Rapid Golgi Stain for Dendritic Spine Visualization in Hippocampus and Prefrontal Cortex

Summary

The protocol describes a modification of the rapid Golgi method, which can be adapted to any part of the nervous system, for staining neurons in the hippocampus and medial prefrontal cortex of the rat.

Abstract

Golgi impregnation, using the Golgi staining kit with minor adaptations, is used to impregnate dendritic spines in the rat hippocampus and medial prefrontal cortex. This technique is a marked improvement over previous methods of Golgi impregnation because the premixed chemicals are safer to use, neurons are consistently well impregnated, there is far less background debris, and for a given region, there are extremely small deviations in spine density between experiments. Moreover, brains can be accumulated after a certain point and kept frozen until further processing. Using this method any brain region of interest can be studied. Once stained and cover slipped, dendritic spine density is determined by counting the number of spines for a length of dendrite and expressed as spine density per 10 µm dendrite.

Introduction

The method of using potassium dichromate and silver nitrate to label neurons was first described by Camillo Golgi^1,2 and subsequently used by Santiago Ramon y Cajal to produce an immense body of work differentiating neuronal and glial subtypes. A recently published book with his illustrations is now available³. Following Ramon y Cajal's studies, which were published more than 100 years ago, very little Golgi impregnation was used. Golgi impregnation is a laborious process that allows three-dimensional visualization of neurons with a light microscope. There have been numerous modific....

Protocol

All experimental procedures are approved by the Sacred Heart University Institutional Animal Care and Use Committee and are in accordance with the NIH Guide for the Care and Use of Animals.

1. Isolation and infiltration of brain tissue

1. Premix solutions A and B of the Golgi staining kit 24 h prior to use and keep in dark bottles and/or in dark. Make approximately 80 mL of solution A and B mix which is sufficient to change the solution after 24 h. Store in airtight bottles.
   NOTE: Perfusion with either saline or paraformaldehyde is not necessary.
2. Sacrifice rats by guillotine following carbon dioxid....

Results

Using the rapid Golgi method, cells are consistently well impregnated so that there are plenty of cells to analyze. This is a marked improvement over prior methods where experiments had to be pooled to have enough data for analysis. Therefore, more samples can be processed at once and brains can be stored frozen until processing. Examples of Golgi impregnated cells in the CA1 region of the hippocampus are shown at low and high power in Figure 3. Counting of spines in a given region yields co.......

Discussion

The present protocol describes a method of Golgi impregnation that allows for rapid simultaneous processing of many sections. It is an improvement over previously described⁵ more labor-intensive methods and consistently yields impregnated neurons for analysis. In addition, there is less exposure to toxic chemicals used in Golgi impregnation. The most challenging part of the process is getting the sections to be flat on the slides, which takes considerable practice. Keeping everything as cold as po.......

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Cardboard slides trays	Fisher Scientific	12-587-10
Coverslips 24 x 60mm	Fisher Scientific	12-545-M
FD Rapid GolgiStain kit	FD Neurotechnologies	PK 401	Stable at RT in the dark for months; Golgi staining kit
Freezing Spray	Fisher Scientific	23-022524
HISTO-CLEAR	Fisher Scientific	50-899-90147	clearing agent
NCSS Software	Kaysville, UT, USA
Permount	Fisher Scientific	SP-15-100	mounting medium
Superfrost Plus Microscope slides	Fisher Scientific	12-550-15
Tissue Tek CTYO OCT Compound	Fisher Scientific	14-373-65	Used to mount brains on cryostat chuck