Table 2.

Effect of t-system Cl⁻ conductance on response to tetanic stimulation

Treatment	50 Hz peak (% max)	100 Hz/50 Hz (%)	50 Hz fade (%)	100 Hz fade (%)
3 mm Cl−	95.4 ± 1.3 (13)	94.5 ± 1.1 (13)	2.6 ± 0.7 (13)a	12.8 ± 3.4 (13)a,b
0 mm Cl−	96.3 ± 2.0 (17)	89.6 ± 1.9 (13)	11.4 ± 3.0 (17)a	36.7 ± 6.4 (13)a
3 mm Cl−+ phorbol	100 (5)	87.5 ± 2.2 (5)	9.2 ± 0.9 (5)	38.9 ± 5.9 (5)b
Paired data
3 mm Cl−	93.1 ± 4.9 (6)	92.0 ± 2.1 (6)*	4.3 ± 0.8 (6)*	8.0 ± 1.8 (6)*
3 mm Cl−+ 9-AC	95.6 ± 1.4 (6)	74.2 ± 6.6 (6)*	8.0 ± 2.3 (6)*	44.0 ± 7.8 (6)*
0 mm Cl−	99.7 ± 1.8 (4)	88.6 ± 3.8 (4)	11.3 ± 2.6 (4)	34.8 ± 4.0 (4)
0 mm Cl−+ 9-AC	98.3 ± 3.2 (4)	89.7 ± 3.1 (4)	13.4 ± 2.7 (4)	41.5 ± 3.5 (4)
Phorbol-treated
3 mm Cl−	100 (5)	87.5 ± 2.2 (5)	9.2 ± 0.9 (5)*	38.9 ± 5.9 (5)*
3 mm Cl−+ 9-AC	100 (5)	84.6 ± 2.3 (5)	13.3 ± 1.2 (5)*	67.1 ± 4.8 (5)*

Values are the mean (±s.e.m.), with number of fibres shown in parentheses, and similar arrangement as in Table 1. Responses elicited as in Fig. 3. Peak tetanic force at 50 Hz is expressed as a percentage of the maximum Ca²⁺-activated force measured in the same fibre following completion of all electrical stimulation; no statistical comparisons of this variable were made between different fibres. In the phorbol-treated fibres the 50 Hz tetanic force is given as 100% because the subsequently measured Ca²⁺-activated maximum was slightly lower. Peak tetanic force at 100 Hz was expressed relative to that at 50 Hz (denoted as 100 Hz/50 Hz); all of these values were significantly less than 100% (P < 0.05). ‘Fade’ was defined as the extent of force decline at the end of the 400 ms stimulation period relative to the peak of the tetanus. Values labelled with same superscript (a or b) were significantly different from each other by one-way ANOVA (as in Table 1); there were no significant differences between the cases with 0 mm Cl⁻ and with 3 mm Cl⁻+ phorbol.

^*Significant difference from indicated paired case (paired t test).