| Summary: | 碩士 === 國立陽明大學 === 解剖學及細胞生物學研究所 === 102 === Background: Stress is the most important factor in posttraumatic stress disorder (PTSD) and major depressive disorder (MDD). Patients with PTSD or MDD often suffer from palpitations, sweating, dry mouth and insomnia that are similar to the symptoms with disturbances in the autonomic nervous system (ANS). Animals change the ANS for fight-or-flight response when they were subjected to the stressor, and reverse to baseline after the stressor is removed. Tremendous pressure or chronic stress may cause imbalance of ANS. Although clinical experience suggests that changes of the ANS may be used as biomarkers for anxiety or major depression, the results of those studies were inconsistent. In order to control the variables that are difficult to control, we used experimental mice to investigate the effects of stress on behavior and the ANS.
Materials and methods: 9~11 week-old male C57BL/6J Narl mice were used for experiments. After implanting the electrode device onto the skull, we can detect ECG, EEG, EMG signals of the mouse wirelessly. Experiments started a week after the operation. Mice received foot-shock stress in an inescapable environment (foot-shock protocol: 120 V, 0.6 mA, 3 sec/shock, shock interval 3-5 min randomly, 90 shocks/6 hrs/day for 3 days. ) The day before foot-shock stress and three days after the 3-day foot-shock stress, we used the escape test, elevated plus maze to measure the emotional behaviors, used the open field test to measure locomotor activity and picked up the EEG, EMG and ECG signals.. The EEG and EMG were used to determine sleep patterns and the ECG was analyzed to get heart rate variability data.
We put the mouse in to a 50 c.c. tube for 3 min as a second minor stressor, then detected changes in the ANS. All of the experimental data were analyzed using the SPSS statistical software.
Results: The mice experiencing foot-shock stress had a higher failure rate in the escape, shorter duration and fewer counts of exploration to the open arm in the EPM test. The mice after foot-shock stress did not show locomotor impairment in the open field test.The mice through foot-shock stress had a shorter total sleep time with increased fragments of paradoxical sleep and quiet sleep, and a higher frequency of arousal. Although no obvious change in the ANS was noted after footshock stresses, the stressed mice had a slower HF recovery after a minor stress in a brief tube-restraint.
Conclusion: After a major stress, some mice might develop depression- or PTSD-like behaviors and disturbed sleep with more fragmentation and arousals. A secondary minor stress added onto the mice ever experiencing a major stress revealed a slower HF recovery, which indicates the possibility of using HRV as a biomarker of stress pathology.
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