Abstract: Objective · To explore whether different test indicators and observation periods in contextual fear conditioning test affect the detection effectiveness of learning and memory ability of 5XFAD transgenic mice. Methods · Twelve 4-month-old female 5XFAD transgenic progeny mice and 14 4-month-old female LM progeny mice were selected, which were produced by crossing male 5XFAD transgenic mice and female C57BL/6 mice, to conduct open field test and contextual fear conditioning test in succession. Total distance and velocity in open field test and average motion index in the first 60 s of training stage in contextual fear conditioning test of the two groups of mice were used to evaluate the difference of locomotor activity. Besides, the first 180 s, 181-360 s and the first 300 s of testing stage for observation were selected to evaluate the selection effects on percent freeze and activity suppression ratio. Then further investigation was launched to explore the effects of different observation periods on the detection effectiveness of percent freeze and activity suppression ratio. Results · The differences of total distance and total velocity of the two groups of mice in open field test were not statistically significant, however the average motion index in the first 60 s of training stage in contextual fear conditioning test of 5XFAD transgenic mice was significantly higher than that of LM mice (P=0.027). The comparison of percent freeze among the three groups of observation periods of LM mice had significant difference (both P<0.05), while there was no statistical significance in activity suppression ratio. The comparisons of percent freeze and activity suppression ratio among the three groups of observation periods of 5XFAD mice had no significant difference. The differences of percent freeze between 5XFAD mice and LM mice was not statistically significant during the three observation periods. However, the activity suppression ratio of 5XFAD mice was significantly higher than that of LM mice in the first 180 s (P=0.038), in the other two observation periods the difference of activity suppression ratio between the two groups of mice was not statistically significant. Conclusion · The average motion index detected in training stage in contextual fear conditioning test is more sensitive than total distance and total velocity detected in open field test for evaluating locomotor activity of 5XFAD mice. In contextual fear conditioning test, different observation periods have effects on the value of percent freeze provided by single strain of mice, while the value of activity suppression ratio remains unaffected. Activity suppression ratio is more precise than percent freeze to reflect the cognitive deficiency of 5XFAD mice. It is more accurate to select the first 180 s of testing stage for observation.

Key words: Alzheimer’s disease (AD), 5XFAD transgenic mouse, open field test, contextual fear conditioning test, observation period