ラットの水迷路による空間学習過程と年齢との関連

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It is well known that aging is associated with the specific impairments of learning and memory in various mammals including elderly humans. These age-related memory impairments usually involve spatial cognitive abilities. However few studies have addressed the comparison of the changes in the performance of spatial learning among various age groups. The present study examined the acquisition of spatial learning using the Morris water maze and variously aged rats. 30 rats were reared and were divided into three age groups, that is, 12 month (12A: n=10), 18 month (18A: n=10), and 24 month (24A: n=10) old groups. Also 3-4 month-old rats (young: n=10) were used as controls. All rats were trained to learn the position of a hidden escape platform (place learning) for four trials per day, with an intertrial interval of approximately 10 minutes, for a total of 4 days. The location of the hidden escape platform remained constant and, on each trial, rats swam for 90 seconds or until they found the platform. The starting location varied randomly across the trials. The fifth day was a probe test in which the platform was retracted, and rats swam for 60 seconds. Then the cue learning was tested subsequently in a single session of 4 trials in which rats swam to the visible escape platform that protruded above the surface of the pool, for 90 seconds on each trial. In the 24A group, the escape latency to the platform was significantly prolonged in the place learning but not in the cue learning compared to that in the control group, almost the same as those in the previously reported studies. Also in the present study, a significant positive correlation between the escape latency and the mean swimming time was observed in the young control group. But the 24A group showed a significant negative correlation. In the 12A and 18A groups, these results were obtained, but not significant, as those in the 24A group. In the present study, the percent time staying in quadrant G3 in which the escape platform was located during the place learning task was significantly decreased in all aging groups. These results suggest that the spatial learning deficits begin to appear around 12 months old and gradually go from bad to worse in later stages, and these deficits in the 12A and 18A groups are probably related to the similar background mechanisms to the 24A group or more elderly groups in which the morphological and functional deteriorations are observed in the entorhinal-hippocampal networks.
福井大学の論文
2003-12-19

著者

吉田和典
福井大学医学部

ラットの水迷路による空間学習過程と年齢との関連

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