Content and Release of Amino-acids and Catecholamines in Monkey Brain

PUSH pull cannulae1were stereotaxically implanted in the regions of the amygdala and putamen of five rhesus monkeys anaesthetized with halothene. Buffered solutions containing 10 µCi/ml. of U-14C-D-glucose (5 mCi/mmole), 20 µCi/ml of 1-14C-γ-hydroxybutyric acid (5 mCi/mmole) or 10 µCi/ml. of U-14C-L-tyrosine (62 mCi/mmole) were perfused through the brain structures at a rate of 1.18 ml. per h. After discarding the perfusate collected during the first 30 min, 1 ml. of perfusate was collected and prepared for analysis. Cerebral blocks of brain were cut out, rinsed with buffered solution and perfused structures were dissected out and frozen in liquid nitrogen. Perfusates and brain extracts were desalted and deproteinized using methods of ion exchange displacement2,3and a modification of the picric acid method4and were then subjected to automated amino-acid analysis. Eluate fractions from the analyser were collected for 1 min intervals and appropriate aliquots were assayed for radioactivity. Endogenous and labelled dopamine and norepinephrine were determined by previously described methods5–7.