The lungs also start to release a small peptide called bradykinin which constricts the smooth muscle wall of the ductus arteriosus and helps the process along.

肺也开始释放缓激肽，收缩动脉导管的平滑肌，有助于动脉导管闭合。

This ischemia is thought to trigger release of adenosine, bradykinin, and other molecules that stimulate nerve fibers in the myocardium that result in the sensation of pain.

心内膜下缺血被认为启动腺苷、缓激肽等分子的释放，这些分子刺激心肌层神经末梢，导致痛觉产生。