Olfaction, cognition and feeding behaviour in rabbit neonates – NEONATOLF

In animals, olfaction plays a decisive role in life by triggering and guiding critical behaviours (mother-young relationships, food choices, avoiding dangers, etc.). In mammals, including humans, olfaction is known to be functional from foetal life, and to influence the first orientations of newborns in contact with the maternal body as they undergo nipple searching to ingest milk. Nevertheless, the chemical nature of the involved odours and the biological mechanisms underlying their processing and perception remain largely unknown. The European rabbit (Oryctolagus cuniculus) is the only species to date in which a pheromone emitted by the mother that plays a key role in the ability of newborns to locate the nipples and suck during the single and brief daily nursing occurring in the species, has been identified. This pheromone, the mammary pheromone (MP), has also a potent cognitive power by being able to promote, in an exceptionally rapid manner (1 trial, 5 min), the learning of new and initially neutral odours: 24h after pairing such an odour with the MP, newborn rabbits respond to the learned odour by displaying the orocephalic behaviour allowing them to locate and orally grasp the nipples, as effectively as they do in response to the MP. This makes the rabbit a highly relevant animal model for studying both olfaction, pheromone perception and odour memory. In this context, the NEONATOLF French-American proposal of basic research, which also aims at an applied purpose, combines the strengths of 3 national (CNRL, CSGA, NutriNeuro Units) and 1 American (Duke University) partners, all experts in chemical senses and olfactory perception, in an unprecedented multidisciplinary work in this species ranging from proteomics to behaviour. It aims to unravel biochemical, physiological, and behavioural processes that contribute to the processing of the MP and new odours learned by MP-pairing to further characterize the memory and evaluate the consequences of these processes on milk intake in newborn rabbits. Our scientific program, based on robust pilot data obtained within our consortium, will explore three original and current questions in rabbit biology: 1) How odour signals inducing an "innate" or a learned behavioural response, such as the MP or MP-paired odours, respectively, are processed at the periphery of the neonatal olfactory system? 2) How the memory of new odours develops in newborns in the context of direct (MP-induced) or indirect (sensory preconditioning) learning procedures? 3) What consequences the peripheral processing (reception, transport, metabolism) of the MP and MP-learned odours have on sucking success and survival in pups? We now have sufficient theoretical/technical experience and expertise to provide innovative results in this domain. In basic research, the outcomes of this project will have relevance for all scientists interested in animal perception of biologically-significant stimuli contained in the environment, which is highly complex and dynamic, such as chemists, ecologists, ethologists, neurobiologists, and psychologists. By promoting a better understanding of odour perception in newborn rabbits, the project will also have a direct relevance to developing multiple odour-based strategies that allow researchers to address the problem of neonatal mortality, which is high in rabbit farming and emotionally and financially painful for breeders. Moreover, odour-based strategies may be useful to optimise the difficult transition from milk to solid food when the pups are getting older (around weaning). Finally, by characterizing certain biological processes that are crucial for the young to interact with their mother at birth, the project will provide the general public with a new vision of this weakly-known animal by highlighting its remarkable sensory, cognitive, and behavioural skills.