The effects of some stimulants and anti-psychotic drugs on urinary unconjugated tyramine levels in the rat.

The effects of intraperitoneal injections of amphetamine and methylphenidate (ritalin) at relatively low and high doses, the anti-psychotic drugs chlorpromazine and haloperidol and combinations of haloperidol with methylphenidate and amphetamine on the urinary excretion levels of unconjugated meta and para tyramine in the rat have been investigated. With the exception of a high dose of methylphenidate, none of the drug treatments changed significantly the urinary excretion level of para tyramine. meta Tyramine was significantly reduced by a low dose of amphetamine and a high dose of methylphenidate but significantly increased by a high dose of amphetamine. Such effects are different from those reported by Juorio (1977a, b) and Danielson, et al (1976) with respect to the rat striatum and mesolimbic systems where para tyramine was decreased and meta tyramine increased. The effect of adding anti-psychotic drugs in these latter studies was to potentiate their differential effects. Such differences indicate perhaps variations in the metabolism of the tyramines in peripheral tissues as compared with certain brain regions.