TH and Parkinson disease: For instance, TH+ neurons increase in the olfactory bulb of PD patients (Huisman et al., 2004, 2008) and the striatum of animal models of PD (Tashiro et al., 1989, 1990; Palfi et al., 2002; Tande et al., 2006; Huot et al., 2007; El Massri et al., 2017).