Effect of nonsedative doses of propofol on an innate anxiogenic situation in rats.
BACKGROUND: The effect of propofol on anxiety has not been well studied. In humans, such investigations are confused by the fact that sedation often coexists with anxiolysis. Therefore, the authors evaluated the effects of minimal sedation with propofol in rats placed in an innate anxiogenic situation, the elevated plus-shaped maze. METHODS: In experiment 1, spontaneous locomotor activity was determined in rats as a measure of sedative effect induced by propofol (0-9 mg/kg administered intraperitoneally). In experiment 2, groups of rats received propofol (0-9 mg/kg) or diazepam (0-2 mg/kg) and then were placed on a plus-shaped maze elevated above the ground that was composed of two opposite closed arms and two opposite open arms. On an initial exposure to the maze, undrugged rats avoid the open arms, with the number of entries into and time spent within the open arms constituting approximately 20% of their total activity. This reflects normal anxiety in a rodent for any elevated open platform. RESULTS: In experiment 1, 0-9 mg/kg propofol did not alter spontaneous activity in rats. In experiment 2, propofol and diazepam significantly increased the number of entries into and the time spent within the open arms. Propofol at a dose of 9 mg/kg significantly increased the rats' level of exploration of the open arms to about 50% of all exploratory activity, and a similar observation was made with 2 mg/kg diazepam. CONCLUSIONS: In a standard animal model, propofol has anxiolytic properties at doses that do not produce sedation.