Melatonin induces hypertrophy of brown adipose tissue in Spermophilus tridecemlineatus

Nonshivering thermogenesis (NST) plays an important role in hibernators during cold exposure and arousal periods. Brown adipose tissue (BAT), an important site of NST, displays seasonal changes in S. tridecemlineatus while cold exposure and short photoperiods stimulate hypertrophy of BAT.The pineal gland and melatonin have been implicated in thermoregulation but relatively little is known about the pineal's role in hibernation. In this investigation chronic melatonin administration via both silicone rubber implants containing 3 mg of melatonin and daily intraperitoneal injections of saline containing 50 μg of melatonin induced hypertrophy of BAT in young-of-the-year S. tridecemlineatus. Chronic melatonin administration appears to mimic the effects of cold exposure and/or short photoperiods on the hypertrophy of BAT.