Golgi's method is a

silver staining In pathology, silver staining is the use of silver to selectively alter the appearance of a target in microscopy of histological sections; in temperature gradient gel electrophoresis; and in polyacrylamide gels. In traditional stained glass, silv ...

technique that is used to visualize

nervous tissue Nervous tissue, also called neural tissue, is the main tissue component of the nervous system. The nervous system regulates and controls body functions and activity. It consists of two parts: the central nervous system (CNS) comprising the brain ...

under light microscopy. The method was discovered by

Camillo Golgi Camillo Golgi (; 7 July 184321 January 1926) was an Italian biologist and pathologist known for his works on the central nervous system. He studied medicine at the University of Pavia (where he later spent most of his professional career) betwee ...

, an

Italian Italian(s) may refer to: * Anything of, from, or related to the people of Italy over the centuries ** Italians, an ethnic group or simply a citizen of the Italian Republic or Italian Kingdom ** Italian language, a Romance language *** Regional Ita ...

physician A physician (American English), medical practitioner (Commonwealth English), medical doctor, or simply doctor, is a health professional who practices medicine, which is concerned with promoting, maintaining or restoring health through th ...

and

scientist A scientist is a person who conducts Scientific method, scientific research to advance knowledge in an Branches of science, area of the natural sciences. In classical antiquity, there was no real ancient analog of a modern scientist. Instead, ...

, who published the first picture made with the technique in 1873. 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

Spanish Spanish might refer to: * Items from or related to Spain: **Spaniards are a nation and ethnic group indigenous to Spain **Spanish language, spoken in Spain and many Latin American countries **Spanish cuisine Other places * Spanish, Ontario, Cana ...

neuroanatomist Neuroanatomy is the study of the structure and organization of the nervous system. In contrast to animals with radial symmetry, whose nervous system consists of a distributed network of cells, animals with bilateral symmetry have segregated, defin ...

Santiago Ramón y Cajal Santiago Ramón y Cajal (; 1 May 1852 – 17 October 1934) was a Spanish neuroscientist, pathologist, and histologist specializing in neuroanatomy and the central nervous system. He and Camillo Golgi received the Nobel Prize in Physiology or Med ...

(1852–1934) to discover a number of novel facts about the organization of the nervous system, inspiring the birth of the

neuron doctrine The neuron doctrine is the concept that the nervous system is made up of discrete individual cells, a discovery due to decisive neuro-anatomical work of Santiago Ramón y Cajal and later presented by, among others, H. Waldeyer-Hartz. The term ''n ...

. 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.

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 An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action po ...

and the

dendrite Dendrites (from Greek δένδρον ''déndron'', "tree"), also dendrons, are branched protoplasmic extensions of a nerve cell that propagate the electrochemical stimulation received from other neural cells to the cell body, or soma, of the n ...

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. 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 A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

and

spinal cord The spinal cord is a long, thin, tubular structure made up of nervous tissue, which extends from the medulla oblongata in the brainstem to the lumbar region of the vertebral column (backbone). The backbone encloses the central canal of the spi ...

. Golgi's staining is achieved by impregnating aldehyde fixed nervous tissue with

potassium dichromate Potassium dichromate, , is a common inorganic chemical reagent, most commonly used as an oxidizing agent in various laboratory and industrial applications. As with all hexavalent chromium compounds, it is acutely and chronically harmful to health ...

and

silver nitrate Silver nitrate is an inorganic compound with chemical formula . It is a versatile precursor to many other silver compounds, such as those used in photography. It is far less sensitive to light than the halides. It was once called ''lunar caustic' ...

. Cells thus stained are filled by microcrystallization of

silver chromate Silver chromate is an inorganic compound with formula Ag2CrO4 which appears as distinctively coloured brown-red crystals. The compound is insoluble and its precipitation is indicative of the reaction between soluble chromate and silver precursor sa ...

Technique

According to SynapseWeb, this is the recipe for Golgi's staining technique: #Immerse a block (approx. 10x5 mm) of

formaldehyde Formaldehyde ( , ) (systematic name methanal) is a naturally occurring organic compound with the formula and structure . The pure compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde (refer to section F ...

-fixed (or

paraformaldehyde Paraformaldehyde (PFA) is the smallest polyoxymethylene, the polymerization product of formaldehyde with a typical degree of polymerization of 8–100 units. Paraformaldehyde commonly has a slight odor of formaldehyde due to decomposition. Paraf ...

glutaraldehyde Glutaraldehyde is an organic compound with the formula . The molecule consists of a five carbon chain doubly terminated with formyl (CHO) groups. It is usually used as a solution in water, and such solutions exists as a collection of hydrates, c ...

-perfused) brain tissue into a 2% aqueous solution of

for 2 days #Dry the block shortly with

filter paper Filter paper is a semi-permeable paper barrier placed perpendicular to a liquid or air flow. It is used to separate fine solid particles from liquids or gases. The raw materials are different paper pulps. The pulp may be made from softwood, hardwo ...

. #Immerse the block into a 2% aqueous solution of silver nitrate for another 2 days. #Cut sections approx. 20–100 µm thick. #Dehydrate quickly in

ethanol Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an Alcohol (chemistry), alcohol with the chemical formula . Its formula can be also written as or (an ethyl ...

, 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 Gold chloride can refer to: * Gold(I) chloride (gold monochloride), AuCl * Gold(I,III) chloride (gold dichloride, tetragold octachloride), Au4Cl8 * Gold(III) chloride (gold trichloride, digold hexachloride), Au2Cl6 * Chloroauric acid Chloroauric ...

then

oxalic acid Oxalic acid is an organic acid with the systematic name ethanedioic acid and formula . It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colorless solution in water. Its name comes from the fact that early inve ...

, followed by removal of the silver by

sodium thiosulphate Sodium thiosulfate (sodium thiosulphate) is an inorganic compound with the formula . Typically it is available as the white or colorless pentahydrate, . The solid is an efflorescent (loses water readily) crystalline substance that dissolves well i ...

. This preserves a greater degree of fine structure with the ultrastructural details marked by small particles of gold.

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

External links

Photomicrograph of a cortex cell stained with Golgi's
IHC Image Gallery.
Golgi impregnations
Images of the brain of flies.
Visualization of dendritic spines using Golgi Method
SynapseWeb. Includes a time-lapse study of Golgi impregnation. * Berrebi, Albert
Cell Biology of Neurons: Structure and Methods of Study
(in PDF) * {{DEFAULTSORT:Golgi's Method Genetics techniques Staining History of neuroscience Neurohistology