Solutions and Reagents:

Fixative Solution:

      3% potassium bichromate  ---------- 60 ml

      10% formalin -------------------------- 20 ml

      Mix well and store at room temperature.

2% Silver Nitrate Solution:

      Silver nitrate ---------------------------- 2 g

      Distilled water -------------------------- 100 ml

      Mix well and store at room temperature.

Procedure:

1. Fix tissue blocks (less than 1 cm thick) in 10% formalin for 24 hours or more. The alternatively you can also use the above fixative solution:

2. Place tissue blocks in 3% potassium bichromate for 3-7 days. Avoid light. Change fresh solution each day.

3. Transfer tissue blocks into 2% silver nitrate solution for 1-3 day at room temperature. Avoid light. (Note: before put blocks into silver nitrate solution, use filter paper to absorb access solution. Change silver nitrate solution (less than regular use) several times until brown participates do not appear).

4. Cut vibratome sections at 60 um thick into distilled water.

5. Mount sections on to Superfrost Plus slides. Air dry for 10 minutes. Dehydrate through 95% Alcohol, 100% alcohol, clear in xylene and coverslip.

Results:

Cortical neurons and processes ----------- black

Positive Controls:  

      Brain (Cortex).