低渗刺激后大鼠视上核星形胶质细胞释放牛磺酸调节神经元的活动

目的:观察低渗刺激大鼠后,视上核(SON)内星形胶质细胞调节神经元活动的机制。方法:大鼠分为4组:(1)等渗对照组,经尾静脉注入生理盐水;(2)低渗刺激组,经尾静脉注入低渗盐水(0.83%葡萄糖+0.3%NaCl);(3)氟代柠檬酸(胶质细胞代谢抑制剂,fluorocitrate,FCA)+低渗刺激组,经侧脑室注射FCA(1 nmol/μl/只)2 h后,再经尾静脉注入低渗盐水;(4)甘珀酸(缝隙连接通道阻断剂,carbennoxolon,CBX)+低渗刺激组,经侧脑室注射CBX(50μg/只,10μg/lμl)2 h后,再经尾静脉注入低渗盐水。各组动物刺激后90 min,常规固定、取材、下丘脑连续冠状切片。应用抗牛磺酸(taurine,Tau)、抗加压素(vasopressin,VP)、抗甘氨酸受体(glycine recep-tor,GlyR)、抗缝隙连接蛋白(connexin43,Cx43)的抗体进行标记,以及Fos/胶质原纤维酸性蛋白(GFAP)双标记的免疫荧光染色方法,观察其在SON神经元和星形胶质细胞内的表达。结果:与对照组相比,低渗刺激组大鼠,SON内星形胶质细胞的胞体增大、突起变粗;Tau,Cx43和GFAP的平均荧光强度(MFI)增强,神经元上的GlyR表达增强,但VP和Fos的表达减弱。FCA,而不是CBX,明显减少星形胶质细胞的Tau,GFAP,Cx43的表达。FCA和CBX均可抑制神经元上的VP、GlyR、Fos阳性反应。结论:低渗刺激激活SON内星形胶质细胞,被激活的星形胶质细胞经Cx43半通道释放牛磺酸而抑制神经元的活性,减少VP的释放。

Hypotonic stimulation induced the astrocytes release taurine and regulate activation of the neurons in the supraoptic nucleus of rats

Objective: To observe the mechanism of the astrocytes regulating activation of the neurons induced by hypotonic stimulation in the supraoptic nucleus(SON) of rat.Methods: Rats 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%NaCl was injected into the caudal vein;(3)The fluorocitrate(FCA,a glial metabolic inhibitor)plus hypotonic stimulation group,FCA(1 nmol/μl/each rat) was delivered into the lateral ventricle,two hours late,hypotonic stimulation was preformatted in the same way as described above;(4) The carbennoxolon(CBX,a gap junction blocker) plus hypotonic stimulation group,CBX(50 μg/ each rat,10 μg/l μl) 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 conventional method,rats were perfused,the brains were removed immediately,and serial coronal forebrain sections through the hypothalamus were cut on a cryostat.The expression of vasopressin(VP),connexin43(Cx43),glycine receptor(GlyR),glial fibrillary acidic protein(GFAP) and Fos were observed in neurons and astrocytes in SON by using single-labeled and double-labeled immunofluorescence staining.Results: Hypotonic stimulation activated SON astrocytes,their cell bodies appeared hypertrophic,the process thickened,the mean fluorescent intensities(MFI) of anti-GFAP,anti-Tau and anti-Cx43 significantly increased.The expression of GlyR-immunoreactivity in SON neurons was increased,whereas expression of VP-and Fos-immunoreactivities was decreased.The responses of Tau,GFAP and Cx43 in the astrocytes were blocked by FCA,but not by CBX.Both FCA and CBX blocked VP-,GlyR-and Fos-immunoreactivities in the neurons.Conclusion: Hypoosmotic stimulation activates SON astrocytes,activated astrocytes release taurine via Cx43 hemichannel,and inhibit the release of VP from SON neurons.