Odors increase Fos in olfactory bulb neurons including dopaminergic cells

Neuronal activity may lead to long lasting changes in cell phenotype through induction of genes such as c-fos which encode transcriptional regulatory factors. Odor-activated olfactory bulb cells exhibit increases in c-fos mRNA expression. The present study examined whether odor stimulation of awake rats also leads to increases in Fos protein in these cells. The phenotype of Fos-immunoreactive cells was partially characterized using double-immunoperoxidase staining. Odor exposure increased Fos-immunoreactivity (IR) in specific sets of olfactory bulb neurons. Fos-IR was not co-localized with IR for glial fibrillary acidic protein, but was co-localized with tyrosine hydroxylase (TH)-IR in a subpopulation of dopaminergic neurons, suggesting that bulbar TH expression may be regulated in part by a Fos mechanism.