Daytime melatonin infusions induce sleep in pigeons without altering subsequent amounts of nocturnal sleep

Daily infusions of melatonin restore sleep suppressed by continuous bright light in pigeons. To test whether melatonin could also induce sleep in pige ons on a 12:12 h light-dark cycle (LD), pigeons received 12-h intravenous m elatonin infusions during the day. Melatonin induced sleep during the day, increased EEG slow wave activity, and decreased body temperature and locomo tor activity. None of these variables were altered during the night followi ng infusions. The induction of extended daytime sleep by melatonin infusion s indicates that melatonin is a principal factor in the regulation of sleep in pigeons. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.