Nicotine is an nAChR agonist and previous studies have shown that other nAChR agonists can protect against nigrostriatal dopamine neuron damage in PD animal models (Dajas et al., 2001; Janson et al., 1988; Maggio et al., 1998; Mudo et al., 2007). Here, CHRNA4 is linked to Parkinson disease.