Tyrosine availability determines stimulus-evoked dopamine release from rat striatal slices.

Direct evidence that precursor levels can affect catecholamine release from brain cells has not previously been presented. We observe a dose-dependent relationship between the tyrosine (Tyr) concentration of the superfusing medium and the amount of dopamine (DA) released from rat striatum by trains of electrical pulses. In the absence of exogenous tyrosine, tissue Tyr and DA levels are reduced following stimulation. These findings suggest that DA release from striatal neurons may not be sustained if fluctuations occur in the supply of Tyr to the brain.