Effects of conformationally restricted 4-piperazinyl-10H-thienobenzodiazepine neuroleptics on central dopaminergic and cholinergic systems

The levels of antidopaminergic and anticholinergic activities of neuroleptics, 4-piperazinyl-10H-thienobenzodiazepines, are modulated by imposing steric impedence to the piperazine ring. The optimum situation in favor of the anticholinergic action is reached in compound 5, 2,3-dimethyl-7-fluoro-4-(4-methyl-1-piperazinyl)-10H-thieno[2,3-b][1,5]benzodiazepine, where a maximum activity (equivalent to hyoscine), as measured by the [3H]QNB receptor binding assay, is obtained. The structure-activity relationships found highlight the importance of certain spatial dispositions of the distal piperazine nitrogen (electron lone pair) with respect to the tricyclic system. The evidence for molecular topography of these compounds is presented from X-ray, NMR, and other physical data. The conformational aspects for correspondence to the relevant receptors are discussed.