Effects of 18 weeks of daily melatonin injection on reproduction and temperature regulation in the mouse, Peromyscus leucopus.

Mice injected daily with 50 microgram of melatonin, 12 hr after lights on, for 18 weeks, underwent gonadal regression after 4-7 weeks and reproductive recrudescence after 15 weeks. Most treated animals molted to the winter pelt after 9-11 weeks of injections, and 2 of the 10 mice experienced bouts of daily torpor after 14 weeks.