Comment in Sensory systems: the hungry sense. [Nat Rev Neurosci. 2014] Inhaling: endocannabinoids and food intake. [Nat Neurosci. 2014]International audienceHunger arouses sensory perception, eventually leading to an increase in food intake, but the underlying mechanisms remain poorly understood. We found that cannabinoid type-1 (CB1) receptors promote food intake in fasted mice by increasing odor detection. CB1 receptors were abundantly expressed on axon terminals of centrifugal cortical glutamatergic neurons that project to inhibitory granule cells of the main olfactory bulb (MOB). Local pharmacological and genetic manipulations revealed that endocannabinoids and exogenous cannabinoids increased odor detection and food intake in fasted mice by decreasing excitatory drive from olfactory cortex areas to the MOB. Consistently, cannabinoid agonists dampened in vivo optogenetically stimulated excitatory transmission in the same circuit. Our data indicate that cortical feedback projections to the MOB crucially regulate food intake via CB1 receptor signaling, linking the feeling of hunger to stronger odor processing. Thus, CB1 receptor-dependent control of cortical feedback projections in olfactory circuits couples internal states to perception and behavior

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Increased consumption of high-fat diet (HFD) leads to obesity and adverse neurocognitive outcomes. Childhood and adolescence are important periods of brain maturation shaping cognitive function. These periods could consequently be particularly sensitive to the detrimental effects of HFD intake. In mice, juvenile and adulthood consumption of HFD induce similar morphometric and metabolic changes. However, only juvenile exposure to HFD abolishes relational memory flexibility, assessed after initial radial-maze concurrent spatial discrimination learning, and decreases neurogenesis. Our results identify a critical period of development covering adolescence with higher sensitivity to HFD-induced hippocampal dysfunction at both behavioral and cellular levels.