Acetylcholine Content of Frozen Brain

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Abstract
Grinding with trichloroacetic acid solution (TCA) and homogenization in acidified saline containing eserine are equally effective in extracting acetylcholine (ACh) from excised unfrozen rat brain. Grinding with TCA or acid saline containing neostigmine are equally effective in extracting ACh from both frozen and unfrozen brain. But much ACh is iost when frozen brain is extracted with acidified saline containing eserine or tetraethylpyrophosphate. Considerably more ACh is found when a whole animal is frozen than when the head is frozen immediately after decapitation. The relationship of various reported figures for the ACh content of normal rat brain is summarized. ACh assays of TCA extracts of brain by means of the frog rectus abdominis, with control of sensitizing substances, and by means of the leech dorsal muscle, uncontrolled, give the same average results. With saline extracts of brain, figures obtained with the leech muscle averaged 25% higher than those obtained with the frog muscle.