Abstract
Purpose :
External visual cues are necessary for place navigation during Morris water maze testing. Posters used for external visual cues were replaced following facility renovations, after which juvenile rats took subjectively longer to complete the water maze testing than before replacement. We performed a retrospective analysis of control animal study data to compare performance prior to and after the change in visual cues.
Methods :
Eight to ten week-old Sprague Dawley rats were used in two toxicology studies. In the first study, three posters with different shapes and conspicuous graphics were used for visual cues, with two posters hung from the ceiling and one placed above the rim of the water maze pool. These posters were replaced by four new posters of different colors, similar shape, and less prominent graphics that were all placed just above the rim of the water maze pool. Forty rats were used in the study with original posters, while fifty were used in the study with the new posters. Over four consecutive days, each rat was given four trial runs per day, starting from a different quadrant of the pool for each run. The time to reach a submerged platform (latency), path length, cumulative distance, and swim speed were documented using EthoVision XT software. Comparison of these values between studies using original and new posters was accomplished using repeated measures analysis of variance with trend testing.
Results :
Both male and female rats displayed an overall increase in latency values when the new posters were used. Male rats demonstrated an overall increase in path length and cumulative distance with the new posters, while females demonstrated a slower decrease in both path length and cumulative distance between days with the new posters. Both male and female rats swam at a faster speed with the new posters.
Conclusions :
Changes in external visual cue number, position, and character significantly altered test performance in juvenile rats. Additional evaluation is necessary to determine the specific etiology of this effect, which could include poster color, contrast, geometry, and positioning.
This is an abstract that was submitted for the 2018 ARVO Annual Meeting, held in Honolulu, Hawaii, April 29 - May 3, 2018.