GDNF and Parkinson disease: Since glomus cells produce not only dopamine but also glial cell line-derived neurotrophic factor (GDNF), which promotes the survival of dopaminergic neurons (Erickson et al., 2001), the carotid body is a potential source of patient-specific stem cells for Parkinson's disease therapy (Espejo et al., 1998, Luquin et al., 1999, Mínguez-Castellanos et al., 2007, López-Barneo et al., 2009).