Role of Glial Cell Line‐Derived Neurotrophic Factor in the Maintenance of Adult Mesencephalic Catecholaminergic Neurons

Background The glial cell line‐derived neurotrophic factor has a potent neuroprotective action on mesencephalic dopamine neurons, which are progressively lost in Parkinson's disease. Intrastriatal administration of this factor is a promising therapy for Parkinson's disease. Glial cell line‐derived neurotrophic factor is naturally produced in restricted cerebral regions, such as the striatum, septum, and thalamus; however, its effects in the adult brain remain under debate. Objectives We sought to clarify the physiologic role of endogenous glial cell line‐derived neurotrophic factor in the survival of catecholaminergic neurons of the substantia nigra pars compacta and the locus coeruleus in adult mice. Methods We used 2 new Cre recombinase‐based mouse models to delete a floxed–glial cell line‐derived neurotrophic factor gene. The first model had Cre expression in the parvalbumin expressing interneurons, as these cells represent the major source of striatal glial cell line‐derived neurotrophic factor. The second model was an estrogen receptor 2‐based inducible Cre triggered by tamoxifen at 2 months of age. Results We found that the floxed–glial cell line‐derived neurotrophic factor gene was resilient to ablation by Cre‐induced recombination and that parvalbumin‐driven Cre was particularly inefficient to do so. The inducible‐Cre model allowed an average 70% to 80% reduction in glial cell line‐derived neurotrophic factor messenger ribonucleic acid and protein in striatum and septum with moderate significant loss of catecholamine neurons in the nigrostriatal pathway and, more markedly, in the locus coeruleus. This was accompanied with mild locomotor decline. Conclusions Our data support qualitatively the view that brain glial cell line‐derived neurotrophic factor is needed for the maintenance of adult central catecholaminergic neurons. © 2020 International Parkinson and Movement Disorder Society