Repetitive post-training exposure to enflurane modifies spatial memory in mice

Background: Previously the authors found that a single posttraining exposure to enflurane or isoflurane, but not halothane, enhanced memory storage in an active avoidance task, which is a behavior with underlying mechanisms that are poorly understood and still debated. In contrast, spatial tasks are known to depend on hippocampal functions. This study investigated the effects of repetitive post-training exposure to enflurane on spatial memory in mice. Methods: Using an eight-arm radial maze, 80 mice were trained to eat a pellet I,laced on the end of each of the eight arms. Training occurred on four consecutive days with one trial per day. The number of errors in the first eight choices was recorded to determine performances for each day of training. Immediately after each training session, mice in the enflurane group received 1 h exposure to 0.5%, 1%, or 2% enflurane in air through a calibrated vaporizer. The performance ratios (the ratio of errors on each day compared with the first day of the 4 days) in the control and the enflurane groups were compared. Results: The performance ratios (which equals the mean of the error in the fourth day/the error in the first day) in the control, and 0.5%, 1%, and 2% enflurane groups were 0.66, 0.65, and 0.32 (P < 0.01, us. control), and 0.46 (p < 0.05, vs. control), respectively. Conclusions: Repetitive post-training exposure to 1% and 2% enflurane significantly enhanced spatial memory in the eight-arm radial maze task. Enflurane enhances consolidation of spatial memory, possibly by affecting hippocampal activity.