Behavioral characterization of acetaldehyde in C57BL/6J mice: locomotor, hypnotic, anxiolytic and amnesic effects

Rationale: Acetaldehyde, the first metabolite of ethanol, was recently suggested to contribute to many behavioral effects of ethanol, although few studies have directly investigated the behavioral effects of acetaldehyde itself. Objectives: The aim of the present study was to characterize the locomotor, hypnotic, anxiolytic-like and amnesic effects of acetaldehyde in C57BL/6J mice. Methods: Increasing doses of acetaldehyde (0 - 300 mg/kg) were injected intraperitoneally and their effects on a series of representative behaviors were investigated. The locomotor effects of acetaldehyde were measured in activity boxes. The duration of the loss of righting reflex was used as an index of the hypnotic effects of acetaldehyde. The anxiolytic-like effects of acetaldehyde were tested with an elevated plus-maze and the amnesic effects with the one-trial passive avoidance test. Finally, brain and blood acetaldehyde concentrations were assessed. Results: Acetaldehyde induced a significant hypolocomotor effect at 170 mg/kg and higher doses. In addition, the hypnotic effects of acetaldehyde were demonstrated by a loss of righting reflex after the administration of 170 and 300 mg/kg acetaldehyde. The elevated plus-maze showed that acetaldehyde does not possess anxiolytic-like properties. Finally, acetaldehyde ( 100 - 300 mg/kg) dose-dependently altered memory consolidation as shown by a reduced performance in the passive avoidance test. Conclusions: The present results show that acetaldehyde induces sedative, hypnotic and amnesic effects, whereas it is devoid of stimulant and anxiolytic-like properties in C57BL/6J mice. However, the behavioral effects of acetaldehyde after intraperitoneal administration were apparent at very high brain concentrations. The present results also indicate that acetaldehyde is unlikely to be involved in the anxiolytic properties of ethanol in mice.