Molecular biological study of sleep-wake regulating mechanisms and its clinical implication

本课题组发现前列腺素（PG） d2具有促睡眠作用，PGE_2具有唤醒作用。本研究项目对这些影响的机制进行了研究。我们利用原位杂交和免疫细胞化学技术发现，脑PGD合成酶（脑中负责PGD_2合成的酶）在覆盖脑表面的轻脑膜以及产生脑脊液（CSF）的脉络丛中大量表达。有趣的是，在与国外研究小组的合作研究中，人类脑脊液中第二丰富的蛋白质-微量蛋白被确定为脑PGD合酶。PGD_2促进睡眠的作用位点位于睡眠中枢视前区；然而，我们最近的实验结果清楚地表明，真正的作用部位位于位于视前区吻侧的基底前脑区域的腹侧。基底前脑区包括腹侧纹状体，即伏隔核和嗅结节。我们还发现，大鼠脑脊液中PGD_2的浓度在白天（动物的睡眠期）高于夜间。因此，我们推测，在基底前脑吻侧腹面下的膜组织中合成的PGD_2在脑区表层起作用，启动睡眠。PGD_2产生的信号可能被传递到负责睡眠-觉醒调节的神经回路。在此过程中，腹侧纹状体中大量表达的A_<2a>-腺苷受体被推断为至关重要的参与，因为A_<2a>-腺苷激动剂CGS21680在同一区域显著促进睡眠，而a_2 -腺苷拮抗剂KF17837抑制PGD_2产生的睡眠促进作用。

Our research group found the sleep-promoting effect of prostaglandin (PG) D_2 and the awaking effect of PGE_2. The mechanisms underlying these effects have been studied in the present research project. We showed by use of in situ hybridization and immunocytochemical techniques that the brain PGD synthase, the enzyme responsible for the synthesis of PGD_2 in the brain, is abundantly expressed in the leptomeninges covering the surface of the brain, as well as choroid plexus, where cerebrospinal fluid (CSF) is produced. Interestingly, the beta-trace protein, the second most abundant protein in the human CSF,was identified as the brain PGD synthase, in the collaborative studies with foreign research groups. The site of action for the sleep-promoting effect of PGD_2 had been postulated to be located in the preoptic area, a sleep center ; however, our recent experimental results clearly showed that the real site of action is located in the ventral surface of a basal-forebrain region located rostral to the preoptic area. This basal-forebrain region includes ventral striatum, i.e., the accumbens nucleus and the olfactory tubercle. We also demonstrated that the concentration of PGD_2 in the CSF of the rat was higher during the daytime, the sleeping period of the animal, than during the night. Thus, it is postulated that PGD_2 synthesized in the membrane tissues underlying the ventral surface of the rostral basal forebrain acts at the surface layr of the brain region to initiate sleep. The signal produced by PGD_2 may be transmitted to neural circuits responsible for the sleep-wake regulation. In the process, A_<2a>-adenosine receptors abundantly expressed in the ventral striatum are inferred to be crucially involved, because CGS21680, an A_<2a>-adenosine agonist, markedly promoted sleep when administered to the same region, whereas KF17837, an A_2-adenosine antagonist, inhibited the sleep promotion produced by PGD_2.