During REM sleep, fluctuation of autonomic nervous system including that of blood pressure, heart rate or respiration occurs. It is probable that such events reflect an emotional change during REM sleep and have some relations with the stress during waking. Brain imaging studies in human have revealed that activity of amygdala increases during REM sleep. During waking, the amygdala is activated by emotional stimuli, mediates emotional responses to cause fluctuation of autonomic nervous system associated with it. To clarify the influence of stress during waking on emotional changes during REM sleep, we examined the effect of stress on blood pressure fluctuation during REM sleep. Then, to test the involvement of amygdala in fluctuation of autonomic nervous system during REM sleep, we examined effect of bilateral electrical lesions of the amygdala on blood pressure fluctuation during REM sleep.
Male rats in a shock chamber were given, every one minute from 16:00 to 17:30, 10 seconds tone of 10 KHz (15 times), which was associated with electric shock (0.7 mA, 1 sec), and of 500 Hz (75 times) without shock. After the shock, rats were moved to the recording chamber to record sleep-wake profiles and blood pressure from 20:00 to 8:00 (dark period), then from 8:00 to 16:00 (light period).
Blood pressure fluctuation during REM sleep is composed of single peak or multi peaks increase, and single peak decrease. After the electric shock, frequency of single peak decrease became 5.7 ± 2.9 counts/h, which was 90 % higher than that in control animals (3.0 ± 3.0 counts/h) (p<0.05).
During dark period, single peak, multi peaks increase and single peak decrease of blood pressure were 2.9±4.1, 9.2±3.2, and 5.9±4.2 counts/h, respectively. During light period, they were 5.4±0.9, 21.9±7.8, and 5.9±3.3 counts/h, respectively. After the electrical lesion of large part of amygdala (500 µA, 60 sec), these fluctuations almost disappeared.
These results suggest that the electrical shock stress associated with sound has some influences on blood pressure fluctuation during REM sleep, and the amygdala plays an important role in blood pressure fluctuation during REM sleep.