Striatal GDNF is likely to play a role in the regulation of the first phase of natural cell death (NCD) at postnatal day (PND)2 in substantia nigra (SN) dopamine (DA) neurons, because apoptosis is suppressed by injection of GDNF and augmented by neutralizing antibodies (Oo et al., J. Neurosci.,2003). In support of this possibility, double transgenic mice overexpressing GDNF in striatum throughout development demonstrate an increased number of SN DA neurons after the first phase of NCD (Kholodilov et al., SFN’02). However, this increase does not persist into adulthood. We now ask whether overexpression of GDNF in mesencephalic DA neuron targets has a lasting effect on their DA innervation. We performed immunohistochemistry for the dopamine transporter (DAT) on complete sets of striatal coronal sections and quantified the number of DAT- positive punctuate structures (DPPS) by stereology. Overexpression of GDNF did not have an effect on the adult number of striatal DPPS: WT=3.1±0.4 (x106) (DPPS/striatum); DT=...