Spontaneous transient outward currents

ZhuGe R, Tuft RA, Fogarty KE, Bellve K, Fay FS, Walsh JV 1999 The influence of sarcoplasmic reticulum Ca2+ concentration on Ca2+ sparks and spontaneous transient outward currents in single smooth muscle cells. J Gen Physiol 113 215—228... 

Benham CD, Bolton TB 1986 Spontaneous transient outward currents in single visceral and vascular smooth muscle cells of the rabbit. J Physiol 381 385—406 Boittin FX, Coussin F, Macrez N, Mironneau C, Mironneau J 1998 Inositol 1,4,5-trisphosphate-and ryanodine-sensitive Ca2+ release channel-dependent Ca2+ signalling in rat portal vein... 

Bolton TB, Imaizumi Y 1996 Spontaneous transient outward currents in smooth muscle cells. Cell Calcium 20 141-152... 

The SR may contribute to excitation-contraction (EC) coupling in two ways firstly, by the release of Ca2+ for contraction as described above, but secondly by modulating membrane excitability. As will be described elsewhere in this book, the SR is an important mediator of surface membrane ion channel activity, and hence, excitability. Spontaneous Ca2+ release from the SR can activate Ca2+-sensitive ion channels. Both K+ (Kca) and Cl- (Clsmooth muscle cell membrane can be activated by SR Ca2+. If Kca channels are activated there will be a hyperpolarization, as K+ ions leave the cell and spontaneous transient outward currents (STOCs) can be recorded (Carl et al 1996, Nelson Quayle... 

FIG. 5. Ca2+ sparks drive electrical activity in myocytes. In contrast to the traditional concept of electrical activity deriving from descending neural control via postsynaptic responses, spontaneous Ca2+ release results in electrical activity in smooth muscle. The figure shows a Ca2+ spark activating sarcolemmal Ca2+-activated Cl- channels and spontaneous transient inward currents (STICs) (current trace above). Whether Ca2+ sparks activate outward STOCs (Ca2+-activated K+ currents) or STICs will depend on the proportion of channels expressed and the resting potential of the myocyte. 

Figure 16.17 Simultaneous recordings of Ca + sparks and spontaneous transient outward Kcal-1 (BK) channel currents (STOCs). Each spark generates a single STOC. A. Original sequence of two-dimensional confocal images obtained every...

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