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RESEARCH PRODUCT

Neural activation induced by an odour mixture perceived elementally or configurally by the newborn rabbit

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National audience; Perception of odours plays a crucial role in mammals facilitating interindividual communication, food choice and detection of danger, even from early in life (e.g. mother-young communication). However, little is known about the brain processing and perception of odorants in mixtures, which is by far the more common situation in life. To better understand how the brain processes odorants in mixtures, we used the newborn rabbit as a model. Rabbit pups display a clear sucking behaviour in response to the mammary pheromone (MP, the single molecule 2MB2) carried in the milk of lactating rabbit females. The MP also promotes associative conditioning and very rapid acquisition of any novel odorant paired with it. Our previous results showed that after MP-induced conditioning to ethyl maltol (odorant A), pups do not respond to odorant B (ethyl isobutyrate) or to the AB mixture (70/30 ratio), but they respond to A and to the A’B’ mixture (32/68 ratio). These results suggest configural perception of AB and elemental perception of A’B’. Here, we investigated by c-Fos immunodetection the neural activation induced by AB or A’B’ in the olfactory bulbs and central regions of 4-day-old rabbit pups, 24h after a single MP-conditioning to odorant A. Our hypothesis was that activated regions, or level of activation of certain regions, should differ depending on the mode of perception of odorants A and B in the mixture. Regarding forebrain regions, preliminary results show a stronger activation in the anterior and posterior piriform cortex, tenia tecta, ventral hippocampus, basal and medial amygdala in pups exposed to A’B’ compared to pups exposed to AB. Within the anterior piriform cortex, the labelled cells are not homogeneously distributed, according to the stimulus. Analyses of the olfactory bulb are in progress. These first results indicate that the same odorants may induce different neural forebrain activation of rabbit neonates, and consecutively different behavioural responsiveness, depending on whether the odorants are perceived as elements in the mixture, or involved in a mixture configuration.