Summary
Cortical spreading depression (CSD) was evoked in anaesthetized rats by intracortical microinjection of 3.4·10−8 mol KCl (the single injection threshold T1). With two simultaneous injections at 1 mm tip separation 59% T1 had to be applied to each point to elicit CSD. For interfocal distances 2, 3 and 4 mm the double injection thresholds T1,2 were 65%, 74% and 97% of T1 respectively. The spatial summation effect was still significant at 3 mm and undetectable at 4 mm tip separation. Recording electrodes placed 1–3 mm from the point of injection detected local slow potential changes which attained with subthreshold KCl injections 16% of the maximum CSD negativity at the 1.5 mm distance. The threshold amount of KCl required to trigger CSD at different intervals (30–480 sec) after initial injection of 0.8 T1, exponentially increased with time from 28.2% t1 at 30 sec to 88.9% at 480 sec with the slope 16.8% T1 for a twofold increase of the interinjection interval. Quantitative analysis of results based on equations describing diffusion from an instantaneous point source indicates that the critical volume of depolarization is reached 61 sec after injection. According to the value of the diffusion coefficient of potassium the critical K+ concentration lies between 45 and 12 mequ/l and is reached at a distance of 600–950 μ from the injection.
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References
Brinley, F.J.: Ion fluxes in the central nervous system. Int. Rev. Neurobiol. 5, 183–242 (1963).
Curtis, D.H.: Microelectrophoresis. In: Nastuk, W.L. (Ed.): Physical techniques in biological research, Vol. V. — Electrophysiological Methods. Part A, pp. 144–192. New York-London: Academic Press 1964.
Grafstein, B.: Mechanism of spreading cortical depression. J. Neurophysiol. 19, 154–171 (1956).
—: Neuronal release of potassium during spreading depression. In: Brazier, M.A.B. (Ed.): Brain function, vol. 1. Berkeley: University of California Press 1963.
Herz, A., Ziegelgänsberger, W., Färber, G.: Microelectrophoretic studies concerning the spread of glutamic acid and GABA in brain tissue. Exp. Brain Res. 9, 221–235 (1969).
Krnjević, K., Mitchell, J.F.: Diffusion of acetylcholine in agar gels and in the isolated rat diaphragm. J. Physiol. (Lond.) 153, 562–572 (1960).
Leao, A.A.P.: Spreading depression of activity in the cerebral cortex. J. Neurophysiol. 7, 359–390 (1944).
Marshall, W.H.: Spreading cortical depression of Leao. Physiol. Rev. 39, 239–279 (1959).
Ochs, S.: The nature of spreading depression in neural networks. Int. Rev. Neurobiol. 4, 1–69 (1962).
Van Harreveld, A.: Brain tissue electrolytes. Washington, D.C.: Butterworths 1966.
Zachar, J., Zacharová, D.: The refractory phase of Leaos spreading cortical depression. Physiol. bohemoslov. 10, 341–348 (1961a).
—: Subthreshold changes at the site of initiation of spreading cortical depression by mechanical stimuli. EEG clin. Neurophysiol. 13, 896–904 (1961b).
—: Initiation of spreading cortical depression. Bratislava: Publishing House of the Slovak Academy of Sciences 1963.
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Visiting scientist from Department of Physiology, Gifu University, School of Medicine, Gifu City, Japan.
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Matsuura, T., Bureš, J. The minimum volume of depolarized neural tissue required for triggering cortical spreading depression in rat. Exp Brain Res 12, 238–249 (1971). https://doi.org/10.1007/BF00237916
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DOI: https://doi.org/10.1007/BF00237916