The effects of administration of meta-tyramine and para-tyramine on dopamine and its metabolites in the rat striatum.

Para-tyramine administration decreased the release of dopamine as indicated by the decline in 3-MT concentrations, increased HVA concentrations at 30 and 60 min and decreased DA concentrations at the same times. DOPAC concentrations declined after 60 min. Meta-tyramine reduced the synthesis of dopamine thus causing a decrease in the concentrations of all its metabolites by 60 min post injection. The failure of the deaminated products of the tyramines to affect the concentrations of dopamine and its metabolites suggested that the effects produced by either meta or para-tyramine were due to the amines and not due to interference with various transport mechanisms. Para-tyramine and meta-tyramine may achieve their actions on dopamine neurotransmission by different mechanisms. Para-tyramine may act as a partial agonist reducing DA release extraneuronally (the decrease in 3-MT levels) or by displacing DA intraneuronally as evidenced by the decline in DA concentrations or increase in HVA concentrations. Meta-tyramine appears to inhibit the synthesis of dopamine.