Brain-derived neurotrophic factor (BDNF) expression changes in the dorsal root ganglion (DRG) and spinal cord in some pain models. Recently, rat BDNF transcripts containing novel 5′ untranslated exons were identified and characterized, and a new numbering system for rat BDNF exons was introduced. We examined the expression profiles of these novel BDNF transcripts in bilateral L4/5 DRGs in an L5-selective spinal nerve ligation (SSNL) model and bilateral L5 DRGs in a complete Freund's adjuvant (CFA) model of rats. L5SSNL increased significantly (P < 0.05) the expression of total BDNF mRNA and exon I, IIA, IIB, IIC, III, IV, VI, and IXA transcripts in ipsilateral L4 DRG. Although expression of total BDNF mRNA remained unchanged in ipsilateral L5 DRG in the L5SSNL model, expression of exon I transcript increased significantly (P < 0.05) and that of exon IV transcript decreased significantly (P < 0.05). The expression profiles of the variant exons in ipsilateral L4 DRG of the L5SSNL model were quite similar to those in ipsilateral DRG of the CFA model, and exon I transcript was the most common BDNF mRNA in these DRGs. Although L5SSNL increased significantly (P < 0.05) the expression of total BDNF mRNA and exon IIC and IXA transcripts in the contralateral L4/5 DRGs, CFA treatment did not alter the expression of total BDNF mRNA or specific transcripts in the contralateral DRGs. These findings suggest that exon I plays an important role in the increase in BDNF expression in ipsilateral DRGs regardless of condition.
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