Extracellular potassium activity, evoked potential and tissue blood flow: Relationships during progressive ischaemia in baboon cerebral cortex

doi:10.1016/0022-510X(77)90014-4

Journal of the Neurological Sciences

Volume 32, Issue 3, July 1977, Pages 305-321

https://doi.org/10.1016/0022-510X(77)90014-4 Get rights and content

Abstract

Extracellular K⁺ activity (K_e), local tissue blood flow and the cortical evoked potential (EP) were measured concurrently in the cerebral cortex of baboons anaesthetised with α-chloralose. Flows were progressively reduced from normal by occlusion of the middle cerebral artery and controlled steps of exsanguination.

Our data suggest that 3 stages may be identified in the disturbance of K⁺ homeostasis produced by progressive ischaemia. In the first stage, at flow levels similar to those sufficient to abolish the EP (12–16 ml/100 g/min), small, self-limiting increases in K_e occur, probably reflecting K⁺ efflux into the extracellular space (ECS) with partial impairment of K⁺ clearance from the ECS. The second stage occurs at distinctly lower (P < 0.01) levels of flow (8–11 ml/100 g/min), and is characterized by a massive (30–80 mM) increase in K_e, which we attribute to an increase in ionic permeability of cell membranes with further impairment or overloading of K⁺ clearance mechanisms. In the third stage, at flows below about 6–8 ml/100 g/min, the data indicate an inverse relationship between flow and K_e with persisting high K_e levels, suggesting complete loss of K⁺ clearance. Transient increases of K_e also occur in the flow range 4–13 ml/100 g/min, the rate of recovery of K_e in their decay phase being positively correlated with flow (P < 0.005).

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^☆: This study was supported by the Medical Research Council.

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Extracellular potassium activity, evoked potential and tissue blood flow: Relationships during progressive ischaemia in baboon cerebral cortex☆

Abstract

Brain Res.

Brain Res.

Exp. Neurol.

Exp. Neurol.

Brain Res.

Brain Res.

Brain Res.

Brain Res.

Exp. Neurol.

Electroenceph. clin. Neurophysiol.

Brain Res.

Cortical evoked potential and extracellular K+ and H+ at critical levels of brain ischaemia

Stroke

Evidence against H+ and K+ as the main factors in the regulation of cerebral blood flow during epileptic discharges, acute hypoxemia, amphetamine intoxication and hypoglycemia — A microelectrode study

Efflux mechanism contributing to the stability of the potassium concentration in cerebrospinal fluid

J. Physiol. (Lond.)

Transport of potassium at the blood-brain barrier

J. Physiol. (Lond.)

Recovery of the cortical evoked response following middle cerebral artery occlusion in baboons — Relation to local blood flow and pO2

Stroke

Potassium movements in the cerebral cortex during asphyxia

Acta morph. neerl.-scand.

Potassium accumulation by bulk prepared neuronal and glial cells

J. Neurochem.

Cortical evoked potential and extracellular K⁺ and H⁺ at critical levels of brain ischaemia

Evidence against H⁺ and K⁺ as the main factors in the regulation of cerebral blood flow during epileptic discharges, acute hypoxemia, amphetamine intoxication and hypoglycemia — A microelectrode study

Recovery of the cortical evoked response following middle cerebral artery occlusion in baboons — Relation to local blood flow and pO₂