GDNF and ischemia: In hippocampal neurons transfected with hRet51-GFP, the presence of GDNF during the incubation period after OGD further decreased cell death to 22%, suggesting that the downregulation of Ret51 receptors indeed decreases the neuroprotective effects of GDNF in hippocampal neurons subjected to in vitro ischemia (Figure 8c).