Reduced Caloric Intake Allows Access-Induced Consumption Differences To Emerge With Concentrated Sucrose Solutions

Rats given intermittent access to 4% (w/v) sucrose solution elevate their consumption of solution relative to rats with continuous access, a difference that does not appear at higher concentrations. Here, we examined the hypothesis that a limit on the intake of sucrose calories prevents rats from demonstrating access-induced differences in consumption of a more concentrated sucrose solution. Energy-replete rats were given every day (ED) or every third day (E3D) access to sucrose solutions adulterated with bitter quinine which reduced solution palatability and consumption levels while intake was measured. In experiment 1, previously collected data were compiled to examine the trajectory of consumption of continuously available 4% sucrose solution which was shown to stabilize by day 3 and then informed group assignment. In experiment 2, daily consumption levels were higher for rats with E3D access to 4% sucrose solution than rats with ED access to the same solution, whereas rats consumed similar amounts of 8% sucrose solution across access schedules. In the first hour of solution availability rats with E3D access showed elevated sucrose solution consumption, relative to rats with ED access, for both 4% and 8% sucrose solution. Upon the addition of quinine (0.005%) sucrose solution consumption decreased and the E3D access group consumed more daily sucrose solution than the ED access group for both 4% and 8% sucrose solution. In experiment 3, four groups of rats were given ED or E3D access to 8% sucrose solution adulterated with 0.0025%, 0.005%, 0.01%, or 0.02% quinine. Quinine adulteration reduced 8% sucrose solution consumption and allowed rats with E3D access to elevate their consumption levels relative to rats with ED access; this effect persisted when all groups were switched to 8% sucrose + 0.02% quinine solution. Thus, daily access-induced consumption differences develop but do not emerge because of a caloric limit on sucrose solution intake. This work underscores the interaction of availability and caloric intake as determinants of sugar consumption and highlights an important distinction between animal models of food addiction and binge eating.