Amygdala is closely related with regulation of emotion and of autonomic nervous systems associated with emotion. During REM sleep, large fluctuations of autonomic signs such as blood pressure, heart rate or body temperature occur and such autonomic fluctuations are considered to reflect the emotional changes during REM sleep. It has been reported both in humans and animals that activity of amygdala or amygdala neurons increases during REM sleep. However, little is known about the profiles of the neurons in the amygdale in relation with sleep and waking, and with fluctuations of autonomic nervous system during REM sleep.
To clarify the functional role of amygdala nuclei in the regulation of sleep and waking especially in the regulation of antonomic nervous system during REM sleep, single neuronal activity during sleep-waking cycles was recorded from several nuclei in the amygdala simultaneously with blood pressure in unanesthetized, head-restrained rats.
More than half (33/62) of the neurons in the lateral part (basolateral and lateral nuclei) and medial part (basomedial and medial nuclei) of the amygdala showed higher firing during REM sleep (PS active neurons). The firing of these PS active neurons are mostly phasic and increase in firing started after the onset of REM sleep. In these areas, neurons most active during slow wave sleep (SWS active neurons) occupied about 26 % (16/62), which was slightly higher than that in the central amygdala (14 %: 3/21). In the central amygdala, waking active neurons occupied 24 % (5/21), while it was less than 10 % (6/62) in the lateral and medial pars of amygdala. Forty three % (13/30) of the neurons recorded from lateral and central amygdala had some correlations with blood pressure fluctuation during REM sleep, while it was 33 % (2/6) in the medial part of the amygdala and was 31 % (5/16) in some nuclei around the amygdala. These results suggest that different part of the amygdala have different roles in the regulation of sleep-waking, especially in inducing changes in autonomic nervous system during REM sleep, rather than switching or initiating sleep or waking state.