Journal of Neuroscience, Vol 16, 702-713, Copyright © 1996 by Society for Neuroscience
Cell-specific differential expression of Na(+)-channel beta 1-subunit mRNA in the olfactory system during postnatal development and after denervation
S Sashihara, CA Greer, Y Oh and SG Waxman
Department of Neurology, Yale University School of Medicine, New Haven, Connecticut 06510, USA.
Activity-dependent mechanisms have been implicated in olfactory system
development but, although such activity requires ion channels, few reports
have described their expression in the olfactory system. We investigated
the developmental and denervation-induced regulation of the Na(+)-channel
beta 1 subunit (Na beta 1) in rat olfactory bulb (OB) and piriform cortex
(PC). In situ hybridization shows that Na beta 1 mRNA expression is
upregulated developmentally, but with different time courses in mitral,
tufted, and pyramidal cells. In mitral cells, label was detected at
postnatal day 4 (P4) and gradually increased to P14. Tufted cells were
devoid of Na beta 1 mRNA before P14, when most cells expressed adult
levels. In pyramidal cells of PC, Na beta 1 expression was not detectable
clearly until P14, with maximal expression at P28. To examine the
regulation of Na beta 1 mRNA, we surgically deafferented the OB at P30 and
compared the effects on Na beta 1 with those for Na(+)-channel
alpha-subunit (Na alpha) mRNAs. Within 5 d of surgery, the Na beta 1 and Na
alpha II signals within tufted cells disappeared almost completely. Na beta
1 and Na alpha II expression was decreased in mitral cells to
low-to-moderate levels. In pyramidal cells, Na beta 1 mRNA expression was
decreased moderately without significant changes in Na alpha II mRNA.
Deafferentation had no detectable effects on Na alpha I or III mRNAs in
either OB or PC. These data indicate that Na beta 1 mRNA is expressed
differentially in subpopulations of cells in the olfactory system during
development and after deafferentation and suggest that the expression of Na
beta 1 is regulated independently of Na alpha mRNAs via cell-specific and
pathway-specific mechanisms.