CELL-SPECIFIC DIFFERENTIAL EXPRESSION OF NA-CHANNEL BETA-1-SUBUNIT MESSENGER-RNA IN THE OLFACTORY SYSTEM DURING POSTNATAL-DEVELOPMENT AND AFTER DENERVATION()

Activity-dependent mechanisms have been implicated in olfactory system development but, although such activity requires ion channels, few re ports have described their expression in the olfactory system. We inve stigated the developmental and denervation-induced regulation of the N a+-channel beta 1 subunit (Na beta 1) in rat olfactory bulb (OB) and p iriform cortex (PC). In situ hybridization shows that Na beta 1 mRNA e xpression is upregulated developmentally, but with different time cour ses in mitral, tufted, and pyramidal cells. In mitral cells, label was detected at postnatal day 4 (P4) and gradually increased to P14. Tuft ed cells were devoid of Na beta 1 mRNA before P14, when most cells exp ressed adult levels. In pyramidal cells of PC, Na beta 1 expression wa s 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 mit ral cells to low-to-moderate levels. In pyramidal cells, Na beta 1 mRN A expression was decreased moderately without significant changes in N a 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 ol factory system during development and after deafferentation and sugges t that the expression of Na beta 1 is regulated independently of Na al pha mRNAs via cell-specific and pathway-specific mechanisms.