“L-tyrosine is a precursor to dopamine, the neurotransmitter that aids in motivation, mood regulation, and pleasure,” says ...
Christensen, H. N., Akedo, H., Oxender, D. L., and Winter, C. G., in Amino Acid Pools, edit. by J. T. Holden, 527 (Elsevier Publishing Co., Amsterdam, 1962).