Brain tyrosine level controls striatal dopamine synthesis in haloperidol-treated rats

Animals received either haloperidol (2 mg/kg) or probenecid (200 mg/kg) in conjunction with tyrosine (100 mg/kg) or its diluent. Striatal homovanillic acid levels increased in probenecid-treated animals to the same range whether they were given tyrosine or not. In haloperidol-treated animals the levels of homovanillic acid were significantly elevated in animals receiving tyrosine. Tyrosine and homovanillic acid levels were highly correlated as determined by linear regression analysis.