The pharmacological profile of a potential hypnotic compound RU 31158.

RU 31158, 6-(orthochlorophenyl)-1, 2-dihydro-2 (N-methylpiperazine-1-yl) methylene-8-nitro-IH, 4H-imidazo [1,2-a] [1,4] benzodiazepin-1-one methanesulphonate, demonstrated potent hypnotic activity compared to diazepam when examined in the mouse and rat. RU 31158 potentiated minimal hypnosis in mice induced by both hexobarbital and chlorprothixene with ED50 values of 2.15 (1.53-3.01) and 0.69 (0.46-1.02) mg/kg p.o. respectively; these compared to values for diazepam of 17.00 (11.25-25.67) and 3.60 (2.25-5.76) mg/kg p.o. RU 31158 also potentiated hexobarbital in the rat with an ED50 value of 1.2 (0.7-2.0) mg/kg p.o. as compared to 32.0 (27.5-38.5) mg/kg p.o. for diazepam. Sleep studies in the rat confirmed the hypnotic properties of RU 31158, and also showed that the duration of action at 8.0 and 16.0 mg/kg p.o. was not longer than 9 hours. RU 31158 also showed potent minor tranquilizer, anxiolytic, and anti-convulsant properties in a series of pharmacological tests.