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

为了阐明脑室内（i. c. v.）给药高渗盐水（HS），在体内和体外研究已经使用免疫组织化学，神经化学和电生理学方法进行。结果表明：（1）侧脑室（i. c. v.）已经检查了施用HS浓度和涉及体液稳态的脑区域中Fos样免疫反应性（FLI）的表达。检查的区域包括终板血管器（OVLT）、正中视前核（MnPO）、穹窿下器（SFO）、室旁核（PVN）、下丘脑视上核（SON）、孤束核（NTS）和最后区（AP）。在清醒大鼠中给予HS，注意中枢[Na^+]的实际变化。在i. c. v.给药期间脑脊液[Na^+]的变化 ...更多信息 HS与预期的热脱水相容。在PVN和NTS中，FLI以剂量依赖性方式增加。虽然加压素V_1受体拮抗剂OPC-21268预处理对中枢盐负荷时的升压反应无明显影响，但室旁核内FLI的表达明显增加。结果表明，外周加压素系统参与负反馈调节PVN神经元的活动，可能是通过直接作用于PVN，以响应中央渗透和/或Na刺激。（2）采用在体脑微透析技术，对清醒大鼠PVN区进行HS直接灌注。测定细胞外一氧化氮（NO）代谢产物的浓度，以及血压（BP）和心率（HR）。HS灌注增加了PVN中的BP、HR和NO代谢产物水平。用NO合成酶抑制剂N-甲基-L-精氨酸（L-NMMA）预处理可减轻HS引起的血压和心率的增加。结果表明，用HS局部灌注PVN区域可引起局部NO释放，这可能介导心血管反应的产生。（3）用可移动电极系统对有意识、自由活动的雄性大鼠PVN神经元进行细胞外记录。单个单位的活动进行了检查，他们的自发放电模式，以及对interro-and extero-ceptive应激源，包括干扰BP，水剥夺，空气喷射刺激，和胆囊收缩素-8（CCK）的全身管理的反应。根据对这些应激源的反应，可以确定推定的加压素分泌神经元。这项技术可能有助于了解当地的PVN内的神经机制，负责在有意识的大鼠的应激反应。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