P2RX4 and arthritic joint disease: Previous studies have identified sensitivity of rat P2X4 to 5-BDBD [37], yet despite the lack of activity at mouse P2X4, 5-BDBD has been employed in several mouse studies to infer a physiological or pathophysiological role for P2X4 including arthritis [38], intracerebral haemorrhage [39], airway inflammation [40], bladder voiding [41], T-cell recruitment [42] and cancer [43].