Kl. Engisch et Mc. Nowycky, CALCIUM-DEPENDENCE OF LARGE DENSE-CORED VESICLE EXOCYTOSIS EVOKED BY CALCIUM INFLUX IN BOVINE ADRENAL CHROMAFFIN CELLS, The Journal of neuroscience, 16(4), 1996, pp. 1359-1369
We used the perforated-patch technique to examine the relationship bet
ween Ca2+ entry and exocytosis of large dense-cored vesicles in bovine
adrenal chromaffin cells. Exocytosis evoked by single-step depolariza
tions was monitored by capacitance detection. Ca2+ entry was varied by
changing external calcium concentration, stepping to different test p
otentials, depolarizing for different durations, or applying blockers
of specific calcium channel subtypes. Regardless of protocol, the amou
nt of exocytosis was strictly related to the integral of the voltage-c
lamped calcium current, raised to a power of similar to 1.5. Thus, des
pite the complexities of transient and nonuniform changes in submembra
ne calcium concentration produced by voltage-gated calcium entry, the
calcium dependence of large dense-cored vesicle fusion under condition
s of minimal stimulation is well approximated by a simple transfer fun
ction of summed calcium entry.