A cannabinoid connection between smell and appetite

The increase in food intake that occurs after smelling food relies on the presence of the cannabinoid type-1 (CB1) receptor in the olfactory bulb, reports a study published online this week in Nature Neuroscience. The work also shows that CB1 receptor activation enhances odor detection leading to food intake, and suggests that these receptors could be a potential pharmacological target for altering feeding behavior that contributes to obesity.

Brief abstinence from food is known to increase the level of endogenous cannabinoids in the mammalian brain. Hunger is also known to enhance our sense of smell and promote ingestion of food. Giovanni Marsicano and colleagues report that the main olfactory bulb of mice contains cannabinoid (CB1) receptors whose activation by endogenous cannabinoids or exogenous cannabinoids (such as those in marijuana) increase fasting-induced food intake. Indeed, an increase in appetite when mice are given exogenous cannabinoids (such as THC, the active ingredient in marijuana) is commonly seen. The authors found that this population of cannabinoid receptors in the olfactory bulb was also necessary to see this increase in feeding behavior.

Because this population of cannabinoid receptors only seems to modulate an increase in food intake when the animal is fasting or hungry, CB1 receptors in the olfactory bulb may represent a potential pharmacological target for altering feeding behavior.

doi: 10.1038/nn.3647

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