VESAMICOL, AN ACETYLCHOLINE UPTAKE BLOCKER IN PRESYNAPTIC VESICLES, SUPPRESSES RAPID EYE-MOVEMENT (REM) SLEEP IN THE RAT

Vesamicol inhibits acetylcholine uptake in presynaptic vesicles and re duces its release. The present study was performed in order to test th e effects of this drug in a cholinergic related function as rapid eye movement (REM) sleep. Wistar male rats were implanted for sleep record ings. In addition, a stainless steel cannula was implanted into the le ft lateral ventricle for intracerebroventricular (ICV) injections. In experiment I, a dose-response curve was performed. Saline or vesamicol (20, 40, 80 and 100 mu g) were injected. Following the ICV injections , animals' sleep was recorded for 8 h. In experiment 2, after adaptati on and baseline recordings, animals received 50 mu g vesamicol ICV at 1000 hours. every 24 h for 2 consecutive days. After each injection an 8-h sleep recording session was performed. Two subsequent recovery re cordings were allowed. Results obtained in experiment 1 showed a dose- response reduction of REM sleep with significant values at 80 mu g and 100 mu g of vesamicol. The main findings in experiment 2 were a reduc tion in REM sleep time and an increase in REM sleep latency. On the re covery days, a dramatic rebound of REM sleep was observed. Vesamicol b ehaved as an anticholinergic drug. It produced a reduction in REM slee p time and a rebound of this sleep stage after its withdrawal.