Selective suppression of endogenous peroxidase activity: application for enhancing appearance of HRP-labeled neurons in vitro.

A simple procedure to suppress selectively the endogenous peroxidase activity of red blood cells in histological sections of the mammalian nervous system is described. Pretreatment of sections with a series of ethanol solutions results in selective abolition of red blood cell staining and also leads to enhanced visualization of neurons that have been injected with horseradish peroxidase (HRP). The method is particularly useful for processing in vitro brain slices that contain HRP-labeled neurons. It can also be used for processing unperfused neural tissue from in vivo HRP labeling experiments. The ethanol pretreatment is compatible with several standard histochemical techniques for the demonstration of HRP.