Nerve growth factor and norepinephrine regulate galanin expression in primary cultures of dorsal root ganglion neurons

Abstract

Nerve growth factor (NGF) is one of the well characterized regulators of galanin expression. NGF deprivation can induce galanin expression in dorsal root ganglion (DRG) neurons. Galanin is recognized as one of the DRG injury markers. Norepinephrine (NE) activates alpha-adrenoreceptors usually expressed in sympathetic neuronal membrane. It has been shown that functional alpha-adrenoreceptors are also expressed in primary sensory neurons. Whether NGF association with NE influences the galanin expression in DRG neurons remains unknown. In the present study, we have evaluated the possible regulation of galanin mRNA or galanin peptide expression by co-administration of NGF and NE in primary cultures of rat DRG neurons. After four days incubation with NGF and/or NE in primary cultures of rat DRG neurons, NGF inhibited and NE promoted galanin mRNA and galanin peptide expression as compared with that in control DRG neuron cultures at the same time point. NGF also inhibited the elevation of galanin expression induced by NE when the cultures were incubated with NGF and NE together. NGF but not NE stimulated neurite outgrowth. The results indicate that NE may affect galanin expression rather than stimulating neurite regeneration, whereas NGF stimulates neurite outgrowth and inhibits galanin expression in the absence or presence of NE on cultured DRG neurons.