Failure of branched-chain amino acids to affect synaptosomal uptake of norepinephrine and dopamine.

Despite evidence for neuroendocrine actions of the branched-chain amino acids (BCAAs) and implications that these amino acids alter the turnover of central catecholamines, the mechanism of these actions of the BCAAs is uncertain. In this study, we tested the effects of the BCAAs on uptake of catecholamines by axon terminals (synaptosomes) isolated from whole mouse brain minus the cerebellum. Neither high physiological (1-2 mM) nor pharmacological levels (10 mM) of an equimolar mixture of the BCAAs altered the uptake of 3H-dopamine and 3H-norepinephrine by synaptosomes. These findings suggest that the BCAAs do not influence the reuptake mechanism for termination of catecholamine-mediated neurotransmission.