REGIONAL γ-AMINOBUTYRIC ACID LEVELS IN RAT BRAIN DETERMINED AFTER MICROWAVE FIXATION

—GABA levels in rat whole brain were compared following three methods of sacrifice: rapid microwave fixation, decapitation into liquid nitrogen, and decapitation at 20°C. Levels were shown to be identical in animals sacrificed by microwave fixation and decapitation into liquid nitrogen. In contrast, rats decapitated at 20°C had 18 per cent higher GABA levels when determined immediately post-mortem and 48 per cent higher levels after 30 min at 20°C. Microwave treatment prevented these post-mortem increases. The increase in GABA after decapitation at 20°C was even greater in hypothalamus than in whole brain. A comparison of 3 GABA extraction methods following microwave fixation demonstrated that sodium acetate was 88 per cent as effective as 80 per cent ethanol and more effective than 0·5 n -perchloric acid in extracting GABA. Fifteen brain regions were dissected from microwave-treated brains and the GABA levels determined.