Psychological stress-induced expression of endogenous substances with regulatory activity against GABA_A receptors and their role under pathophysiological state.

1.本研究结果表明，社会隔离应激导致小鼠戊巴比妥(PB)睡眠减少的部分机制是：(1)抑制GABA_A受体的神经类固醇(NS)增加，如硫酸孕烯醇酮；(2)易化GABA_A受体的NS，如别孕酮和异四氢脱氧皮质酮减少，或(Iii)两者均参与。除了对GABA_A受体具有调节活性的神经类固醇外，研究发现，具有反向BZD激动剂特性的内源性BZD受体配体也参与了社会隔离应激导致的小鼠PB睡眠减少。越参中具有抗应激活性的主要皂苷成分Majonoside-R2可逆转社会隔离应激引起的PB睡眠减少。这一作用可被孕烯醇酮硫酸酯拮抗，提示神经类固醇参与了大黄皂苷-R2.4的抗应激作用。应用原位杂交和RT-PCR技术，研究了脑内苯二氮卓类受体的内源性配体安定结合抑制物(DBI)的基因表达。与以前的报道一致，DBI mRNA在第三脑室区域和下丘脑有密集表达。RT-PCR实验显示，社会隔离应激引起下丘脑DBI基因表达下调，但在其他脑区未见表达，提示DBI和神经类固醇等内源性物质的表达和/或增加在长期社会心理应激诱导的脑功能病理生理学中起重要作用。

1. The data obtained in this reseach suggested that social isolation stress-induced decrease in pentobarbital (PB) sleep in mice is mediated partly by : i) an increase in neurosteroids (NS) such as pregnenolone sulfate with suppressive action on GABA_A receptors or ii) a decrease in NS such as allopregnanolone and allotetrahydrodeoxycorticosterone with facilitatory action on GABA_A receptors, or iii) both.2. In addition to neurosteroids with modulatory activity against GABA_A receptors, it was found that endogenous benzodiazepine (BZD) receptor ligands with an inverse BZD agonist property are also involved in social isolation stress-induced decrease in PB sleep in mace.3. Majonoside-R2, a major saponin component of Vietnamese ginseng with anti-stress activity, reversed the decrease in PB sleep caused by social isolation stress. This effect was antagonized by pregnenolone sulfate, suggesting that neurosteroids are involved in the anti-stress action of majonoside-R2.4.Gene expression of diazepam binding inhibitor (DBI), a putative endogenous ligand for benzodiazepine receptors in the brain, was investigated using in situ hybridization and RT-PCR techniques. Consistent with previous reports, DBI mRNA was densely expressed in the third ventricle area and hypothalamus. RT-PCR experiments revealed that social isolation stress caused the dicrease in DBI mRNA expression in the hypothalamus but not in other brain areas.These findings suggest that indection and/or increase of endogenous substances such as DBI and neurosteroids play important role in long-term socio-psychological stress-induced pathophysiology of brain funbtion.