|Seeing through a glass darkly (source)|
We have previously discussed how neuroscientists use calcium to watch cells in action, but a surprising amount of information can be gleaned from simply staining fixed (inactive) cells.
There are so many ways to stain fixed cells that I have to write this in parts. First we'll discuss two of the oldest techniques still commonly used, the Nissl stain and the Golgi stain.
One of the earliest techniques to allow for the visualization of neurons is the Nissl Stain.
|Nissl stain of visual cortex (source)|
The Nissl stain reacts with most of the cells in a brain slice (both neurons and glial cells), so it is not great for seeing the detailed morphology of a single neuron. However, it is great for seeing the cellular patterns of a particular brain area. The image above clearly shows the different layers of the visual cortex. Layer 1 has almost no cells, but layer 4 has tons.
This technique can be used to visualize the results of a certain mutation or drug treatment on the brain. It is often also used as a control experiment to confirm that a treatment did not kill cells or damage the brain.
(side note: If you want to do this stain yourself, numerous protocols are available online)
In contrast to the Nissl stain which stains almost all the cells, the Golgi stain impregnates only a few of them.
|Golgi stain of Hippocampal neuron (source)|
This technique can be used to test whether a mutation or drug treatment alters the growth of cell dendrites.
(There are protocols online for this stain as well)
A group at Leicester University in the UK has developed a protocol that combines the Nissl and Golgi stains, so you can have the best of both worlds.
|Pilati et al., 2008 Figure 3|
Using this technique, they were able to more accurately characterize the morphology of neurons in specific areas of the brain. They also found that the Nissl stain underestimates the soma size compared to the Golgi stain.
Pilati N, Barker M, Panteleimonitis S, Donga R, & Hamann M (2008). A rapid method combining Golgi and Nissl staining to study neuronal morphology and cytoarchitecture. The journal of histochemistry and cytochemistry : official journal of the Histochemistry Society, 56 (6), 539-50 PMID: 18285350