The expression of both purinergic receptors altered in GERD, i.e., P2RX3 and P2RX7, is positively correlated to the expression of transient receptor potential vanilloid receptor 1 (TRPV1), nerve growth factor and glial-derived neurotrophic factor [31]. The gene discussed is P2RX2; the disease is gastroesophageal reflux disease.