Metabolic mapping of functional activity in the rat olfactory system after a bilateral transection of the lateral olfactory tract.

The effects of the bilateral transection of the LOT on the patterns of 2-deoxyglucose uptake within the olfactory bulb and the olfactory projections were studied in adult rats. Animals were exposed to a pure neutral odor, ethyl acetoacetate (EAA) or to a biological alarming odor, fox odor. In intact animals, the patterns of glomerular activity elicited by EAA and fox odor appeared complex. An average number of 30-40 foci of 2-DG uptake was noted in each bulb and the optical density of the foci spread out according to a continuous gradient. These patterns were largely overlapping on the lateral aspect and the third-to-posterior part of the medial aspect of the bulb. Nevertheless, they were somewhat different and the spatial distribution of the darkest foci seemed particularly relevant for the pattern recognition. In lesioned animals, the same spatial distribution of the foci as in intact rats, was observed in the lateral and the medial aspects of the bulb. Nevertheless, lesioned animals presented some quantitative changes in their patterns of glomerular labeling. Moreover, these patterns appeared different according to the biological meaning of the odor tested. The bilateral transection of the LOT brought about a very strong decrease of the optical density in the direct olfactory projections. No evident change of 2-DG uptake was noted in the different tertiary olfactory projections. These 2-DG results confirm the anatomical data relating to the LOT projections.