Tulen J H, Smeets F M, Man in 't Veld A J, van Steenis H G, van de Wetering B J, Moleman P
Department of Psychiatry, University Hospital Rotterdam Dijkzigt, The Netherlands.
J Cardiovasc Pharmacol. 1993 Jul;22(1):112-9.
Effects of four intravenous (i.v.) doses (0.25, 0.5, 1, and 2 micrograms/kg) of the alpha 2-adrenoceptor agonist clonidine (CLO) were studied in 7 normotensive male volunteers in a placebo-controlled double-blind randomized design to evaluate the role of alpha 2-adrenoceptors in spontaneous short-term cardiovascular fluctuations. Heart rate (HR), systolic and diastolic blood pressure (SBP, DBP; Finapres device), stroke volume (SV) and total peripheral resistance (TPR) were monitored for 1 h after infusion of CLO while the subjects rested in a semirecumbent position. For HR, SBP, and DBP, power spectra and variation coefficients were calculated for consecutive time segments of 2.5 min. Power density was assessed for three frequency bands: low (LFB, 0.02-0.06 Hz), mid (MFB, 0.07-0.14 Hz), and high (HFB, 0.15-0.40 Hz). Per time-segment, baroreflex sensitivity (BRS) was estimated as the gain (or modulus) in MFB between systolic pressure values and R-R interval times. Decreases in mean levels of SBP and DBP were observed within 15 min after infusion of > or = 0.5 micrograms/kg CLO. HR first showed a slight increase 15 min after infusion of 0.5, 1, and 2 micrograms/kg CLO, but decreased subsequently as in all doses, including placebo. SV and TPR decreased after a dose of 2 micrograms/kg CLO. LFB and MFB power of HR were reduced after 2 micrograms/kg CLO, but only during the first 30 min after infusion; during this period, respiratory depth was also diminished, indicating that these effects may reflect a reduction in sympathetic outflow as well as a reduction in vagal outflow.(ABSTRACT TRUNCATED AT 250 WORDS)
在一项安慰剂对照的双盲随机设计中，对7名血压正常的男性志愿者研究了四种静脉注射剂量（0.25、0.5、1和2微克/千克）的α2 -肾上腺素能受体激动剂可乐定（CLO）的作用，以评估α2 -肾上腺素能受体在自发性短期心血管波动中的作用。在输注CLO后，受试者半卧位休息1小时，监测心率（HR）、收缩压和舒张压（SBP、DBP；采用Finapres设备）、每搏输出量（SV）和总外周阻力（TPR）。对于HR、SBP和DBP，计算2.5分钟连续时间段的功率谱和变异系数。评估三个频段的功率密度：低频（LFB，0.02 - 0.06赫兹）、中频（MFB，0.07 - 0.14赫兹）和高频（HFB，0.15 - 0.40赫兹）。每个时间段，压力反射敏感性（BRS）估计为收缩压值与R - R间期时间之间MFB的增益（或模量）。输注≥0.5微克/千克CLO后15分钟内观察到SBP和DBP平均水平下降。输注0.5、1和2微克/千克CLO后15分钟，HR首先略有增加，但随后在所有剂量（包括安慰剂）下均下降。输注2微克/千克CLO后，SV和TPR下降。输注2微克/千克CLO后，HR的LFB和MFB功率降低，但仅在输注后的前30分钟内；在此期间，呼吸深度也减小，表明这些影响可能反映交感神经输出减少以及迷走神经输出减少。（摘要截断于250字）
