GDNF increases the density of cells containing calbindin but not of cells containing calretinin in cultured rat and human fetal nigral tissue

Among the dopaminergic neurons in substantia nigra pars compacta and in the ventral tegmental area, subpopulations express the calcium-binding protein s calbindin (CB) and calretinin (CR), and the CB-containing neurons are sup posed to be less prone to degeneration in Parkinson's disease. Glial cell l ine-derived neurotrophic factor (GDNF) is a potent survival factor for nigr ostriatal dopaminergic neurons. Using free-floating roller-tube (FFRT) cult ures derived from fetal rat (E14) ventral mesencephalon we found that GDNF (10 ng/ml) significantly increased the number of surviving tyrosine hydroxy lase (TH)-immunoreactive neurons. The possible effects of GDNF treatment on CB-immunoreactive (CB-ir) and CR-ir neurons in such cultures were examined in the present study. The neuronal cell densities were measured by quantif ying the numbers of CB-ir and CR-ir neurons in areas of sections through th e most extensive parts of the spherical cultures. In 4-day-old and 8-day-ol d cultures GDNF treatment increased the density of CB-ir neurons by 50% and 59%, respectively. Partial co-existence of TH and CB was shown using the m ethod of double immunolabeling. The density of CR-containing neurons was un affected by GDNF treatment as confirmed by Western blotting for CR. Paralle l effects of GDNF treatment were obtained for cultures of human fetal ventr al mesencephalon (8 weeks postconception). In conclusion, our findings iden tify GDNF as a potent factor for fetal rat and human nigral CB-ir neurons a ble to promote their survival in culture. Referring to a suggested neuropro tective role of CB, the results may be of relevance in the context of neuro nal transplantation of patients suffering from severe Parkinson's disease.