Golgi's method is a
silver staining 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) bet ...
, an
Italian physician
A physician, medical practitioner (British English), medical doctor, or simply doctor is a health professional who practices medicine, which is concerned with promoting, maintaining or restoring health through the Medical education, study, Med ...
and
scientist
A scientist is a person who Scientific method, researches 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, philosophers engag ...
, 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 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 (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 ' ...
. 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 American and British English spelling differences#-re, -er, spelling differences) is a long, slender cellular extensions, projection of a nerve cell, or neuron, ...
and the
dendrite
A dendrite (from Ancient Greek language, Greek δένδρον ''déndron'', "tree") or dendron is a branched cytoplasmic process that extends from a nerve cell that propagates the neurotransmission, electrochemical stimulation received from oth ...
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
The brain is an organ (biology), organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It consists of nervous tissue and is typically located in the head (cephalization), usually near organs for ...
and
spinal cord
The spinal cord is a long, thin, tubular structure made up of nervous tissue that extends from the medulla oblongata in the lower brainstem to the lumbar region of the vertebral column (backbone) of vertebrate animals. The center of the spinal c ...
.
Golgi's staining is achieved by impregnating aldehyde-fixed nervous tissue with
potassium dichromate 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 causti ...
. Cells thus stained are filled by
microcrystallization of
silver chromate.
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 an organic compound with the chemical formula and structure , more precisely . The compound is a pungent, colourless gas that polymerises spontaneously into paraformaldehyde. It is stored as ...
-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
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 typically different pulp (paper), paper pulps. The pulp may be ...
.
#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 (also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound with the chemical formula . It is an Alcohol (chemistry), alcohol, with its formula also written as , or EtOH, where Et is the ps ...
, 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
Oxalic acid is an organic acid with the systematic name ethanedioic acid and chemical formula , also written as or or . It is the simplest dicarboxylic acid. It is a white crystalline solid that forms a colorless solution in water. Its name i ...
, followed by removal of the silver by
sodium thiosulphate. 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