Centrifugal projections to the main olfactory bulb revealed by trans‐synaptic retrograde tracing in mice

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Schneider, Nanette | Chaudy, Sylvie | Epstein, Alberto L. | Viollet, Cécile | Benani, Alexandre | Pénicaud, Luc | Grosmaître, Xavier | Datiche, Frédérique | Gascuel, Jean

Edité par CCSD ; Wiley -

International audience. A wide range of evidence indicates that olfactory perception is strongly involved in food intake. However, the polysynaptic circuitry linking the brain areas involved in feeding behaviour to the olfactory regions is not well-known. The aim of this paper was to examine such circuits. Thus, we described, using hodological tools such as trans-synaptic viruses (PRV152) transported in a retrograde manner, the long-distance indirect projections (2-3 synapses) onto the main olfactory bulb (MOB). The b-subunit of the cholera toxin (CTb) which is a monosynaptic retrograde tracer was used as a control to be able to differentiate between direct and indirect projections. Our tracing experiments showed that the arcuate nucleus of the hypothalamus, as a major site for regulation of food intake, sends only very indirect projections onto the MOB. Indirect projections to MOB also originate from the solitary nucleus which is involved in energy homeostasis. Other indirect projections have been evidenced in areas of the reward circuit such as VTA and accumbens nucleus. In contrast, direct projections to the MOB arise from MCH- and Orx neurons in the lateral hypothalamus. Functional significances of these projections are discussed in relation to the role of food odors in feeding and reward-related behavior.

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