Fos mapping of brain activation induced by the mammary pheromone in the newborn rabbit

poster confidentielInternational audienceThe female European rabbit, Oryctolagus cuniculus, displays a surprising maternal behaviour. Indeed, she comes into the nest only once per day and for a very brief period (3-4 minutes), almost exclusively to nurse. A pheromonal signal identified as the 2-methylbut-2-enal and named the mammary pheromone (MP) is emitted in milk by all lactating rabbit females. This chemosensory cue induces typical head-searching and oral-seizing movements in newborn rabbits usually involved in the localisation of the nipples. The MP therefore appears as a biological signal important for sucking, survival and growth in pups. To date, only few data are available regarding the neuronal substrate which sustains the MP processing. In our study, we used three groups of 4-day-old rabbit pups: a MP group stimulated by the Mammary Pheromone, a group stimulated by a control odorant carrying no significance for the newborns, and finally a non-odour group which was manipulated but not exposed to any chemical cue. All manipulations/odour exposures were 10 minutes long. Fos neuroimaging was used to map the cerebral activation in each group. Ninety minutes after the stimulation of one pup, the brain was processed for Fos immunocytochemistry. Besides the main olfactory bulb, we observed in the three groups immunolabeled cells in the anterior and posterior subdivisions of the piriform cortex. To date (analyses are still running), Fos expression was further noticed in the hypothalamus, in the lateral habenula and in the cortical amygdala nucleus. Cell counts are in progress in order to compare the level of Fos expression in all groups. It will allow to investigate whether a differential cerebral activation is observed when the animal is stimulated by a highly relevant biological signal in comparison with an non significant odour