SPREADING DEPRESSION IN ISOLATED SPINAL-CORD

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 (standard deviation) mV amplitude and 1.2 +/- 0.5 min duration concomitantly with a reversible [K+], increase up to 21.1 +/- 4.6 mM in the extracellular fluid. 4. Potassium salt solution can trigger SD waves that spread at 12 +/- 4.7 mm/min. 5. SD waves occur ''spontaneously'' in preparations superfused by Ringer solutions with very low [Cl-] (<20 mM). The frequency of these waves decreases, and they may stop if [Mg2+] is increased.