Expression of α7 nAChRs in these brain regions play multiple roles in nicotine addiction; they aid in the formation of functional synapses [49], promote the net excitatory effect on midbrain DA neurons of the reward pathway [60], and enhance postsynaptic excitation through NMDA receptors in the hippocampus and prefrontal cortex [49,60]. This evidence concerns the gene CHRNA7 and nicotine dependence.