Analysis of sleep EEGs by the interval histogram method--validity of the baseline night as a control and the effect of ethyl loflazepate (CM6912)

The effects of an anxiolytic drug, ethyl loflazepate (CM6912) on sleep EEGs were investigated by the interval histogram method originally developed. EEGs were classified into each of the delta 2-beta 2 and sigma 1 wave-form parameters, and the individual frequencies were determined on the third baseline, second drug and the first recovery nights in each sleep stage. In comparison with the second baseline night, the sigma 1 waves in stage 2 sleep and the delta 1 waves in REM sleep were decreased and the alpha and sigma 1 waves in stage 3 sleep were increased on the third baseline night. In consideration of the 5% significance level and the remarkable influence of drug administration, described below, no major problems were encountered in the use of the night as a control in this experimental schedule. The main characteristics of administration of CM6912 manifested as decreases in the slow wave, increases in the fast wave, and an increase in the sigma 1 wave in sleep stages other than stage 1. These tendencies were remarkable on the second drug night and were still evident even on the recovery night. Increases in sigma 1 wave were related to increases in sleep spindles. The increases in the beta 2 wave were particularly remarkable in REM sleep.