Neuropharmacology of a new psychotropic 2,3-benzodiazepine.

1-(3-Chlorophenyl)-4-methyl-7,8-dimethoxy-5H-2,3-benzodiazepine (GYKI 51189) is a new analogue of tofisopam. Due to the novel chemical structure this molecule displays a peculiar spectrum of pharmacological activity. In many respects tofisopam and its new analogue differ from the traditional 1,4-benzodiazepines, e.g. in that they possess selective anxiolytic action without muscle relaxant and anticonvulsive activity, as well as they do not show any affinity for the 1,4-benzodiazepine receptors. This new compound exerts more pronounced anxiolytic potency than tofisopam. In addition to its main action it possesses significant antidepressant activity. It attenuates psychomotor agitation and exerts significant antiaggressive effect by reducing both spontaneous and induced aggressiveness. Vegetative responses (rise in blood pressure and heart rate) induced by electric stimulation of the hypothalamus are also inhibited by this compound, while motor functions remain unaffected and no somnolence is induced. The new tofisopam analogue fails to exert any potentiating effect either on ethanol or on barbiturates. GYKI-51189 has a highly favourable therapeutic index and only few side effects. Neither tolerance nor dependence was observed during the chronic toxicological investigations.