Louise Eygret

Nutrition and Integrative Neurobiology laboratory (NutriNeuro), INRAE, UMR 1286, Université de Bordeaux, Bordeaux INP, Bordeaux, France

Title

Olfaction and feeding behaviour: Neuronal substrates underlying odour modulation of food intake regulating neuronal circuits

Abstract

A growing proportion of the population is having problems maintaining a stable body weight. Therapeutic drug strategies deployed to modulate food intake are often accompanied by side effects. Olfactory system plays an important role in food intake, thus it could offer safer alternative strategies to regulate eating behaviour. Food intake is essentially regulated by the hypothalamic neurons of the melanocortin network: AgRP (Agouti Related Peptide) and POMC (Pro-opiomelanocortin) neurons, respectively orexigenic and anorexigenic. Previous studies showed that the presentation of food rapidly modulates the activity of these neurons in mice even before eating suggesting the involvement of sensory cues in this modulation. However, the determinants of this modulation have not been identified. Our study presents the modulatory effects of appetitive odorant molecules on hypothalamic neurons involved in the control of food intake.
We selected attractive food odorants on both males and females based on investigating times in individual cages. Food intake was quantified in automated monitoring cages to characterize the appetitive effect of the chosen odours. This led us to identify attractive food odours that increased food intake in mice namely without preliminary association with food. The electrical activity of POMC and AgRP neurons was recorded in brain slices obtained from mice exposed to these odorants or to the solvent only. The POMC neurons from animals exposed to appetitive odours showed a modulation of their electrical activity with a lower spontaneous action potential firing. In AgRP neurons, odour exposure had less impact. Using fiber photometry coupled to breathing activity monitoring, we measured a decrease of activity in AgRP neurons when animals were actively sniffing appetitive odours.
Our results highlight the appetitive effect of some food odours, some of which show an innate effect on food intake. Electrophysiological and fiber photometry recordings suggest that odours are capable of modulating the electrical activity of neurons in healthy melanocortin networks. Future work will attempt to identify the olfactory projections involved in this modulation of the arcuate nucleus of the hypothalamus.