Sato K, Chatani F, Ando T
Drug Safety Research Laboratories, Takeda Chemical Industries, Limited, Osaka, Japan.
Chronobiol Int. 1999 Mar;16(2):171-83. doi: 10.3109/07420529909019084.
Circadian rhythmicity in the hypotensive effects of sodium nitroprusside (SNP) was determined to characterize the rhythmicity in hypotension mediated by nitric oxide (NO) donor in rats. When SNP was infused for 90 seconds every hour for 48 hours and the mean blood pressure was determined automatically by telemetry under light-dark conditions (LD), the degree of SNP-induced hypotension was shown to be minimal at the onset of the dark phase and to have marked circadian rhythmicity. The possible relationship between the circadian rhythm of the sympathetic nervous system (SNS) activity and SNP-induced hypotension was examined under LD conditions. The SNS activity assessed by blood pressure beat-to-beat variability analysis using the maximum entropy method (MEM) was higher at the preinfusion time at the onset of the dark phase than during the middle of the light phase. In addition, pretreatment with an alpha-blocker, phentolamine, followed by SNP infusion at the onset of the dark phase restored the SNP-induced hypotension and consequently dampened the daily variation in the degree of SNP-induced hypotension. The circadian rhythmicity determined by MEM was weakened, but persisted, in constant dark conditions (DD), suggesting partial involvement of endogenously driven circadian rhythms. In conclusion, the hypotensive effect of hourly infused SNP in rats was decreased in the dark phase in LD, especially at the onset of the dark phase, and clearly showed circadian rhythmicity in both LD and DD. The SNP-induced hypotension may be affected by rapid activation of the SNS at the onset of the dark phase in LD, and regulation of the circadian rhythm in SNP-induced hypotension in rats may be affected by both exogenous light stimuli and the endogenous biological clock.
为了表征一氧化氮（NO）供体介导的大鼠低血压节律，研究了硝普钠（SNP）降压作用的昼夜节律性。当每小时输注SNP 90秒，持续48小时，并在明暗条件（LD）下通过遥测自动测定平均血压时，SNP诱导的低血压程度在暗期开始时最小，并具有明显的昼夜节律性。在LD条件下，研究了交感神经系统（SNS）活动的昼夜节律与SNP诱导的低血压之间的可能关系。使用最大熵方法（MEM）通过逐搏血压变异性分析评估的SNS活动在暗期开始时的输注前时间高于明期中间。此外，在暗期开始时用α受体阻滞剂酚妥拉明预处理，然后输注SNP，可恢复SNP诱导的低血压，从而减弱SNP诱导的低血压程度的每日变化。在持续黑暗条件（DD）下，由MEM确定的昼夜节律性减弱，但仍然存在，这表明内源性驱动的昼夜节律部分参与其中。总之，在LD条件下，每小时输注SNP对大鼠的降压作用在暗期降低，尤其是在暗期开始时，并且在LD和DD中均明显表现出昼夜节律性。LD条件下暗期开始时SNS的快速激活可能会影响SNP诱导的低血压，大鼠中SNP诱导的低血压的昼夜节律调节可能受外源性光刺激和内源性生物钟的影响。
