Hypothermia impairs performance in the Morris water maze.

Fifteen rats were trained to learn the location of a spatially fixed platform hidden in a Morris water maze (14-16 degrees C). Asymptotic performance was achieved over six training days (10 trials/day). Then retention of the task was assessed immediately after lowering core body temperature (Tc) to 28 degrees or 30 degrees C or stabilizing at 37 degrees C (the normothermic control). The hypothermia treatment order was counterbalanced according to a Latin-square design. Hypothermia significantly impaired all measures of spatial performance. Hypothermic animals were then rewarmed in a 40 degrees C water bath to 37 degrees C Tc and spatial performance tested again. Artificial rewarming resulted in complete recovery of all measures of spatial performance. These results demonstrate that hypothermia impairs performance in the Morris water maze, possibly by an amnesic mechanism, and that returning Tc to normothermic levels initiates recovery of performance.