Objective To investigate the mechanisms of astrocytes modulating neurons in rat supraoptic nucleus induced by hypotonic stimulation and the effect of 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1,1dioxide HCl(TAG,a antagonist for taurine) or carbenoxolone(CBX,a gap junction blocker)on the responses of astrocytes and neurons in SON.Methods Adult male Sprague-Dawley rats were divided into four groups: the control group was injected with 5.5ml/kg 0.9% NaCl solution into the caudal vein;the hypotonic group was injected with 5.5 ml/kg hypo-saline(0.83% glucose plus 0.3% NaCl);TAG + hypotonic and CBX + hypotonic groups were injected with TAG(100?mol/L) or CBX(10g/L) into the lateral ventricle respectively,and were injected 2 hours later with hypotonic saline into the caudal vein.With anti-Fos,anti-vasopressin(VP),anti-glycine receptor(GlyR),anti-glial fibrillary acidic protein(GFAP) and anti-connexin43(Cx43) immunofluorescent staining methods,the responses of neurons and astrocytes in SON were studied.Results In control rats,Fos-,VP-,and GlyR-expression in the neurons and GFAP-or Cx43-expression in the astrocytes were lower.In hypotonic rats,GFAP-,Cx43-and GlyR signals were more than those in control rats,while Fos-and VP-signals were less.Compared with those in hypotonic rats in TAG + hypotonic or CBX + hypotonic rats,GFAP-and Cx43-signals in the astrocytes were the same,GlyR-signals in the neurons decreased,and Fos-and VP-signals increased.Conclusion Hypotonic stimulation activates SON astrocytes,which then release taurine through gap junction signaling to the neurons and inhibit the release of VP from the neurons.