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Meal patterns and foraging in melanocortin receptor knockout mice
C H Vaughan1, Marcus C Moore, C Haskell-Luevano
1Department of Psychology, University of Florida, Gainesville, Fl 32611-2250, USA.
Physiology & Behavior
|January 12, 2005
Summary
Meal patterns in mice lacking melanocortin receptors (MC3RKO or MC4RKO) were studied. Foraging costs did not significantly alter meal-taking strategies in these mice, though MC4RKO mice lost weight.
Area of Science:
- Neuroscience
- Behavioral Neuroscience
- Metabolic Regulation
Background:
- Melanocortin receptors play a crucial role in regulating energy homeostasis.
- Understanding the specific roles of melanocortin type 3 (MC3R) and type 4 (MC4R) receptors in feeding behavior is essential.
Purpose of the Study:
- To investigate the meal patterns of mice with MC3R or MC4R gene deletions (MC3RKO or MC4RKO) compared to wild-type (WT) mice.
- To examine how varying foraging costs influence meal-taking strategies in these genetically modified mice.
Main Methods:
- Mice were housed in operant chambers where lever presses (procurement fixed ratio - PFR) initiated access to food pellets (consumatory fixed ratio - CFR).
- Meal patterns, including meal frequency and size, were recorded under different PFR conditions.
- Body weight and food intake were monitored for all genotypes.
Main Results:
- At low foraging costs, all mouse genotypes exhibited similar meal patterns (5-7 meals/day, ~35 pellets/meal).
- Increased foraging costs led to fewer meals and slightly reduced total intake across all groups.
- Despite being obese, MC4RKO mice consumed less food in the operant chambers and lost weight, irrespective of foraging cost.
Conclusions:
- Meal-taking strategies in response to foraging costs are not critically dependent on MC3 or MC4 receptors.
- The experimental setup did not fully capture the hyperphagic potential of MC4RKO mice, as they lost weight under these conditions.