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Olfaction participates in the elaboration of the hedonic value of foods, food choice and the regulation of food intake. Reciprocally, the detection of food odors is influenced by metabolic state and thereby contributes to the initiation and termination of eating behavior. Fasting increases olfactory performances, notably by increasing neuronal activation in the olfactory bulb (OB) (Prud’homme et al, 2009), the first integration site of olfactory signals towards the central nervous system. Within the OB glomeruli, glutamatergic synapses between olfactory sensory neurons and mitral cells are regulated by periglomerular neurons and astrocytes.

Olfaction participates in the elaboration of the hedonic value of foods, and play an important role in food choice and regulation of food intake. Reciprocally, the detection of food odors is influenced by the metabolic state (hunger/satiety), thereby contributing to the initiation and termination of eating behavior. Fasting increases olfactory performances, notably by increasing neuronal activation in the olfactory bulb (OB) (Prud’homme et al, 2009), the first integration site of olfactory signals towards the central nervous system. Within the OB glomeruli, the glutamatergic synapses between olfactory sensory neurons and mitral cells are regulated by peri-glomerular neurons and astrocytes. Astrocytes are now fully recognized as synaptic partners (Halassa & Haydon 2010) and are thought to generate some kind of “metaplasticity” in the central nervous (Min et al, 2012) as well as in the OB glomerular region (Roux et al, 2011). The neuron-astrocyte cross-talk in the glomeruli albeit poorly known, may be a central player in the metabolic regulation of olfactory response. To test the hypothesis that OB glomeruli astrocytes are involved in the metabolic sensing of the olfactory system, we have compared the expansion of the astroglial processes within glomeruli in fed or fasted rats. We have characterized the fasting status of 5-week-old Wistar rats after 17h, 24h or 48h of food deprivation. The astroglial deployment within the OB glomeruli was evaluated by immunohistochemical quantification of the GFAP area. We have also quantified the expression of the NPY-Y1 receptor, a major orexigenic peptide. Our results show that 24h- and 48h-fasting rats exhibit strong food seeking behavior, moderate to high weight loss, low glycemia, and strongly decreased leptinemia, and changes in the GFAP deployment within the glomeruli as compared to fed rats. Fasting also alters the expression of the NPY-Y1R, which is mainly located on the astrocytes, in the OB. These results show that the deployment of astroglial processes within the OB glomeruli varies according to the metabolic status of the rats. This morphological plasticity may be influenced by peptides involved in food intake regulation, such as NPY, and may participate to the adaptation of olfactory sensitivity to food intake.

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Olfaction participates in the elaboration of the hedonic value of foods and play an important role in food choice and the regulation of food intake. Reciprocally, the detection of food odors is influenced by the metabolic state (hunger/satiety), thereby contributing to the initiation and termination of eating behavior. Fasting increases olfactory performances , notably by increasing neuronal activation in the olfactory bulb (OB) (Prud’homme et al, 2009), the first integration site of olfactory signals towards the central nervous system. Within the OB glomeruli, the glutamatergic synapses between olfactory sensory neurons (OSN) and mitral cells are regulated by peri-glomerular neurons and astrocytes. Astrocytes are now fully recognized as synaptic partners (Halassa & Haydon 2010) and are thought to generate some kind of “metaplasticity” in the central nervous (Min et al, 2012) as well as in the OB glomerular region (Roux et al, 2011). The neuron-astrocyte cross-talk in the glomeruli albeit poorly known, may be a central player in the metabolic regulation of olfactory response. To test the hypothesis that OB glomeruli astrocytes are involved in the metabolic sensing of the olfactory system, we have compared the expansion of the astroglial processes within the glomeruli in fed or fasted rats. We have characterized the fasting status of 5-week-old Wistar rats after 17h, 24h or 48h of food deprivation by measuring their food olfactory seeking behavior, body weight loss, glycemia and leptinemia. The astroglial deployment within the OB glomeruli was evaluated by immunohistochemical quantification of the GFAP area. We have also quantified the expression (by western-blotting) of the Y1 receptor of NPY, a major orexigenic peptide involved in food intake regulation. Our results show that 24h- and 48h-fastinged rats exhibiting strong food seeking behavior, moderate (-6.4%) to high (-18%) weight loss, low glycemia, and strongly decreased leptinemia (-82% after 48h of fasting), also have a lower GFAP deployment within the dorsal glomeruli (-30%, p

Mieux comprendre les liens entre olfaction et prise alimentaire. La perception olfactive confère aux aliments une valeur hédonique, qui, en étant modulée par l’état nutritionnel, participe aux processus d’appétence et de satiété, par des mécanismes encore mal connus. Les travaux de NOeMI démontrent l’existence de modulations des signaux olfactifs au sein de la muqueuse et du bulbe olfactifs par l’état nutritionnel (jeûne/satiété) et les peptides/hormones qui régulent la prise alimentaire (Baly et al 2007, Prud’homme et al 2009, Negroni et al 2012). Pour tenter d’avancer sur ces mécanismes, notre projet cible les interactions neurones-astrocytes au niveau du bulbe olfactif. La zone d’interactions neuronales et gliales au sein des glomérules du BO constitue un site potentiel d’intégration des régulations s’exerçant sur la perception olfactive (métaboliques, émotionnelles, cognitives…). Le rôle des astrocytes y est souligné par quelques travaux récents (Roux et al 2011, Martin et al 2012). L’expertise de NuReLice permet d’explorer les fonctions astrocytaires régulant la synapse glutamatergique (Grintal et al 2009, Potier et al 2010, Latour et al 2013). Les astrocytes sont des partenaires à part entière de la synapse (Halassa et al 2007), considérés comme des méta-régulateurs de la neurotransmission dans le système nerveux central, notamment en coordonnant des réseaux neuronaux en réponse à des stimuli hormonaux et environnementaux (Min et al 2012).

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