The portion of the vertebrate brain that is directly continuous with the spinal cord is the medulla oblongata, often simply called the medulla. The medulla is composed of both gray matter and white matter, but unlike most other regions of the brain, the medulla’s white matter is exterior to the gray matter it contains, which surrounds a ventricle. Nerve centers located in the medulla play an important regulatory role in a number of different involuntary nervous activities, such as respiration, digestion, and sleeping. The medulla is also important for the integration of various signals as well as the coordination of large-scale movement. The majority of descending axons that transmit movement-related signals cross over to the opposing side of the nervous system as they pass from the medulla to the top of the spinal cord. Thus, the right side of the brain chiefly controls the movement of the left side of the body and the left side of the brain dictates most of the movement of the right side of the body.

In order to visualize neurons and astroglia in a rat brain horizontal tissue section (shown above), the specimen was immunofluorescently labeled with mouse anti-NF-P and rabbit anti-GFAP primary antibodies followed by goat anti-mouse and anti-rabbit secondary antibodies conjugated to Alexa Fluor 568 (pseudocolored blue) and Alexa Fluor 488, respectively. Hoechst 33342 (pseudocolored red) was employed 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 unless otherwise noted above.