The normal function of the urinary bladder is to store and void urine in a controlled manner. During the filling stage the bladder exhibits spontaneous non-voiding contractions yet the mechanisms underlying these contractions are unclear. The internal lining of the bladder (urothelium/lamina propria) is an important regulator of bladder function by its involvement in sensory mechanisms and via releasing chemical mediators. In addition, the urothelium/lamina propria also exhibits spontaneous contractions which are mediated by unknown mechanisms. This activity may influence contractions of the bladder and play an important role in bladder function. The present study aimed to investigate the spontaneous contractions of the urothelium/lamina propria to identify receptors which modulate the activity.