Panel A shows line traces with two superimposed records of calcium ion flux. The horizontal axis represents time, and the vertical axis represents flux in millimeters per second. The presence of a conditioning pulse reduces the peak flux elicited by the test pulse from Pref to Pcond. The difference Pref-Pcond, called suppression, is approximately equal to the decay of flux (Pc-Sc) elicited by the conditioning pulse. Conditioning does not change the steady value S reached at the end of the test pulse. Panel B displays a set of line traces showing fluxes elicited by pairs of pulses in rat EDC muscle. A large test pulse follows a conditioning pulse of variable amplitude. The horizontal axis represents time, and the vertical axis represents flux in millimeters per second. Panel C is a scatter plot showing the values of decay in the flux elicited by the conditioning pulses of panel B, plotted against the suppression induced in the test flux. The horizontal axis represents the inactivating component of prepulse in percent per millisecond, and the vertical axis represents the suppression in percent per millisecond. Panel D is a scatter plot showing replications of the same plot in different animals. The horizontal axis represents the inactivating component of prepulse in percent per millisecond, and the vertical axis represents the suppression in percent per millisecond.
Quantal Ca 2+ release and deterministic inactivation. (A) Superimposed records of flux elicited by the two-pulse patterns shown in a voltage clamped frog myofiber. The presence of a conditioning pulse reduces the peak of the flux elicited by the large test pulse Pref to a value Pcond. The difference Pref-Pcond, called “suppression,” is approximately equal to “decay” of flux (Pc-Sc) elicited by the conditioning pulse. Conditioning does not change the steady value S reached at the end of the test pulse. Reproduced from Pizarro et al. (1997). (B) A set of fluxes elicited by pairs of pulses in rat EDC muscle; a large test pulse follows a conditioning pulse of variable amplitude. (C) The values of decay in the flux elicited by the conditioning pulses of panel B, plotted vs. the suppression induced in the test flux. (D) Replications of the same plot in different individuals. From Szentesi et al. (2000), authorized by Péter Szentesi and László Csernoch. Fig. 6 reprinted with permission from Journal of Physiology.