REPETITIVE POST-TRAINING EXPOSURE TO ENFLURANE MODIFIES SPATIAL MEMORY IN MICE

Background: Previously the authors found that a single posttraining ex posure to enflurane or isoflurane, but not halothane, enhanced memory storage in an active avoidance task, which is a behavior with underlyi ng mechanisms that are poorly understood and still debated. In contras t, spatial tasks are known to depend on hippocampal functions. This st udy investigated the effects of repetitive post-training exposure to e nflurane 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 on e trial per day. The number of errors in the first eight choices was r ecorded to determine performances for each day of training. Immediatel y 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 va porizer. The performance ratios (the ratio of errors on each day compa red with the first day of the 4 days) in the control and the enflurane groups were compared. Results: The performance ratios (which equals t he 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, an d 0.32 (P < 0.01, us. control), and 0.46 (p < 0.05, vs. control), resp ectively. Conclusions: Repetitive post-training exposure to 1% and 2% enflurane significantly enhanced spatial memory in the eight-arm radia l maze task. Enflurane enhances consolidation of spatial memory, possi bly by affecting hippocampal activity.