Department of Integrative Physiology and Center for Neuroscience, University of Colorado, Boulder, CO 80309-0354, USA.
Exp Neurol. 2010 Jul;224(1):271-81. doi: 10.1016/j.expneurol.2010.04.002. Epub 2010 Apr 9.
Serotonin plays an important role in the regulation of anxiety states and physiological responses to aversive stimuli. Intracerebroventricular (i.c.v.) injection of the stress- and anxiety-related neuropeptide urocortin 2 (Ucn 2) increases c-Fos expression in serotonergic neurons in the dorsal (DRD) and caudal (DRC) parts of the dorsal raphe nucleus. These regions contain a subset of serotonergic neurons that projects via the dorsal raphe periventricular tract to periventricular structures, including the subfornical organ and ependymal layer, and to the ventricular system. To determine if Ucn 2 activates ventricle/periventricular-projecting serotonergic neurons in the midbrain raphe complex, we made i.c.v. injections of the retrograde tracer Fluoro-Gold into the lateral ventricle, followed 7 days later by i.c.v. injection of Ucn 2. The DRD at -8.18 mm and the DRC at -8.54 mm and -9.16 mm bregma were analyzed using a combined bright field and immunofluorescence technique. Approximately 40% of the ventricle/periventricular-projecting neurons in the subdivisions sampled were serotonergic. Urocortin 2 increased c-Fos expression in ventricle/periventricular-projecting serotonergic neurons in the DRC and in non-ventricle/periventricular-projecting serotonergic neurons in the DRD and DRC. Of the total population of ventricle/periventricular-projecting serotonergic neurons in the DRC at -8.54 and -9.16 mm bregma, 35% expressed c-Fos following Ucn 2 injections. These data are consistent with previous studies showing that i.c.v. injection of Ucn 2 activates subpopulations of serotonergic neurons restricted to the mid-rostrocaudal DRD and DRC and further demonstrate that these include both subsets of serotonergic neurons that do and do not project to the ventricle/periventricular system.
5-羟色胺在调节焦虑状态和对厌恶刺激的生理反应方面发挥着重要作用。脑室内（i.c.v.）注射应激和焦虑相关神经肽 Ucn2 会增加背侧（DRD）和尾侧（DRC）背侧中缝核中 5-羟色胺能神经元的 c-Fos 表达。这些区域包含一组 5-羟色胺能神经元，它们通过背侧中缝核室旁束投射到室旁结构，包括穹窿下器官和室管膜层，并投射到脑室系统。为了确定 Ucn2 是否激活中脑中缝核复合体中的脑室/室旁投射 5-羟色胺能神经元，我们将逆行示踪剂 Fluoro-Gold 脑室内注射到侧脑室，7 天后再脑室内注射 Ucn2。使用明场和免疫荧光技术联合分析 -8.18mm 的 DRD 和 -8.54mm 和 -9.16mm 前囟的 DRC。在取样的细分中，约 40%的脑室/室旁投射神经元是 5-羟色胺能的。Ucn2 增加了 DRC 中脑室/室旁投射 5-羟色胺能神经元和 DRD 和 DRC 中非脑室/室旁投射 5-羟色胺能神经元的 c-Fos 表达。在 -8.54mm 和 -9.16mm 前囟的 DRC 中，总脑室/室旁投射 5-羟色胺能神经元的 35%在 Ucn2 注射后表达 c-Fos。这些数据与先前的研究一致，表明脑室内注射 Ucn2 激活了局限于中-尾侧 DRD 和 DRC 的 5-羟色胺能神经元的亚群，并进一步证明这些亚群包括投射到脑室/室旁系统的和不投射到脑室/室旁系统的 5-羟色胺能神经元的两个子集。
