New pyridobenzodiazepine derivatives: modifications of the basic side chain differentially modulate binding to dopamine (D(4.2), D(2L)) and serotonin (5-HT(2A)) receptors.

A series of new pyridobenzodiazepines with variation of the basic side chain were synthesized and evaluated for their binding to D(4.2), D(2L), and 5-HT(2A) receptors in comparison with clozapine, haloperidol, and two parent compounds previously described, 8-chloro-6-(4-methyl-1-piperazinyl)-11H-pyrido[2,3-b][1,4]benzodiazepine (8) and 8-methyl-6-(4-methyl-1-piperazinyl)-11H-pyrido[2,3-b][1,4]benzodiazepine (9). In the piperazine series, replacing the N-methyl group by a N-phenyl moiety (15-17, 30-32) provided a dramatic decrease of affinity for all receptors (K(i) > 1000 nM).