EFFECTS OF INTRAVENOUSLY ADMINISTERED VITAMIN-B-12 ON SLEEP IN THE RAT

Vitamin B-12 (VB12) has been reported to normalize the entrainment of circadian rhythms in the non-24-h sleep wake cycle and delayed sleep p hase insomnia in humans. The purpose of this work was to clarify wheth er the peripheral administration of VB12 has any sleep-promoting effec t on the sleep-wake rhythm in freely moving rats. After a baseline day of saline infusion, VB12 (500 mu g/kg/day) was administered continuou sly for 4 days via the jugular vein. Polysomnographic recordings were carried out concurrently. In both the light and the 24-h periods, the amount of non-rapid eye movement (NREM) sleep increased significantly on VB12-days 2 and 3, while the amount of REM sleep increased signific antly on VB12-day 2. In the light period, the increase in NREM sleep w as due to increased duration of the episode, while the tendency to an increase in REM sleep was due to an increased number of episodes. Chan ges in the diurnal sleep-wake rhythm tended to appear in the earlier l ight period. The serum VB12 concentrations in the VB12 group were 40 t imes higher than in controls. These findings suggest that peripherally infused VB12 has promoting effects on the rat's sleep, especially in the light period.