Roles of NMDA and dopamine in food-foraging decision-making strategies of rats in the social setting

Fang Li, Wen-Yu Cao, Fu-Lian Huang, Wen-Jing Kang, Xiao-Lin Zhong, Zhao-Lan Hu, Hong-Tao Wang, Juan Zhang, Jian-Yi Zhang, Ru-Ping Dai, Xin-Fu Zhou, Chang-Qi Li

In highly complex social settings, an animal's motivational drive to pursue an object depends not only on the intrinsic properties of the object, but also on whether the decision-making animal perceives an object as being the most desirable among others. Mimetic desire refers to a subject's preference for objects already possessed by another subject. To date, there are no appropriate animal models for studying whether mimetic desire is at play in guiding the decision-making process. Furthermore, the neuropharmacological bases of decision-making processes are not well understood. In this study, we used an animal model (rat) to investigate a novel food-foraging paradigm for decision-making, with or without a mimetic desire paradigm. Faced with the choice of foraging in a competitive environment, rats preferred foraging for the desirable object, indicating the rats' ability for decision-making. Notably, treatment with the non-competitive N-methyl-D-aspartate receptor antagonist MK-801, but not with the dopamine D1 or D2 receptor antagonists, SCH23390 and haloperidol, respectively, suppressed the food foraging preference when there was a competing resident rat in the cage. None of these three antagonists affected the food-foraging preference for palatable food. Moreover, MK-801 and SCH23390, but not haloperidol, were able to abolish the desirable environment effect on standard food-foraging activities in complex social settings. These results highlight the concept that mimetic desire exerts a powerful influence on food-foraging decision-making in rats and, further, illustrate the various roles of the glutamatergic and dopaminergic systems in mediating these processes.