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INVITED DISCUSSION 
FREE AMINO ACIDS IN BRAIN AFTER ADMINISTRATION 
OF IMIPRAMINE, CHLORPROMAZINE 
AND OTHER PSYCHOTROPIC DRUGS 
He Be LALLAN 
Geigy Research Laboratories, Ardsley, N.Y. (U.S.A.) 
The effects produced by psychotropic agents on the free amino acids of the brain 
have received much study in recent years, particularly in connection with changes 
brought about in the concentrations of y-aminobutyric acid (GABA), glutamic acid, 
and glutamine. These studies derive much impetus from the fact that certain amino 
acids and their derivatives occur, to any large extent, only in the brain and, therefore, 
may be concerned in some way in the functioning of this tissue. Accordingly, the 
effect of a psychotropic drug on such an amino acid could provide a valuable clue 
to the mode of action of the drug. In the present work, the effects on the complete 
spectrum of amino acids of an antidepressant, imipramine, as well as of its mono- 
methyl analog, desmethyl-imipramine, have been studied. These effects have been 
compared to those produced by the tranquilizers chlorpromazine and reserpine and 
to the action of hydroxylamine. 
Female Wistar rats bred in our own colony were employed. The animals weighed 
between 130 and 230g. Dosage schedules were as follows: imipramine, 25 mg/kg 
subcutaneously every day for 7 days, with sacrifice 4.5 h after the last injection; 
desmethyl-imipramine - HCl, the same, but at a dosage of 15 mg/kg; chlorprom- 
azine: HCl, a single dose of 50mg/kg intraperitoneally 5.5 h before sacrifice; 
reserpine, 5 mg/kg intraperitoneally, either 3 or 18h before sacrifice; hydroxyl- 
amine: HCl, 60 mg/kg intraperitoneally 100 min before sacrifice. Except for a 
single rat given reserpine 18h before death, pairs of animals of the same weight 
were treated together. The animals were decapitated, the brains were quickly re- 
moved, combined, and homogenized in 6% perchloric acid, and the precipitated 
proteins were separated by centrifugation. The cloudy supernatant solution was 
adjusted to pH 4.0 with 2 N KOH and, after being kept at 4° overnight, the 
precipitate of potassium perchlorate (and lipid-like material) was removed by 
centrifugation. Suitable portions of the clear supernatant fluid were analyzed on 
a Beckman Spinco Model 120 Amino Acid Analyzer, using the procedures for phys- 
iological fluids of SPACKMAN, STEIN AND Moore}. Acetylaspartic acid was measured 
after a preliminary separation on Dowex-1 by hydrolysis and determination of the 
liberated aspartic acid on the Amino Acid Analyzer. A portion of the brain extract, 
usually 1.0 ml, was applied to a 0.55 x 5.5-cm column of Dowex-1-X-8 (screened 
wet through a 200-mesh sieve), which had been washed with 2 ml of 2 N NaOH 
and 5 ml of water. The sample was followed by 2 ml of water, 5 ml of 2 N acetic 
acid, and 5 ml of 2 N HCL. A drop of concentrated HCl was added to the HCl fraction, 
which contained the acetylaspartic acid, before the solution was made to exactly 
References p. 469/470 
