C-fos expression and 2-deoxyglucose uptake in the olfactory bulb of odour-stimulated awake rats

Using a selective monoclonal Fos antibody, we have studied the expression of the c-fos proto-oncogene in the olfactory bulb of awake rats stimulated with propionic acid vapours. We have perfected a method which allows the comparison of patterns of either cellular c-fos immunoreactivity or glomerular 2-deoxyglucose uptake in the same olfactory bulb. C-fos was expressed in local bulbar interneurones, principally granule cells. We observed that the low level of basal c-fos expression raised significantly under olfactory stimulation in the bulbar column defined by the foci of high 2-deoxyglucose glomerular uptake. This is the first demonstration that c-fos expression can be triggered by afferent olfactory input in the olfactory bulb in normally breathing awake rats. These data support the assumption that the olfactory bulb is a suitable model to elucidate the priming conditions and functional involvement of Fos protein synthesis triggered by physiological sensory stimulation.