Elevation and clearance of extracellular K+ following contusion of the rat spinal cord.
The elevation and clearance of extracellular potassium following a standard contusion injury was studied in the thoracic spinal cord of rats. Animals were anesthetized, paralyzed, laminectomized at T9-T11, then artificially ventilated. A 10-g rod was released 5.0 cm above the cord with the dura intact. After impact, the dura-arachnoid and pial membranes were incised to allow penetration of K(+)-selective microelectrodes. Electrodes utilized a valinomycin ionophore and were double-barreled, with tip diameters of 3-5 microns. Extracellular potassium activity ([K+]o) increased with the depth of penetration. The maximum values of [K+]o occurred at depths greater than 500 microns, and remained so with time after injury. These data indicate that a dorsal-ventral gradient of [K+]o develops in spinal cords contused from the dorsal surface, with the greatest elevation of [K+]o in the gray matter. In 8 preparations, the maximum [K+]o was 65 +/- 8 mM (mean +/- S.E.M.) at 5 +/- 1 min after injury. The [K+]o peak values decayed with a half-time of 11.0 +/- 3.4 min. Compared with data available for the injured cat spinal cord, the peak [K+]o recovered relatively rapidly. Although a simple diffusion model could account for the rapid clearance of [K+]o, the persistence of dorsal-ventral [K+]o gradients could not be explained by such a model. It is postulated that secondary injury processes contributed to the persistent [K+]o gradients.
Department of Neurosurgery, New York University Medical Center, NY 10016.
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Chesler
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Sakatani
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Hassan
D000818:Animals; D001794:Blood Pressure; D005110:Extracellular Space / Q000502:physiology; D005260:Female; D008297:Male; D008839:Microelectrodes; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D013116:Spinal Cord / Q000378:metabolism / Q000503:physiopathology*; D013119:Spinal Cord Injuries / Q000503:physiopathology*; D013997:Time Factors
D011188:Potassium