We next investigated the effect of nicotine withdrawal on energy balance. First, we confirmed that chronic nicotine administration for 8 days resulted in marked negative energy balance, as demonstrated by reduced body weight (Fig. 4A), decreased feeding (Fig. 4B), and lowered fat mass (Fig. 4C; without affecting lean mass). At the same time we observed increased EE (Fig. 4D; area under the curve: vehicle: 100 ± 4.1; nicotine: 121 ± 6.2; withdrawal: 103.9 ± 2.1; P < 0.05 vehicle vs. nicotine; P < 0.05 nicotine vs. withdrawal), elevated LA (Fig. 4E), and decreased RQ (Fig. 4F). Withdrawal of nicotine treatment shifted all of the above parameters toward the level of vehicle-treated rats.
