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Overeating and Opioids: New clues?

It’s happened to you before: you eat one tasty chocolate treat thinking, “It’s small, no big deal,” and the moment it’s gone, you want another.  The urge is hard to resist and before you know it, you have consumed nearly all of them.

As it turns out, laboratory rats have a similar behavior pattern when it comes to these tasty treats!  Recent evidence points to a specific region of the brain that may be mainly responsible for this kind of overfeeding behavior.

New research from the laboratory of Kent Berridge at the University of Michigan provides evidence that the anteromedial dorsal region of the neostriatum, a small part of the central brain structure known as the basal ganglia, may generate the motivation to over-consume.  This finding is especially interesting as this brain region had previously been identified only as part of physical movement processing.

During the experiment rats were presented with chocolate treats as their levels of enkephalin and dynorphin, both opioid peptides, were measured in the anteromedial dorsal neostriatum.  While eating the treat, enkephalin levels became elevated but dynorphin levels remained the same.  A similar surge in enkephalin was not observed when rats were chewing wooden blocks or other non-food items.  Furthermore, DAMGO, a potent agonist of the µ-opioid receptor, was injected into the same region of the neostriatum resulting in twice the treat consumption than in animals not injected or injected in different regions of the brain.

Put together, these results open up the possibility of a new region of the brain to explore in the ongoing efforts to fight compulsive behaviors, such as overeating.

What do you think?

What might cause the endogenous surge in enkephalin levels during chocolate-eating?

Would consumption of normal food cause the same surge?

Further Reading:

Difeliceantonio AG, Mabrouk OS, Kennedy RT, Berridge KC. (2012). Enkephalin Surges in Dorsal Neostriatum as a Signal to Eat.  Curr Biol.  Sep 18. pii: S0960-9822(12)00942-6.