<p>28796 The Effects of Functional Group Position and Carbon Number on Activity Patterns Evoked by Alcohols in the Rat Olfactory Bulb Sepideh Saber Mentor: Michael Leon</p><p>The olfactory bulb is an organ in the brain that senses and processes odors. Even at very low concentrations, the olfactory system is able to distinguish among a virtually infinite number of chemical compounds. In order to understand how odorants with very similar molecular structures can be encoded in the rat brain, rats were exposed to a series of seven-carbon alcohols with varying hydroxyl group positions in a first study, and to homologous series of primary and secondary five-carbon to eight-carbon alcohols in a second and third study. The response patterns were studied by mapping the [14C]-2-deoxyglucose uptake in the glomerular layer of the olfactory bulb. Each of the four heptanol isomers was found to evoke unique patterns of activity in the glomerular layer, with the responses to 2-heptanol, 3-heptanol, and 4-heptanol being more similar to each other than to the 1-heptanol-evoked response. These results support the prediction that each odorant is recognized by a unique combination of olfactory receptors (Johnson et al., 1998). In both primary and secondary alcohol chain length studies, a chemotopic representation of the odorants could be observed since each odorant-evoked pattern was mostly similar to the pattern of the odorant with one more or one fewer carbon. These findings support the hypothesis that neighboring receptors recognize parts or features that are adjacent to each other within the odorant molecule (Johnson and Leon, 2000). </p>