Combinatorial receptor codes for odors

The discriminatory capacity of the mammalian olfactory system is such that thousands of volatile chemicals are perceived as having distinct odors. Her e we used a combination of calcium imaging and single-cell RT-PCR to identi fy odorant receptors (ORs) for odorants with related structures but varied odors. We found that one OR recognizes multiple odorants and that one odora nt is recognized by multiple ORs, but that different odorants are recognize d by different combinations of ORs. Thus, the olfactory system uses a combi natorial receptor coding scheme to encode odor identities. Our studies also indicate that slight alterations in an odorant, or a change in its concent ration, can change its "code," potentially explaining how such changes can alter perceived odor quality.