural system plays an important role in filtering out familiar or recurring input. Thus, it is critical in regulating states of arousal, awareness, and attention. The reticular formation is also thought to be involved with motor functions and cardiac reflexes. According to some studies, irregularities in this part of the brain may be linked to attention deficit hyperactivity disorder.

The sagittal section of rat brain depicted above was immunofluorescently labeled for glial fibrillary acidic protein (expressed in various astroglia and neural stem cells) with rabbit anti-GFAP antibodies visualized with goat anti-rabbit secondary antibodies conjugated to Alexa Fluor 568. In addition, to target neurofilaments, the specimen was treated with mouse anti-NF-P antibodies followed by goat anti-mouse secondary antibodies conjugated to Alexa Fluor 488. DNA was 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.