Effect of tyrosine on brain catecholamine turnover in reserpine-treated rats

The injection of reserpine [2.5 mg/kg, intraperitoneally (i.p.)] increased brain concentration of tyrosine and of the major catecholamine metabolites, 3-methoxy-4-hydroxy-phenylethylene--glycol-sulfate (MHPG-SO4) in the rat. In reserpine-treated animals, tyrosine administration (200 mg/kg, i.p.) caused further increases in brain tyrosine, DOPAC, and HVA, but not in brain MHPG-SO4. The increases in DOPAC and HVA levels were observed in a dopaminergic brain region (the corpus striatum) and a noradrenergic region (the cerebellum). These results support previous observations that catecholamine synthesis and release in both dopaminergic and noradrenergic neurons can depend in part upon brain tyrosine levels.