How to discriminate male and female?

[Cousin Beatrice]

Is there any (simple) way to determine if cells are XX or XY in tissue 
slices? I know that FISH technic would probably be possible, but first 
it is not simple, and second in this case, I would need a rat specific 
probe for Y chromosom. Does anyone know if such a probe exist and where 
I could find it.
Thank you in advance for answers
Beatrice