The aim of this study is to investigate the response of astrocytes (AS) in rat supraoptic nucleus (SON) to different osmolar stimulation and the mechanism of affecting the activation of neurons.The experiments were performed both in vivo and in vitro.The adult male Sprague-Dawley rats were divided into two groups,(1) The model group:rats under anesthesia,0.15 M NaCl-(IS),1.5 M NaCl-(HS) and 0.83% glucose + 0.3% NaCl-(LS) solution (5.5 ml/kg B.W) was injected into the femoral vein (i.v.) respectively,as IS,HS and LS models.(2) The secondgroup was pretreated with carbenoxolone (CBX,a gap junction blocker),or 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1,1-dioxide (TAG,a taurine antagonist) or artificial cerebrospinal fluid (ACSF) containing Ca2+ (2.5 mM).CBX,TAG or ACSF with Ca2+ was injected into the lateral ventriculum,after 2 h performed IS,HS and LS models.At 0 min before and 45min after IS,HS or LS i.v.injection,blood (5.5mL/kg,B.W.)was drew from the femoral veins of 5 rats in each group for radioimmunoassay of plasmic VP concentration.