Combination effects of chloral hydrate and nitrous oxide/oxygen in the mouse staircase test.

The effects of chloral hydrate and/or nitrous oxide were assessed in the mouse staircase test. In this paradigm, the number of steps ascended is thought to reflect locomotor activity, whereas the number of rears is an index of anxiety. Chloral hydrate alone produced a dose-dependent decrease in the number of rears but no change in the number of steps ascended except at the highest dose. Nitrous oxide alone produced a concentration-related increase in the number of steps ascended but no change in rearing. When the two drugs were combined, nitrous oxide appeared to potentiate the rearing suppressant activity of chloral hydrate. Analysis of our experimental findings suggests that chloral hydrate exerts a specific anxiolytic drug effect that can be potentiated by concurrent treatment with nitrous oxide.