Water Deprivation Evokes Changes in Glutamate Neurotransmission in Magnocellular Neurosecretory Cells of the Hypothalamic Supraoptic Nucleus

The regulation of vasopressin (AVP) is critical to maintaining body fluid homeostasis, and the activity of magnocellular neurosecretory cells (MNCs) correlates to the amount of hormone secreted into circulation. The balance of excitatory and inhibitory inputs are important elements of activity, however the mechanisms leading to changes in AVP regulation are not fully understood. Water deprivation (WD), a physiological challenge, was used to examine changes in excitatory neurotransmission in MNCs, measured using patch-clamp electrophysiology and ratiometric calcium imaging. An adeno-associated virus construct containing an AVP gene promoter and enhanced green fluorescent protein (EGFP) reporter allowed us to distinguish vasopressin from oxytocin MNCs. In EGFP-labeled cells (GFP+ MNCs), 48-hour WD treatment resulted in significantly greater mini-excitatory postsynaptic current (mEPSC) amplitude as compared to euhydrated animals. GFP+ MNCs exhibited greater calcium mobilization than GFP- MNCs independent of treatment group, and we observed less cytosolic calcium mobilization with 48H WD treatment.