BRAIN EXTRACELLULAR POTASSIUM AND ENERGY METABOLISM DURING ISCHEMIA IN JUVENILE RATS AFTER EXPOSURE TO HYPOXIA FOR 24 h

Abstract

Abstract— The ischemia‐induced change of brain extracellular potassium concentration [K⁺]_e and brain energy metabolism was studied following decapitation of normal 7‐dav‐old rats and 7‐day‐old rats exposed to a simulated altitude of 6000 m (pO₂= 70 mm Hg) for 24 h. Initially there was in both groups a slow rate of rise of [K ⁺]_e followed by a faster rise until a steep increase occurred. In the group exposed to hypoxia the initial rate of rise was lower and the duration until the steep increase twice as long as in the normal group. Energy consumption expressed as Δ#P and the rates of lactate accumulation were similar in the two groups in the first minute following decapitation. After 2 min the Δ#P and the rate of lactate accumulation was higher in the group exposed to hypoxia. These findings are explained by a doubling of the glucose concentration in the brain of the rats exposed to hypoxia, permitting anaerobic glycolysis to maintain ATP regeneration for a longer time during ischemia.