Downregulation of Na+ channel mRNA in olfactory bulb tufted cells following deafferentation

Unilateral naris cauterization blocks odorant access to ipsilateral olfactory receptor cells and results in functional deafferentation of the olfactory bulb (OB). We used naris cauterization on postnatal day 2 (P2) to study the effects of deafferentation on the expression of Na+ channel subunits in OB. In situ hybridization at P18 showed that expression of Na+ channel alpha II and beta I mRNA was dramatically downregulated in tufted cells, while signals in mitral cells showed no detectable changes. Our observations suggest that during critical periods of development in some neurons, Na+ channel expression may be modulated by physiological activity. The differential response in the tufted and mitral cells may reflect varying degrees of dependence on afferent input or fundamental differences in cell properties.