Abstract: Using the mongolian gerbil model of transient forebrain ischemia by bilateral carotid arteries occlusion, the levels of phosphorylation and the amount of DARPP-32 in striatum were measured by back-phosphorylation and Western-blotting assay in vitro. Transient forebrain ischemia had no effect on the immunoreaction of DARPP-32 in striatum, but the state of phosphorylation of DARPP-32 showed a significant change. The [32P] phosphate incorporation in DARPP-32 decreased after 2, 7 or 10 min of ischemia, but increased after a 5-min ischemia. In contrast, the result of back-phosphorylation in vivo was opposite to that obtained in vitro.