At the end of nicotine treatment, animals were euthanized with an overdose of sodium pentobarbital, and the brains were dissected out immediately after decapitation. After brain slices were cut in a dish containing ice-cold saline using a Stoelting tissue slicer (Chicago, IL), bilateral punches were excised from the amygdala, anterior area of the hippocampus, NA, PFC, striatum, and VTA using a bilateral 2.0-mm-diameter brain punch tissue set (myNeuroLab.com, St. Louis, MO) according to the coordinates of Paxinos and Watson (1986). All tissues were stored at −80°C until RNA isolation.
