Pharmacological changes induced by repeated exposure to phenylethylamine.

Mice receiving daily injections of phenylethylamine (PEA) exhibited an enhanced PEA-induced motor stimulation, beginning on day 21 of administration. The mice receiving PEA were also more sensitive to the stimulatory effect of amphetamine and PCP. There was no change in brain or hepatic monoamine oxidase activity nor in hepatic mixed function oxidase after this treatment, indicating that altered metabolism was not a factor in the sensitization. Striatal dopamine receptors, labelled by spiroperidol, were increased after the long-term PEA, suggesting that the sensitization may be due to increased dopaminergic receptor activity.