Furthermore, Nakayama et al. established that achieving serum osmolality >350 mOsm/L with continuous infusion of conivaptan, a V1 and V2 antagonist, attenuated cerebral edema [45], thereby demonstrating that the effect of aquaporin-4 to decrease cerebral edema occurs through osmotic gradients, as opposed to a specific intravenous osmotic agent itself (e.g., 7.5% hypertonic saline). The gene discussed is AQP4; the disease is brain edema.