Fig. 2. (A–D) Effect of anoxia, exposure to a high K⁺ concentration and forced energy deficiency on the extracellular level of GABA and glutamate. In A,B, the filled circles represent the anoxia-exposed fish, while open circles represent control fish kept in normoxia during the whole experiment. Iodoacetate (IAA) was used to create energy deficiency during anoxia. The horizontal lines mark the periods of anoxia (N₂ exposure), when a high-K⁺ Ringer was pumped through the microdialysis probe or when IAA was superfused onto the brain. Values are means ± S.E.M. from 6–8 fish. Redrawn from Hylland and Nilsson (1999).