This image shows vasopressin-releasing neurons of the supraoptic nucleus (magenta) expressing Fos (cyan) following activation by systemic sodium mediated in part by the ion channel Nax. These neurons maintain homeostasis in response to hypertonicity and hypernatremia. Nax expression on brain structures called sensory circumventricular organs is required for maintenance of body fluid balance, but whether the expression of this channel in vasopressin neurons plays a role in hypertonicity or hypernatremia homeostatic responses is unknown. Salgado-Mozo et al. used the depicted method and others to investigate this. See their manuscript on pages 8306–8316 for more information. Cover image: Sandra Salgado-Mozo.