Presentation Details
| Identification of an olfactory receptor involved in newborn rabbits' responsiveness to the mammary pheromone: behavioral evidence Gérard Coureaud1, Hiroaki Matsunami2, Victoria Ko2, Patricia Duchamp-Viret1. 1Lyon Neuroscience Research Center - ENES team, CNRS/Inserm/Lyon 1 and Jean Monnet Universities, Lyon, France.2Department of Molecular Genetics and Microbiology, Duke University School of Medicine, Durham, NC, USA |
Abstract
European newborn rabbits (Oryctolagus cuniculus) rely on olfaction to find and grasp their mother’s nipples during her brief daily visit to the nest for nursing. In particular, they are predisposed to respond to the mammary pheromone (MP; 2-methylbut-2-enal), which is emitted in milk by lactating females and triggers the orocephalic movements typical of pups’ nipple-search behavior. MP is processed by the main olfactory system, where it strongly activates olfactory sensory neurons. Until now, the molecular receptor(s) involved in its peripheral processing had remained unknown. Here, we first used molecular profiling and identified a MP (2D2-like) receptor candidate, MPR. We then screened potent odorant antagonists in vitro (Ko et al., this conference). Second, we tested pups’ behavioral responsiveness to MP mixed with MPR antagonist - β-ionone (β) or damascenone (Da) - or with a non-antagonist control, ethyl isobutyrate (EI). MP was used at an optimal concentration for behavioral effects (10-6 g/ml) and mixed with the other odorants at various concentrations (10-2 to 10-12 g/ml). At very high concentrations, all three odorants reduced responsiveness to MP, likely due to non-specific masking, whereas at the lowest concentrations, none impaired responses. A key finding was the disappearance of responsiveness to MP+β or MP+Da at an intermediate concentration corresponding to the MP/antagonist ratio of 1.5, indicating that antagonistic mechanisms at the level of MPRs result in a loss of MP perception (EI had no effect at this ratio). Combined with the findings of Ko et al., these results demonstrate that MPR plays a key role in the peripheral processing and detection of MP in newborn rabbits, thereby facilitating the behavioral response that guides them towards the nipples for sucking.
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