The Interrelation Between Brain Oxidative Metabolism and Extracellular Potassium in the Unanesthetized Gerbil

Abstract

The unanesthetized gerbil model was used to study the interrelation between metabolic, electrical and ionic activities in the brain. A combined K+DC surface electrode with a fiber optic light guide was implanted above the parietal cortex and cemented to the skull. The subjects were exposed to various pathological and physiological conditions such as anoxia, hypoxia, spreading cortical depression, and ischemia. During anoxia a leakage of cellular K⁺e was detected simultaneously with an increased level of NADH. The recovery phase in a few animals was followed by a spreading depression phenomenon. Exposing the brain to spreading depression led to a typical oxidation cycle of NADH, and the shape of this cycle was affected by hypoxia. Unilateral carotid artery ligation induced localized ischemia that affected cellular and K⁺e responses to spreading depression. Bilateral carotid artery occlusion increased NADH concentration to its maximum level; as a result, K⁺e also accumulated. Complete restoration of NADH and K⁺e to normoxic levels occurred after a few minutes, depending on the duration of the occlusion.