Co-administration of nerve growth factor and butyrate regulates vanilloid receptor 1 and substance P levels in cultures of rat dorsal root ganglion neurons

Abstract

The aim of the present study was to investigate whether co-administration of nerve growth factor (NGF) and butyrate regulates vanilloid receptor 1 (VR1) and substance P (SP) levels in cultures of rat dorsal root ganglion (DRG) neurons. DRG was dissected out from embryonic 15-day-old Wistar rat and cultured as dissociated cells for 2 days then exposed to NGF (10 ng/ml), butyrate (1 mmol/L), NGF (10 ng/ml) plus butyrate (1 mmol/L) for another 4 days. The neurons cultured continuously in media served as normal control. After that, the cultures were processed for detecting expression of mRNA for VR1 and SP in DRG neurons by RT-PCR, and expression of VR1 protein by Western blot. SP basal release levels were measured by radioimmunoassay (RIA). Capsaicin-evoked SP release was measured by RIA after stimulation with capsaicin (100 nmol/L) for 10 minutes. The neurons exposed to vehicle solution served as vehicle control. Either NGF (10 ng/ml) or butyrate (1 mmol/L) promoted expression of SP mRNA, VR1 mRNA, and VR1 protein in DRG neurons and capsaicin-evoked SP release from DRG neurons. Co-administration of NGF and butyrate showed a synergistic effect on expression of VR1 mRNA, and VR1 protein in DRG neurons and capsaicin-evoked SP release from DRG neurons and a ceiling effect on SP mRNA expression. The elevation of SP mRNA, VR1 mRNA, and VR1 protein promoted by NGF and/or butyrate may be associated with increases of SP release evoked by capsaicin. The mechanisms of the effects of co-administration of NGF and butyrate should be clarified by further study.