Abstract
Motivation for food reinforcers in mouse models of type 2 diabetes was examined in three experiments. In all experiments, physiological measures indicated the presence of type 2 diabetes. In Experiment 1, high-fat fed Swiss TO mice and lean controls showed a preference for high-fat corn oil reinforcers over high-sugar syrup reinforcers in a T-Maze task, but there were no differences between the two groups. In Experiment 2, high-fat fed Swiss TO mice and lean controls responded for corn oil or food pellet reinforcers on progressive ratio schedules. While break point numbers were higher for corn oil than food pellets, and satiation or extinction reduced break points, there were no differences between the groups. In Experiment 3, streptozotocin treatment was used to induce type 2 diabetes in C57Bl/6 j mice that were compared with controls while responding for corn oil or food pellet reinforcers on progressive ratio schedules. While break point numbers were higher for corn oil than food pellets before and after streptozotocin treatment, and satiation or extinction reduced break points, there were no differences between the groups. Parameters for a more complex method of assessment of progressive ratio behaviour derived from Killeen’s Mathematical Principles of Reinforcement were also computed. While the parameter associated with incentive value was higher for corn oil than for food pellets, parameters were not significantly affected by streptozotocin treatment. Overall, a range of behavioural measures of food motivation failed to reveal effects of changes relative to controls in mice that showed physiological evidence of type 2 diabetes.
Highlights
Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder that manifests in hyperglycaemia, insulin resistance and pancreatic beta-cell dysfunction
Over the last 10 trials both groups showed a preference for the corn oil T-maze arm, selected by the high-fat group (n = 8) on 72.5 % of trials and by the standard diet group (n = 6) on 63.6 % of trials
The present findings add to the limited knowledge of the behavioural effects of the high-fat diet model of obesity induced diabetes and of the STZ-induced model
Summary
Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder that manifests in hyperglycaemia, insulin resistance and pancreatic beta-cell dysfunction. An underexplored area in diabetes research relates to mechanisms underlying key behaviours in relation to food preference (Wing & Hill, 2001). In this regard, the use of animal models is beneficial to elucidate underlying mechanisms. One popular animal model in diabetes research is the diet-induced model which involves feeding a high-fat diet to rodents over an extended period. This results in progressive weight gain and elevated blood glucose concentrations and replicates the gradual development of obesity induced T2DM evident in humans (Winzell & Ahren, 2004). The high-fat diet mouse model is widely accepted as a useful model of (http://creativecommons.org/licenses/by/4.0/)
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