Effects of repeated doses of scopolamine on the electroencephalographic stages of sleep in normal volunteers.

Single doses of scopolamine markedly alter sleep patterns in man. This study intended to evaluate the persistence of these changes during continued administration. The design consisted of a sequence of habituation, no-medication, saline (control), scopolamine (0.006 mg/kg intramuscularly 3 consecutive nights), and saline. The first dose of scopolamine markedly retarded the onset of stage rapid eye movement (REM) sleep (p less than 0.005) and diminished the total amount of REM sleep during the night (p less than 0.025). A decrease in total number of eye movements (p less than 0.05) and an increase in body movements (p less than 0.025) were also observed. Changes after the second dose of scopolamine were less marked but still significant. The third dose of scopolamine produced less marked changes than the preceding two. When compared with the first scopolamine night, the onset of stage REM was retarded to a lesser extent (p less than 0.05) and the total amount of REM sleep was increased (p less than 0.05). An increase in the duration of the first REM period was also observed. Rebound effects on the appearance of the first REM period (p less than 0.01), number of eye movements (p less than 0.001), total amount of REM sleep (p less than 0.01), and body movements were observed in the last saline night.