Fig. 7. Isoflurane protection of hippocampal neurons after profound hypothermia/rewarming (PH/RW) involves N -methyl-D-aspartate (NMDA) receptors but not γ-aminobutyric acid (GABA) receptors. (A ) Isoflurane (Iso) and the competitive NMDA receptor antagonist AP5 both reduce PH/RW injury in slice cultures. (B ) Isoflurane and AP5 prevent increases in intracellular Ca²⁺in cultures exposed to 4 h PH and 1 h RW. (C ) Typical images of calcium green fluorescence in slice cultures at baseline (37°C), after PH/RW, after PH/RW with the competitive NMDA receptor antagonist AP5, and after PH/RW when isoflurane was present. (D ) Lack of involvement of GABA^Areceptors in isoflurane protection against PH and RW injury. The GABA^Aantagonists bicuculline (Bicuc, 50 μM) and picrotoxin (Picro, 100 μM) were present during PH and RW. Bar graphs show means ± SEM. The number of cultures in each treatment group is indicated with numbers above the bars . The lines  and asterisks  above the error bars  describe statistical differences between different treatment groups as follows: *P  less than 0.05, **P  less than 0.01, and ***P  less than 0.001, measured with analysis of variance and a Tukey multiple comparison posttest.