Mice develop an addiction to chocolate

Obesity and related medical disorders pose a problem of great magnitude in the developed countries where prevalence has continued to grow significantly in recent years. The latest studies have linked obesity and food intake disorders with diseases with an addiction profile that might share similar biological substrates with those involved in drug addiction.

A study published on 6 May in Neuropsychopharmacology, directed by Rafael Maldonado, director of the Neuropharmacology Laboratory of the Department of Experimental and Health Sciences (CEXS) at UPF, shows that it is possible to induce eating addictive-like behaviour in mice and that they show symptoms similar to those accepted in the latest edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) to define drug addiction criteria.

This study enables a new breakthrough in the understanding of food-induced behavioural disorders and understanding the neurobiological bases of these disorders, which could be new indicators to define vulnerability to suffering an eating disorder.

As Maldonado explains, "this type of addictive behaviour was induced in the animals through the administration of highly palatable chocolate-flavoured pellets that the mice had to actively seek in an operant behaviour chamber", adding that "after lengthy training in the search for this type of food, the mice that developed this addictive behaviour performed between 600 and 2,000 active lever responses to get a single 20 mg chocolate-flavoured food pellet".

As the article shows, these mice persisted with the active lever response, despite it giving rise to a small, unpleasant electricalstimulation, before receiving the food pellet. They also lose their ability to control the seek response of the pellet.

Maldonado adds that "this compulsive behaviour and loss of control had previously been described in rodents seeking highly addictive drugs such as cocaine", and the originality of this study lies in highlighting it now in mice seeking chocolate-flavoured food.

The same receptor is involved in addiction to chocolate and drugs

The specimens that developed this addictive-type behaviour had significant alterations in the methylation of the DNA sequence coding for the CB1 cannabinoid receptor, which also plays a crucial role in drug addiction.

The genetic absence or pharmacological blockade of the CB1 receptor prevented the mice from developing this addictive-type behaviour despite receiving the same training to seek this chocolate-flavoured food.

Proteomics studies have enabled identifying the precise changes that appear in certain brain structures of these mice and could represent the neurobiological substrate that develops this addictive process promoted by highly palatable food.

This study has involved members of UPF's CEXS Neuropharmacology Laboratory, together with researchers from the University of Teramo and the Santa Lucia Foundation of Rome (Italy) and the Karolinska Institute in Stockholm (Sweden), directed by Rafael Maldonado.

Reference work:

S. Mancino, A. Burokas, J. Gutiérrez-Cuesta, M. Gutiérrez Martos, E. Martín-García, M. Pucci, A. Falconi, C. D'Addario, M. Maccarrone, R. Maldonado, (2015), " Epigenetic and Proteomic Expression Changes Promoted by Eating Addictive-like Behavior", Neuropsychopharmacology, May 6. doi: 10.1038 / npp.2015.129.