Master of Science (MSc)
Faculty of Science
Rats given ~24 h access to a 4% sucrose solution every 3rd day (E3DA) consume about 100 g more solution than rats with continuous, everyday access (EDA). Under the same EDA-E3DA conditions rats will consume similar amounts of a more concentrated 8 or 16% sucrose solutions (Eikelboom, Hewitt, & Adams, Unpublished). It maybe that with these more concentrated solutions rats hit a satiety limit that prevents a difference between EDA and E3DA consumption from being evident. Experiment 1 was conducted to investigate the effect of adding quinine to 4% and 8% sucrose solutions with the intention of reducing consumption to allow the emergence of an EDA-E3DA consumption difference with 8% sucrose. Rats were given EDA or E3DA access to 4% or 8% sucrose with or without added .005% quinine. An EDA-E3DA consumption difference emerged with 8% sucrose + .005% quinine where the quinine addition lowered consumption. However, in this experiment the EDA-E3DA consumption profile of 4% sucrose was smaller than typically seen.
Rats show considerable variability in sucrose consumption and experiment 2 was conducted to explore the effects of using a pre-exposure period to determine group assignment. Rats were pre-exposed to 4% sucrose continuously for 6 days. Consumption during this pre-exposure was used to assign rats to 4% or 8% sucrose with or without added .005% quinine who were then assigned to EDA or E3DA conditions. In this experiment the pre-exposure helped create eight equal groups and the 4% sucrose group demonstrated an EDA-E3DA consumption difference. However, the .005% quinine concentration did not reduce 8% sucrose consumption as severely as it had in experiment 1 and failed to produce an EDA-E3DA difference with 8% sucrose.
Experiment 3 explored the effects of a pre-exposure on 8% sucrose + .005% quinine consumption as a pre-exposure was a critical difference in the first two experiments. The results of experiment 3 suggested that a 4% sucrose pre-exposure would not change future 8% sucrose + .005% quinine consumption levels.
Experiment 4 was conducted to investigate the effect of varying the quinine concentration on 8% sucrose + quinine consumption. Rats were given EDA or E3DA to 8% sucrose adulterated with .0025%, .005%, .01%, or .02% quinine. Quinine concentration-dependently reduced consumption levels, and allowed for an EDA-E3DA consumption difference to emerge.
Collectively these experiments suggest that rats’ regulate their consumption of a supplementary sucrose solution based on the value of the solution and its availability in an integrated fashion. That is, the ability for intermittent access to elevate consumption depends on the value of the food being consumed. This is evidenced by the efficacy of quinine adulteration to degrade the value, and consequently intake, of an 8% sucrose solution which permitted an EDA-E3DA difference, normally only seen with 4% sucrose, to emerge.
Valyear, Milan D., "A Bittersweet Investigation of Availability and Nutritive Value as Determinants of Volitional Sucrose Consumption" (2014). Theses and Dissertations (Comprehensive). 1673.