This is only one aspect of the so-called brain-body cross-talking, but an important one: on the one hand the aspects of the composition of the infused fluids, such as osmolarity, can interfere with the brain, whereas on the other hand, brain disorders such as diabetes insipidus and inappropriate secretion of antidiuretic hormone (SIADH) can cause severe disturbances in the plasma composition [1,2]. The gene discussed is AVP; the disease is inappropriate ADH syndrome.