2.7. Body weight and serum corticosterone measurement
The body weight of the animal was measured daily at 7:00 am during the exposure to stress for 10 consecutive days. The day after the elevated plus-maze, both stressed and non-stressed mice were subjected to two conditions either restraint stress for 2 h using the procedure described above or left undisturbed in their home cages until the blood collection. Immediately after the above condition, they were injected with an overdose of sodium pentobarbital (50 mg/kg, i.p.) and the blood was taken from the heart. Blood was collected between 13:00 and 15:00, centrifuged (2200g for 20 min) at 4 °C, and supernatants were collected and stored at −30 °C until the measurement. The concentration of corticosterone in the serum was determined using a correlate-enzyme immunoassay kit (Assay Designs Inc., Ann Arbor, MI, USA) according to the manufacturer's protocol.
2.8. Statistical analyses
Results are represented as mean±standard error of the mean (SEM) from 8 to 10 animals per group. Statistical differences of the mean were analyzed using one-way analysis of variance (ANOVA) followed by Dunnett's post hoc test for a significance level when the “P” value was less than 0.05. Simple comparison between two groups (control vs. stress) was performed using Student's t-test. All statistical analyses were performed using PASW Statistics 18 (SPSS Inc., Chicago, USA).