Among psychostimulants, nicotine is the primary component of tobacco that maintains smoking habits. The drug acts as a nicotinic acetylcholine receptor agonist to produce relaxation and enhanced cognitive performance, and is strongly addictive. Pharmacological and genetic studies have provided evidence for a critical role for the opioid system in nicotine addiction (for recent reviews, see (Berrendero et al., 2010; Drews and Zimmer, 2010; Hadjiconstantinou and Neff, 2011; Tuesta et al., 2011), and knockout studies addressing nicotine reward and withdrawal are summarized in Table 4.
