Journal of Neurophysiology, Vol 38, Issue 1 158-166, Copyright © 1975 by APS
Techniques for termination of reverberating spreading depression in rats
M. Shibata and J. Bures
Reverberation of cortical spreading depression (CSD) around a circular
obstacle (thermocoagulation lesion) in the frontal cortex of anesthetized
rats was elicited by appropriately timed and spaced applications of KCl.
The probability of continued reverberation was increased by a
pyrrolopyrimidine drug BW 58-271 (10 mg/kg) from 0.93 to 0.98. Three
methods of reverberation arrest were tested: a) CSD propagation was blocked
by an interfering CSD wave which was initiated in the rear of the
reverberating wave, passing through a narrow segment of the circular
pathway, and collided with the reverberating wave on the opposite side of
the obstacle; b) CSD propagation through a part of the circular pathway was
blocked by a 10-min application of 10% MgCl2 on the exposed cortical
surface; c) 1-min asphyxia stopped RCSD by increasing the overall
refractoriness of cortical tissue. Least reliable was the interference
method which stopped reverberation, even with optimum timing, only in 42%
of the trials. The magnesium blockade was reliable but slow, the
reverberation stopping only 30 min after MgCl2 application. Asphyxia evoked
in any phase of the reverberation cycle stopped RCSD reliably and
immediately. The results obtained with the interference method confirm the
predictions of the mathematical model of impulse reverberation in sheets of
excitable tissue. Anoxia seems best suited for practical control of CSD
reverberation in functional decortication studies.
