To stain the mast cells selectively you need to use a
cationic dye (such as toluidine blue) at a low pH
such as 1.0. If the pH is higher than about 2.5 you
will also see neurons (Nissl) and nuclei of all cells.
If the method is done correctly the mast cell granules
are metachromatic (red) and the RNA and DNA are
stained blue. Often the red metachromasia is more of
a purple, however, and in a densely cellular tissue
such as brain it can be easy to miss mast cells.
In the rat's brain they occur around blood vessels
in the thalamus, but not usually in great numbers.

An alternative approach is to use alcian blue, a
cationic dye that stains the heparin in mast cells
but not nucleic acids. It can be used at pH 1 or 2.5,
and you can apply a pink counterstain to enhance
contrast. 

The literature of mast cells in the brain goes back
quite a long way. See, for example:
J. Anat. 121:303-311 (1976)
Dev. Neurosci. 4:220-224 (1981)
-- 
-------------------------------
John A. Kiernan
Department of Anatomy and Cell Biology
The University of Western Ontario
London,   Canada   N6A 5C1
   kiernan[AT]uwo.ca
   http://publish.uwo.ca/~jkiernan/
   http://instruct.uwo.ca/anatomy/530/index.htm
_______________________________
Amira Fitieh wrote:
> 
> 
> Hi all,
> 
> 
> 
> We are looking for the Mast cells in rat brain. I have free floating tissue sections. The whole brain is fixed in formalin, sucrose and finally cryo-preserved in glycerol, ethylene glycol and PBS. I would like to know what would be the most suitable protocol for staining the Mast cells with Toludine blue. I would also like to know if I could use positively charged glass slides instead of gelatin coated. Finally, I would like to know the most stable concentration for Toludine blue stock solution.
> 
> Best regards,
> 
> Amira
> 
> **********************************************************************************************************************************
> Amira Fitieh
> Research student
> Arvid Carlsson Institute for Neuroscience
> Göteborg University
> Medicinaregata 11
> Box 432
> 405 30 Göteborg
> ***************************************************************************************************


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