Abstract: Objective To study the dynamic change of the level of ACTH、CORT、CK and ALT in serum of rats caused by cold restraint stress, and the possible mechanisms. Methods Fifty-six SD rats of 50 days old were divided randomly into 7 groups with testing time of 0 h, 0.5 h, 1.0 h, 1.5 h, 2.0 h,2.5 h，3.0 h. After putting each group rats under testing environment by using the cold restraint stress method in specified group testing time, the level of ACTH、CORT、CK、ALT and UI in serum were analyzed. Results ① The ACTH level in serum rises quickly with time increasing for the rats under cold restraint stress, it reaches the highest value at 0.5 h, and then it starts to fall quickly. (2) The CORT level rises gradually with time increasing, it reaches the highest value at 1.5 h，and then it starts to fall quickly.③ The CK and ALT levels rise gradually with time increasing for the rats under cold restraint stress.④ The UI level rises quickly with time increasing, it reaches the highest value at 2.5 h. Conclusion The cold restraint stress can cause rising of the ACTH and CORT level in serum of rat, after it reaches the highest value, it falls back quickly. It can cause CK and ALT to rise with time increasing. Cold restraint stress can cause acute gastric ulcer of rats, with the worst at 2.5 h. It suggests that the best time for creating cold restraint stress model in rat is 2.5 h.

Key words: Cold restraint stress, Rats, ACTH, CORT, CK, ALT