Editing Golgi's method

{{Short description|Silver staining technique for visualizing nervous tissue under light microscopy}}
[[Image:GolgiStainedPyramidalCell.jpg|thumb|A human neocortical [[pyramidal neuron]] stained via Golgi technique. Notice the apical dendrite extending vertically above the soma and the numerous basal dendrites radiating laterally from the base of the cell body. Photo by Bob Jacobs, Colorado College.]]
[[Image:Golgi Hippocampus.jpg|right|thumb|Drawing by Camillo Golgi of a [[hippocampus]] stained with the silver nitrate method]]
[[Image:Purkinje cell by Cajal.png|thumb|Drawing of a [[Purkinje cell]] in the [[cerebellum]] [[Cerebellar cortex|cortex]] done by Santiago Ramón y Cajal, clearly demonstrating the power of Golgi's staining method to reveal fine detail]]
'''Golgi's method''' is a [[silver staining]] technique that is used to visualize [[nervous tissue]] under light microscopy. The method was discovered by [[Camillo Golgi]], an [[Italy|Italian]] [[physician]] and [[scientist]], who published the first picture made with the technique in 1873.<ref>{{Cite book|title=Origins of neuroscience : a history of explorations into brain function|last=Finger|first=Stanley|publisher=Oxford University Press|year=1994|isbn=9780195146943|pages=45|oclc=27151391|quote=In 1873, Golgi published the first brief but "adequate" picture of ''la reazione nera'' (the black reaction), which showed the whole nerve cell, including its cell body, axon, and branching dendrites.}}</ref>  It was initially named the '''black reaction''' (''la reazione nera'') by Golgi, but it became better known as the '''Golgi stain''' or later, Golgi method.

Golgi staining was used by [[Spain|Spanish]] [[neuroanatomist]] [[Santiago Ramón y Cajal]] (1852–1934) to discover a number of novel facts about the organization of the nervous system, inspiring the birth of the [[neuron doctrine]]. Ultimately, Ramón y Cajal improved the technique by using a method he termed "double impregnation". Ramón y Cajal's staining technique, still in use, is called Cajal's stain.{{citation needed|date=April 2016}}

==Mechanism==

The cells in nervous tissue are densely packed, and little information on their structures and interconnections can be obtained if all the cells are stained. Furthermore, the thin filamentary extensions of neural cells, including the [[axon]] and the [[dendrite]]s of neurons, are too slender and transparent to be seen with normal staining techniques. Golgi's method stains a limited number of cells at random in their entirety. The mechanism by which this happens is still largely unknown.<ref>{{cite book |last=Nicholls |first=J. G. |title=From neuron to brain |year=2001 |publisher=Sinauer Associates |isbn=0878934391 |pages=[https://archive.org/details/fromneurontobrai00arob/page/5 5] |url-access=registration |url=https://archive.org/details/fromneurontobrai00arob/page/5 }}</ref> Dendrites, as well as the cell soma, are clearly stained in brown and black and can be followed in their entire length, which allowed neuroanatomists to track connections between neurons and to make visible the complex networking structure of many parts of the [[brain]] and [[spinal cord]].

Golgi's staining is achieved by impregnating aldehyde-fixed nervous tissue with [[potassium dichromate]] and [[silver nitrate]]. Cells thus stained are filled by [[crystallization|microcrystallization]] of [[silver chromate]].

==Technique==
According to SynapseWeb,<ref>{{Cite web |author=Spacek, J., Fiala, J. |date=2002-06-28 |url=http://synapses.clm.utexas.edu/learn/visualize/visualize.stm |title=Visualization of Dendritic Spines |publisher=SynapseWeb |access-date=2010-06-17 |url-status=dead |archive-url=https://web.archive.org/web/20100626160944/http://synapses.clm.utexas.edu/learn/visualize/visualize.stm |archive-date=2010-06-26 }}</ref> this is the recipe for Golgi's staining technique:

#Immerse a block (approx. 10x5 mm) of [[formaldehyde]]-fixed (or [[paraformaldehyde]]- [[glutaraldehyde]]-perfused) brain tissue into a 2% aqueous solution of [[potassium dichromate]] for 2 days
#Dry the block shortly with [[filter paper]].
#Immerse the block into a 2% aqueous solution of silver nitrate for another 2 days.
#Cut sections approx. 20–100&nbsp;[[Micrometre|μm]] thick.
#Dehydrate quickly in [[ethanol]], clear and mount (e.g., into Depex or Enthalan).

This technique has since been refined to substitute the silver precipitate with gold by immersing the sample in [[gold chloride]] then [[oxalic acid]], followed by removal of the silver by [[Sodium thiosulfate|sodium thiosulphate]]. This preserves a greater degree of fine structure with the ultrastructural details marked by small particles of gold. <ref>{{Cite web | url=http://www.springerlink.com/(f0cb2ybwsglgtnuip5efub55)/app/home/contribution.asp?referrer=parent&backto=issue,5,11;journal,215,243;linkingpublicationresults,1:100182,1 | title=Home – Springer }}{{dead link|date=February 2020|bot=medic}}{{cbignore|bot=medic}}</ref>

==Quote==
Ramón y Cajal said of the Golgi method:

:'' I expressed the surprise which I experienced upon seeing with my own eyes the wonderful revelatory powers of the chrome-silver reaction and the absence of any excitement in the scientific world aroused by its discovery.''
: ''Recuerdos de mi vida, Vol. 2, Historia de mi labor científica''. Madrid: Moya, 1917, p. 76.

== References ==
{{reflist|2}}

==External links==
* [http://www.ihcworld.com/imagegallery/images/special-stain/Golgi-g.jpg Photomicrograph of a cortex cell stained with Golgi's]. IHC Image Gallery.
* [https://web.archive.org/web/20080415214431/http://flybrain.neurobio.arizona.edu/Flybrain/html/atlas/golgi/ Golgi impregnations]. Images of the brain of flies.
* [https://web.archive.org/web/20110830095802/http://synapses.clm.utexas.edu/learn/visualize/golgi2.stm#GolgiTime Visualization of dendritic spines using Golgi Method]. SynapseWeb. Includes a time-lapse study of Golgi impregnation.
* Berrebi, Albert: [https://web.archive.org/web/20051014230419/http://ihcworld.com/imagegallery/displayimage.php?album=4&pos=13 Cell Biology of Neurons: Structure and Methods of Study]. (in PDF)
* {{BrainMaps|Golgi-stained|Golgi-stained neurons}}

{{DEFAULTSORT:Golgi's Method}}
[[Category:Genetics techniques]]
[[Category:Staining]]
[[Category:History of neuroscience]]
[[Category:Neurohistology]]