Differential effects of thioridazine, clozapine and metoclopramide on the induction of adrenomedullary enzymes by apomorphine.

The induction of two adrenomedullary enzymes, ornithine decarboxylase and tyrosine hydroxylase, by apomorphine was studied in rats receiving dopamine antagonists known to by specific in their site of action. Metoclopramide, a drug that acts predominantly on the A9 dopamine system, was effective in blocking the induction of the two enzymes by apomorphine. Thioridazine and clozapine, two antipsychotic drugs that act preferentially on the A10 dopamine systems, did not impair this induction and possibly potentiated it. The results suggest that the site of action of apomorphine responsible for the induction of adrenomedullary ornithine decarboxylase and tyrosine hydroxylase is located in the striatum.