Structures of tested pyrrolo[3,4-d]pyridazinone derivatives: (2a) 3,5,7-trimethyl-6-phenyl-1-[[3-[(4-phenylpiperazin-1-yl)methyl]-2-thioxo-1,3,4-oxadiazol-5-yl] methoxy]pyrrolo[3,4-d]pyridazin-4-one; (2b) 6-butyl-3,5,7-trimethyl-1-[[3-[(4-phenylpiperazin-1-yl)methyl]-2-thioxo-1,3,4-oxadiazol-5-yl] methoxy]pyrrolo[3,4-d]pyridazin-4-one; (3a) 1-[[3-[[4-(4-chlorophenyl)-4-hydroxy-1-piperidyl]methyl]-2-thioxo-1,3,4-oxadiazol-5-yl] methoxy]-3,5,7-trimethyl-6-phenyl-pyrrolo[3,4-d]pyridazin-4-one; (3b) 6-butyl-1-[[3-[[4-(4-chlorophenyl)-4-hydroxy-1-piperidyl]methyl]-2-thioxo-1,3,4-oxadiazol-5-yl] methoxy]-3,5,7-trimethyl-pyrrolo[3,4-d]pyridazin-4-one.