Individual Differences in Sensory Processing in the Rattus as Assessed Through the Bimodal Preference Profile for the Artificial Sweetener Sucralose

Rats display marked variability in their willingness to consume the artificial sweetener sucralose. Most rats are classified as sucralose avoiders (~75%; SA) while the remaining subset can be classified as sucralose preferrers (~25%; SP). Here, I have shown that these phenotypic differences in the consumption of sucralose are the result of highly consistent and robust behaviors and potentially represent a meaningful, physiological difference in sensory processing with functional consequences for diet choice and weight gain. Specifically, the emergence of a sucralose preference profile is stable across both sexes and at least two rat strains. Furthermore, utilizing an adaptation of the two-response taste discrimination psychophysical paradigm, I have demonstrated that the differences in the consumption of sucralose are sensory based. The taste quality of sucralose appears to be sufficient to split rats into their respective phenotypic groups. These sensory differences appear to generalize to other artificial sweeteners and stimuli with a putative, binary sweet-like and bitter-like taste profile as SA and SP differ in their intakes of concentrated saccharin solutions and quinine-adulterated sucrose in a manner consistent with their responses to sucralose. These sensory differences appear to be mediated by a disparity in the processing of 'sweet' tastes. Immunohistochemical analysis of patterns of neuronal activation demonstrate that SA may perceive a more salient 'bitter' percept from sucralose, most likely due to a reduced sensitivity to the 'sweet'-like qualities of sucralose. Conversely, SP perceive identical concentrations of sucralose as a mixture of 'sweet' and 'bitter' with the most salient quality being that of a sucrose-like 'sweet' taste; a sensory profile consistent with a number of other artificial sweeteners. These differences in sensory processing may be the result of a genetic mutation in one of the Tas1R genes that encode the two proteins that form the functional 'sweet-taste' receptor. Evidence for such a conclusion is provided by the observed differential intake of sucralose and at least one other artificial sweetener, as well as differences in the avidity for sucrose solutions as assessed through brief-access licking tests. The demonstrated variation in sensory processing may play a central role in SP, relative to SA, failing to regulate caloric intake, and their subsequent increased propensity for weight gain, when given access to a highly palatable diet. As the increased availability to highly palatable, energy-dense foods has been identified as a contributing factor to the current obesity epidemic, these data may provide a direct, testable model for examining the influence of a 'sweet-tooth' on diet choice and excessive weight gain.