The effect of various chlorpromazine derivatives on the apomorphine-elicited inhibition of synaptosomal tyrosine hydroxylase activity.

The effects of chlorpromazine and of some metabolites of chlorpromazine on the apomorphine-elicited inhibition of synaptosomal tyrosine hydroxylase activity were investigated. Chlorpromazine, nor1-chlorpromazine and 7-hydroxychlorpromazine reverse the apomorphine-elicited inhibition of tyrosine hydroxylase activity while nor1-chlorpromazine sulfoxide and nor2-chlorpromazine sulfoxide have no effect on this inhibition. 6-Hydroxychlorpromazine and promethazine also reverse the enzyme inhibition by apomorphine but are less potent than chlorpromazine or 7-hydroxychlorpromazine. These results show that chlorpromazine and its metabolites with antipsychotic activity are more effective in reversing the apomorphine-elicited inhibition of tyrosine hydroxylase than those metabolites which are devoid of antipsychotic activity.