Effect of NGF, BDNF, bFGF, aFGF and cell density on NPY expression in cultured rat dorsal root ganglion neurones

The effect of neurotrophic factors on neuropeptide Y (NPY) expression was s tudied in adult rat dispersed dorsal root ganglion (DRG) cultures. Nerve gr owth factor (NGF), brain-derived neurotrophic factor (BDNF), acidic fibrobl ast growth factor (aFGF) or basic FGF was included in the culture medium du ring incubation for 72 h. In untreated cultures, around 18% of all neurones (visualized by antibodies to PGP 9.5) expressed NPY-like immunoreactivity (LI). In contrast, in vivo uninjured neurones do not contain detectable lev els of NPY-LI. In the immunohistochemical analysis aFGF increased the perce ntage of NPY-immunoreactive (-IR) neurones 1.8-fold, while NGF, BDNF or bFG F had no significant effect on NPY expression. When the effect of these gro wth factors was monitored with non-radioactive in situ hybridization, both aFGF and bFGF caused a significant increase (2.25- and 1.8-fold, respective ly), whereas, again, NGF and BDNF had no effect. The results also showed an effect of cell density on NPY expression, whereby fewer neurones expressed NPY in high than in low density cultures. This difference was seen in untr eated as well as growth factor-treated cultures. The present results suppor t the hypothesis that DRG neurones in culture are in an axotomized state, s ince they express NPY to about the same extent as axotomized DRG neurones i n vivo. Surprisingly, two growth factors of the FGF family enhance NPY expr ession in DRG neurones, which is in apparent contrast to a published in viv o study [Ji, R.-R., Zhang, Q., Pettersson, R.F., Hokfelt, T., 1996. aFGF, b FGF and NGF differentially regulate neuropeptide expression in dorsal root ganglia after axotomy and induce autotomy. Reg. Pept. 66, 179-189.]. Finall y, NPY expression was also influenced by cell density. (C) 2000 Elsevier Sc ience B.V. All rights reserved.