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Objective This study is to observe the mechanism of the astrocytes regulating activation of the neurons induced by hypotonic stimulation in rat supraoptic nucleus.Methods Rats used for this study were divided into four groups: (1) The isotonic control group, physiological saline was injected into the caudal vein; (2) The hypotonic stimulation group, a solution containing 0.83% glucose and 0.3% NaC1 was injected into the caudal vein; (3) The fluorocitrate (FCA) plus hypotonic stimulation group, FCA was delivered into the lateral ventricle, two hours late, hypotonic stimulation was preformatted in the same way asdescribed above; (4) The carbennoxolon (CBX) + hypotonic stimulation group, CBX was injected into the lateral ventricle, two hours late, hypotonic stimulation was preformatted in the same way as described above.At 90 min after hypotonic stimulation, by using convention method, rats were perfused, the brains were removed immediately, and serial coronal forebrain sections through the hypothalamus were cut on a cryostat.Four sets of six serial sections through the SON from each rat were collected.By using single labeled and double labeled immunofluorescence staining method, we observed the expression of vasopressin (VP), connexin43 (Cx43), glycine receptor (GlyR), glial fibrillary acidic protein (GFAP) and Fos in neurons and astrocytes in SON.Results Hypotonic stimulation activated SON astrocytes, their cell bodies appeared hypertrophic, the process thickened, the MFI of GFAP, Tau and Cx43 significantly increased, this response was blocked by FCA, but not by CBX.GlyR positive SON neurons were increased, FCA and CBX blocked ClyR increase, while Fos and VP positive neurons were decreased compared isotonic stimulation group.Conclusion Hypoosmotic stimulation activated SON astrocytes, activated astrocytes release taurine via Cx43 hemichannel, and inhibit the release of VP from SON neurons.