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Morris Water Maze Protocol(from Tonkiss, Shultz & Galler: Physiology and Behavior, Vol. 55, 1994)

Distal-Cue Test

1. A 1.5 m diameter, 45 cm deep Morris water maze was filled with water to a depthof26.5 cm.

2. The water temperaturewas adjusted according to the age of the rats: 29 C(0.5)

for PND 16 20; 27(0.5) for PND 20-27 and 25(0.5) for adult rats.

3. A circular platform, 25 cm high and 12 cm in diameter was placed into the tank at a

fixed location in the center of one of four imaginary quadrants.

4. Approximately 1.5 liters of milk was used to make the water opaque.

5. Immediately prior to behavior testing, the rats were allowed an adaptation periodof10-15 minutes (to adapt to white light).

6. The rats were then given 1 min. upon the platform before undergoing 3 swim training

trials.

7. During each training trialthe rat was removed from the stand and released facing the

platform at a distance of 12-18 inches.

8. The rat was then guided by the experimenter to swim to the platform.

9. A rest period of 30 s was followed by 12 test trials: two sets of 6 trials - 4 trialsfrom each of the 3 start positions, with a rest period of 30-45 min (in a small heated

cage in a different room) separating the two test periods.

10. During the test trialthe rats were released into the water at one of the three different

starting positions, facing the wall and were required to use distal cues (e.g. cabinets,

doors, posters, etc.) to navigate to the platform.

11. The start positionswere all equidistant from the platform, located immediately

adjacent to the wall in the center of the three quadrants that did not contain the

platform.

12. The rat was allowed to swim for up to 1 min to locate the platform. If it failed to

locate the platform within that time, escape was assisted.

13. Pups (PND 16-20) were given a 60 s intertrial intervalon the platform, while older

rats (>20 days) were given a 35 s intertrial interval.

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14. Distance traveled and escape latency were measured on each trial. Swim speeds, in

cm/s were calculated by dividing the distance traveled by the escape latency.