An Operant Conditioning Model Combined with a Chemogenetic Approach to Study the Neurobiology of Food Addiction in Mice.

The study of food addiction comprises 3 hallmarks that include the persistence to response without an outcome, the strong motivation for palatable food, and the loss of inhibitory control over food intake that leads to compulsive behavior in addicted individuals. The complex multifactorial nature of this disorder and the unknown neurobiological mechanistic correlation explains the lack of effective treatments. Our operant conditioning model allows deciphering why some individuals are vulnerable and develop food addiction while others are resilient and do not. It is a translational approach since it is based on the Diagnostic and Statistical Manual of Mental Disorders 5th edition (DSM-5) and the Yale Food Addiction Scale (YFAS 2.0). This model allows to evaluate the addiction criteria in 2 time-points at an early and a late period by grouping them into 1) persistence to response during a period of non-availability of food, 2) motivation for food with a progressive ratio, and 3) compulsivity when the reward is associated with a punishment such as an electric foot-shock. The advantage of this model is that it allows us to measure 4 phenotypic traits suggested as predisposing factors related to vulnerability to addiction. Also, it is possible to evaluate the long food addiction mouse model with mice genetically modified. Importantly, the novelty of this protocol is the adaptation of this food addiction model to a short protocol to evaluate genetic manipulations targeting specific brain circuitries by using a chemogenetic approach that could promote the rapid development of this addictive behavior. These adaptations lead to a short food addiction mouse protocol, in which mice follow the same behavioral procedure of the early period in the long food addiction protocol with some variations due to the surgical viral vector injection. To our knowledge, there is no paradigm in mice allowing us to study the combination of such a robust behavioral approach that allows uncovering the neurobiology of food addiction at the brain circuit level. We can study using this protocol if modifying the excitability of a specific brain network confers resilience or vulnerability to developing food addiction. Understanding these neurobiological mechanisms is expected to help to find novel and efficient interventions to battle food addiction.