Silva Fernanda C, Paiva Franciny A, Müller-Ribeiro Flávia C, Caldeira Henrique M A, Fontes Marco A P, de Menezes Rodrigo C A, Casali Karina R, Fortes Gláucia H, Tobaldini Eleonora, Solbiati Monica, Montano Nicola, Dias Da Silva Valdo J, Chianca Deoclécio A
Laboratory of Cardiovascular Physiology, Department of Biological Sciences, Institute of Exact and Biological Sciences, Federal University of Ouro PretoOuro Preto, Brazil; Graduate Program in Biological Sciences - CBIOL/NUPEB, Federal University of Ouro PretoOuro Preto, Brazil.
Laboratory of Hypertension, Institute of Biological Sciences, Department of Physiology and Biophysics, Federal University of Minas Gerais Belo Horizonte, Brazil.
Front Physiol. 2016 Jul 26;7:305. doi: 10.3389/fphys.2016.00305. eCollection 2016.
A low resting heart rate (HR) would be of great benefit in cardiovascular diseases. Ivabradine-a novel selective inhibitor of hyperpolarization-activated cyclic nucleotide gated (HCN) channels- has emerged as a promising HR lowering drug. Its effects on the autonomic HR control are little known. This study assessed the effects of chronic treatment with ivabradine on the modulatory, reflex and tonic cardiovascular autonomic control and on the renal sympathetic nerve activity (RSNA). Male Wistar rats were divided in 2 groups, receiving intraperitoneal injections of vehicle (VEH) or ivabradine (IVA) during 7 or 8 consecutive days. Rats were submitted to vessels cannulation to perform arterial blood pressure (AP) and HR recordings in freely moving rats. Time series of resting pulse interval and systolic AP were used to measure cardiovascular variability parameters. We also assessed the baroreflex, chemoreflex and the Bezold-Jarish reflex sensitivities. To better evaluate the effects of ivabradine on the autonomic control of the heart, we performed sympathetic and vagal autonomic blockade. As expected, ivabradine-treated rats showed a lower resting (VEH: 362 ± 16 bpm vs. IVA: 260 ± 14 bpm, p = 0.0005) and intrinsic HR (VEH: 369 ± 9 bpm vs. IVA: 326 ± 11 bpm, p = 0.0146). However, the chronic treatment with ivabradine did not change normalized HR spectral parameters LF (nu) (VEH: 24.2 ± 4.6 vs. IVA: 29.8 ± 6.4; p > 0.05); HF (nu) (VEH: 75.1 ± 3.7 vs. IVA: 69.2 ± 5.8; p > 0.05), any cardiovascular reflexes, neither the tonic autonomic control of the HR (tonic sympathovagal index; VEH: 0.91± 0.02 vs. IVA: 0.88 ± 0.03, p = 0.3494). We performed the AP, HR and RSNA recordings in urethane-anesthetized rats. The chronic treatment with ivabradine reduced the resting HR (VEH: 364 ± 12 bpm vs. IVA: 207 ± 11 bpm, p < 0.0001), without affecting RSNA (VEH: 117 ± 16 vs. IVA: 120 ± 9 spikes/s, p = 0.9100) and mean arterial pressure (VEH: 70 ± 4 vs. IVA: 77 ± 6 mmHg, p = 0.3293). Our results suggest that, in health rats, the long-term treatment with ivabradine directly reduces the HR without changing the RSNA modulation and the reflex and tonic autonomic control of the heart.
静息心率较低对心血管疾病大有裨益。伊伐布雷定——一种新型的超极化激活环核苷酸门控(HCN)通道选择性抑制剂——已成为一种有前景的降低心率药物。其对自主心率控制的影响鲜为人知。本研究评估了伊伐布雷定长期治疗对调节性、反射性和紧张性心血管自主控制以及肾交感神经活动(RSNA)的影响。雄性Wistar大鼠分为2组,连续7或8天接受腹腔注射溶媒(VEH)或伊伐布雷定(IVA)。大鼠进行血管插管,以便在自由活动的大鼠中记录动脉血压(AP)和心率。静息脉搏间期和收缩期AP的时间序列用于测量心血管变异性参数。我们还评估了压力反射、化学反射和贝佐尔德-雅里什反射敏感性。为了更好地评估伊伐布雷定对心脏自主控制的影响,我们进行了交感和迷走自主神经阻滞。不出所料,接受伊伐布雷定治疗的大鼠静息心率(VEH:362±16次/分钟 vs. IVA:(260\pm14)次/分钟,(p = 0.0005))和固有心率(VEH:369±9次/分钟 vs. IVA:326±11次/分钟,(p = 0.0146))较低。然而,伊伐布雷定长期治疗并未改变标准化心率频谱参数低频(nu)(VEH:24.2±4.6 vs. IVA:29.8±6.4;(p>0.05));高频(nu)(VEH:75.1±3.7 vs. IVA:69.2±5.8;(p>0.05)),任何心血管反射,也未改变心率的紧张性自主控制(紧张性交感迷走指数;VEH:0.91±0.02 vs. IVA:0.88±0.03,(p = 0.3494))。我们在乌拉坦麻醉的大鼠中进行了AP、心率和RSNA记录。伊伐布雷定长期治疗降低了静息心率(VEH:364±12次/分钟 vs. IVA:207±11次/分钟,(p<0.0001)),但不影响RSNA(VEH:117±16 vs. IVA:120±9个脉冲/秒,(p = 0.9100))和平均动脉压(VEH:70±4 vs. IVA:77±6 mmHg,(p = 0.3293))。我们的结果表明,在健康大鼠中,伊伐布雷定长期治疗直接降低心率,而不改变RSNA调节以及心脏的反射性和紧张性自主控制。