Staining neurons with Golgi techniques in degenerative diseases of the brain

A detailed morphological study of neurons in healthy and pathological conditions requires reasonably a number of special techniques, which may visualize the majority of neu-rons in a thick three-dimensional arrangement. A detailed visualization of neurons must include the cell body, most of the dendritic arbor, the dendritic spines, the axon, the axonal collaterals and the synapses. An ideal morphological technique for the study of degeneration and regeneration processes of the central nervous system must also visualize clearly the long and short neuronal circuits, as well as the dendritic and axonal bands and tracks. It is also of substantial necessity that the histological techniques must enable the precise and accurate morphometric estimation of the dendritic spines, which is of great value for the study of aging, and the processes of neuronal degen-erations and regeneration. The neuroscientist endeavors to study and follow precisely all the spatiotemporal morphological alterations, which occur during the various degenera-tive processes continuously, resulting in neuronal death and in serious degradation of the neuronal networks. In histological preparations and in tissue cultures, degenerated and dead neurons may be detected by application of various techniques based on the different staining properties of living and dead cells. Among them, silver impregnation technique may be characterized as instrumental for the precise visualization and estimation of the morphological alterations of neurons and neuronal circuits in various pathological conditions. Silver staining was introduced in histology by Camillo Golgi in 1873, more than 140 years ago, as 'reazione nera' (black reaction) (Golgi, 1873). The philosophy of this revolutionary technique was based on the gradual impregnation of the nerve cells and their processes by silver chromate, which could give them a deep dark, almost black appearance, on a yellow background. The technical procedure consists basically in the immersion of the formalin fixed brain in a solution of potassium chromate and potassium dichromate, followed by impregnation with silver nitrate, resulting in the formation of silver chromate eventually. For many years, Golgi technique and its numerous versions and modifications remain ideal methods enabling to obtain clear insight in the morphological profile and the morphometric characters of the dendritic arbor, the den-dritic branches, the spines and the estimation of the spine density in thick paraffin sections. The technique was extensively utilized and evaluated by Santiago Ramon y Cajal, in his unique description of the histology of the nervous system and in the validation and eventual establishment of the 'neuronal …