原发性高血压进程中下丘脑内神经元型一氧化氮合酶和血管紧张素Ⅱ1型受体的共表达

目的:观察Wistar-Kyoto(WKY)大鼠和自发性高血压大鼠(SHR)下丘脑室旁核(PVN)和视上核(SON)内神经元型一氧化氮合酶(nNOS)和血管紧张素Ⅱ1型受体(AT-1R)的共表达,以及加压素(AVP)和nNOS基因水平的表达差异.方法:应用免疫荧光双标染色结合RT-PCR技术.结果:SHR和WKY大鼠PVN和SON内都有大量的nNOS和AT-1R免疫阳性神经元分布并部分共存,但SHR组nNOS和AT-1R共存率明显高于对照组.与之一致,SHR组PVN和SON内nNOS和AVP mRNA含量都高于对照组.结论:在高血压发病进程中,NO发生代偿性增加,可部分负反馈抑制中枢肾素-血管紧张素系统,但这种抑制不能完全逆转过度激活的血管紧张素Ⅱ和AVP.     

加压素在自发性高血压大鼠与正常大鼠下丘脑视上核、室旁核神经元内表达

目的观察加压素(AVP)在自发性高血压大鼠(SHR)与正常大鼠下丘脑视上核(SON)、室旁核(PVN)内的分布。方法应用光镜和免疫细胞化学技术。结果SHR的AVP阳性细胞内分泌颗粒密集呈棕黄色,正常大鼠组则染色较浅。SHR大鼠SON内AVP阳性神经元百分数(69.30±18.10%)明显多于正常大鼠(59.53±16.97%,P<0.05),而两组大鼠PVN内AVP的表达无明显差异。结论AVP在下丘脑的血压调节活动中起着重要的介导作用,中枢AVP含量的异常增加可能与高血压的发病有关。     

原发性高血压状态下血管紧张素Ⅱ1型受体在下丘脑及延髓头端腹外侧区的表达

目的观察WKY大鼠和自发性高血压大鼠(SHR)下丘脑室旁核(PVN)、视上核(SON)和延髓头端腹外侧区(RVLM)内血管紧张素Ⅱ1型受体(AT-1R)的表达。方法应用免疫荧光染色技术。结果两组大鼠PVN、SON、RVLM内AT-1R免疫阳性神经元的分布与形态基本类似。SHR大鼠PVN、SON和RVLM内AT-1R阳性细胞数目较WKY组多,荧光强度也较对照组强。结论本研究提示AT-1R在下丘脑和RVLM内的血压神经内分泌调节活动中起着重要的介导作用,原发性高血压的发生发展与脑内AT-1R的异常增加所致的对AngⅡ反应性增强有关。     

LPS对大鼠下丘脑视上核nNOS和c-fos表达的影响

为探讨下丘脑视上核(SON)在神经免疫调节中的作用,本实验应用免疫组化技术观察了腹腔注射脂多糖(LPS)后大鼠下丘脑视上核nNOS和c-fos表达的变化。结果表明:LPS可使大鼠视上核内nNOS和c-fos阳性细胞的OD值显著增高,且视上核内部分神经元可同时表达nNOS和c-fos。结果提示,视上核可能为免疫调节的高级整合中枢之一,可能通过NO和／或c-fos途径调节免疫功能。     

自发性高血压大鼠中脑导水管周围灰质nNOS阳性神经元的变化

目的观察自发性高血压大鼠(spontaneously hypertensiverats,SHR)中脑导水管周围灰质内神经元型一氧化氮合酶(neuronal nitric oxide synthase,nNOS)阳性神经元的变化。方法取SHR和京都种威斯特大鼠(Wistar-Koytorats,WKY)大鼠各30只,分别于3月(14周)龄,6月龄和12月龄测血压并处死,ABC免疫细胞化学方法显示nNOS阳性神经元。结果SHR血压随鼠龄的增长逐渐升高,于12～14周龄时血压在高位稳定,且均高于WKY大鼠(P<0.05)维持在[(20.8±1.1)～(26.3±1.0)]kPa(P<0.05);WKY大鼠各时期血压无明显差异,维持在[(13.7±1.6)～(15.1±1.7)]kPa。中脑导水管周围灰质nNOS阳性神经元以小细胞为主,突起有2-4个,许多朝中脑水管方向延伸。定量结果显示,SHR大鼠nNOS阳性神经元随着血压升高呈逐渐减少的趋势,12月龄与3月龄和6月龄相比均有显著差异(P<0.01),而各个时期WKY大鼠PAGnNOS阳性神经元均无明显变化。结论SHR中脑导水管周围灰质nNOS阳性神经元的减少可能通过影响延髓的血压调节中枢调控高血压的发生,并有可能与高血压的痛觉过敏有关。     

疲劳应激大鼠下丘脑腹内侧核和背内侧核神经元中一氧化氮合酶的表达

为研究下丘脑腹内侧核和背内侧核中神经元型一氧化氮合酶 (nNOS)与运动疲劳的关系,采用雄性大鼠经 4周大强度游泳训练制成运动性疲劳模型,用ABC免疫组织化学方法观测两核中nNOS阳性神经元的表达状况,并进行图像分析和统计学处理。结果显示:疲劳组大鼠两核中nNOS阳性神经元的数量和阳性产物面积均大于对照组 (P<0. 001 ),即两核中nNOS出现上调。结论:下丘脑腹内侧核和背内侧核中的nNOS神经元与运动疲劳的形成密切相关,NO可能在两核对疲劳应激反应的调节中发挥重要作用。     

糖尿病大鼠下丘脑视上核nNOS免疫阳性神经元的变化

目的：观察糖尿病大鼠下丘脑视上核神经元型一氧化氮合酶(nNOS)免疫阳性神经元数量的变化。方法：用链脲佐菌素诱导建立糖尿病大鼠模型；免疫细胞化学染色显示nNOS免疫阳性神经元，并进行定量分析。结果：糖尿病视上核nNOS免疫阳性神经元着色深浅不一，着色较深的阳性神经元散在分布，神经元的形态多样，突起较少。对照组大鼠视上核nNOS免疫阳性神经元较稀疏，各时期无明显改变。糖尿病2w，nNOS免疫阳性神经元数量与对照组无显著差异；7w，nNOS阳性神经元较密集，明显多于对照组；12w，nNOS免疫阳性神经元数量略低于7w，但仍多于对照组。结论：糖尿病大鼠下丘脑视上核nNOS免疫阳性神经元数量明显增多。     

免疫抑制剂雷帕霉素对LPS免疫激发大鼠脑内免疫相关核团神经元Fos和nNOS表达的影响

观察免疫抑制剂雷帕霉素对大鼠中枢免疫核团Fos和nNOS表达的影响,并探讨雷帕霉素对中枢免疫调节的作用。将大鼠分为雷帕霉素(10mg/kg)实验组和生理盐水对照组。两组动物分别给药后,腹腔注射免疫激发剂细菌脂多糖(LPS,25mg/kg),用免疫组织化学方法显示并计数下丘脑室旁核、视上核和孤束核中Fos蛋白阳性、nNOS样免疫阳性神经元和Fos/nNOS双标神经元数量,并对数据进行统计学处理。结果显示:实验组动物的下丘脑室旁核、视上核和孤束核内Fos、Fos/nNOS神经元数目较对照组均显著减少(P<0.01)。这一结果表明免疫抑制剂雷帕霉素降低了中枢免疫相关核团内因LPS免疫应激所引起的nNOS的表达,提示雷帕霉素在抑制机体免疫机能的同时,也降低了神经-内分泌系统对免疫的抑制作用。     

自发性高血压大鼠第三脑室触液神经元内一氧化氮合酶与加压素的共表达

目的:观察自发性高血压大鼠(SHR)与SD大鼠第三脑室触液神经元(CSFCN)内一氧化氮合酶(NOS)与加压素(VP)的分布和共存。方法:应用还原型尼克酰胺嘌呤二核苷酸磷酸脱氢酶(NADPH-d)组织化学方法,结合ABC免疫组织化学技术。结果:在SHR视前区至室间核后大细胞亚核平面的第三脑室室壁均有NOS阳性CSFCN的分布;在SHR第三脑室室壁的CSFCN内NOS与VP具有共存性,且SHR组第三脑室的CSFCN内NOS与VP共存率较SD组高。结论:一氧化氮(NO)与VP在下丘脑的血压神经内分泌活动调节中起着重要的介导作用,也可能对高血压的发生发展有影响。     

自发性高血压大鼠弓状核β-内啡肽免疫反应阳性神经元的变化

目的：为探讨弓状核与高血压的关系提供形态学基础。材料和方法：用免疫组织化学ＰＡＰ法和像分析技术对７只雌性自发性高血压大鼠（ＳＨＲ）和７只雌性正常血压大鼠（ＷＫＹ）下丘脑弓状核β－内啡肽免疫反应阳笥神经元的形态、数目的灰度值进行了观察。结果ＳＨＲ鼠下丘脑弓核核β－内啡肽免疫反应阳怀神经元较密集,以着色深的强阳性细胞为主,ＷＫＹ鼠下丘脑弓状核β－内啡肽免疫反应阳性神经元则较稀疏,以着色浅的弱阳性细胞     

Spontaneous variations in arterial blood pressure, heart rate and sympathetic nerve activity in conscious normotensive and spontaneously hypertensive rats

In the present study we have recorded spontaneous variations in mean arterial blood pressure (MAP), heart rate (HR) and mean rectified splanchnic nerve activity (SNA) in conscious undisturbed normotensive Wistar Kyoto rats (WKY) and spontaneously hypertensive rats (SHR). The variability in blood pressure was not significantly different but HR variability tended to be lower in SHR. The variability in SNA expressed as % change from mean value was not significantly different between SHR and WKY. By computer techniques the correlation between HR, MAP and SNA could be calculated during spontaneous variations of these parameters. The slope of the regression line correlating HR and SNA was significantly steeper in SHR than in WKY (0.73, 0.47 resp.). Thus a certain change in HR was associated by a greater change in SNA in SHR compared with WKY. Spontaneous changes in SNA could be divided in principally two different patterns. One typical pattern was a rise in SNA in parallel with a drop in MAP. This pattern was most likely triggered by the arterial baroreceptors and was called a "baroreceptor-pattern". Marked spontaneous excitations in SNA and HR was also observed during natural behaviours such as eating, drinking and explorative behaviour, a so called "centrally mediated pattern".     

Circulatory events following spontaneous muscle exercise in normotensive and hypertensive rats

In previous studies we have shown that spontaneously hypertensive rats (SHR) develop a running behaviour and, secondary to the running behaviour, develop an endorphin-mediated analgesic effect. In the present study the role of the central endorphin system in the cardiovascular responses to spontaneous exercise in normotensive Wistar Kyoto rats (WKY) and SHR was investigated. The experimental design allowed us to record mean arterial pressure (MAP) and heart rate (HR) continuously for more than 1 week without interfering with the daily activities of the animals. They were active in running wheels during the dark period (19.00-07.00 h) and the activity was accompanied by a marked rise in HR. In SHR, a clear depression of blood pressure lasting for about for about 50 min was noted following each running period. The MAP during the post-running depression was 131.4 +/- 1.6 mmHg which was significantly lower than the pre-running control value (145.2 +/- 2.3 mmHg, P less than 0.01). In contrast, MAP in the post-running period in WKY was not significantly different from the pre-running values. In addition, the depression period of SHR had a mean post-running length of 49.7 +/- 3.4 min, which is significantly longer than in the WKYs (37.8 +/- 3.5 min, P less than 0.05). In control rats, naloxone infusion had no effect on blood pressure but a marked bradycardia was observed. In nine running SHR receiving a naloxone infusion, their MAP during the depression period was not different from the control pressure. Our study indicates that endorphin systems are involved in the regulating of blood pressure and HR during muscle exercise in SHR. These systems trigger the transient depression of blood pressure observed immediately after a running period in the SHR.     

Chronic absence of baroreceptor inputs prevents training-induced cardiovascular adjustments in normotensive and spontaneously hypertensive rats

We investigate whether arterial baroreceptors mediate the training-induced blood pressure fall and resting bradycardia in hypertensive (SHR) and normotensive rats (WKY). Male SHR and WKY rats, submitted to sino-aortic denervation (SAD) or sham surgery (SHAM group), were allocated to training (T; 55% of maximal exercise capacity) or sedentary (S) protocols for 3 months. Rats were instrumented with arterial and venous catheters for haemodynamic measurements at rest (power spectral analysis) and baroreceptor testing. Kidney and skeletal muscles were processed for morphometric analysis of arterioles. Elevated mean arterial pressure (MAP) and heart rate (HR) in SHAM SHRS were accompanied by increased sympathetic variability and arteriolar wall/lumen ratio [+3.4-fold on low-frequency (LF) power and +70%, respectively, versus WKYS, P < 0.05]. Training caused significant HR (∼9% in WKY and SHR) and MAP reductions (−8% in the SHR), simultaneously with improvement of baroreceptor reflex control of HR (SHR and WKY), LF reduction (with a positive correlation between LF power and MAP levels in the SHR) and normalization of wall/lumen ratio of the skeletal muscle arterioles (SHR only). In contrast, SAD increased pressure variability in both strains of rats, causing reductions in MAP (−13%) and arteriolar wall/lumen ratio (−35%) only in the SHRS. Training effects were completely blocked by SAD in both strains; in addition, after SAD the resting MAP and HR and the wall/lumen ratio of skeletal muscle arterioles were higher in SHRT versus SHRS and similar to those of SHAM SHRS. The lack of training-induced effects in the chronic absence of baroreceptor inputs strongly suggests that baroreceptor signalling plays a decisive role in driving beneficial training-induced cardiovascular adjustments.     

Brainstem oxytocinergic modulation of heart rate control in rats: effects of hypertension and exercise training

Oxytocinergic brainstem projections participate in the autonomic control of the circulation. We investigated the effects of hypertension and training on cardiovascular parameters after oxytocin (OT) receptor blockade within the nucleus tractus solitarii (NTS) and NTS OT and OT receptor expression. Male spontaneously hypertensive rats (SHR) and Wistar–Kyoto (WKY) rats were trained (55% of maximal exercise capacity) or kept sedentary for 3 months and chronically instrumented (NTS and arterial cannulae). Mean arterial blood pressure (MAP) and heart rate (HR) were measured at rest and during an acute bout of exercise after NTS pretreatment with vehicle or OT antagonist (20 pmol of OT antagonist (200 nl of vehicle)^–1). Oxytocin and OT receptor were quantified (³⁵S-oligonucleotide probes, in situ hybridization) in other groups of rats. The SHR exhibited high MAP and HR ( P < 0.05). Exercise training improved treadmill performance and reduced basal HR (on average −11%) in both groups, but did not change basal MAP. Blockade of NTS OT receptor increased exercise tachycardia only in trained groups, with a larger effect on trained WKY rats (+31 ± 9 versus +12 ± 3 beats min⁻¹ in the trained SHR). Hypertension specifically reduced NTS OT receptor mRNA density (–46% versus sedentary WKY rats, P < 0.05); training did not change OT receptor density, but significantly increased OT mRNA expression (+2.5-fold in trained WKY rats and +15% in trained SHR). Concurrent hypertension- and training-induced plastic (peptide/receptor changes) and functional adjustments (HR changes) of oxytocinergic control support both the elevated basal HR in the SHR group and the slowing of the heart rate (rest and exercise) observed in trained WKY rats and SHR.     

Blood pressure and heart rate responses to mental stress in spontaneously hypertensive (SHB) and normotensive (WKY) rats on various sodium diets

Normotensive (WKY) and hypertensive rats (SHR) were, from 5 to 12 weeks of age, given 'low' (LNa), 'control' and 'high' (HNa) Na diets (0.5, 5 and 50 mmol X 100 g-1 food, respectively, during weekly recordings of body weight, conscious indirect systolic blood pressure (SBP) and heart rate (HR). During the last week, mean arterial pressure (MAP) and HR responses to standardized stress stimuli (air jet) were recorded before and after sequential cardiac nerve blockade. While resting, SBP was about equal in all WKY groups, but it was significantly reduced in SHR-LNa (152 mmHg versus 174 and 178 mmHg in SHR controls and HNa; P less than 0.05). In both LNa groups HR was elevated nearly 25% compared with controls, being in SHR 513 versus 419 bpm (P less than 0.01) and in WKY 489 versus 393 bpm (P less than 0.01). Cardiac nerve blockade indicated that this HR elevation was about equally due to elevations of sympathetic activity and 'intrinsic' pacemaker activity. SHR-LNa also showed attenuated MAP elevations to acute mental stress. There were, however, no significant differences between groups concerning haematocrit or plasma Na-K levels. The results suggest that SHR have a greater salt requirement than WKY, as Na restriction to one-tenth of normal led to a considerable MAP reduction in SHR despite compensatory sympathetic activation, and also to attenuated pressor responses to mental stress. Further, the cardiovascular effects in SHR were much more extensive when on a low-Na diet than when Na intake was increased tenfold above normal.     

Involvement of the paraventricular nucleus (PVN) of hypothalamus in the cardiovascular alterations to head up tilt in conscious rats

We evaluated the involvement of paraventricular nucleus (PVN) in the changes in mean arterial pressure (MAP) and heart rate (HR) during an orthostatic challenge (head up tilt, HUT). Adult male Wistar rats, instrumented with guide cannulas to PVN and artery and vein catheters were submitted to MAP and HR recording in conscious state and induction of HUT. The HUT induced an increase in MAP and HR and the pretreatment with prazosin and atenolol blocked these effects. After inhibition of neurotransmission with cobalt chloride (1 mM/100 nl) into the PVN the HR parameters did not change, however we observed a decrease in MAP during HUT. Our data suggest the involvement of PVN in the brain circuitry involved in cardiovascular adjustment during orthostatic challenges.     

Sodium appetite as well as 24-h variations of fluid balance, mean arterial pressure and heart rate in spontaneously hypertensive (SHR) and normotensive (WKY) rats, when on various sodium diets

Young SHR and WKY rats were compared, first, concerning sodium (Na) appetite during 'rest', mild social stress and ACTH injections, second, concerning the diurnal patterns of water intake, urine output, mean arterial pressure (MAP) and heart rate (HR) while on various Na diets: 0.5 mmol Na(LNa), 5 or 12-13 mmol Na (CNa), 50 (HNa) or 120 mmol Na (vHNa) per 100 g food. Sodium appetite and water intake were about 50% higher in SHR than in WKY (4-4.5 vs 2.5-3 mmol Na per 100 g body wt day-1). It was modestly increased by both social stress and ACTH, and more so in WKY, thereby approaching that in SHR. Concerning the various Na diets and their influences, daytime resting MAP was modestly lowered in LNaSHR and slightly increased in vHNaSHR compared with CNaSHR but largely equal in all WKY groups. Food-water consumption was concentrated to the active night period, but even high Na-water intakes caused no signs of sustained hypervolaemia, because each intake bout was in both SHR and WKY eliminated by urine within 30-40 min. However, particularly the vHNa diet in SHR also increased the frequency of drinking, and each bout caused transient, evidently neurogenic MAP and HR increases which occurred too rapidly to be consequences of blood volume expansion. As a result, the diurnal MAP-HR patterns in SHR varied markedly with the Na diets, in vHNa group resulting in considerably raised average diurnal MAP levels even though resting daytime MAP was here nearly the same as in CNaSHR. These findings illustrate how largely continuous diurnal recordings are needed to judge correctly the relationships between, for example, Na intake, volume equilibrium and MAP. Finally, the relevance of these results in rats for also judging the control of Na balance in man is discussed.     

Interaction between "mental stress" and baroreceptor reflexes concerning effects on heart rate, mean arterial pressure and renal sympathetic activity in conscious spontaneously hypertensive rats

Spontaneously hypertensive rats (SHR) and normotensive Wistar Kyoto rats (WKY) were compared concerning the interactions between cortico-hypothalamic alerting responses and baroreflex influences on neurogenic cardiovascular control. For this purpose mean arterial pressure (MAP), heart rate (HR) and renal sympathetic nerve activity (RSNA) were continuously recorded during night time in conscious, otherwise undisturbed rats. Baroreceptor sensitivity was assessed as percentage HR and RSNA reductions per mmHg MAP elevation when a standardized phenylephrine infusion was performed. A state of acute "mental stress" could be induced by a likewise standardized sudden blowing of air. These two opposing influences on neurogenic cardiovascular control were also experimentally superimposed in various ways and the effects on MAP, HR and RSNA followed. During "rest" RSNA was higher in SHR than in WKY and it also increased more during "mental stress". The baroreflex sensitivity was clearly reduced in SHR and WKY concerning HR reduction (0.44 +/- 0.06 vs. 0.78 +/- 0.08%/mmHg; p less than 0.01) but not so concerning RSNA, which was similar in SHR and WKY (2.6 +/- 0.2 vs. 2.9 +/- 0.4%/mmHg). If expressed (HR + 1 +/- 3%; p less than 0.025 vs. SHR and RSNA + 11% +/- 10, p less than 0.01 vs. SHR). These results) (0.10 +/- 0.02 vs. 0.06 +/- 0.01 microV/mmHg; p less than 0.12). Also single fibre recordings in anaesthetized rats showed the same principle difference between SHR and WKY.(ABSTRACT TRUNCATED AT 250 WORDS)     

Blood pressure and heart rate responses to mental stress in spontaneously hypertensive (SHR) and normotensive (WKY) rats on various sodium diets

Normotensive (WKY) and hypertensive rats (SHR) were, from 5 to 12 weeks of age, given ‘low’ (LNa), ‘control’ and ‘high’ (HNa) Na diets (0.5, 5 and 50 mmol-100 g^-1 food, respectively, during weekly recordings of body weight, conscious indirect systolic blood pressure (SBP) and heart rate (HR). During the last week, mean arterial pressure (MAP) and HR responses to standardized stress stimuli (air jet) were recorded before and after sequential cardiac nerve blockade. While resting, SBP was about equal in all WKY groups, but it was significantly reduced in SHR-LNa (152 mmHg versus 174 and 178 mmHg in SHR controls and HNa; P < 0.05). In both LNa groups HR was elevated nearly 25% compared with controls, being in SHR 513 versus 419 bpm (P < 0.01) and in WKY 489 versus 393 bpm (P < 0.01). Cardiac nerve blockade indicated that this HR elevation was about equally due to elevations of sympathetic activity and ‘intrinsic’ pacemaker activity. SHR-LNa also showed attenuated MAP elevations to acute mental stress. There were, however, no significant differences between groups concerning haematocrit or plasma Na-K levels. The results suggest that SHR have a greater salt requirement than WKY, as Na restriction to one-tenth of normal led to a considerable MAP reduction in SHR despite compensatory sympathetic activation, and also to attenuated pressor responses to mental stress. Further, the cardiovascular effects in SHR were much more extensive when on a low-Na diet than when Na intake was increased tenfold above normal.