GDNF and Parkinson disease: Glial-derived neurotrophic factor (GDNF) therapy has been shown to be beneficial in treating Parkinson’s disease when EP1 receptor is blocked or ablated, resulting in a 60% enhancement in GDNF, which suggests that selective inhibition of EP1 receptor signaling might be a means to augment GDNF secretion in diseased regions of the brain (Li et al., 2012).