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Rat Brain Tissue Sections

Medulla Oblongata

The medulla oblongata is the part of the brain that is continuous with the spinal cord, with which it merges at the foramen magnum, a large orifice located at the base of the skull. The pons is situated rostral to the medulla, and both of these segments of the brain stem are divided from the cerebellum by the fourth ventricle.

Medulla Oblongata

When the external surface of the brain is viewed, the brain stem is obscured by the cerebrum, but median sagittal sections can reveal many of the details of its components. Blood is supplied to the medulla by several arteries, including the vertebral artery, the anterior spinal artery, and the posterior inferior cerebellar artery, and the last seven cranial nerves emerge from the structure. Two important crossings (decussations) of nerve fibers occur in the transitional region between the medulla and the spinal cord.

A number of functional centers that regulate autonomic activities of the body, such as respiration, circulation, and digestion, are found in the medulla oblongata. The brain stem structure also is important as a relay between the spinal cord and the rest of the brain, and it plays a role in the regulation of motion and the sleep-wake cycle. Some of the activities associated with the medulla are influenced by other parts of the brain stem as well. The central core of the brain stem is known as the reticular formation, and it is this area that can affect the excitability of neurons and thereby govern states of arousal. Some imaging studies suggest that abnormal activity in the reticular formation may be linked to the fatigue and lack of concentration characteristic of certain disorders.

In a double immunofluorescence experiment, this sagittal section of rat brain featuring the medulla oblongata was fixed, permeabilized, blocked with 10-percent normal goat serum, and then treated with primary chicken antibodies against NF-H (heavy chain neurofilament subunits) and rabbit antibodies against GFAP (glial fibrillary acidic protein). The primary targets were then visualized with goat anti-chicken secondary antibodies conjugated to Alexa Fluor 488 (green emission) and anti-rabbit antibodies conjugated to Alexa Fluor 568 (red). DRAQ5 (pseudocolored cyan) was employed as a nuclear counterstain. Images were recorded with a 40x oil immersion objective using a zoom factor of 1.6 and sequential scanning with the 488-nanometer spectral line of an argon-ion laser, the 543-nanometer line from a green helium-neon laser, and the 633-nanometer line of a red helium-neon laser. 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.

Additional Confocal Images of Rat Medulla Oblongata Tissue Sections

Immunofluorescently Detecting GFAP and NF-H in Medulla Oblongata Tissue - Glial fibrillary acidic protein (GFAP) is a type III intermediate filament protein that is a primary structural element of the star-shaped glial cells known as astrocytes and neural stem cells. The protein was targeted in a coronal section of rat medulla oblongata tissue by immunofluorescently labeling the specimen with primary rabbit anti-GFAP antibodies followed by goat anti-rabbit Fab fragments conjugated to Alexa Fluor 568. The section was also stained for neurofilaments (specific to neurons) with chicken anti-NF-H antibodies visualized with goat anti-chicken secondary antibodies conjugated to Alexa Fluor 488. Nuclear DNA was counterstained with the red-absorbing dye DRAQ5.

Contributing Authors

Nathan S. Claxton, Shannon H. Neaves, and Michael W. Davidson - National High Magnetic Field Laboratory, 1800 East Paul Dirac Dr., The Florida State University, Tallahassee, Florida, 32310.