Coincident detection of CSF Na+ and osmotic pressure in osmoregulatory neurons of the supraoptic nucleus

Behavioral and neuroendocrine responses underlying systemic osmoregulation are under the concerted control of centrally located osmoreceptors and cerebrospinal fluid (CSF) Na+ concentration (Na+]) detectors. Although the process underlying osmoreception is understood, the mechanism by which Na+] is detected and integrated with cellular information derived from osmoreceptors is unknown. Here, we show that shifts in extracellular Na+] (Na+]0) cause proportional changes in the relative Na+ permeability of mechanosensitive cation channels responsible for signal transduction in the osmosensory neurons of the supraoptic nucleus. This effect causes the generation of Na+ specific receptor potentials under isotonic conditions and modulates osmoreceptor potentials and electrical responsiveness during osmotic perturbation. These results provide a cellular basis for Na+-sensing and for the coordinated detection of CSF Na+] and osmolality in central osmoregulatory neurons.