GDNF and ischemic stroke: Glial cell line-derived neurotrophic factor (GDNF), another neurotrophic factor secreted by astrocytes, has been shown to induce the neural differentiation of precursor cells and facilitate striatal neurogenesis after ischemic stroke in adult rats [22].Nerve growth factor (NGF), expressed by astrocytes, has been shown to be upregulated in the peri-infarct region after ischemic stroke and improve the survival of newly generated cells in the ipsilateral striatum and SVZ [23].