Improved visualization of neurons labeled with horseradish peroxidase: silver-intensification of the pyrocatechol/p-phenylenediamine reaction product.
A silver intensification procedure suitable for use with pyrocatechol/p-phenylenediamine (PC-PPD) product of the horseradish peroxidase (HRP) reaction is described. Qualitative and quantitative results from retrogradely labeled neurons in the cat cortex after thalamic injection of HRP demonstrate an increase of the intensity of labeling and in the number of darkly labeled cells after the intensification procedure. In both the non-intensified and the intensified PC-PPD reacted tissue the sensitivity was comparable to that of TMB-treated material. The ratio of lightly to darkly labeled neurons was very similar in intensified PC-PPD and TMB material, suggesting that the lightly labeled cells may have fewer terminals present at the level of the injected target.
Fitzpatrick, D; Cheema, S; Merchenthaler, I; Rustioni, A
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