Naive rats with (n = 4, Set II) or without BrdU (n = 5, Set I), naive trained (n = 3, Set I), nondependent (n = 5, Set I), dependent (n = 4, Set I), prolonged nondependent (n = 6, Set II), and prolonged dependent rats (n = 4, Set II) were anesthetized with chloral hydrate and perfused transcardially as described previously (Mandyam et al., 2004). Serial coronal 40 μm sections were obtained on a freezing microtome, and sections from the mPFC (bregma 3.7 to 2.2) and hippocampus (bregma −1.4 to −6.7; (Paxinos and Watson, 1997) were stored in 0.1% NaN3 in 1X PBS at 4°C.
