Dopaminergic agonists: comparative actions of amine and sulfonium analogues of dopamine

We have investigated the possibility that structural modifications of the sulfonium analogue of dopamine (4) would produce the same pattern of biological activity as structural modifications of dopamine. A series of methyl- tetralinyl -, and naphthalenylsulfonium analogues 5-7 were prepared and tested for their ability to inhibit the potassium-evoked release of [3H]acetylcholine from striatal slices. All compounds were tested under normal conditions and after depletion of dopamine stores with reserpine and alpha-methyl-p-tyrosine. The amine and sulfonium analogues 2-6 all showed direct agonist activity. The sulfonium analogue 7 produced, predominantly, indirect activity. In contrast to the amine analogues, chemical modifications of the sulfonium compounds produced little change in their dopamine agonist activity.