To summarize these studies of the DA system, there is extensive evidence that nicotine administration and smoking result in activation of the brain DA mesolimbic pathway, resulting in increased DA release and turnover in the VST/NAc. Because dopaminergic input to the NAc modulates neurotransmission through cortico–basal ganglia–thalamic circuitry (Haber and Fudge 1997), smoking-induced increases in DA concentration may explain some of the clinical effects of smoking, as discussed in Sect. 4.
