Department of Biology, Bates College, Lewiston, ME 04240, USA.
Department of Biology, Bates College, Lewiston, ME 04240, USA.
Respir Physiol Neurobiol. 2023 Oct;316:104118. doi: 10.1016/j.resp.2023.104118. Epub 2023 Jul 17.
Chronic hypoxia (CH) from birth attenuates the acute hypoxic ventilatory response (HVR) in rats and other mammals, but CH is often reported to augment the HVR in adult mammals. To test the hypothesis that this transition - from blunting to augmenting the HVR - occurs in the third or fourth postnatal week in rats, juvenile and adult rats were exposed to normobaric CH (12% O) for 7 days and the HVR was assessed by whole-body plethysmography. No transition was observed, however, and the acute HVR was reduced by 61 - 85% across all ages studied. The failure to observe an augmented HVR in adult rats could not be explained by the substrain of Sprague Dawley rats used, the duration of the CH exposure, the order in which test gases were presented, the level of hypoxia used for CH and to assess the HVR, or the effects of CH on the metabolic response to hypoxia and the hypercapnic ventilatory response. A literature survey revealed several distinct patterns of ventilatory acclimatization to hypoxia (VAH) in adult rats, with most studies (77%) revealing a decrease or no change in the acute HVR after CH. In conclusion, the effects of CH on respiratory control are qualitatively similar across age groups, at least within the populations of Sprague Dawley rats used in the present study, and there does not appear to be one "typical" pattern for VAH in adult rats.
慢性低氧（CH）从出生开始会减弱大鼠和其他哺乳动物的急性低氧通气反应（HVR），但 CH 常被报道会增强成年哺乳动物的 HVR。为了测试以下假说，即在大鼠的第三或第四周，这种从抑制到增强 HVR 的转变会发生，幼年和成年大鼠暴露于常压低氧（12%O）7 天，并通过全身 plethysmography 评估 HVR。然而，没有观察到这种转变，并且在所有研究的年龄中，急性 HVR 降低了 61-85%。在成年大鼠中未能观察到增强的 HVR 不能用使用的 Sprague Dawley 大鼠亚系、CH 暴露的持续时间、测试气体呈现的顺序、用于 CH 和评估 HVR 的低氧水平或 CH 对代谢对低氧和高碳酸血症通气反应的影响来解释。文献调查显示，成年大鼠对低氧的通气适应（VAH）有几种不同的模式，大多数研究（77%）表明 CH 后急性 HVR 降低或没有变化。总之，CH 对呼吸控制的影响在不同年龄组之间在定性上是相似的，至少在本研究中使用的 Sprague Dawley 大鼠群体中是这样，而且成年大鼠的 VAH 似乎没有一种“典型”模式。
