Macrophages express GDNF after striatal injury

Full text: Striatal injury causes neurite outgrowth and activation of the nigrostriatal dopamine pathway. Dopamine neurite outgrowth in vitro and in vivo after application of GDNF suggests that GDNF could mediate the dopaminergic sprouting seen after striatal injury. To determine whether local production of GDNF increases after striatal injury, 5-6 weeks old C57/BL6 mice were anaethesised (Nembutal 70mg/kg i.p.) and the left striata were lesioned using a Scouten wire knife. The mice were sacrificed by Nembutal overdose and 20μ coronal sections of snap-frozen brains were thaw-mounted on silane treated slides. In situ hybridisation using a pair of [γ-33P]ATP-labelled 50-mer oligonucleotide probes, revealed that after injury GDNF expression increased rapidly (p<0.0002 at 3 days) and remained elevated for at least 4 weeks post lesion (p<0.0002). Increased GDNF expression was seen predominantly over yellow pigmented cells . These cells are usually considered to be macrophages containing the haemoglobin catabolite haemosiderin. Peris stain confirmed that the yellow pigment was haemosiderin while non-specific esterase staining confirmed that these cells are brain macrophages. Thus GDNF expression does increase after striatal injury and macrophages appear to be the major source of the GDNF. Copyright (1998) Australian Neuroscience Society