The brain of mammals and of other animal species studied is the only organ which contains measurable amounts of r-aminobutyric acid (GABA). The metabolism in brain of this amino acid, which is formed from glutamic acid ( 14)) has been studied extensively, as has its role in brain physiology. Most of the available information has been reviewed (5, 6). There is still a great deal of interest in GABA and there is a need for a rapid and accurate method for its determination in brain. Paper chromatography and chromatography on ion-exchange columns have been used as methods to determine GABA, but neither is suitable for routine assays. The method of Baxter and Roberts ( 7) is fast and accurate, but not adaptable to all types of experimentation; with their method, one cannot measure formation of labeled GABA because it is an indirect method. The method reported by Berl and Waelsch (8) is too cumbersome and again not easily adapted to routine assays.
A method is reported here that is relatively simple, is reproducible, and requires no special equipment. The method is based on the fact that most ninhydrin reactive substances present in brain can be eluted from a small column of Dowex 50 by a buffer of pH 3.1. Under these conditions, GABA and the basic amino acids are retained by the resin. GABA is eluted from the resin by a buffer of pH 5.1. The basic amino acids are previously removed by means of a weakly acidic resin (Amberlite CG-50) so that elution at pH 5.1 will result in the removal of GABA only.
MATERIALS AND METHOD
Dowex 50-X8, 200400 mesh is treated with alkali, washed, and buffered to pH 3.1 with 0.2 M citrate buffer2 as described by Moore and Stein (9). Amberlite CG-50, 200400 mesh is purified and buffered to