GDNF and Parkinson disease: To investigate whether the cells were transplantable and whether low oxygen tension also affected differentiation of midbrain and forebrain neuronal precursors after micro-transplantation into striatal slice cultures (simplified model of the dopamine-depleted striatum in Parkinson's disease), cells were pre-differentiated for 4 DIV according to the CK4-protocol (sequential addition of FGF8, Shh, GDNF and Forskolin) and seeded onto one-day old mouse striatal slice cultures (1000 cell/culture) and grown at either high or low oxygen tension for 13 days (Fig. 7).