TABLE 1.

Quantitative and kinetic parameters of the amperometric spikes detected during exocytosis of bovine chromaffin cells

	All spikes n = 1390	Spikes W/O foot n = 905	Spikes W foot n = 485
Imax (pA)	25 ± 2	23 ± 2	30 ± 3
Q (fC)	950 ± 70	850 ± 90	1140 ± 110
t1/2 (ms)	32.5 ± 1.0	33.0 ± 1.0	32.0 ± 1.0
t20–90 (ms)	8.5 ± 0.5	8.5 ± 0.5	8.5 ± 0.5
Log (Q)	2.75 ± 0.01	2.65 ± 0.02	2.91 ± 0.02

(n = 32 cells from six different experiments), as a function of the presence (noted W for “with”) or absence (noted W/O for “without”) of a foot preceding the spike. I_max is the maximum oxidation current of the spike, Q is its total electrical charge, t_1/2 is its half-width, and t_20–90 is a measurement of its rise time, i.e., the delay between I = 20% of I_max and I = 90% of I_max. Mean values of log (Q) reported here are means of the Gaussian curves fitting the statistical distribution of all log (Q) values in each condition (Fig. 4) and not the direct average calculation of these values (see text for details). Catecholamines release from chromaffin cells was elicited by a 10-s injection of a Ba²⁺ 2 mM solution. Data are presented as mean ± SE.