Intrastrain variations in anxiolytic effect of nitrazepam in mice

This study investigated the individual differences in the baseline anxiety and anxiolytic effect of nitrazepam in Balb/c mice. Initially mice were sorted according into low, intermediate and high anxiety groups (LA, IA and HA) based on the number of entries to and time spent in open arms in elevated plus maze. Later, anxiolytic effect of nitrazepam (2 mg/kg, p.o) in LA, IA and HA mice was evaluated using hole board and light/dark tests. In Hole board test, LA mice made more number of head dippings and spent more time during head dippings, while HA mice made less number of head dippings and spent less time during head dipping when compared to that of IA mice. In light/dark test LA mice made more reentries to and spent more time in bright compartment, while HA mice made few reentries to and spent less time in bright compartment. Results suggest that mice of a single strain differ in their baseline anxiety and anxiolytic effect of nitrazepam.