Integrative studies on central osmolality receptive mechanisms : Modification by novel peptides and environmental stress

目的：阐明脑室注射(i.c.v)后适应性反应的机制。使用免疫组织化学、神经化学和电生理学方法进行了体内和体外的高渗盐水(HS)注射研究。所得结果如下：(1)脑室内(i.c.v.)给药浓度和Fos样免疫反应(FLI)在参与体液动态平衡的脑区进行了检测。观察区域包括终板血管器(OVLT)、视前正中核(MnPO)、穹隆下器(SFO)、室旁核(PVN)、视上核(SON)、孤束核(NTS)和最后区(AP)。在清醒大鼠中给予HS，同时注意中枢[Na+]的实际变化。静脉注射期间脑脊液[Na~+]的变化。…的管理更多的HS与预期的热脱水相容。在PVN和NTS，FLI呈剂量依赖性增加。尽管加压素V1受体拮抗剂OPC-21268对中枢盐负荷时的升压反应无明显影响，但可显著增强下丘脑室旁核中Fli的表达。结果提示，外周加压素系统参与负反馈调节PVN的神经元活动，可能是通过对中枢渗透压和/或Na的刺激直接作用于PVN。(2)采用在体脑微透析技术对清醒大鼠的PVN区进行HS直接灌流。测定细胞外一氧化氮(NO)代谢产物浓度、血压(BP)和心率(HR)。HS灌流可增加PVN的BP、HR和NO代谢产物水平。预先给予一氧化氮合酶抑制剂L的N^g-甲基-L-精氨酸可减弱直接输注HS引起的血压和心率的升高。结果提示，HS局部灌流PVN区可引起局部NO释放，这可能参与心血管反应的产生。(3)用可移动电极系统记录清醒、自由活动雄性大鼠PVN内神经元的胞外记录。研究单位活动的自发放电模式，以及对内外应激源的反应，包括血压紊乱、缺水、空气喷射刺激和全身注射CCK(CCK)。根据对这些应激源的反应，可以识别出假定的加压素分泌神经元。这项技术可能有助于理解PVN内负责清醒大鼠应激反应的局部神经机制。较少

To elucidate the mechanisms responsible for adaptive responses following intracerebroventricular(i.c.v.) administration of hypertonic saline(HS), in vivo and in vitro studies have been performed using immunohistochemical, neurochemical, and electrophysiological methods. The results obtained are as follows :(1)The quantitative relationship between the intracerebroventricularly(i.c.v.) administered HS concentration and the expression of Fos-like immunoreactivity(FLI) in brain regions involved in the homeostasis of body fluid has been examined. The regions examined were the organum vasculosum lamina terminalis(OVLT), the median preoptic nucleus(MnPO), the subfornical organ(SFO), the paraventricular nucleus(PVN), the supraoptic nucleus(SON) of the hypothalamus, the nucleus of the solitary tract(NTS), and the area postrema(AP). HS was delivered in conscious rats with attention to the actual changes in central [Na^+]. The changes in cerebrospinal fluid [Na^+] during i.c.v. administration of … More HS were compatible with those expected for thermal dehydration. FLI increased in a dose-dependent manner in the PVN and NTS. Although the pressor responses during central salt loading were not significantly affected by pretreatment with vasopressin V_1 receptor antagonist OPC-21268, FLI expression in the PVN was significantly augmented. The result suggests that the peripheral vasopressin system participates in negative feedback to modulate neuronal activities in the PVN, probably through direct action at the PVN in response to central osmotic and /or Na stimulation.(2)Direct perfusion of the PVN region with HS was performed in conscious rats by using an in vivo brain microdialysis technique. The extracellular concentration of nitric oxide(NO) metabolites was measured, as were the blood pressure(BP) and heart rate(HR). HS perfusion increased the BP, HR, and NO metabolite levels in the PVN. Pretreatment with N^g-methyl-L-arginine (L-NMMA), an inhibitor of NO synthase, attenuated the increases in the BP and HR induced by direct infusion of HS. The result suggests that local perfusion of the PVN region with HS elicits a local release of NO, which may mediate the production of cardiovascular responses.(3)Extracellular recordings of neurons in the PVN of consciously, freely moving male rats were performed using a movable electrode system. Single-unit activities were examined for their spontaneous firing patterns, as well as responses to intero-and extero-ceptive stressors, including disturbance in BP, water deprivation, air-jet stimulation, and systemic administration of cholecystoknin-8(CCK). On the basis of the responses to these stressors, putative vasopressin-secreting neurons could be identified. This technique may contribute to understanding of local neural mechanisms within the PVN that are responsible for stress responses in conscious rats. Less