Stauss Harald M, Rarick Kevin R, Deklotz Richard J, Sheriff Don D
Dept. of Integrative Physiology, The Univ. of Iowa, 410 Field House, Iowa City, IA 52242, USA.
Am J Physiol Heart Circ Physiol. 2009 May;296(5):H1607-16. doi: 10.1152/ajpheart.01262.2008. Epub 2009 Feb 27.
Previously, we demonstrated that very low-frequency (VLF) blood pressure variability (BPV) depends on voltage-gated L-type Ca(2+)-channels, suggesting that autoregulation of blood flow and/or myogenic vascular function significantly contributes to VLF BPV. To further substantiate this possibility, we tested the hypothesis that the frequency response characteristic of whole body autoregulation of blood flow is consistent with the frequency range of VLF BPV (0.02-0.2 Hz) in rats. In anesthetized rats (n = 11), BPV (0.016-0.5 Hz) was induced by computer-regulated cardiac pacing while blood pressure, heart rate, and cardiac output (CO) were recorded during control conditions (NaCl, 1 ml/h iv) and during alpha(1)-adrenergic receptor stimulation (phenylephrine, 1 mg.ml(-1).h(-1) iv) that has been reported to facilitate myogenic vascular function. Baroreceptor-heart rate reflex responses were elicited to confirm a functional baroreflex despite anesthesia. During control conditions, transfer function analyses between mean arterial pressure (MAP) and CO, and between MAP and total vascular conductance (CO/MAP) indicated autoregulation of blood flow at 0.016 Hz, passive vascular responses between 0.033 and 0.2 Hz, and vascular responses compatible with baroreflex-mediated mechanisms at 0.333 and 0.5 Hz. Stimulation of alpha(1)-adrenergic receptors extended the frequency range of autoregulation of blood flow to frequencies up to 0.033 Hz. In conclusion, depending on sympathetic vascular tone, whole body autoregulation of blood flow operates most effectively at frequencies below 0.05 Hz. This frequency range overlaps with the lower end of the frequency band of VLF BPV in rats. Baroreceptor reflex-like mechanisms contribute to LF (0.2-0.6 Hz) but not VLF BPV-induced vascular responses.
此前，我们证明极低频（VLF）血压变异性（BPV）依赖于电压门控L型Ca（2+）通道，这表明血流的自动调节和/或肌源性血管功能对VLF BPV有显著贡献。为了进一步证实这种可能性，我们检验了以下假设：大鼠全身血流自动调节的频率响应特性与VLF BPV（0.02 - 0.2 Hz）的频率范围一致。在麻醉大鼠（n = 11）中，通过计算机调节心脏起搏诱导BPV（0.016 - 0.5 Hz），同时在对照条件下（静脉注射1 ml/h NaCl）以及在据报道可促进肌源性血管功能的α（1）-肾上腺素能受体刺激（静脉注射去氧肾上腺素，1 mg·ml（-1）·h（-1））期间记录血压、心率和心输出量（CO）。尽管处于麻醉状态，仍引发压力感受器 - 心率反射反应以确认功能性压力反射。在对照条件下，平均动脉压（MAP）与CO之间以及MAP与总血管电导（CO/MAP）之间的传递函数分析表明，在0.016 Hz时存在血流自动调节，在0.033至0.2 Hz之间存在被动血管反应，在0.333和0.5 Hz时存在与压力反射介导机制相符的血管反应。刺激α（1）-肾上腺素能受体将血流自动调节的频率范围扩展至高达0.033 Hz的频率。总之，取决于交感神经血管张力，全身血流自动调节在低于0.05 Hz的频率下最有效。该频率范围与大鼠VLF BPV频段的低端重叠。压力感受器反射样机制对低频（0.2 - 0.6 Hz）有贡献，但对VLF BPV诱导的血管反应无贡献。
