APStracts 2:0143N, 1995.

SPREADING DEPRESSION IN ISOLATED SPINAL CORD. STREIT, D.S., C. R. FERREIRA, and H. MARTINS-FERREIRA. Faculdade de Medicina de Petr[acute]opolis , Instituto Biom[acute]edico da Universidde Federal Fluminense and Instituto de Biof[acute]isica Carlos Chagas da Universidade Federal do Rio de Janeiro, R J 21949-900 , Brazil.

APStracts 2:0143N, 1995.

SUMMARY AND CONCLUSIONS
1 - Isolated spinal cord of amphibians is able to express Leao's spreading depression (SD). 2 - SD can be evoked when the spinal cord is in an appropriated medium. There are two conditions that favor its elicitation: hypotonicity and low [Cl - ] levels in the extracellular microenvironment. 3 - Spinal cord SD is accompanied by a stereotyped negative extracellular voltage transient of 17.3 +/- 4.9 mV amplitude and 1.2 +/- 0.5 min duration concomitantly with a reversible [K + ] o increase up to 21.1 +/- 4.6 mM in the extracellular fluid. 4 - Potassium salt solution can trigger SD waves which spread at 12 +/- 4.7 mm.min -1 . 5 - SD waves occur "spontaneously" in preparations superfused by Ringer solutions with very low [Cl - ](less than 20mM). The frequency of these waves decreases and they may stop if [Mg 2+ ] is increased.

Received 22 November 1994; accepted in final form 25 April 1995.
APS Manuscript Number J766-4.
Article publication pending J. Neurophysiol.
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 16 May 1995.