缺血性眩晕大鼠模型的建立

目的建立缺血性眩晕大鼠模型,为研究相关治疗药物奠定基础。方法采用手术结扎右侧颈总动脉（common carotid artery,CCA）和右侧锁骨下动脉（subclavian artery,SCA）致大鼠右侧半脑不完全脑缺血建立缺血性眩晕大鼠模型。记录逃避电刺激所需的时间（潜伏期）作为衡量眩晕严重程度的指标,测量造模前后右侧前庭神经核组织血流量,计算血流量变化率,评价脑供血状况。结果 1.与假手术组相比,模型组大鼠潜伏期明显延长（P〈0.01）,造模成功;与模型组比较,盐酸地芬尼多和天保宁能够明显缩短大鼠潜伏期（分别缩短61.9%、52.0%,P〈0.01）。2.结扎右侧CCA及SCA后,与对照组相比,模型组大鼠前庭神经核组织血流量明显减少（P〈0.01）,造模成功;与模型组相比,天保宁能明显增加结扎动脉后组织血流量,在结扎后5、10、15、20、25、30 min血流量分别增加92.8%、83.8%、77.3%、77.9%、65.7%、55.8%（P〈0.01）。结论该模型持久稳定,动物脑部缺血明显,并且能够很好地反映动物眩晕时间及眩晕程度,可有效应用于抗缺血性眩晕药物的实验研究。     

阻断子宫动脉建立FGR大鼠模型的研究

目的通过暂时阻断妊娠期大鼠子宫血供的方法建立子宫缺血引起胎儿生长受限的动物模型。方法根据大鼠子宫动脉是卵巢动脉的一个分支的解剖特点,于孕鼠妊娠第15天时施行手术暂时阻断卵巢动脉并于第21天行剖宫产术,术后称量新生胎仔体重及胎盘、脑、心、肝、肺、肾等重要脏器重量,对比各组间新生胎仔的预后的不同,并对照研究阻断血供10、20、30及40 min对胎仔的不同影响。结果妊娠晚期阻断孕鼠卵巢动脉20min可成功构建胎儿生长受限模型,这种方法与阻断动脉血流30或40 min相比,手术时间短,技术要求不高,胎仔死亡率与对照组差异无显著性(P>0.05)。各实验组较对照组新生胎仔体重及胎盘、各重要脏器重量均明显降低(P<0.05)。结论通过阻断卵巢动脉从而阻断子宫动脉血流,成功建立缺血缺氧性FGR孕鼠模型。该模型重复性好,操作简便,并可成功设立同体对照,为进行FGR相关的产科理论研究提供了一个有利的技术平台。     

大鼠颈总动脉端-侧吻合模型的建立

目的建立大鼠颈总动脉端-侧吻合模型,以期对欲进行显微血管吻合训练或相关实验的同道提供帮助。方法成年SD大鼠10只,将左侧颈总动脉远端穿过颈前肌肉群和气管之间的隧道,与右侧颈总动脉行端-侧吻合。结果成功建立大鼠颈总动脉端-侧血管吻合动物模型,手术成功率约为100%,平均吻合所需8针,平均血管吻合所需时间(35±5)min。吻合3个月后观察通畅率100%,HE染色示吻合口愈合良好。结论吻合成功的关键是提高显微操作技术水平,同时注意保护术野中小的血管和神经。此模型可以较好的应用于显微血管缝合训练。     

Kinetics of Regional Blood-Brain Barrier Glucose Transport and Cerebral Blood Flow Determined with the Carotid Injection Technique in Conscious Rats

Anesthetics, particularly barbiturates, have depressive effects on cerebral blood flow and metabolism and likely have similar effects on blood-brain barrier (BBB) transport. In previous studies utilizing the carotid injection technique, it was necessary to anesthetize the animals prior to performing the experiment. The carotid injection technique was modified by catheter implantation in the external carotid artery at the bifurcation of the common carotid artery. The technique was used to determine cerebral blood flow, the Km, Vmax, and KD of glucose transport in hippocampus, caudate, cortex, and thalamus-hypothalamus in conscious rats. Blood flow increased two to three times from that seen in the anesthetized rat. The Km in the four regions ranged between 6.5 and 9.2 mM, the Vmax ranged between 1.15 and 2.07 mumol/min/g, and the KD ranged between 0.015 and 0.035 ml/min/g. The Km and KD in the conscious rat did not differ from the values seen in the barbiturate anesthetized rat. The Vmax, on the other hand, increased two- to three-fold from that seen in the anesthetized rat and was nearly proportional to the increase in blood flow seen in the conscious rat. The development of the external carotid catheter technique now allows for determination of BBB substrate transport in conscious animals.     

Cardiovascular responses to V1-vasopressinergic antagonism in conscious versus anesthetized rats

Experiments were performed to compare the possible effect of endogenous arginine vasopressin on renal hemodynamics between anesthetized, surgically stressed rats and conscious rats. Animals were instrumented with arterial and venous catheters as well as with a pulsed Doppler flow probe on the left renal artery. The rats were studied under the following conditions: (1) conscious and unrestrained; (2) anesthetized only; (3) anesthetized with minor surgical stress; and (4) anesthetized with major surgical stress. Two anesthetic agents were also compared, a mixture of ketamine (110 mg/kg i.m.) and acepromazine (1 mg/kg i.m.), and sodium pentobarbital (50 mg/kg i.p.). Baseline mean arterial blood pressure was significantly higher in pentobarbital-anesthetized rats following surgical stress compared with conscious animals, but blood pressure was not affected by ketamine-acepromazine anesthesia. After baseline measurements of blood pressure, heart rate, and renal blood flow, a specific V1-vasopressinergic antagonist (d(CH2)5Tyr(Me) arginine vasopressin, 10 mg/kg i.v.) was administered to each group. Mean arterial blood pressure, heart rate, and renal blood flow were monitored for an additional 15 min. Mean arterial blood pressure and renal blood flow decreased after V1 antagonism in ketamine-acepromazine-anesthetized rats with major surgical stress, but were not affected in pentobarbital-anesthetized animals. Heart rate and renal vascular resistance were not affected following V1 blockade with either anesthetic agent. These data suggest that arginine vasopressin plays a role in maintaining blood pressure and renal perfusion in ketamine-acepromazine-anesthetized rats following surgical stress, but does not have a significant effect on renal hemodynamics under pentobarbital anesthesia.     

Dynamics of coronary circulation in rats]

The blood flow velocities in left anterior descending coronary artery and ascending aorta have been measured in anesthetized rats by high frequency Doppler technique. The measurement of coronary blood flow velocity by miniature ultrasonic probe (2.0 x 1.5 mm) was performed through myocardial surface. Two different forms of coronary blood flow curves were recorded. These forms of the curves depend on the value of the coronary blood flow velocity and are connected with the ascending aorta blood flow velocity. The dynamics of the coronary blood flow reactions under coronary artery occlusion and asphyxia in the rat is similar to the one in the cat and the dog, but less expressive. In experiments with vasodilators the direct dependence between linear and volume coronary artery velocities under the measurement through myocardial surface was found.     

Characteristics of hemodynamics in the right and left common carotid arteries in the cat

The correlation between volumetric and linear blood flow rate, recorded synchronously in two common carotid arteries, has been analyzed in anesthetized cats after repeated injections of adrenaline and noradrenaline (2-10 micrograms/kg) and in intact animals. No correlation has been found in the volumetric blood flow parameters; in the right artery the parameters were more dependent on the diastolic flow. In the right artery, a negative correlation with BP was observed, while in the left artery, the correlation was noted with heart rate. The results show great autoregulatory and myogenic activity of the right artery vascular bed.     

Ischemic Postconditioning Fails to Protect against Neonatal Cerebral Stroke

The lack of efficient neuroprotective strategies for neonatal stroke could be ascribed to pathogenic ischemic processes differentiating adults and neonates. We explored this hypothesis using a rat model of neonatal ischemia induced by permanent occlusion of the left distal middle cerebral artery combined with 50 min of occlusion of both common carotid arteries (CCA). Postconditioning was performed by repetitive brief release and occlusion (30 s, 1 and/or 5 min) of CCA after 50 min of CCA occlusion. Alternative reperfusion was generated by controlled release of the bilateral CCA occlusion. Blood-flow velocities in the left internal carotid artery were measured using color-coded pulsed Doppler ultrasound imaging. Cortical perfusion was measured using laser Doppler. Cerebrovascular vasoreactivity was evaluated after inhalation with the hypercapnic gas or inhaled nitric oxide (NO). Whatever the type of serial mechanical interruptions of blood flow at reperfusion, postconditioning did not reduce infarct volume after 72 hours. A gradual perfusion was found during early re-flow both in the left internal carotid artery and in the cortical penumbra. The absence of acute hyperemia during early CCA re-flow, and the lack of NO-dependent vasoreactivity in P7 rat brain could in part explain the inefficiency of ischemic postconditioning after ischemia-reperfusion.     

Blood flow of the right and left submandibular gland during unilateral carotid artery occlusion in rat: role of nitric oxide

The aim of the present study was to investigate the effect of unilateral carotid artery occlusion on the blood flow of submandibular gland in anesthetized rats and identify the role of nitric oxide (NO) in blood flow changes after the artery occlusion. L-NAME (N omega-nitro-L-arginine-methyl-ester; 10 mg/kg/day, per os) dissolved in tap water was used to block nitric oxide synthase. Glandular blood flow was measured using Sapirstein's indicator (86Rb) distribution technique. In the control animals the blood flow of left (ligated side) submandibular gland was lower than in the right (unligated side) one (right: 76.4+/-15.4 ml/min/100 g, 64.1+/-13.4 ml/min/100 g, p<0.01). The blood flow of submandibular glands decreased in NOS blocked group versus control. The vascular resistance after L-NAME treatment was elevated (control: 11+/-2.3 R/kg, L-NAME: 17.5+/-4.1 R/kg, p<0.001). In L-NAME group the difference between blood flow value of the left and right submandibular gland was significantly lower than in the control group (control: -16%, NAME: -8%, p<0.01). Conclusion: The maintenance of the blood flow in the left submandibular gland during ligation of the left common carotid artery could be due to the good vascular anastomotic system at these regions and adaptation of the submandibular vessels to the decreased perfusion pressure. Nitric oxide may have a role in the regulation of blood flow tinder this condition.     

Ventilatory effects of high and pulsatile blood flow in the pulmonary circulation

The mechanism of ventilatory stimulation that accompanies increases in cardiac output is unknown. Previous studies addressing this issue have been inconclusive. However, only steady pulmonary blood flow was used. The effect of flow pulsatility merits consideration, because increasing cardiac output raises not only mean pulmonary arterial pressure but also pulse pressure; mechanoreceptors with an important dynamic component to their responses may cause a response to pulsatile, but not steady, flow. Studies were done on anesthetized cats (n = 4) and dogs (n = 4). The right pulmonary artery was cannulated within the pericardium, and systemic blood was pumped from the left atrium to the right pulmonary artery. The right pulmonary circulation was perfused at different levels of flow, which was either steady or pulsatile. Steady-state flow of up to 150 ml.kg-1.min-1 (270 ml.kg-1.min-1 when corrected for the proportion of lung tissue perfused) did not affect breathing pattern. When high pulmonary flow was made pulsatile (pulse pressure approximately 23 mmHg), breath duration decreased from 3.7 +/- 0.72 to 3.4 +/- 0.81 (SD) s (P less than 0.01), representing a change in frequency of only 9%. There was no change in peak inspiratory activity. It was concluded that pulmonary vascular mechanoreceptors are not likely to contribute significantly to the increase in ventilation in association with increases in cardiac output.     

Regional cerebral blood flow measurement in rats with radioactive microspheres

The effect of the method of heart catheterization on the measurement of cerebral blood flow (CBF) with radioactive microspheres was evaluated during various experimental procedures in male Sprague-Dawley rats. Catheters were inserted into the left ventricle via the right carotid or right subclavian artery or directly into the left atrium for microsphere injections. CBF was measured in cerebral cortical and subcortical tissues under control anesthetized (70 % N₂O, 30 % O₂), hypoxic or hypercapnic test conditions. Under control conditions, CBF was similar in the right vs the left cerebral hemisphere in subclavian artery and atrial catheterized rats but was greater in the left vs the right cortex in carotid catheterized animals (p<.05). During hypoxia and hypercapnia CBF increased equally in both cerebral hemispheres in atrial catheterized rats. The increase in CBF was significantly attenuated in the cerebral hemisphere ipsilateral to carotid catheterization during hypoxia and hypercapnia, although the percentage increase in flow was similar in both hemispheres. The results indicate the limitations of measuring regional CBF changes under experimental test conditions in rats with a ligated carotid artery and suggest that atrial catheterization is the method of choice when comparable changes in CBF are desired in both cerebral hemispheres.     

Glutamate measured by 6-s resolution brain microdialysis: capillary electrophoretic and laser-induced fluorescence detection application

In the present experiment the combination of brain microdialysis and CZE–LIFD permitted the measurement of glutamate in 100 nl microdialysis samples collected every 5 or 6 s. Samples were collected every 6 s, in rats anesthetized with two different anesthetic agents (ketamine and sodium thiopental). A microdialysis probe was inserted in the cortex of an anesthetized rat in the territory irrigated by the middle cerebral artery. The artery was clamped for 30 s and then released. The samples were derivatized with fluorescein isothiocyanate I (FITC) by means of a continuous-flow reactor, collected and injected into a home-made CZE–LIFD instrument. Glutamate decreased immediately after clamping the artery in ketamine anesthetized rats and increased 1 min after the onset of the ischemia in sodium thiopental anesthetized rats. In another experiment a 60 mM KCl solution was injected through a microdialysis probe inserted in the hippocampus of an anesthetized rat. In the first 5 s after the KCl solution reached the tissue, glutamate increased but γ-aminobutytic acid and glutamine did not. The experiments show that time resolution of brain microdialysis can be reduced to a few seconds if the analytical technique is the proper one.     

The role of the cardiac-pulmonary blood volume in the changes in left ventricle output during stimulation of the afferent fibers of somatic nerves

Stimulation of tibial nerve afferent fibers has revealed heterogeneous shifts of left ventricular output, as well as pulmonary artery and posterior vena cava blood flow in anesthetized cats. Uniform changes in left ventricular output and pulmonary artery blood flow were noted in the majority of cases, with venous return most often exceeding pulmonary artery blood flow. beta-adrenoreceptor blockade failed to influence changes in pulmonary artery blood flow. It is concluded that the increase in pulmonary artery blood flow depends on the rise in venous return, but not on neurogenic influence upon the right ventricle. The reduction in left ventricular output is the result of decreased right ventricular outflow due to its overload caused by pulmonary vasoconstriction.     

Intravital Video Microscopy Measurements of Retinal Blood Flow in Mice

Alterations in retinal blood flow can contribute to, or be a consequence of, ocular disease and visual dysfunction. Therefore, quantitation of altered perfusion can aid research into the mechanisms of retinal pathologies. Intravital video microscopy of fluorescent tracers can be used to measure vascular diameters and bloodstream velocities of the retinal vasculature, specifically the arterioles branching from the central retinal artery and of the venules leading into the central retinal vein. Blood flow rates can be calculated from the diameters and velocities, with the summation of arteriolar flow, and separately venular flow, providing values of total retinal blood flow. This paper and associated video describe the methods for applying this technique to mice, which includes 1) the preparation of the eye for intravital microscopy of the anesthetized animal, 2) the intravenous infusion of fluorescent microspheres to measure bloodstream velocity, 3) the intravenous infusion of a high molecular weight fluorescent dextran, to aid the microscopic visualization of the retinal microvasculature, 4) the use of a digital microscope camera to obtain videos of the perfused retina, and 5) the use of image processing software to analyze the video. The same techniques can be used for measuring retinal blood flow rates in rats.     

The effect of dipyridamole on the initiation phase of postischemic acute renal failure in rats

Several previous observations support the hypothesis that increased adenosine production and release mediate, at least in part, the reductions in renal blood flow and glomerular filtration rate in ischemic acute renal failure (ARF). If this hypothesis is correct, dipyridamole should potentiate these changes, since it blocks cellular adenosine uptake, thereby increasing the concentration and potentiating the effects of extracellular adenosine. Moreover, theophylline should block the effects of dipyridamole, since it is an adenosine receptor antagonist. These predictions were tested in three groups of anesthetized rats. All rats were subjected to 30 min of left renal artery occlusion; 30 min after relieving the occlusion, a 45-min clearance period was begun. The control group was given saline i.v.; the two experimental groups received either dipyridamole (24 micrograms X min-1 X kg-1) or dipyridamole plus theophylline i.v. (111 mumol/kg as a prime, 1.1 mumol X min-1 X kg-1 as an infusion). In the control group, the previously ischemic left kidneys exhibited decreased clearances of para-aminohippurate and inulin (CPAH and CIn), filtration fraction (FF), and urine/plasma inulin concentration (U/PIn), and increased urine flow (V), Na excretion (UNaV), and fractional Na excretion (FENa) in comparison with the contralateral right kidney. Dipyridamole pretreatment did not affect the right kidney, but it intensified the reductions in left kidney CPAH, CIn, and FF. Theophylline blocked all these effects of dipyridamole on the left kidney, and increased renal plasma flow (CPAH/PAH extraction), despite a decrease in systemic arterial blood pressure. These results are further support for the hypothesis that adenosine mediates, at least in part, the hemodynamic changes in postischemic ARF in rats.     

当归注射液对脑缺血/再灌注神经元代谢物的影响

目的：研究当归注射液对脑缺血／再灌注时神经元代谢物及血流速度的作用,阐明当归对脑缺血损伤神经修复过程的影响。方法：雄性SD大鼠69只,体重150～170g,随机分成假手术组(n=4)、缺血损伤组(n=30)和当归治疗组(n=35)。制作右大脑中动脉血供阻断(MCA0)模型。缺血2h后,当归治疗组立即腹腔注射当归注射液(5g／kgbw)。在再灌注后3～4h和5～6h,以磁共振成像(MRI)技术研究大脑T2加权成像(T2WI)和局域质子谱(^1H MRS)的变化,观察当归对成像和神经元代谢物N-乙酰天门冬氨酸(NAA)、肌酸／磷酸肌酸(Cr／PCr)和胆碱(Cho)的影响。激光多普勒血流仪观察当归注射液对血流速度的影响,测定脑表面血管密度。结果：与缺血损伤组比较,当归治疗组的高信号强度区信号减弱、体积小,NAA值大,Cr/NAA和Cho/NAA比值小,再灌注时的血流速度显著加快,单位面积内的血管长度增加。结论：当归注射液加快缺血脑组织的血液循环,改善神经元的代谢。     

Role of afferent nerves and sensory peptides in the mediation of hepatic artery buffer response.

Intrahepatic arteries are richly innervated by both adrenergic and sensory vanilloid-sensitive (capsaicin-sensitive) fibers. Stimulation of capsaicin sensitive fibers has been shown to dilate the intrahepatic vessels by both releasing sensory neuropeptides and by modulating the adrenergic tone. However the participation of capsaicin-sensitive fibers in the mediation of the hepatic artery buffer response (HABR) has not been investigated yet. To explore the involvement of sensory innervation and sensory neuropeptides in the HABR, the experiments were performed on capsaicin-denervated Wistar rats. In addition, we used selective CGRP and tachykinin receptor antagonists to test the participation of CGRP, substance P and NK-A in HABR in the rat. In anesthetized rats the hepatic artery blood flow (HABF), microcirculatory hepatic blood flow (HBF) and portal blood flow (PBF) were determined. The HABR was induced by partial occlusion of the portal vein and maintaining the PBF at 10% of its control preocclusive value. In the control HABR the hepatic artery blood flow increased by 89% (p< 0.005) whilst the HBF at the same time decreased by 32% (p< 0.005) in comparison to preocclusive HABF and HBF values. In sensory-denervated rats the resting HBF and PBF were increased by 23% (p< 0.05) and 34% (p< 0.05), respectively in comparison to the control HBF and PBF values. In this group the induction of the HABR increased the hepatic artery blood flow by only 55% (p< 0.05), whilst the HBF was reduced by 45% (p< 0.05). Pretreatment with CGRP 8-37 (CGRP receptor antagonist) and NK-1 but not NK-2 nor NK-3 receptor antagonists significantly reduced the HABF by 43% (p< 0.05) and 25% (p< 0.05) as compared to the HABF value in the control HABR group. These findings support the hypothesis that the hepatic artery buffer response induced by reduction of the portal inflow to the liver by 90% is partially mediated by activation of capsaicin-sensitive sensory fibers in the liver, probably due to local tissue ischemia and hypoxia. The observed vasodilation in the vascular bed of the hepatic artery is due to stimulation of CGRP and NK-1 receptors.     

The effect of desflurane on ameliorating cerebral infarction in rats subjected to focal cerebral ischemia-reperfusion injury

To obtain more information on the cerebral ischemia and reperfusion injury under desflurane anesthesia, we compared the infarct volume and lactate dehydrogenase (LDH) activity in rats subjected to focal cerebral ischemia during different concentration of desflurane anesthesia. Male Long-Evans rats weighing 270-350 g were anesthetized with desflurane in air at 1.0, 1.25 or 1.5 MAC whereas rats in the control group received intraperitoneal chloral hydrate (400 mg/kg) anesthesia. Cerebral infarction was induced by microsurgical procedures with ligation of the right middle cerebral artery (MCA) and clipping of the bilateral common carotid arteries (CCA) for 60 minutes. The rats were sacrificed 24 hours later, serial brain slices of 2mm thickness were taken and stained for the measurement of the infarct area. Cellular damage was evaluated by measuring the LDH level in the plasma. Desflurane (1.0, 1.25 or 1.5 MAC by inhalation) and chloral hydrate (400 mg/kg; ip.) did not produce any changes in pH, blood gases, heart rate or mean arterial blood pressure. In the rats subjected to focal cerebral ischemia, the volume of infarction was significantly less in the desflurane groups in all three different concentrations than in the chloral hydrate group. The changes of LDH activity in plasma also correlated with the result of the infarct volume. Our study suggests that desflurane may offer a neuroprotective effect such as decreased infarct volume after focal cerebral ischemia.     

Lower Brainstem Pathways Regulating Sympathetically Mediated Changes in Cutaneous Blood Flow

1. When the individual is alerted by painful or salient stimuli, there is a vigorous sympathetically mediated constriction of the cutaneous vascular bed. We investigated central pathways mediating this response using chronically implanted Doppler ultrasonic probes to measure cutaneous blood flow in the rabbit ear pinna and in the rat tail.2. Blockade of neuronal function in the amygdala prevents cutaneous vasoconstriction elicited by salient stimuli, but does not prevent the response to painful stimuli. Blockade of neuronal function in raphe magnus/pallidus and the parapyramidal region in anesthetized rabbits prevents cutaneous vasoconstriction elicited by painful stimuli. A similar region of the medullary raphe regulates tail artery vasoconstriction in rats. Inhibition of neuronal function in this region reverses cutaneous vasoconstriction induced by cooling the animal.3. Bulbospinal presympathetic neurons in the rostral medullary raphe region appear to regulate cutaneous blood flow responses occurring as part of the response to painful or dangerous environmental events and as part of the regulation of body temperature.     

A role for the angiotensin IV/AT4 system in mediating natriuresis in the rat

Angiotensin II (AngII) or Angiotensin IV (AngIV) was infused into the renal artery of anesthetized rats while renal cortical blood flow was measured via laser Doppler flowmetry. The infusion of AngII produced a significant elevation in mean arterial pressure (MAP) with an accompanying decrease in cortical blood flow, glomerular filtration rate (GFR), urine volume, and urine sodium excretion. The infusion of AngIV induced significant increases in renal cortical blood flow and urine sodium excretion, without altering MAP, GFR, and urine volume. Pretreatment infusion with a specific AT1 receptor antagonist, DuP 753, blocked or attenuated the subsequent AngII effects, while pretreatment infusion with the specific AT4 receptor antagonist, Divalinal-AngIV, blocked the AngIV effects. These results support distinct and opposite roles for AngII and AngIV, i.e. AngII acts as an anti-natriuretic agent, while AngIV acts as a natriuretic agent.