In situ nick end-labeling detects necrosis of hippocampal pyramidal cells induced by kainic acid

It is believed that in situ nick end-labeling (ISNEL) is an easy and selective method for detecting apoptosis in situ. To test whether ISNEL selectively detects apoptosis but not necrosis, we investigated the kainic acid (KA)-induced neuronal death with ISNEL, comparing with the results of gel electrophoresis and electron microscopy. Many degenerating neurons (ca. 50%) in the hippocampal CA1 area and amygdaloid complex were intensely stained with ISNEL 1-3 days after intraperitoneal injection of KA. Although most of the ISNEL-positive neurons displayed a pathological feature of necrosis, a small number of them displayed apoptosis-like changes when examined by electron microscopic observation. It should be noteworthy that ISNEL recognizes at least a certain form of necrosis and is not selective for apoptosis.