The action potential and net membrane currents in isolated human detrusor smooth muscle cells

The basic electrophysiological properties of the human detrusor have been investigated in vitro using isolated single cells obtained by collagenase digestion of bladder biopsy specimens. Recordings were made using the 'whole-cell patch clamp' technique using either a physiological filling solution or one in which cesium was used to block any outward current. Spontaneous and stimulated action potentials have been recorded and we have performed the first voltage clamp analysis of the currents that underlie the action potential in human detrusor. The depolarising phase of the action potential occurs by an inward current of Ca2+ ions which can be shown to be of sufficient magnitude to support the rate of upstroke. Repolarisation occurs due to an outward K+ current that is partially Ca2+ dependent. The techniques described here permit the investigation of the ionic basis for the control of contractility in the human bladder and may permit the characterisation of any underlying abnormality in the overactive detrusor.