Module 7: Figure autonomous Ca2+ sparks
Electrical recruitment of Ca2+ sparks in ventricular cells.
The line scan images at the top record the appearance of sparks in response to three different depolarizations. There were very few sparks for the depolarization to −40 mV. The current trace at the bottom recorded the inward Ca2+ current (ICa), which shows that there was very little entry of trigger Ca2+ for this small depolarization. When depolarization was increased to −20 mV, a distinct line of sparks appeared. However, there were some gaps, and some sparks showed a long latency (white arrowheads) that resulted in a sluggish transient, as seen in the middle trace, which shows the spatially averaged F/F0 values. At the larger depolarization to 0 mV, the response was uniform and much sharper. Reproduced from Song, L.-S., Sham, J.S.K., Stern, M.D., Lakatta, E.G. and Cheng, H. (1998) Direct measurement of SR release flux by tracking “Ca2+ spikes” in rat cardiac myocytes. J. Physiol. 512:677–691, with permission from Blackwell Publishing; see Song et al. 1998.