Abstract：
The baroreflex involves cardiovascular homeostatic mechanisms that buffer the system against acute deviations in arterial blood pressure. It is comprised of the cardiac limb which involves adjustments in heart rate and the peripheral limb which involves adjustments in vascular resistance. This negative feedback loop mechanism has been investigated in numerous species of adult vertebrates, however our understanding of the maturation and functional importance of the reflex in developing animals remains poorly understood. In egglaying species, our knowledge of this mechanism is limited to the domestic chicken embryo and the embryonic alligator. While each of these species possess a cardiac baroreflex prior to hatching, they differ in the timing when it becomes functional, with the embryonic chicken possessing the reflex at 90% of incubation, while the alligator possesses the reflex at 70% of incubation. In an effort to determine if bird species might share similar patterns of active baroreflex function, we studied embryonic emus (Dromiceius novaehollandiae). However, we hypothesized that emus would possess a pattern of baroreflex function similar to that of the American alligator given the emu embryo possesses functional vagal tone at 70% of incubation, possibly indicating a more mature collection of cardiovascular control mechanism than those found in embryonic chickens. Our findings illustrate that emu embryos possess a hypotensive baroreflex at 90% of incubation. Therefore, our data fail to support our original hypothesis. While only two species of birds have been studied in this context, it could indicate that baroreflex function is not essential for cardiovascular homeostasis in birds for the majority of in ovo development.
摘要：
压力反射涉及心血管稳态机制，该机制可以缓冲系统以抵抗动脉血压的急性偏差。它包括涉及心率调整的心脏肢体和涉及血管阻力调整的外周肢体。这种负反馈回路机制已经在许多成年脊椎动物中进行了研究，然而，我们对发育中动物反射的成熟和功能重要性的理解仍然知之甚少。在蛋类中，我们对这种机制的了解仅限于家鸡胚胎和鳄鱼胚胎。虽然这些物种在孵化前都有心脏压力反射，它们在发挥作用的时间上有所不同，胚胎鸡在90%的孵化过程中具有反射，而短吻鳄在70%的孵育时具有反射。为了确定鸟类是否可能具有类似的主动压力反射功能模式，我们研究了胚胎emus（Dromiceiusnovaehollandiae）。然而,我们假设emus具有类似于美国短吻鳄的压力反射功能，因为emu胚胎在70％的孵化时具有功能性迷走神经张力，可能表明心血管控制机制的收集比在胚胎鸡中发现的更成熟。我们的发现表明，emu胚胎在90％的孵育时具有低血压的压力反射。因此,我们的数据不能支持我们最初的假设。虽然在这种情况下只研究了两种鸟类，这可能表明压力反射功能对于大多数卵内发育的鸟类心血管稳态并不是必需的。
