The presence of the A ring of aporphines and the addition of substituents to it and to other portions of the aporphine ring systems can extend explorations of the dimensions and other characteristics of the dopamine receptors. Accordingly, the synthesis and some physical and pharmacological properties of a series of (-)-2,10,11-trihydroxyaporphines (3a-g) are described. Structure-activity relationships among mono-, di-, and trihydroxyaporphines were evaluated against the high-affinity (nanomolar) binding of [3H]apomorphine (APO) and [3H]spiroperidol (SPR) with a subcellular fraction (P4) of caudate nucleus from bovine brain. In addition, DA-sensitive adenylate cyclase activity was evaluated in homogenates of rat brain striatal tissue. The rank order of displacement of [3H]APO by potent aporphines (IC50 less than or equal to 30 nM) correlated approximately with their ability to stimulate cyclic AMP synthesis. Potency orders against two ligands were dissimilar; for example, increasing the size of N6-alkyl substituents increased potency vs. [3H]SPR but not vs. [3H]APO binding. Moreover, [3H]SPR binding correlated poorly with cyclase activity or [3H]APO binding, suggesting a closer relationship of [3H]APO binding to dopamine-sensitive adenylate cyclase activity.