延髓腹外侧区微量注射L-NAME对内脏-减压反应的影响

目的:内脏器官或其传入神经受到一定强度的刺激后,可以引起血压下降,这种现象称为内脏-减压反应.在临床工作中,也常见到腹腔脏器疼痛引起心血管系统功能的障碍,如可使血压下降乃致休克,使心率或心律改变等.在我们以往的实验中发现,当静脉注射L-硝基精氨酸甲酯(L-NAME)后,可使内脏-减压反应发生翻转现象.本实验的目的在于,探讨延髓腹外侧区是否参与了内脏-减压反应的调控,是否与内源性NO有关.方法:Sprague-Dawley 大鼠,雄性;记录和刺激仪器为MacLab/4e套装;Chart软件;立体定位仪器为江湾I型C;微电极操纵器为上海蝶来仪表厂MD-1型;L-NAME和L-精氨酸为Sigma公司产品.手术过程用我们以往的方法,从腹膜后位暴露内脏大神经,于腹腔神经节近端结扎并剪断,将中枢端置于铂丝双极电极上,用于刺激.左股动脉插管连接血压传感器;于颅底暴露延髓腹外侧部,将动物仰卧位固定于立体定位仪上,按Paxinos & Watson鼠脑图谱定位..     

奥美沙坦通过延髓腹外侧区AT1受体减弱自发高血压大鼠血管紧张素Ⅱ引发的中枢性升压反应

目的 探讨奥美沙坦对自发性高血压大鼠(SHR)外源性血管紧张素Ⅱ(AngⅡ)引发的中枢性升压反应的影响以及与延髓腹外侧头端区(RVLM)血管紧张素Ⅱ1型受体(AT1)的关系.方法 实验大鼠分为SHR对照组(n=20,正常饮水)、奥美沙坦组(n=20,给予奥美沙坦30 mg·kg-1·d-1)和WKY组(n=20,WKY大鼠,正常饮水).4 w后,三组大鼠腹腔麻醉,开颅定位RVLM后,股动静脉插管,观察注射AngⅡ前后血压和心率.采用逆转录-聚合酶链反应(RT-PCR)和免疫印迹方法检测各组RVLM内AT1受体mRNA和蛋白的水平,并进行光密度测定.结果 饲养中奥美沙坦组鼠尾血压能够达标.RVLM微量注射AngⅡ后三组大鼠的平均动脉压(MAP)不同程度升高,奥美沙坦组MAP升高幅度明显低于SHR组[(26.3±0.75)vs(47.2±1.41)mmHg,P＜0.01],但仍高于WKY组[(21.5±0.72)mmHg,P＜0.05].三组大鼠心率(HR)均有所升高,但差异无统计学意义.奥美沙坦组RVLM内AT1受体mRNA平均光密度明显低于SHR组[(0.94±0.41) vs (2.41±0.37),P＜0.01],但高于WKY组(0.81±0.22,P＜0.05).奥美沙坦组RVLM内AT1受体蛋白平均光密度明显低于SHR组[(0.51±0.09) vs (0.93±0.07),P＜0.01)],但高于WKY组(0.43±0.03,P＜0.05).结论 长期口服奥美沙坦能够通过降低RVLM组织中AT1受体水平,显著减弱SHR RVLM区微量注射AngⅡ引起的升压反应.     

大鼠延髓腹外侧注射食欲刺激素对动脉压和心率的影响

目的 探讨在大鼠延髓腹外侧注射食欲刺激素是否影响动脉压和心率.方法 成熟雄性大鼠(n=19)腹腔内麻醉,微量注射食欲刺激索于延髓腹外侧头端(RVLM)及延髓腹外侧尾端(CVLM)内,记录动脉压和心率.用免疫组化的方法检测RVLM、CVLM内生长激素促分泌素(GHS)受体蛋白的表达,并在显微镜下观察孤束核、RVLM、CVLM区切片,记数阳性细胞数进行对比.结果 微量注射食欲刺激素(0.4、0.8 mmol/L)于RVLM内,可增加动脉压( 3.0±1.1)mmHg和心率( 8.1±4.1)次/min,但差异没有统计学意义.同样微最注射食欲刺激素0.8 mmol/1,于CVLM内对动脉压[(-0.3±1.3)mmHg]及心率[(-5.0±3.3)次/min]的影响.差异也没有统计学意义.免疫组化显示孤束核[(38.7±3.6)%]、RVLME(20.0±2.7)%]、CVLME(24.7±1.6)%]内均有GHS受体的分布.但是,孤柬核的GHS受体阳性细胞数明显多于RVLM、CVLM(P＜0.05).结论 食欲刺激素在大鼠延髓腹外侧内对动脉压和心率影响不大.     

气道上皮在支气管哮喘气道高反应性中的作用

目的探讨气道上皮和L-精氨酸-一氧化氮(L-Arg-NO)通路在支气管哮喘(简称哮喘)气道高反应性中的作用。方法建立大鼠离体气管条张力的测定方法,观察气管条乙酰胆碱(Ach)浓度反应曲线和最大收缩反应的变化。结果哮喘大鼠(n=10)离体气管条经亚硝基-L-精氨酸甲酯(L-NAME)10-5mol/L孵育后对Ach的最大收缩反应从孵育前(123±39)mg上升到(187±53)mg,最大收缩反应差异有统计学意义(P<0.01),浓度反应曲线上移,而L-Arg可以逆转L-NAME的作用,单用L-Arg2×10-5mol/L和L-Arg10-3mol/L孵育气管条,对哮喘大鼠气管条的最大收缩反应和浓度反应曲线无明显影响。与上皮完整气管条比较,去上皮可使哮喘大鼠气管条的反应性显著增高(P<0.01),而L-Arg、L-NAME+L-Arg和L-NAME孵育去上皮气管条对其反应性均无明显影响。结论气道上皮在哮喘大鼠气道高反应性起重要作用,气道上皮损伤造成哮喘发作与NO合成减少有关。     

延髓腹外侧头端活性氧介导室旁核血管紧张素Ⅱ的交感兴奋作用

目的 探讨延髓腹外侧头端(RVLM)活性氧(ROS)是否介导室旁核(PVN)血管紧张素Ⅱ(AngⅡ)的交感兴奋作用.方法 实验在去压力感受器神经支配和双侧迷走神经切断的麻醉大鼠上进行.采用立体定位仪进行核团定位微量注射,在体记录肾交感神经放电活动(RSNA)、平均动脉压(MAP).结果 PVN内微量注射AngⅡ剂量依赖性地引起RSNA增强和MAP升高.应用超氧阴离子清除剂4-羟基-2,2,6,6-四甲基哌啶(Tempol)或内源性超氧化物歧化酶拟似物聚乙二醇-超氧化物歧化酶(PEG-SOD) 清除RLVM内ROS对RSNA和MAP没有显著影响,但可抑制PVN内微量注射AngⅡ引起的交感兴奋作用.应用NAD(P)H氧化酶抑制剂夹竹桃麻素(Apocynin)或氧化酚砷(PAO)抑制RLVM内ROS的生成也可减弱AngⅡ的效应.结论 RLVM内NAD(P)H氧化酶来源的ROS介导了PVN内AngⅡ的交感兴奋作用.     

老年高血压病并发阻塞性睡眠呼吸暂停综合征患者血压特点及与炎症因子的关系

目的研究并发中重度阻塞性睡眠呼吸暂停综合征（obstructive sleep apnea syndrome,OSAS）的老年高血压患者血压的变化情况及炎症因子的水平,从而揭示此类患者的疾病特点。方法将60例年龄大于60岁的研究对象根据诊所血压、24 h动态血压和多导睡眠图监测结果分为单纯高血压病组（n=30）和并发OSAS组（高血压病并发中重度睡眠呼吸暂停综合征,n=30）。用ELISA法测定白介素-6（IL-6）、sCD40L、超敏C反应蛋白（hs-CRP）、可溶性细胞间黏附分子1（ICAM-1）及血管细胞黏附分子1（VCAM-1）的浓度。结果①并发OSAS组中非杓型血压的发生率为67%,明显高于单纯高血压组的发生率37%（P<0.05）。②并发OSAS组24 h、白天、夜间平均脉压（mean arterial blood pressure,MAP）分别为（51±13）mmHg（1 mmHg=0.133 kPa）,（50±13）mmHg和（51±17）mmHg均明显高于单纯高血压组（45±7）mmHg,（46±8）mmHg和（44±6）mmHg,并有统计学意义（P<0.05）。③并发OSAS组的IL-6、sCD40L、hs-CRP、ICAM-1、VCAM-1浓度明显高于单纯高血压组。④并发OSAS组的hs-CRP、ICAM-1、VCAM-1浓度变化与呼吸紊乱指数、睡眠血氧下降程度正相关（r=0.852,P<0.05）。hs-CRP与MAP呈正相关（P<0.01）,ICAM-1与夜间血压下降率呈负相关（P<0.05）。结论中重度睡眠呼吸暂停影响老年人血压昼夜节律的变化,同时对脉压产生明显影响,炎症反应也明显加重。     

经微量泵静脉注射硝普钠治疗高血压急症的疗效观察

目的:观察经微量泵静脉注射硝普钠治疗高血压急症的疗效。方法:高血压急症84例随机分为硝普钠治疗组(n=43)和硝酸甘油对照组(n=41),两组经微量注射泵持续给药,硝普钠组50mg加入5%葡萄糖50ml,0.25μg/kg.min开始,5min监测血压1次,据血压调整给药剂量;硝酸甘油组:硝酸甘油10mg加入5%葡萄糖48ml,10μg/min开始,据血压调整速度,观察头痛、胸闷、气促等不良反应,记录血压、心率、心电图等资料。结果:硝普钠组42例(97.7%)显效,1h内收缩压从治疗前的(203.3±15.5)mmHg降至(167.2±16.4)mm-Hg(P<0.05),舒张压也显著下降[(124.6±13.9)mmHg∶(103.0±15.8)mmHg,P<0.05];两组显效率有显著差异(97.7%∶82.9%,P<0.05)。结论:硝普钠治疗高血压急症更有效,经微量注射泵持续给药更安全。     

缬沙坦及贝那普利联合用药对高血压患者尿微量白蛋白的影响

目的观察血管紧张素II受体拮抗剂（ARB）类药物缬沙坦及血管紧张素转换酶抑制剂（ACEI）类药物贝那普利联合用药与大剂量单药（缬沙坦或贝那普利）对原发性高血压患者尿微量白蛋白（MAU）的影响。方法此研究为随机双盲实验。将119名有微量白蛋白尿的原发性高血压患者随机分为贝那普利组（10mg/d,n=42）、缬沙坦组（160mg/d,n=37）和联合用药组（贝那普利5mg/d＋缬沙坦80mg/d,n=40）。半量治疗4周后能耐受者增加至目标剂量,随访4周。分别于研究开始、治疗4周、8周时测定MAU和血压。结果治疗8周后降压幅度为：贝那普利组〔n=35,（15.8±3.4）/（10.0±1.8）mmHg〕,缬沙坦〔n=35,（14.7±3.7）/（9.8±1.6）mmHg〕,联合用药组〔n=38,（15.3±3.6）/（10.2±1.4）mmHg〕,3组比较血压差异无统计学意义;MAU降低幅度为：贝那普利组〔（65.4±9.5）mg/24h〕,缬沙坦〔（67.8±11.5）mg/24h〕,联合用药组〔（95.8±12.2）mg/24h〕,联合用药组较单药组效果显著,P均〈0.01。结论缬沙坦和贝那普利联合用药较加大剂量单药治疗的血压控制无差异,但对高血压患者的肾脏保护作用更强。     

下丘脑减压区神经降压素对压力感受性反射的影响

于大鼠双侧下丘脑前部减压区注射微量神经降素（ｎｅｕｒｏｔｅｎｓｉｎ，ＮＴ）及其抗血清（ａｎｔｉｎｅｕｒｏｔｅｎｓｉｎｓｅｒｕｍ，ＡＮＴＳ）．观察对压力感受性反射的影响。结果表明，大鼠双侧下丘脑前部减压区注入ＮＴ后，可明显抑制静脉注射新福林所致的升压反应（Ｐ＜０．０１），从而加强压力感受性反射的活动；而注射ＡＮＴＳ则产生相反结果（Ｐ＜０．０１）。揭示下丘脑前部减压区ＮＴ参与压力感受性反射的调节过程。     

迷走神经刺激治疗心肌梗死性心力衰竭

目的 自主研发植入型迷走神经刺激（VNS）和心电采集系统,探索多因素（VNS的频率、强度、脉宽、时间）电刺激迷走神经的最佳效果参数值,并观察VNS对血压、心率以及心功能的影响.方法 实验组（正常新西兰兔10只）使用自主研发的植入型VNS和心电采集系统,在适宜的程控刺激模式：频率20 Hz、强度1mA、脉宽0.5 ms、间隔刺激（开25 s,停250 s）,与对照组（正常新西兰兔10只）进行体外实时监测心电和遥控VNS 4周,对比血压、心电图结果;心功能不良实验组（新西兰兔5只）,使用自主研发的植入型VNS和心电采集系统,程控刺激模式：频率20 Hz、强度1mA、脉宽0.5ms、间隔刺激：开25 s,停250 s与心功能不良对照组（新西兰兔5只）,进行体外实时监测心电和遥控VNS 4周,对比血压、心电图以及超声结果.结果 本实验的程控刺激可使新西兰兔心率下降10％～20％,正常条件下,实验组收缩压（123.6±2.6）mmHg（1 mmHg=0.133 kPa）,舒张压（94.3±1.5） mmHg,心率（233.4±7.4）次/min;对照组收缩压（126.0±3.3）mmHg,舒张压均值（95.0±1.9） mmHg,心率（256.0±7.4）次/min.心功能不良条件下,实验组收缩压（117.6±2.6）mmHg,舒张压（76.8±2.2）mmHg,心率（193.6±4.7）次/min,射血分数0.55±0.01;对照组收缩压（116.2±9.3） mmHg,舒张压均值（79.2±4.9）mmHg,心率（211.0±7.9）次/min,射血分数0.49±0.02.VNS对于血压影响差异无统计学意义,对于心率和心功能有改善作用.结论 自主研发的植入型VNS和心电采集系统是可行的,实验程控刺激模式下VNS治疗心功能不良是有效的.     

Clonidine Antagonizes Pressor Effect of N-Methyl-D-Aspartate in the Rostral Ventrolateral Medulla of Rats

The purpose of the present study was to investigate the modulatory actions of adrenoreceptor agonists on N-methyl-D-aspartate (NMDA)-induced pressor effect in rostral ventrolateral medulla (RVLM). These drugs were locally applied into RVLM of urethane-anesthetized Sprague-Dawley rats through multibarrel pipettes. Microinjection of NMDA increased the arterial pressure, an effect which was abolished by pretreatment with clonidine, whereas neither the β-adrenergic agonist isoproterenol nor the α₁-adrenergic agonist phenylephrine did alter this pressor response. Previous experiments demonstrated that clonidine binds to noradrenergic α₂ and imidazoline receptors in the RVLM. Norepinephrine, which has high affinity for the α₂ receptor and low affinity to the imidazoline receptor, partially antagonized NMDA-induced hypertension. On the other hand, administration of selective imidazoline receptor antagonist idazoxan partially reversed clonidine-mediated antagonism of NMDA. Taken together, these results suggest that clonidine may modulate the excitatory amino acid -induced pressor response through noradrenergic α₂ and imidazoline receptors in the RVLM.     

Neural mechanism of acupuncture-induced gastric relaxations in rats

Acupuncture has been used to treat gastrointestinal symptoms in China for more than 3000 years. However, the mechanism of the beneficial effects of acupuncture remains unknown. Strain gauge transducers were implanted on the serosal surface of the stomach to record circular muscle contractions in thiobutabarbital-anesthetized rats. Acupuncture on the right lower abdomen caused a transient relaxation of the stomach. Acupuncture-induced gastric relaxations were abolished by guanethidine, propranolol, splanchnic ganglionectomy, spinal cord transection, and spinomedullary transection. In contrast, N ^G-nitro-l-arginine, phentolamine, truncal vagotomy, and pontomedullary transection had no effect. Acupuncture increased the number of c-Fos immunopositive cells at the ventrolateral medulla (VLM). It is concluded that acupuncture-induced gastric relaxations are mediated via the somatosympathetic reflex. Its afferent limb is composed of abdominal cutaneous and muscle afferent nerves. Its efferent limb is the gastric sympathetic nerve and the reflex center is within the medulla. VLM neurons may play an important role in mediating this reflex.     

Arterial Pressure and Plasma Vasopressin: Regulation by Neurons in the Caudal Ventrolateral Medulla of the Rabbit

Experiments in the anesthetized rabbit have demonstrated that the caudal ventrolateral medulla oblongata contains tonically active vasodepressor neurons which are themselves inhibited by GABAergic and glycine-like inputs. Alteration of neuronal function in this region also elevates plasma vasopressin levels, contributing to, but not completely accounting for, the hypertension and pulmonary edema observed after destruction of neurons in the region.     

Beta-Alanine and Taurine Microinjected into the Rat Caudal Ventrolateral Medulla Increase Blood Pressure

Unilateral microinjections of GABA, glycine, β-alanine and taurine into the caudal ventrolateral medulla (CVLM) of the rat, led to an increase in blood pressure and heart rate. The responses to glycine, β-alanine and taurine but not to GABA could be blocked by strychnine. The responses to taurine and β-alanine but not to GABA and glycine could be blocked by 6-aminomethyl-3-methyl-4H-1,2,4-benzothiadiazine-1,1-dioxide (TAG), an antagonist of taurine. The taurine antagonist alone injected bilaterally into the CVLM produced a decrease in blood pressure. From CVLM areas microperfused with Krebs solution, spontaneous release of GABA, glycine, β-alanine and taurine was detected and high K⁺ stimulation caused a calcium-dependent release of GABA, β-alanine and taurine. These results suggest that β-alanine and taurine as well as GABA may be involved in modulation of the cardiovascular control within the CVLM.     

Effects of Pergolide,A Dopamine Receptor Agonist,and Clondine on Cardiovascular Responses Evoked by Activation of Peripheral Sympathetic Outflow in Rats

In pentobarbital anesthetized rats, pergolide (10.0 μ/kg, i.v.) and clonidine (3.0 μ/kg, i.v.) produced similar significant decreases in heart rate and carotid artery pressure. Sulpiride (0.3 mg/kg, i.v.) did not change the effects of clonidine but inhibited entirely the hypotension and partly the bradycardia produced by pergolide. However, yohimbine (0.3 mg/kg) antagonized the cardiovascular effects of clonidine and reduced the bradycardia produced by pergolide. In pithed rats with an experimental, submaximal tachycardia evoked by sustained electrical stimulation of the thoracic sympathetic outflow pergolide and clonidine decreased heart rate. This effect was antagonized by yohimbine (0.1 mg/kg, i.v.) but by not sulpiride (0.3 mg/kg, i.v.). In adrenalectomized, propranolol pretreated pithed rats the pressor responses to 15 sec periods of electrical stimulation of the entire spinal cord were depressed only by pergolide. This effect was blocked by sulpiride. These findings indicate that in the pithed rat the inhibition of neural sympathetic tachycardia by clonidine and pergolide is mediated by stimulation of cardiac presynaptic α₂-adrenoceptors. However, only pergolide decreased significantly the pressor responses evoked by electrical stimulation of the peripheral sympathetic outflow and this effect resulted from activation of dopamine receptors located on postganglionic sympathetic neurons innervating resistance blood vessels. Thus, vascular presynaptic α₂-adrenceptors do not appear to contribute to the significant hypotensive effect exerted by 3.0 μ/kg, i.v.     

Medullo-Spinal Modulation of Sympathetic Output and Spinal Afferent Input

Associated Inhibition of Sympathetic and Afferent Activities. In intact animals, it is important that most "tonic" sympathetic activity be regulated by brainstem systems that have access to "central commands" from higher centers and to highly specific cranial nerve afferents. The importance of this supraspinal regulation is manifested by severe derangements of sympathetic regulation after spinal cord injury. A major component of these derangements is an exaggerated responsiveness of sympathetic neurons to visceral and somatic afferent activity. Although much is known about medullo-spinal systems that excite sympathetic preganglionic neurons, little is known about those systems that, in intact animals, isolate preganglionic neurons from spinal afferent input. This brief review will consider the evidence that either identical or cospatial medullary systems regulate the output of sympathetic preganglionic neurons and afferent input to the spinal cord. Further, evidence from this laboratory is presented, which indicates that a recently described system in the rostral cervical spinal cord, perhaps in concert with medullary systems, may play an important role in regulating the excitation of sympathetic preganglionic neurons by spinal afferents.     

Abdominal Vagal Inputs to Catecholamine Neurons in the Ventrolateral Medulla

Stimulation of the abdominal vagus nerve increases arterial pressure and causes secretion of vasopressin. We have shown in rabbits that the arterial pressure increases are mediated by activation of barosensitive bulbospinal neurons in the C1 region of the rostral medulla. Secretion of vasopressin involves activation of neurons in the A1 region of the caudal ventrolateral medulla. Neuroanatomical studies with Fos indicate that approximately 50% of the C1 area cells are C1 neurons. Approximately 70% of the A1 area cells are A1 neurons. These neurons may mediate physiological responses occurring during abdominal malaise resulting from ingestion of toxins. Our discovery of a major excitatory input to A1 and C1 neurons from the abdominal vagus should prove useful in studies of the function of these neurons.     

Responsiveness of α2-adrenoceptor/I1-imidazoline receptor in the rostral ventrolateral medulla to cardiovascular regulation is enhanced in conscious spontaneously hypertensive rat

Stimulation of α2-adrenoceptor/I1-imidazoline receptors in the rostral ventrolateral medulla decreases the blood pressure via sympathoinhibition. However, alteration of receptor responses in genetically hypertensive rats remains unclear. We examined cardiovascular responses of α2-adrenoceptor/I1-imidazoline receptor agonist and antagonists microinjected into the rostral ventrolateral medulla of conscious spontaneously hypertensive rats and normotensive Wistar Kyoto rats. Injection of 2-nmol clonidine—an α2-adrenoceptor/I1-imidazoline receptor agonist—unilaterally into the rostral ventrolateral medulla decreased the blood pressure, heart rate, and renal sympathetic nerve activity; the responses were significantly enhanced in spontaneously hypertensive rats than in Wistar Kyoto rats. Co-injection of 2-nmol 2-methoxyidazoxan (a selective α2-adrenoceptor antagonist) or 2-nmol efaroxan (an I1-receptor antagonist) with 2 nmol of clonidine attenuated the hypotensive and bradycardic effects of clonidine-only injection. Injection of 2-methoxyidazoxan alone increased the blood pressure and heart rate in spontaneously hypertensive rats, but not in Wistar Kyoto rats. These results suggest enhanced responsiveness of α2-adrenoceptor/I1-imidazoline receptors in the rostral ventrolateral medulla of spontaneously hypertensive rats.