Breath-to-breath hypercapnic response in neonatal rats: temperature dependency of the chemoreflexes and potential implications for breathing stability
Breath-to-breath hypercapnic response in neonatal rats: temperature dependency of the chemoreflexes and potential implications for breathing stability
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DOI：
10.1152/ajpregu.91011.2008
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发表时间：
2009-07-01
影响因子：
2.8
通讯作者：
Frappell, Peter B.
中科院分区：
文献类型：
--
作者：
Cummings, Kevin J.;Frappell, Peter B.
Cummings KJ，Frappell PB.新生大鼠的呼吸-呼吸高碳酸反应：化学反射的温度依赖性和呼吸稳定性的潜在意义。Am J Physiol Regul Integr Comp Physiol 297：R124-R134，2009。首次发表于2009年5月6日; doi：10.1152/ajpregu.91011.2008。新生儿的呼吸因温暖的温度而不稳定。我们假设，在未麻醉，完整的新生大鼠，体温（T-B）影响外周化学反射反应（PCR反应）高碳酸血症。为了测试这一点，我们向出生后第4-5天（P4-P5）的大鼠提供了空气中8%CO2的方波挑战，这些大鼠被保持在30 ℃的T-B下（冷组，n = 11），33 ℃ 35 ℃热中性区组[TNZ组，n = 11]，同时用呼吸速度计和面罩直接测量通气量（点E上的（V））。用8% CO2平衡空气或高氧（n = 10）对冷动物进行攻击，以确定PCR反应。对30次室内空气呼吸和1分钟CO2挑战的每次呼吸进行呼吸-呼吸分析。正如预期的那样，较热的T-B与室内空气中不稳定的呼吸模式相关：TNZ动物的（V）对点E的变异系数（（V）对点E的CV%）是保持在较冷T-B的动物的两倍（P < 0.001）。高氧显著抑制了前10次呼吸（或类似于4s）的高碳酸血症性反应，表明该域由PCR反应主导。与低温动物相比，TNZ动物的PCR反应（P = 0.03）和总反应（P = 0.04）显著更高。总反应与（V）/点CO2呈显著负相关（R-2 = 0.53; P < 0.001）。呼吸稳定性与总反应呈正相关（R-2 = 0.36; P < 0.001），在较小程度上与PCR反应呈正相关（R-2 = 0.19; P = 0.01），与点CO2（V）呈负相关（R-2 = 0.34; P < 0.001）。ANCOVA证实单独T-B对呼吸稳定性有显著影响（P < 0.01），（V）对点CO2（P = 0.41）、PCR反应（P = 0.82）或总（V）对点E反应（P = 0.08）没有独立影响。我们的数据表明，在出生后的早期，CO2的化学反射反应的高度影响T-B，而与呼吸稳定性，是不是稳定性的预测因素后，占T-B的独立效果。
Cummings KJ, Frappell PB. Breath-to-breath hypercapnic response in neonatal rats: temperature dependency of the chemoreflexes and potential implications for breathing stability. Am J Physiol Regul Integr Comp Physiol 297: R124-R134, 2009. First published May 6, 2009; doi:10.1152/ajpregu.91011.2008.-The breathing of newborns is destabilized by warm temperatures. We hypothesized that in unanesthetized, intact newborn rats, body temperature (T-B) influences the peripheral chemoreflex response (PCR response) to hypercapnia. To test this, we delivered square-wave challenges of 8% CO2 in air to postnatal day 4-5 (P4-P5) rats held at a T-B of 30 degrees C (Cold group, n = 11), 33 degrees C (Cool group, n = 10), and 35 degrees C thermoneutral zone group [thermoneutral zone (TNZ) group, n = 11], while measuring ventilation ((V) over dot E) directly with a pneumotach and mask. Cool animals were challenged with 8% CO2 balanced in either air or hyperoxia (n = 10) to identify the PCR response. Breath-to-breath analysis was performed on 30 room air breaths and every breath of the 1-min CO2 challenge. As expected, warmer T-B was associated with an unstable breathing pattern in room air: TNZ animals had a coefficient of variation in (V) over dot E ((V) over dot E CV%) that was double that of animals held at cooler T-B (P < 0.001). Hyperoxia markedly suppressed the hypercapnic ventilatory response over the first 10 breaths (or similar to 4s), suggesting that this domain is dominated by the PCR response. The PCR response (P = 0.03) and total response (P = 0.04) were significantly greater in TNZ animals compared with hypothermic animals. The total response had a significant, negative relationship with (V) over dot CO2 (R-2 = 0.53; P < 0.001). Breathing stability was positively related to the total response (R-2 = 0.36; P < 0.001) and to a lesser extent, the PCR response (R-2 = 0.19; P = 0.01) and was negatively related to (V) over dot CO2 (R-2 = 0.34; P < 0.001). ANCOVA confirmed a significant effect of T-B alone on breathing stability (P < 0.01), with no independent effects of (V) over dot CO2 (P = 0.41), the PCR response (P = 0.82), or the total (V) over dot E response (P = 0.08). Our data suggest that in early postnatal life, the chemoreflex responses to CO2 are highly influenced by T-B, and while related to breathing stability, are not predictors of stability after accounting for the independent effect of T-B.