DRUGS AND FREE AMINO ACIDS IN BRAIN 487 
with some amino acids, and since their sensitivity to ninhydrin staining is not 
predictable’, a change in peptide concentration might alter the values for the amino 
acids. In an attempt to overcome this hindrance two chromatographic separations 
of the amino acids were performed before and after a prolonged acid hydrolysis. 
On the other hand, hydrolysis may modify or destroy some amino acids. Therefore, 
a decrease of an amino acid after hydrolysis is considered as a chemical alteration, 
NH, + ETHANOL AMIN 









GLUTAMINE 
1) cysTeic acio ORNITHINE 
ASPARTICACIO SERINE / GLUTAM ACID 
THRE y-NH;-BUTYRIC ACID LYSINE 
TAURINE | 
| ol ALAN. | HISTIDINE 
0.5 

50 100 150 200 250 550 600 650 700 750 
SYNTHETIC MIXTURE 
GLy- PHOE TH ANOL 
05 \ pro-€rHanct 
~~ \ 

50 100 150 200 250 
NORMAL RAT BRAIN 


50 100 150 200 250 550 600 650 70 80” 750 
FY A | 
Fig. 1. Spectrum of the amino acids in rat brain. 
while an increase is viewed as evidence of the presence of conjugated amino acids 
in the extract. 
The method used is briefly described as follows: the brains of four Sprague-Dawley 
rats were pooled and homogenized with five times their weight of ice-cold distilled 
water in a Potter-Elvehjem homogenizer. The extraction of the amino acids was 
performed according to HAMILTON AND VAN SLYKE®: # using picric acid. All details 
concerning the preparation of samples for chromatography, the preparation of the 
resins (Dowex-2-X-8 and Dowex-50-X-4) and the fractionation were similar to 
those described by Moore, STEIN AND TALLAN ef al.3, °, ®. Total free amino acids 
before chromatography and the single fractions after chromatography were analyzed 
according to MooRE AND STEIN’ using the ninhydrin reaction. Hydrolysis was 
carried out with 6 N HCl at roo° for 24 h. 
Table I shows that the recovery of a mixture of known amino acids was quanti- 
References p. 492 
