C. B. Metz

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.

Simultaneous visualization of chromatolytic neurons and neurons retrogradely labeled with horseradish peroxidase.

A method is described for visualization of neurons retrogradely labeled with horseradish peroxidase (HRP) in celloidin-embedded brain slabs. The preservation of cellular detail obtained with this technique facilitates (1) accurate delimination of nuclei or laminae in which HRP-positive neurons are found and (2) simultaneous identification of cells of origin of two central fiber systems, by combining the retrograde transport of HRP and the retrotrade degeneration technique. The latter approach has been used in adult cats and in kittens to identify cortical neurons which project to the dorsal column nuclei and to the spinal cord.