[D-ala2,D-leU5]enkephalin (DADLE) increases expression of glial cell line-derived neurotrophic factor (GDNF) in brain tissues. Enzyme-linked immunosorbent assays (ELISA) revealed that the levels of GDNF proteins, but not nerve growth factor (NGF), were significantly higher in striatal and cortical tissues harvested from ischemic animals treated with DADLE compared with those treated with saline. Data are expressed as mean percent of control ± S.E.M. Asterisk indicates P <0.05. n = 6 samples for each neurotrophic factor examined.