Animals with chronic LAD infarcts exhibited significantly higher expression of both P2RX3 (26.2% ± 3.9% in MI vs. 12.2% ± 1.9% in normal animals, P = 0.005) and CGRP (17.3% ± 2.0% in LAD-MI vs. 10.3% ± 0.8% in normal animals, P = 0.005), which are receptors and peptides, respectively, involved in nociceptive neurotransmission. The gene discussed is P2RX3; the disease is myocardial infarction.