Abstract: Objective To compare the spatial learning and memory function of heat stroke rats in different periods, to explore the long- term impairment. Methods 42 Sprague-Dawley rats were randomly divided into heat stroke 7 days group (HS7, n=21), heat stroke 21 days group (HS21, n=21), and another 18 rats were performed femoral artery intubation as surgery control group (sham, n=18). They were tested with Morris water maze 7 days and 21 days after modeling respectively for 5 days. The escaping latency, the frequency of crossing the platform area and the duration in the target quadrant were recorded. Results Compared with the sham group, the escaping latency prolonged in HS7 group in all the time (P<0.05), and 4th and 5th days in HS21 group (P<0.05). Compared with HS7 group, the escaping latency shortened in HS21 group on the 3rd, 4th and 5th days (P<0.05). The duration in the target quadrant shortened in HS7 group compared with the sham group (P<0.05), and prolonged in HS21 group compared with HS7 group (P<0.05). The frequency of crossing the platform decreased both in HS7 group and HS21 group compared with the sham group (P<0.05), and no difference was found between the later 2 groups (P> 0.05). Conclusion The impairment of spatial learning and memory is the most seriously 7 days after heat stroke in rats, and it may remain for long time.

Key words: heat stroke, spatial learning and memory, Morris water maze, long-term impairment, rats