Taurine is concentrated in glial cells in the hypothalamus and released in an osmo-dependent manner through volume-sensitive anion channels.Released taurine acts on glycine receptors on vasopressin neurons to control vasopressin secretion.Water channel AQP4 is abundant in astrocytes in osmosensory areas such as the supraoptic nucleus of hypothalamus.An HPLC-based method was established to quantify taurine release from isolated hypotha lamus tissues in wildtype and AQP4 knockout mice.Under the basal condition,there was no difference in taurine release from AQP4+/+ and AQP4-/-hypothalamuses.Taurine release from AQP4-/-hypothalamus under hypoosmotic stimulation was significantly lower than that from AQP4+/+ mice.AQP4 expression in the glial cells of the hypothalamus may play an important role in osmoregulation of taurine release and subsequent vasopressin secretion.