sucrose pretreatment for frozen sections

[MGLinWS]

You should be aware that some histochemical stains do not work if the
tissue has been exposed to formalin for an extended period of time.  I
have found that paraformaldehyde is less problematic for many stains and
for long term storage following cryoprotection.

Also, after cutting the brain, I once left the sections in paraform for
several weeks (Neuro meeting through Thanksgiving) before staining the
tissue and there were no adverse effects.

Best of Luck. 

Mark Laubach