Nicotine, Tobacco Use, and the 55th Nebraska Symposium on Motivation.- Synaptic Plasticity Within Midbrain Dopamine Centers Contributes to Nicotine Addiction.- Molecular Mechanisms Underlying the Motivational Effects of Nicotine.- Targeting Reward-Relevant Nicotinic Receptors in the Discovery of Novel Pharmacotherapeutic Agents to Treat Tobacco Dependence.- Multiple Motivational Forces Contribute to Nicotine Dependence.- The Role of Nicotine in Smoking:...