Reduced glucose availability induces torpor in Siberian hamsters

Siberian hamsters kept in long photoperiods (16 h light/day) at 10 degrees C do not display torpor when provided with food ad libitum but do reduce their body temperatures (Tb) from 37 degrees C to as low as 15 degrees C for several hours each day in response to food restriction. Female hamsters maintained in a long photoperiod and fed ad libitum were injected with 2-deoxy-D-glucose (2-DG), a glucose analogue that reduces cellular glucose oxidation, or mercaptoacetate (MA), a drug that disrupts fatty acid oxidation. Dosages of 2-DG in excess of 1,500 mg/kg body mass reliably induced torpor with latencies of approximately 50 min from time of injection to a decrease in Tb below 30 degrees C; 79% of females displayed torpor at a dosage of 2,500 mg/kg. MA was uniformly ineffective in inducing torpor and did not increase incidence of torpor when combined with 2-DG treatment or food restriction. Decreased availability of glucose may be the major metabolic signal for inducing torpor in Siberian hamsters; availability of fatty acids appears to play little if any role in regulating this behavior.