Protection of dopaminergic nigrostriatal afferents by GDNF delivered by microspheres in a rodent model of Parkinson's disease

The use of glial cell line-derived neurotrophic factor (GDNF) appears to be a promising strategy to promote survival and function of the nigrostriatal dopaminergic pathway damaged in Parkinson's disease (PD). However, effective intracerebral administration is required for optimal therapeutic benefit and tools to evaluate such therapies must be developed. A rodent model of PD was therefore developed using striatal injection of 6-hydroxydopamine (6-OHDA) with simultaneous implantation of GDNF-delivering microspheres. The effects of GDNF released from microspheres were assessed by classical methods such as amphetamine-induced rotating behavior and tyrosine hydroxylase (TH) immunoreactivity, as well as by quantitative autoradiography using PE2I, a dopamine transporter (DAT) radiotracer, which is also suitable for SPET imaging in humans. 6-OHDA-lesioned animals that received microspheres without GDNF were used as controls. During the first 3 weeks after simultaneous lesion and implantation, the amphetamine-induced rotating behavior of GDNF-treated rats was improved compared to controls and an increase in TH expression (+26%) was measured in the striatum 6 weeks after lesion. In accordance with these results, an increase in striatal PE2I-labeled DAT density was obtained (+17%) after 3 and 6 weeks of treatment. In conclusion, this study demonstrates the neuroprotective action of GDNF delivered by microspheres and suggests that PE21 may be an appropriate radiotracer for use in SPET scintigraphy to follow up treatment of PD in humans. (C) 2002 Wiley-Liss, Inc.