Dopaminergic innervation of forebrain by ventral mesencephalon in organotypic slice co-cultures: Effects of GDNF

Numerous studies have verified the ability of glial cell line-derived neurotrophic factor (GDNF) to protect or rescue neurons in models of Parkinson's disease. However, the role of GDNF in the development of dopaminergic (DA) neurons remains unclear. We investigated the hypothesis that GDNF is a target protein for the DA neurons of the mesencephalon forming the nigrostriatal pathway in an in vitro rat model. Organotypic slice cultures were prepared from tissue isolated from postnatal rat pups including but not limited to the substantia nigra (SN), striatum, and cerebral cortex. These cultures were maintained for up to 100 days in vitro. In the absence of exogenous GDNF, DA neurons from the SN grew into the striatum but not the cerebral cortex or hippocampus as determined by immunostaining for tyrosine hydroxylase. The addition of exogenous GDNF increased the survival of DA neurons and also enhanced the number of dopaminergic processes innervating the striatum. GDNF also induced DA innervation of the cerebral cortex but not hippocampus. In conclusion, our studies indicate that the normal pattern of innervation by DA neurons of the mesencephalon can be recapitulated with organotypic co-cultures and that this pattern can be altered by GDNF.