Photoperiod modulates torpor and food intake in Siberian hamsters challenged with metabolic inhibitors.

Siberian hamsters, Phodopus sungorus, exposed to a short photoperiod (SP) were challenged with 2-deoxy-D-glucose (2DG), which disrupts glycolysis and induces torpor in animals maintained in long photoperiods (LP), or mercaptoacetate (MA), which disrupts fatty acid oxidation. SP decreased rather than facilitated the induction of torpor by 2DG; decreased torpor in response to 2DG coincided with onset of spontaneous torpor in SP hamsters. In contrast, MA induced hypothermia in hamsters kept in SP but not LP, but did not induce full torpor. We conclude that short day lengths do not induce spontaneous torpor by increasing responsiveness to glucose availability; instead, responsiveness to glucoprivation is, if anything, blunted in SP. The occurrence of spontaneous torpor may be unrelated to concurrent metabolic fuel availability. Although 2DG and MA had different effects on thermoregulation in short vs. long day lengths, each treatment decreased 24-h food intake in hamsters in both photoperiods.