Morning sickness is just the side effect of a new tachykinin that the placenta secretes to improve local blood flow

摘要

The tachykinins are an ancient family of important biologically active peptides that are usually restricted to neural tissue and have a variety of effects on the vasculature and the immune and endocrine systems, but they can also cause nausea and vomiting (Steinhoff et al. 2014). The tachykinin, endokinin, is expressed in many tissues throughout the body including the placenta and lung and in tumor cell lines derived from these tissues (Page et al. 2003). Thus, as its name suggests, it can behave as an endocrine hormone by being released into the blood stream. As the naturally secreted form of endokinin has been found in the placenta (Page et al. 2003), it would stimulate local tachykinin receptors to improve blood flow both in the placenta and uterus and may be involved in the further integrating vascularization that is important for efficient transfer of nutrients and gases. Unfortunately, this placental endokinin will also spill into the mother’s general circulation that would then stimulate the tachykinin receptors in the brain (Andrews & Rudd 2004) that are known to cause nausea/vomiting.