REDUCED GLUCOSE AVAILABILITY INDUCES TORPOR IN SIBERIAN HAMSTERS

Siberian hamsters kept in long photoperiods (16 h light/day) at 10 deg rees C do not display torpor when provided with food ad libitum but do reduce their body temperatures (T-b) from 37 degrees C to as low as 1 5 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 r educes cellular glucose oxidation, or mercaptoacetate (MA), a drug tha t disrupts fatty acid oxidation. Dosages of 2-DG in excess of 1,500 mg /kg body mass reliably induced torpor with latencies of similar to 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 unifor mly ineffective in inducing torpor and did not increase incidence of t orpor when combined with 2-DG treatment or food restriction. Decreased availability of glucose may be the major metabolic signal for inducin g torpor in Siberian hamsters; availability of fatty acids appears to play little if any role in regulating this behavior.