1. Department of Biophysics and Biochemistry, Graduate School of Science, The University of Tokyo, Tokyo 113-0032, Japan
2. Department of Physiology, Graduate School of Medicine, The University of Tokyo, Tokyo 113-0033, Japan
3. Research Institute for Microbial Diseases, The Osaka University, Osaka 565-0871, Japan
4. Laboratory for Behavioral Genetics, Brain Science Institute, RIKEN, Saitama 351-0198, Japan
5. Laboratory of Veterinary Ethology, The University of Tokyo, Tokyo 113-8657, Japan
6. These authors contributed equally to this work.

Correspondence to: Hitoshi Sakano¹ Correspondence and requests for materials should be addressed to H.S. (Email: sakano@mail.ecc.u-tokyo.ac.jp).

Abstract

The mammalian olfactory system mediates various responses, including aversive behaviours to spoiled foods and fear responses to predator odours. In the olfactory bulb, each glomerulus represents a single species of odorant receptor. Because a single odorant can interact with several different receptor species, the odour information received in the olfactory epithelium is converted to a topographical map of multiple glomeruli activated in distinct areas in the olfactory bulb. To study how the odour map is interpreted in the brain, we generated mutant mice in which olfactory sensory neurons in a specific area of the olfactory epithelium are ablated by targeted expression of the diphtheria toxin gene. Here we show that, in dorsal-zone-depleted mice, the dorsal domain of the olfactory bulb was devoid of glomerular structures, although second-order neurons were present in the vacant areas. The mutant mice lacked innate responses to aversive odorants, even though they were capable of detecting them and could be conditioned for aversion with the remaining glomeruli. These results indicate that, in mice, aversive information is received in the olfactory bulb by separate sets of glomeruli, those dedicated for innate and those for learned responses.

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