A specific receptor in the brain explains how hunger improves sense of smell and drives feeding behaviour in mice.

To probe the mechanism that links hunger, olfaction and eating, Giovanni Marsicano at the French National Institute of Health and Medical Research in Bordeaux and his colleagues focused on the CB1 receptor, which is activated by a number of molecules, including THC, the active ingredient in marijuana. They found that the receptor is expressed in neurons that reach into the brain's olfaction centre. Blocking this receptor in mice that had fasted for 24 hours decreased their food intake. Stimulating the receptor with THC boosted sensitivity to odours and feeding in the hungry animals.

The CB1 olfactory circuitry could offer a target for the treatment of eating disorders, the authors say.

Nature Neurosci. http://dx.doi.org/10.1038/nn.3647 (2014)