A new psychoactive 5H-2,3-benzodiazepine with a unique spectrum of activity.

The neuropharmacological effects of 1-(4-amino-phenyl)-4-methyl-7,8-dimethoxy-5H-2,3-benzodiazepine (GYKI 52 322) were investigated and compared with those of chlordiazepoxide and chlorpromazine. This novel 2,3-benzodiazepine displays neuroleptic activity in the apomorphine-climbing (ED50 = 1.15 mg/kg i.p.) and swim-induced grooming (ED50 = 6.9 mg/kg i.p.) tests in mice and it inhibits the conditioned avoidance response in rats (ED50 = 8.2 mg/kg i.p. and 9.8 mg/kg p.o.). However, it does not antagonize apomorphine-evoked vomiting in dogs; or stereotypy, hypermotility and turning in rats even at as high a dose as 50 mg/kg i.p. On the other hand it is active in the hole board test in mice (MED (minimal effective dose) = 0.5 mg/kg i.p.) and in the lick conflict assay in rats (MED = 5 mg/kg i.p.), indicating anxiolytic property. It shows antiaggressive effect in the fighting mice test (ED50 = 8.1 mg/kg p.o.) and the carbachol-rage procedure in cats (active at 10 mg/kg i.p.) According to the biochemical findings, this compound does not bind to the central dopamine receptors (IC50 greater than 10(-4) mol/l), but it shows affinity to the 5-HT1 receptors (IC50 = 7.1 x 10(-6) mol/l) and inhibits brain cAMP-phosphodiesterase (IC50 = 2.4 x 10(-5) mol/l). The substance causes no elevation of dopamine turnover and serum prolactin level suggesting fewer side effects. So the term "atypical neuroleptic agent" is proposed to characterize this molecule.