Prolongation of hibernation bout duration by continuous intracerebroventricular infusion of melatonin in hibernating ground squirrels.

Melatonin was infused intracerebroventricularly into hibernating golden-mantled ground squirrels (Citellus lateralis) maintained at 5 degrees C in darkness. Continuous infusion at a rate of 0.5 microliter/h was accomplished using an osmotic minipump. The effect of melatonin on hibernation bout duration was determined with reference to the natural trend in bout duration for each animal. At doses of 200 and 400 ng/h, melatonin produced a dose-related increase in bout duration. No effect was observed following control infusions of artificial cerebrospinal fluid or lower doses of melatonin.