Study objectives: To determine the effects of temporary functional inactivation of the central nucleus of the amygdala on sleep and on activity in an arousing environment, an open field.
Design: Rats were implanted with electrodes for recording the electroencephalogram (EEG) and electromyogram (EMG), and with guide cannulae aimed into CNA. Sleep was recorded for 22 h (10 h light, 12 h dark) following microinjections of tetrodotoxin (TTX: 5.0 ng/0.2 microl given unilaterally [TTXUH] or bilaterally [TTXBH], and 2.5 ng/0.1 microl given bilaterally [TTXBL]) or saline (SAL) alone on separate days. Activity during 1 h in an OF was recorded after microinjections of TTXBH and SAL.
Setting: NA.
Patients or participants: Three-month-old Wistar rats (n=12).
Interventions: Functional inactivation of the central nucleus of the amygdala with TTX.
Measurements and results: Compared to SAL, all TTX microinjections significantly shortened NREM latency, but did not alter total NREM during either light or dark periods. During the light period, TTXBH significantly reduced total REM and REM episode number, and TTXBL decreased REM episode number. All TTX microinjections increased EEG slow wave activity (0.5-4 Hz, SWA) during wakefulness, NREM and REM. Activity in OF was decreased after TTXBH compared to SAL.
Conclusions: Functional lesions of the amygdala, including the central nucleus of the amygdala, decreased REM sleep and reduced arousal, as indicated by shortened NREM latency and decreased activity in an arousing environment. These findings suggest that the amygdala plays a broad role in modulating spontaneous sleep and wakefulness and in modulating responsiveness in arousing situations.