par- 27 janvier 2014
Bureau : 110
Olfaction and eating behaviors are intimately intermingled. Olfaction takes part in each step of the food intake from food choice, to its consumption. At the reverse, satiation reduces olfactory perception which contributes in meal interruption. Thus, olfactory cued reward responses to food stimuli are one of the important factors controlling food intake. In the face of obesity epidemic and the prevalence of various kinds of eating disorders, it is essential to better understand how olfaction is modulated by the nutritional status in a normal context and in which extend it is disrupted in pathological eating behaviors.
Our group has been one of the first to demonstrate in animal that the olfactory signal is under metabolic influences. Indeed we have shown that fasted animals have greater olfactory sensitivity than satiated ones. The action of molecules modulating food-intake is mainly established at the level of hypothalamic sub-nuclei. Here we tested the hypothesis that they also exert a powerful action on olfactory structures. Our behavioral experiments in rat showed that odor perception thresholds are modulated by intracerebro-ventricular infusion of ghrelin (orexinergic peptide) and insulin (anorexinergic peptide) which increased and decreased olfactory threshold, respectively. Moreover, we have investigated the influence of the metabolic state and intracerebro-ventricular infusion of insulin on the modulation of sniffing strategies known to be important in odorant intensity and identity perception. Insulin was shown to abolish the increase in sniffing frequency observed in fasted animal in response to food odor. Taken together, our results demonstrate that the olfactory system is intimately linked with the endocrine systems in order to optimize the olfactory processing to the nutritional needs of the organism.
Currently we investigate in normal and pathological contexts (metabolic disorders) (i) the influences of nutritional states on olfactory processing and (ii) the impact of metabolic cues on the olfactory system. To address these questions, we use a multidisciplinary set of convergent and interactive approaches to better understand the cellular basis of the olfactory sensitivity to metabolic cues and to characterize the olfactory processing in various pathological context (metabolic disorders).