GDNF and neuroblastoma: Of particular relevance to the current study are the effects of neurotrophic factors on TH synthesis: NGF has been found to enhance TH synthesis in adult rat major pelvic ganglion cultures [56]; neurturin reduced the upregulation of TH expression in cultured pelvic parasympathetic neurons [53]; and, GDNF has been demonstrated to downregulate expression of TH in dopamine neurons upon overexpression in vivo [96], but to upregulate the expression of TH in a neuroblastoma cell line by increasing the activity of the TH gene promoter and stabilizing TH mRNA [97].