P2RX4 and chronic cystitis: The possibility cannot be ruled out that P2X4 and/or P2X7 expressed in non-macrophage cells might be involved in the CPA-induced CSE upregulation, cystitis and bladder pain, because the expression of, P2X4 and P2X7 in neurons and of P2X4 in the bladder lamina propria has been reported [33,34,35].