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/6j 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.
Bibliographical noteThis paper is a respectful tribute to the late Jim Wright who is remembered both for his personal kindness and integrity and his unfailing commitment to the experimental analysis of behaviour.
The first author was supported by a PhD studentship from the Department for Employment
and Learning Northern Ireland. We are indebted to Peter Killeen for providing the Solver program in Microsoft Excel to derive parameter estimates in Experiment 3.
- Type 2 diabetes
- mouse models of diabetes
- progressive ratio schedule
- high-fat diet
- streptozotocin treatment