I don't know if you are talking about fixated frozen sections or raw tissue? 
Anyway, I have had good luck letting them dry over night at rt, however 
those were fixated in NBF prior to freezing. I have also done it on raw 
frozen tissue, - fixated them in acetone for 5 mins. after cutting and 
leaving them in the fumehood untill next day. However, the last method has a 
worse outcome than the first, why I usually make extra sections. Then again, 
brain tissue can be quite troublesome. If your study allows you to do 
fixation prior to freezing, you should do it in 10% neutral buffered 
formalin or 4% paraformaldehylde (dissolved by cooking in PBS) and leave it 
to fix in the fridge for 2-4 hours. Then wipe off excess liquid and freeze 
the sections as usual. Hope this helps.
Kind regards Andrea


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