PARP1 and brain ischemia: However, since similar U-shaped dose-response curve has been observed with structurally distinct PARP inhibitors such as 3,4-dihydro 5-[4-(1-piperidinyl) butoxy]-1(2H)-isoquinolinone (DPQ) in response to cerebral ischemia [52], it can be hypothesized that high doses of PARP-1 inhibitors could impair DNA repair in the peri-infarcted area that otherwise would have been rescued.