Fig. 1. Typical changes in extracellular [K+] in a frog brain during 5 h of anoxia. While monitoring [K+], brain samples were frozen during normoxia, at 1 h of anoxia and at the marked events (arrows) for measurement of ATP levels.
Fig. 3. Brain ATP levels during normoxia and during anoxia when extracellular [K+] started to increase (beginning of depolarization) and when anoxic depolarization had been reached. Values are means + S.E.M., N=5. *Statistically different from the normoxic value (P<0.05).
Fig. 4. Traces showing changes in extracellular [K+] in frog brain after administration of ouabain (Ou, arrow) during air respiration (normoxic) and after 2 h of 100 % N2 respiration (anoxic).
Fig. 5. Time taken to increase extracellular [K+] by 1 mmol l1 above basal values after superfusion with ouabain during normoxia, after 2 h of anoxia, during normoxia in the presence of theophylline and after 2 h of anoxia in the presence of theophylline. Values are means + S.E.M., N=5. *Statistically different from the value for the corresponding normoxic group (P<0.05).