Table 2.

Effects of prolonged applications of ivabradine on AP parameters of rabbit sino-atrial node preparations

	Rate	APA	dV/dt max	MDP	TOP	DDR	APD50
Control	211±6	74.4±3.2	5.3±0.9	−64.1±1.9	−51.7±1.7	84.8±9.7	82.5±3.1
Vehicle	214±7	76.9±5.1	7.4±1.9	−66.0±2.4	−51.4±1.8	101.3±8.9	82.2±1.9
Control	221±3	72.2±4.1	5.7±1.4	−63.1±2.5	−50.9±4.0	115.2±8.7	83.4±3.4
Ivabradine 0.1 μM	199±1*	73.4±0.7	4.3±0.8	−64.3±1.7	−52.4±2.7	62.0±13.4*	94.0±4.4*
Control	228±7	78.0±3.0	10.5±1.8	−65.9±1.9	−51.0±1.5	103.7±10.3	77.1±2.8
Ivabradine 0.3 μM	196±5*	88.6±2.8	18.1±5.4	−73.9±1.9	−64.2±2.5*	40.1±2.6*	82.2±3.5*
Control	224±8	67.2±3.0	3.9±1.1	−61.1±2.6	−52.3±3.4	91.2±7.9	82.4±3.4
Ivabradine 1 μM	185±7*	78.2±1.8*	3.7±1.3	−67.0±2.6*	−59.0±3.5*	42.0±6.9*	92.4±3.3*

Abbreviations: APA, action potential amplitude (mV); APD50, action potential duration at 50% of total repolarization (ms); DDR, diastolic depolarization rate (mV s⁻¹); MDP, maximal diastolic potential (mV); dV/dt max, maximal upstroke velocity (V s⁻¹); Rate, spontaneous pacemaker rate (APs min⁻¹); TOP, take-off potential (mV).

Spontaneous APs recorded at the beginning of the experiments (control) and at the end of exposure to ivabradine, that is 3 h for 0.1 μM and vehicle, 2 h for 0.3 μM and 1.5 hours for 1 μM. Values are expressed as means±s.e.m. for five experiments per groups.

^*P⩽0.05 vs vehicle group (Student's unpaired t-test preceded by a Welch test when needed).