Table 1.

Effect of [K⁺]_o reduction on membrane potential under various ionic compositions

	Test solution	n	Vrest(con) (mV)	Vrest (test) (mV)	ΔVrest (mV)	Percentage of firing (mV)
A	0.1 K+	99	−76.1 ± 0.3	−137.7 ± 2.3	19.8 ± 1.6	62.6
B	K+ free	11	−75.8 ± 0.6	−154.7 ± 4.3*	14.3 ± 3.1	54.5
C	0.1 K+	26	−74.3 ± 0.9	−144.0 ± 4.0	26.4 ± 3.0	100.0
	La3+, 0.1 K+	26	−75.5 ± 0.8	−157.6 ±1.3 *	12.1 ± 1.2 *	3.8
D	NMDG, 0.1 K+	12	−73.4 ± 0.8	−144.2 ± 4.8	19.2 ± 2.8	75.0
E	Asp, 0.1 K+	9	−75.4 ± 1.0	−146.4 ± 5.8	23.1 ± 5.4	77.8
F	10 EGTAi, 0.1 K+	27	−73.0 ± 0.3	−134.2 ± 4.5	26.1 ± 4.4	70.4
G	10 BAPTAi, 0.1 K+	16	−74.4 ± 0.4	−147.0 ± 1.6 *	29.0 ± 4.9	75.0

Test solutions in A–F were introduced after normal Tyrode solution. n, number of experiments; V_rest (con), resting membrane potential measured as the most negative potential (V_rest) in normal Tyrode solution given by means ±s.e.m.; V_rest (test), V_rest in the presence of low [K⁺]_o; ΔV_rest, depolarization amplitude as the largest positive deflection from V_rest; percentage of firing, percentage of the trials associated with firing of action potentials. 0.1 K⁺, 0.1 mm[K⁺]_o; La³⁺, 0.1 mm La³⁺; Asp, aspartate; 10 EGTA_i, in the presence of 10 mm EGTA in the pipette solution. 10 BAPTA_i, in the presence of 10mm BAPTA in the pipette solution.

^*Denotes the significant differences compared with A, except for C where control experiments were done using the same cells.