a b s t r a c tA series of new benzolactam derivatives was synthesized and the derivatives were evaluated for their affinities at the dopamine D 1 , D 2 , and D 3 receptors. Some of these compounds showed high D 2 and/or D 3 affinity and selectivity over the D 1 receptor. The SAR study of these compounds revealed structural characteristics that decisively influenced their D 2 and D 3 affinities. Structural models of the complexes between some of the most representative compounds of this series and the D 2 and D 3 receptors were obtained with the aim of rationalizing the observed experimental results. Moreover, selected compounds showed moderate binding affinity on 5-HT 2A which could contribute to reducing the occurrence of extrapyramidal side effects as potential antipsychotics.Ó 2009 Elsevier Ltd. All rights reserved.Dopamine (DA) is a major neurotransmitter in the central nervous system (CNS) that plays important roles in behaviour and cognition, ranging from movement to emotion, sensitization to addiction, and development to plasticity. All DA receptors belong to a superfamily of large peptides that are coupled to G-proteins and modified by attached carbohydrate, lipid-ester or phosphate groups. They are characterized by having seven hydrophobic transmembrane-spanning regions, as well as a functionally critical third intracytoplasmic loop that interacts with G-proteins and other effector molecules to mediate the physiological and neurochemical effects of the receptors. Based on their pharmacological profiles, including their effects on different signal transduction cascades, these receptors are currently divided into two families: the D 1 -like family or adenylyl-cyclase stimulators, which includes D 1 and D 5 receptors, and the D 2 -like family or adenylyl-cyclase inhibitors, which includes D 2 , D 3 and D 4 receptors. 1 The D 3 dopamine receptor was first identified and clonated by Sokoloff et al. 2 in 1990 and has been shown to be an interesting target for different CNS diseases. Although its structure and pharmacology are very similar to dopamine D 2 , the D 3 receptor is generally less abundant than the D 2 receptor, and the difference is particularly striking in the caudate putamen, where D 2 receptors are densest and D 3 receptors are poorly represented. 3 Moreover, D 3 -binding sites and mRNA encoding D 3 receptors are concentrated in the limbic brain areas known to be associated with cognitive and emotional functions. 4 Due to this, the D 3 receptor has been suggested to be a potential target in the treatment of neurological disorders such as schizophrenia, and drug abuse. 5 In schizophrenia, a blockade of D 2 receptors has been considered to be the main mechanism responsible for the efficacy of antipsychotics, 6 but the complex profiles of some atypical drugs challenged this assumption, that is, clozapine exhibits activity at multiple receptors. 7 Now there is an increasing body of clinical evidence that supports the notion that multi-target ligands may be more efficacious than strictly selective ...