Table 1.

Amplitude and frequency of action potentials recorded in bovine chromaffin cells before and during application of histamine (5 μm)

	Action potential amplitude (mV)				Action potential frequency (Hz)
	Before histamine	n	During histamine	n	Before histamine	During histamine
Perforated whole-cell
Control	64.5 ± 7.7	13 (132)	47.3 ± 4.2a	13 (242)	0.17 ± 0.07	0.31 ± 0.11a
Cs+ pipette solution	73.6 ± 4.9	5 (60)	66.5 ± 3.5a	5 (95)	0.04 ± 0.02	0.06 ± 0.03
Apamin (100 nm)	76.1 ± 6.7	6 (72)	51.1 ± 5.3a	6 (153)	0.20 ± 0.09	0.43 ± 0.14a
Glibenclamide (10 μm)	78.2 ± 7.1	3 (20)	52.5 ± 3.9	3 (50)	0.11 ± 0.11	0.28 ± 0.13a
Tetrodotoxin (10 μm)	33.1	1 (5)b	41.1 ± 5.4	6 (101)	0.08b	0.28 ± 0.08
Thapsigargin (100 nm)	61.9 ± 13.7	7 (53)	46.3 ± 13.6a	7 (112)	0.22 ± 0.05	0.47 ± 0.27
Ca2+-free solution	76.9 ± 26.0	2 (6)c	73.0 ± 2.9	3 (60)	0.01 ± 0.01	0.33 ± 0.22
Open-tip whole-cell
Control	85.95 ± 8.7	5 (27)	79.5 ± 7.9	5 (51)	0.14 ± 0.04d	0.14 ± 0.03d
					0.02 ± 0.02e	0.21 ± 0.17e

n values stated are the number of cells, with the total number of action potentials measured in parentheses.

^aSignificant difference before compared with during histamine, P < 0.05, Student's paired t test.

^bSpontaneous action potentials were only recorded in one of six cells in the presence of tetrodotoxin prior to application of histamine, but in all cells during histamine application.

^cSpontaneous action potentials were only recorded in two of four cells in the presence of Ca²⁺-free solution prior to application of histamine, and three of four cells during histamine application.

^dAverage action potential frequencies for cells in which histamine failed to cause a sustained depolarization in open-tip whole-cell configuration (three of seven cells).

^eAverage action potential frequencies for the cells in which histamine caused a sustained depolarization in open-tip whole-cell configuration and spontaneous action potentials were observed (two of four cells).