486 
INVITED DISCUSSION 
FREE AMINO ACIDS IN BRAIN AFTER TREATMENT 
WITH ESYCHOTROPIC DRUGS 
E. MUSSINI anp F. MARCUCCI 
Department of Pharmacology, Medical School, University of Milano, Milano (Italy) 
Only little is known about the distribution and function of free amino acids in brain, 
although the metabolism of a few has been extensively investigated in these last 
years}: 2. 
The lack of suitable analytical methods, at the same time reproducible, simple and 
sensitive, is one of the main handicaps in this field of research. This explains also 
why the data available on the relationship between central effects of drugs and changes 
in the composition of free amino acids in brain are so scarce. 
TABLE I 
RECOVERY OF STANDARDS 


. . Amount present Amount found Recovery 
aus ve (ue) (ue) (4) 
Cysteic acid 182 164 go 
Taurine 180 161.8 90 
Aspartic acid 190 203 106 
Serine 150 130 87 
Glutamic acid 186 163 88 
a-Alanine 122 122 100 
a-Amino-n-butyric acid 107 193 115 
Valine 161 105 103 
Cystine 150 142 95 
Methionine 187 166 89 
Isoleucine 162 149 2 
Leucine 162 170 105 
f/-Aminoisobutyric acid 167 140 83 
Tyrosine 212 199 94 
Phenylalanine 206 192 93 
y-Aminobutyric acid 167 156 93 
Ornithine 225 182 80 
Lysine 212 173 81 
Histidine 225 173.8 Taf, 
One of our first problems was the choice of a quantitative method. After a careful 
suvery it was decided to use the technique of column chromatography with ion- 
exchange resins. However, an additional problem was the fact that there are no 
methods able to extract free amino acids without also extracting peptides of small 
molecular weight. Since these peptides are eluted from the column in correspondence 
References p. 492 

