Alpha-adrenergic-mediated reflex responses to induced muscular contraction are changed with age in dogs.
Alpha-adrenergic-mediated reflex responses to induced muscular contraction are changed with age in dogs.
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α-肾上腺素能介导的对诱导肌肉收缩的反射反应随着狗的年龄而变化。
DOI：
10.1152/ajpheart.1993.265.6.h1899
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发表时间：
1993
期刊：
影响因子：
--
通讯作者：
Haidet,GC
中科院分区：
文献类型：
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作者：
Haidet,GC
衰老显著影响麻醉犬对诱导肌肉收缩的反射性心血管（CV）反应。为了进一步研究α -肾上腺素能介导的肌肉收缩反应的年龄相关变化是否有助于这些先前报道的与高龄相关的CV反应的年龄相关变化，我们在α -氯氯糖麻醉下，对年龄较大（8-14岁）和年龄较小（2-3岁）的比格犬进行了α - ab阻断（α - ab）前后的基线和后肢收缩（HLC）期间的血流动力学和区域血流（BF）反应进行了评估。与年龄无关，α - ab联合酚妥拉明可显著（P < 0.05）降低hplc前和期间的平均动脉压。然而，在α - ab之前观察到的系统性血管阻力、心输出量和卒中容量反应的年龄相关差异，在酚妥拉明后被消除，因为这些对α - ab的反应都存在年龄相关差异。无论年龄大小，8个腹部器官中有7个在α - ab后的基线BF（微球）不变。然而，在HLC期间，年轻犬的8个腹部器官中有7个器官的BF减少在α - ab后减弱，但在老年犬的这些器官中没有减少，这表明老年犬在HLC期间这些器官中α介导的血管收缩减弱。此外，在α - ab之前，所有8个腹部器官的联合BF减少的年龄相关差异在α - ab之后被消除。最后，无论年龄如何，α - ab后，4块收缩肌肉中2块的BF增加，以及所有4块收缩肌肉的血流量的综合增加都有所减弱。这些结果表明，α -阻断消除了在α - ab之前观察到的CV对HLC反应的许多年龄相关差异，并表明α -肾上腺素能介导的对HLC的反应随着年龄的变化而变化。
Aging significantly affects reflex cardiovascular (CV) responses to induced muscular contraction in anesthetized dogs. To further investigate whether age-related changes in alpha-adrenergic-mediated responses to muscular contraction contribute to these previously reported age-related changes in CV responses associated with advanced age, hemodynamic and regional blood flow (BF) responses at baseline and during hindlimb contraction (HLC) were evaluated both before and after alpha-blockade (alpha-AB) in older (8-14 yr old) and in younger (2-3 yr old) beagles during alpha-chloralose anesthesia. alpha-AB with phentolamine resulted in significant (P < 0.05) reductions in mean arterial pressure before and during HLC, regardless of age. However, age-related differences in the systemic vascular resistance, cardiac output, and stroke volume responses to HLC, observed before alpha-AB, were eliminated after phentolamine as the result of an age-related difference in each of these responses to alpha-AB. Baseline BF (microspheres) was unchanged after alpha-AB in seven of eight abdominal organs, regardless of age. However, reductions in BF during HLC were attenuated in seven of eight abdominal organs in the younger dogs after alpha-AB, but in none of these organs in the older dogs, indicative of diminished alpha-mediated vasoconstriction in these organs in the older dogs during HLC. Furthermore, the age-related difference in the combined BF reduction to all eight abdominal organs before alpha-AB was eliminated after alpha-AB. Finally, BF increases to two of four contracting muscles, as well as the combined increase in blood flow to all four contracting muscles, were attenuated after alpha-AB, regardless of age. These results demonstrate that alpha-blockade eliminates many of the age-related differences in CV responses to HLC observed before alpha-AB and suggest that alpha-adrenergic-mediated responses to HLC change with age in beagles.