Question

I am learning about the Golgi staining of neurons. I know that to this day it is unknown why some but not all neurons in a tissue get stained. I have read online that to harden the neural tissue, Golgi submersed samples for up to 45 days in a 2.5% potassium dichromate solution. He then soaked the samples in a 0.5-1% silver nitrate solution for different amounts of time to dye some of the cells black.

I have read a number of online sources about Golgi staining but none of them explain why neurons turn black. Is it a chemical reaction between potassium dichromate and silver nitrate that turns the neurons black?

Answer 1

The black coloration of neurons in Golgi staining arises from the chemical reaction between potassium dichromate and silver nitrate. Golgi's method stains a subset of neurons, revealing intricate structures, which helped advance neuroscience. For identifying new neurons, scientists use BrdU and fluorescent markers to visualize cell division within brain tissue.

Step-by-step explanation:

The Golgi staining technique, developed by Camillo Golgi, involves using potassium dichromate and silver nitrate to visualize neurons. The exact reason why certain neurons turn black as a result of this process is not completely understood. However, it is the chemical reaction between the potassium dichromate and silver nitrate that leads to the precipitation of silver chromate within the cells, which is visible as a black coloration. This solution selectively stains a small proportion of neurons in their entirety, including dendrites, cell bodies, and axons, providing important insights into neuron structure.

To identify and study new neurons, scientists employ techniques like incorporating bromodeoxyuridine (BrdU) into the DNA of dividing cells and using immunohistochemistry to fluorescently label these cells. This allows the visualization of new neurons in the brain tissue under fluorescent microscopy. For instance, in the hippocampus of a rat, newly generated neurons incorporating BrdU can be seen as brightly labeled cells when observed through fluorescence microscopy.