freezing samples for microarray - (Feb/23/2011 )

I am performing my first microarray in the next few weeks but need to freeze a few brains b/c my mice are symptomatic now. My co-mentors suggested removing the brains and flash freezing them, however one of them thinks I should perfuse in PBS 1st b/c he thinks the blood could contribute significantly to my RNA. Does anybody do this? Is this a circumstantial step (you are using small section of brain, etc) or is it common?

a friend of mine collects, dissects and freezes his mouse brains on dry ice. then he stores them in a -70C freezer until he needs them to extract rna for the array. no perfusion.