RECEPTOR AFFINITIES OF APORPHINE ENANTIOMERS IN RAT-BRAIN TISSUE

R(-) and S(+) enantiomers of apomorphine, N-n-propylnorapomorphine and 11-hydroxy-N-n-propylnorapomorphine were screened for affinity at over 40 representative sites in rat brain tissue that included amine, purine, amino acid and peptide receptors, transporters, ion channels, and effector components; only dopamine receptors and alpha-adrenoceptors showed appreciable affinity that was quantified further. The aporphines showed R(-)> S(+) isomeric selectivity as well as D-2 > D-1 selectivity at dopamine receptors. While R(-) isomers preferred alpha(2)-adrenoceptors, S(+)-aporphines were alpha(1)-selective, with similar affinity at alpha(1)-adrenoceptors and dopamine D-2 receptors. Interactions of S(+)-aporphines at alpha(1)-adrenoceptors as well as dopamine D-2 receptors may contribute to their unusual behavioral properties.