New Brain Peptide Abolishes the “Munchies”

Readers may be well aware that the use of cannabis or “hashish” can induce the “munchies”, an acute craving for highly palatable foods.

Now Garron Dodd and colleagues from the University of Manchester, UK, have identified a new brain peptide called hemopressin that acts through cannabinoid receptors to reduce food intake in rats and mice. Their findings are published in the latest edition of the Journal of Neuroscience.

Hemopressin is a short, nine amino acid peptide found in the rat brain that behaves as an inverse agonist at the cannabinoid receptor CB(1), where it inhibits agonist-induced receptor internalization.

In their studies, Dodd and colleagues found that this peptide dose-dependently decreases night-time food intake in normal male rats and mice, as well as in obese ob/ob male mice, when administered centrally or systemically, without any obvious adverse side effects.

Hemopressin specifically blocks the hyperphagic response to CB(1) receptor agonists, while having no effect on eating behaviour in CB(1) receptor null mutant male mice.

Obviously, the discovery of this peptide not only increases our understanding of the complex neurobiology of ingestive behaviour but may also lead the way to new treatments for obesity.

It should however be noted that we have already had potent inhibitors of the CB(1) receptor for the treatment of obesity (readers will recall rimonabant), which were withdrawn from the market due to increased incidence of depression.

Nevertheless, it may well be that endogenous inhibitors of the endocannabinoid system (like hemopressin) may well be better tolerated previous inhibitors of this system.

Perhaps we have not seen the last of our attempts to decrease appetite by blocking the endocannabinoid system just yet.

AMS
Edmonton, Alberta

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Dodd GT, Mancini G, Lutz B, & Luckman SM (2010). The peptide hemopressin acts through CB1 cannabinoid receptors to reduce food intake in rats and mice. The Journal of neuroscience : the official journal of the Society for Neuroscience, 30 (21), 7369-76 PMID: 20505104