Pharmacological properties of presynaptic dopamine receptor agonists.

Selective presynaptic dopamine receptor agonists appear to offer promise as putative antipsychotic agents with a low risk of extrapyramidal side-effects, including tardive dyskinesia. However, no such agent with a reasonable degree of selectivity has yet reached the stage of clinical trial. In the present paper the particular pharmacological profile of presynaptic dopamine receptor (autoreceptor) agonists is described, and underlying mechanisms are discussed. Special attention is paid to the compound 3-(3-hydroxyphenyl-N-n-propylpiperidine(3-PPP), especially its levotatory enantiomer. This agent shows affinity for both pre- and postsynaptic dopamine receptors. Its intrinsic activity in different locations varies between virtually zero and 100%, leading to a mixture of agonist and antagonist properties. It is suggested that this variability depends on the adaptive properties of the dopamine receptor.