EFFECTS OF FOOD-DEPRIVATION AND RESTRICTION, AND METABOLIC BLOCKERS ON FOOD HOARDING IN SIBERIAN HAMSTERS

Syrian hamsters do not increase their food intake following several metabolic challenges, including food deprivation and blockade of metabolic fuel utilization, in contrast to the response of other small rodents to these challenges. Perhaps hamsters respond to such challenges differently, for example by altering hoarding. In the present experiments, we have begun to question the role of food hoarding in the total energy balance of Siberian hamsters. Therefore, we developed a simulated burrow system, where food was available outside the burrow for consumption and/or hoarding during a 15-h period surrounding the 8-h dark portion of the photocycle. Food hoarding, but not food intake, increased dramatically after 32- and 56-h fasts and was greater following the longer fast. Food-restricted weight-reduced hamsters (80% of ad libitum-fed controls) were refed and given the opportunity to hoard. Initially, when body weights were low, food hoarding was maximal and then decreased gradually to control levels as body weights reached those of the ad libitum-fed controls. Food intake was not affected. Neither hoarding nor food intake was affected by treatment with long-acting protamine zinc insulin, given to enhance the storage of metabolic fuels, at any dose tested. Finally, neither food intake nor hoarding was affected by treatment with the glucose utilization blocker a-deoxy-D-glucose, the fatty acid utilization blocker methyl palmoxirate, or a combination of the two treatments, all at doses that stimulate food intake in laboratory rats. Collectively, these results show that Siberian hamsters respond to food deprivation and restriction by increasing food hoarding but not food intake; however, they do not increase their food hoarding in response to all energetic challenges. These data suggest that hoarding in Siberian hamsters is more responsive to shifts in long-term energy stores (fat) than to short-term fluctuations in metabolic fuel availability. Finally, it should be noted that food intake and food hoarding were dissociated from one another, suggesting different underlying neural/hormonal bases for the behaviors.