Abstract: Aim To compare the anxiolytic effects of reduced metabolite of progesterone and benzodi-azepine.Methods The effects of allopregnanolone and diazepam on spontaneous locomotor activity and on exploration in the elevated plus-maze were studied in C57 mice 20 min after vehicle or drug intraperitoneal administration.Results Allopregnanolone (0.1mg·kg^-1,ip)elicited marked anxiolytic effects in terms of significantly reducing the latency to enter the open arm from (31.30±8.39)s to (8.80±6.00)s,(P<0.001),and significantly increasing both the number of open arm entries from 1.20±0.42 to 4.80±1.75,(P<0.001)and the proportion of total time spent on the open arm from 7.13%to 32.50%,(P<0.001).Mean-while,the diazepam (0.25mg·kg^-1)produced a lower anxiolytic effect comparing to that of the allopregnanolone.Analysis of spontaneous locomotor activity showed while 0.5mg·kg^-1of diazepam decreased the locomotor activity (P<0.01),neither 0.1mg·kg^-1of allopreg-nanolonenor 0.25mg·kg^-1of diazepam affect the locomotor activity score.Conclusion Together,these results provide evidence for differential behavioral actions of the neurosteroids and benzodiazepines.Since the allopregnanolone produce a selective anxiolytic effect without affecting the spontaneous locomotor activity,the allopregnanolone may be a better alternative for diazepam in treating anxiety.

Key words: allopregnanolone, diazepam, anxiety, elevated plus-maze, anxiolytic, sponta-neous locomotor activity