Melatonin Production Accompanies Arousal from Daily Torpor in Siberian Hamsters

• DOI: 10.1086/375436
• Publication Date: 2003-09-30T20:55:09Z
• Authors: Jennie E. Larkin; Steven M. Yellon; Irving Zucker
• Keywords: Torpor; Hibernation; Basal (medicine); Darkness

Arousal from deep hibernation is accompanied by a transient rise of melatonin (Mel) in circulation; there are no comparable analyses Mel concentrations species that undergo much shallower, shorter duration episodes daily torpor. Serum were determined during arousal both natural torpor and induced 2‐deoxy‐D‐glucose (2‐DG) treatment (2,500 mg/kg, intraperitoneal [IP]); blood samples drawn the retro‐orbital sinus anesthetized Siberian hamsters. For animals kept darkness torpor, highest early when thermogenesis maximal, they decreased as body temperature increased returned to baseline once euthermia was reestablished. In hamsters light bout, elevated above basal values arousal, but response significantly blunted comparison with recorded darkness. Increased detected only (either or 2‐DG induced) not simply result drug treatment; remained euthermic manifested mild hypothermia after maintained concentrations. We propose production may reflect enhanced sympathetic activation associated intense rather than an adjustment circadian rhythm secretion.