Effect of β_3-adrenoceptor activation on ventricle fibrillation threshold and effective refractory period in rats with heart failure

AIM: To observe the effect of β3-adrenoceptor (AR) on ventricle fibrillation threshold (VFT) and effective refractory period (ERP) in rats with heart failure.METHODS: Rats were randomized into control group and heart failure group. The expression of β3- AR mRNA was detected with RT-PCR. The VFT, ERP, left ventricle end-systolic pressure(LVESP),left ventricle end-diastolic pressure(LVEDP), +dp/dtmax and -dp/dtmax were measured at the same time with administration of BRL37344 (β3-AR agonist).RESULTS: ① Both the expression of β3-AR mRNA and the proportion (β3/β1+β2+β3) were increased in failure rats comparied with those in control rats (0.028 vs 0.011 and 5.4% vs 1.2%, P0.05). ② ERP was longer in rats with heart failure than that in control group (70.5 ms±5.5 ms vs 59.5 ms±6.4 ms, P0.05). No difference in ERP in rats with heart failure was observed before and after administration of BRL37344 (73.0 ms±4.8 ms vs 70.5 ms±5.5 ms, P0.05). ③ VFT was lower in rats with heart failure than that in control group (10.9 mV±0.8 mV vs 30.5 mV±1.3 mV, P0.05) and decreased obviously in rats with heart failure after administration of BRL37344 (7.1 mV±0.6 mV vs 10.9 mV±0.8 mV, P0.05). The decrease in VFT correlated with the effect of LVESP, +dp/dtmax, -dp/dtmax with BRL37344 and the expression of β3-AR mRNA (correlation coefficient: 0.788, 0.708, 0.759, 0.787; P0.05). CONCLUSION: The expression of β3-AR mRNA in left ventricle is obviously increased in rats with heart failure. The activation of β3-AR has no effect on ERP but can decrease VFT which correlates with the effect of β3-AR on LVESP, +dp/dtmax, -dp/dtmax and the expression of β3-AR mRNA.