Effects of zopiclone on sleep spindles studied with an improved waveform recognition method

The effects of zopiclone on sleep spindles were analyzed in six normal volunteers by using an improved waveform recognition method. The appearance rate of spindles during stage 2 of NREM sleep showed a significant increase on the drug night, which returned to the baseline on the withdrawal night. The mean duration of spindles was significantly prolonged on the drug night. No definite changes were observed in the average spindle frequency. The mean amplitude of spindles had a tendency to decrease on the drug night. On the withdrawal night, the mean amplitude decreased significantly compared with that of the baseline. Our results indicate that zopiclone is one of the spindle enhancing drugs, and that its property resembles that of benzodiazepines.