Elevation and clearance of extracellular K+ following graded contusion of the rat spinal cord.
The elevation and clearance of extracellular potassium concentration ([K+]e) were studied following graded contusion injury of the rat thoracic spinal cord. Animals were anesthetized, paralyzed, laminectomized at T9-T10, and then artificially ventilated. A 10-g rod was dropped 1.25, 2.5, or 5 cm onto the dorsal thoracic cord with the dura intact. After impact, and incision of the dura-arachnoid and pial membranes, double-barreled, potassium-selective microelectrodes were inserted midway between the midline and lateral edge of the cord. For all three injury levels, the elevation of [K+]e was greatest within the first 1000 microns from the dorsal surface. In 50 g-cm injuries, increasing [K+]e was sometimes observed between 250 and 1000 microns; however such gradients were not typically observed in 25 and 12.5 g-cm injuries. Measured at 3-7 min after injury, the mean peak elevations of [K+]e were significantly different, measuring 13 +/- 2.4, 27 +/- 5.5, and 44 +/- 4.2 mM following 12.5, 25, and 50 g-cm contusions, respectively. The exponential half-times of [K+]e clearance averaged 5.8 +/- 1.0, 9.2 +/- 1.8, and 17 +/- 5.7 min for the same respective injury levels. These results indicate that elevation of [K+]e following traumatic injury to the spinal cord is a graded phenomenon, dependent on the energy of impact. This finding is consistent with a mechanism in which simple mechanical injury of cell membranes is the proximate cause of potassium release.
Chesler
M
M
Department of Neurosurgery, New York University Medical Center, New York 10016.
Young
W
W
Hassan
A Z
AZ
Sakatani
K
K
Moriya
T
T
D000818:Animals; D003288:Contusions / Q000378:metabolism* / Q000503:physiopathology; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D008297:Male; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D013119:Spinal Cord Injuries / Q000378:metabolism* / Q000503:physiopathology; D013997:Time Factors
D011188:Potassium