Dopaminergic inhibition of adrenergic neurotransmission as a model for studies on dopamine receptor mechanisms.

Dopamine and apomorphine produced concentration-dependent inhibition of adrenergic neurotransmission in the isolated, perfused, rabbit ear artery. The inhibitory action of both dopamine and apomorphine was competitively antagonized by haloperidol and several other antipsychotic drugs. The calculated affinities of these drugs for the dopaminergic receptor correlate closely with both the pharmacological potencies of these drugs in vivo and their reported potencies as inhibitors of [3H]haloperidol binding to "dopamine receptors" in brain homogenates.