Abstract
Outbred rats display variable preferences for bittersweet solutions, expressed as preference or avoidance of high concentrations of artificial sweeteners over water. This may reflect individual differences in appetitive/aversive conflict processing that may have predictive validity for disorders of motivation. Here we use a homecage two-bottle choice procedure to examine the test/retest stability and between-tastant consistency in sucralose preference to determine the reliability of bittersweet taste preference. Sucralose is a non-caloric artificial sweetener that is preferred by some rats and avoided by others. We sought to determine whether sucralose preference is consistent with preference of sucrose/quinine solutions that have known sweet and bitter taste qualities, respectively. We give fluid restricted rats 45-minutes homecage access to water and ascending concentrations of sucralose (SUCRA; 0.0025-10mM) or a compound solution of sucrose (116mM) + quinine (0.002-2mM) (SQ). We use a within-subject counterbalanced design (SUCRA or SQ testing) to determine preference of each bittersweet solution relative to water. We observed individual variability in preference for SUCRA and SQ, such that some rats preferred bittersweet solutions over water (preferring) while other rats preferred water over bittersweet solutions (avoiding). Within tastant, this preference remained stable across repeated testing. Between solutions, SUCRA preference scores correlated with SQ scores, suggesting consistent taste conflict processing for both bittersweet solutions. Population level analyses confirmed that preference generalizes across bittersweet solutions, and that rats’ preferences for bittersweet solutions relative to water are stable over time. The test/retest and between-tastant reliability of this taste conflict screening procedure support the potential utility of this model for exploring individual variability in appetitive/aversive conflict processes mediating motivated behavior.
Highlights
Substance use disorder (SUD) develops only in a subset of individuals that engage in recreational drug use
We sought to determine whether outbread rats show individual differences in homecage sucralose preference that are 1) stable over time, and 2) consistent with preference of a known bittersweet compound solution of sucrose + quinine
We observed a range of preference scores at the isohedonic concentrations, demonstrating that individual rats vary along the bittersweet preference/avoidance continuum [4, 8, 9]
Summary
Substance use disorder (SUD) develops only in a subset of individuals that engage in recreational drug use. Testing trait stability over time and consistency between stimuli is a critical first step for determining whether the taste conflict assay has utility for exploring individual variability in appetitive/aversive conflict processes in outbred rats. Artificial sweeteners have both bitter and sweet taste qualities at high concentrations [5, 6]. This work suggests bittersweet taste preference generalizes across bittersweet solutions, and may reflect trait differences in preference for bittersweet taste stimuli This possibly has not been rigorously examined using individual and population level analyses to determine the stability and consistency of bittersweet taste preferences using homecage choice tests. We used within-subject and population level analyses to determine 1) stability of preference over time and 2) consistency between SUCRA and SQ preference
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