THE EFFECTS OF TRANSDERMAL SCOPOLAMINE ON AUTONOMIC NERVOUS ACTIVITY DURING SLEEP

We studied the effect of transdermally applied scopolamine (scopolamin e-TTS) on autonomic nervous activity during sleep. The double-blind, r andomized, crossover study was carried out in six healthy male volunte ers by applying 1.5 mg scopolamine-TTS or placebo patch on the retroau ricular skin and by monitoring heart rate, cardiac ballistogram, respi ration and body movements by using electrocardiogram and static charge sensitive bed. Scopolamine did not decrease the time the subjects des ired to sleep (516 min after TTS, 511 min after placebo) or the number of body movements of 3-5 s duration the subjects spontaneously perfor med during sleep (47 after TTS, 58 after placebo). No adverse effects of scopolamine were reported spontaneously. Scopolamine-TTS slowed the mean heart rate during quiet sleep from 53.2 to 44.9 beats.min(-1), a nd increased the duration of bradycardia in response to body movements (MIB-reflex) from 12.5 to 14.7 s with a significant difference betwee n scopolamine and placebo effects. The bradycardias were not associate d with disturbances in cardiorespiratory or central nervous system fun ctions. The cardiac vagomimetic action of scopolamine-TTS could be exp lained by low plas ma drug concentrations (175 pg/ml) primarily blocki ng only neuronal inhibitory prejunctional muscarinic receptors which r egulate acetylcholine release from the autonomic ganglia and parasympa thetic nerve-endings. Because of the central role of acetylcholine in the physiological regulation of sleep, the effect of scopolamine-TTS o n sleep merits further investigations.