Changes in Amino Acid Concentrations over Time and Space around an Impact Injury and Their Diffusion Through the Rat Spinal Cord

• Published in: Experimental neurology Vol. 159; no. 2; pp. 538 - 544
• Main Authors: McAdoo, David J., Xu, Guo-Ying, Robak, Gregory, Hughes, Michael G.
• Format: Journal Article Conference Proceeding
• Language: English
• Published: Amsterdam Elsevier Inc 01.10.1999; Elsevier
• Subjects: amino acids; Amino Acids - metabolism; Animals; Arginine - metabolism; Aspartic Acid - metabolism; Biological and medical sciences; Citrulline - metabolism; diffusion; excitotoxicity; glutamate; Glutamic Acid - metabolism; Glycine - metabolism; Injuries of the nervous system and the skull. Diseases due to physical agents; Male; Medical sciences; Microdialysis; Rats; Rats, Sprague-Dawley; Spinal Cord - metabolism; Spinal Cord - pathology; Spinal Cord Injuries - metabolism; Spinal Cord Injuries - pathology; Spinal Cord Injuries - physiopathology; spinal cord injury; Taurine - metabolism; Threonine - metabolism; Time Factors; Traumas. Diseases due to physical agents; spinal cord injury; diffusion; microdialysis; excitotoxicity; glutamate; amino acids; Nervous system diseases; Spinal cord; Pathophysiology; Rat; Rodentia; Concentration; Glutamate; Trauma; Vertebrata; Mammalia; Microdialysis; Animal; Central nervous system disease; Neurotoxin; Excitatory aminoacid; Evolution; Spinal cord disease; Release
• ISSN: 0014-4886; 1090-2430
• DOI: 10.1006/exnr.1999.7166

Release of amino acids, particularly the neurotoxin glutamate, in and around the site of an experimental spinal cord injury was characterized over time by microdialysis. Increases in amino acid concentrations caused by injury decline steeply and then slowly over distance from the impact area, becoming undetectable beyond about 5 mm from the injury epicenter. Diffusion profiles determined in the cord by administering amino acids through one microdialysis fiber and sampling them in a parallel fiber declined steeply with distance. Distant increases coincided temporally with those in the injury epicenter. We conclude that elevated amino acids more than about 1 mm into the periimpact zone are predominantly released in that region rather than diffusing into it from the trauma epicenter. In the outer areas of lesion development, glutamate does not appear to reach concentrations ordinarily toxic, and elevated concentrations do not persist nearly as long as the therapeutic window of NBQX in any part of the lesion. Therefore, the mechanisms whereby excitatory amino acid antagonists reduce the dimensions of injury lesions are unclear. However, sensitization of neurons following impact injury could be important in amino acid neurotoxicity.