What is your model in which you are going to observe drug-induced changes. You have to compare the drug treated serial sections with the control/untreated sections of various regions of the brain. You may access more information in
Craigie's Neuroanatomy of the Rat by Zeman, W., & Innes, J. R. M. (1963).New York: Academic Press.
Attached is one of our publication for yr reference.