Food and Behaviour Research

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Opiate-like effects of sugar on gene expression in reward areas of the rat brain.

Spangler R, Wittkowski KM, Goddard NL, Avena NM, Hoebel BG, Leibowitz SF. (2004) Brain Res Mol Brain Res. 124(2): 134-42. 

Web URL: View this and related abstracts via PubMed here


Drugs abused by humans are thought to activate areas in the ventral striatum of the brain that engage the organism in important adaptive behaviors, such as eating. In support of this, we report here that striatal regions of sugar-dependent rats show alterations in dopamine and opioid mRNA levels similar to morphine-dependent rats.

Specifically, after a chronic schedule of intermittent bingeing on a sucrose solution, mRNA levels for the D2 dopamine receptor, and the preproenkephalin and preprotachykinin genes were decreased in dopamine-receptive regions of the forebrain, while D3 dopamine receptor mRNA was increased.

While morphine affects gene expression across the entire dopamine-receptive striatum, significant differences were detected in the effects of sugar on the nucleus accumbens and adjacent caudate-putamen. The effects of sugar on mRNA levels were of greater magnitude in the nucleus accumbens than in the caudate-putamen. These areas also showed clear differences in the interactions among the genes, especially between D3R and the other genes. This was revealed by a novel multivariate analysis method that identified cooperative interactions among genes, specifically in the nucleus accumbens but not the caudate-putamen.

Finally, a role for these cooperative interactions in a load-sharing response to perturbations caused by sugar was supported by the finding of a different pattern of correlations between the genes in the two striatal regions.

These findings support a major role for the nucleus accumbens in mediating the effects of naturally rewarding substances and extend an animal model for studying the common substrates of drug addiction and eating disorders.


This study adds to the existing evidence that sugar can activate the same brain reward systems as opioids and other drugs of abuse. See:

The current findings add more support to the validity of 'food addiction' as a useful concept. 

This term still remains controversial, as addiction remains very difficult to define, invovling psychological as well as physical components.  But with many features in common with drug addiction, this concept offers new approaches to the management of obesity and other eating disorders, which are very much needed.

For more information on this subject, please see: