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 co exists with anxiolysis, Therefore, the authors evaluated the effects of min imal sedation with propofol in rats placed in an innate anxiogenic situatio n, 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 adminis tered 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 arm s 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 w ithin 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 acti vity in rats. In experiment 2, propofol and diazepam significantly increase d the number of entries into and the time spent within the open arms. Propo fol at a dose of 9 mg/kg significantly increased the rats' level of explora tion of the open arms to about 50% of all exploratory activity, and a simil ar 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.