蓝斑参与调节室旁核对心血管活动的作用

为探讨化学刺激室旁核对心血管活动的影响及蓝斑在这一效应中的作用,给乌拉坦和氯醛糖混合液麻醉的Wistar系雄性大鼠室旁核微量注射L-谷氨酸,观察了血压、心率和肾交感神经放电活动的变化以及用红藻氨酸损毁蓝斑对刺激室旁核效应的影响.另外,为进一步研究室旁核与蓝斑功能联系的机制,也观察了蓝斑核区微量注射血管升压素对心血管活动的影响.结果表明:①室旁核内注射L-谷氨酸引起血压下降、心率减慢和肾交感神经活动减弱;②损毁蓝斑后,刺激室旁核引起的心血管效应明显减弱;③蓝斑区注射血管升压素导致血压升高、心率加快、肾交感神经放电增加.提示:①L-谷氨酸兴奋室旁核抑制心血管活动;②室旁核的上述效应可能与交感神经紧张性降低有关;③蓝斑参与室旁核对心血管活动的调节过程;④血管升压素刺激蓝斑引起心血管活动加强.     

蓝斑参与调节室旁核对心血管活动的应用

为探讨化学刺激室旁核对心血管活动的影响及蓝斑在这一效应中的作用,给乌拉坦和氯醛糖混合液麻醉的Ｗｉｓｔａｒ系雄大鼠室旁核微量注射Ｌ－谷氨酸,观察了血压、悯率和肾交感神经放电活动的变化以及用红藻氨酸损毁蓝斑对刺激室旁核效应的影响。另外,为进一步研究旁核与蓝斑功能联系的机制,也观察了蓝斑核区微量注射血管升压素对心血管活动的影响。结果表明：①室旁核内注射Ｌ－谷氨酸引起血压下降、心率减慢和肾交感神经活动减弱     

下丘脑室旁核对大鼠胃缺血——再灌注损伤调控的神经机制

采用夹闭大鼠腹腔动脉30min,松开动脉夹血流复灌1h的胃缺血-再灌注损伤模型,观察了电和化学刺激以及电损毁下丘脑室旁核（paraventricular nucleus,PVN）对大鼠胃缺血-再灌注损伤(gastric ischemia-reperfu-sion injury,GI-RI）的影响,并对其调控的神经机制进行了初步研究。结果表明：①电刺激PVN或PVN内注射L-谷氨酸后,GI-RI均显著减轻;②电解损毁双侧PVN则能加重GI-RI;③损毁双侧孤束核（nucleus tractus solitarius,NTS）后,能取消电刺激PVN对GI-RI的减轻作用;④去除脑垂体后不影响电刺激PVN对GI-RI的作用;⑤分别切断膈下迷走神经和切除腹腔交感神经节后,电刺激PVN使GI-RI较单纯电刺激PVN组明显减轻。提示：PVN是对GI-RI具有保护作用的特异性中枢部位,孤束核以及外周迷走神经、交感神经均参与了PVN对GI-RI的调控,而与室旁核-垂体通路似无关系。     

损毁下丘脑室旁核尿崩症动物模型的建立及评价

目的建立下丘脑室旁核损伤引起的中枢性尿崩症的大鼠模型.方法选择SD清洁级大鼠,采用立体定向技术向下丘脑室旁核注射海人藻酸而损毁之;对照组则注射人工脑脊液.注射30 min后收集1 h尿量,并用放免法检测血浆精氨酸加压素（AVP）水平,同时取注药部位的脑组织作组织学检查,观察室旁核神经元活性.结果下丘脑室旁核损毁后的大鼠尿量明显多于对照组（P＜0.05）;血浆AVP水平明显低于对照组（P＜0.05）.组织学观察表明实验组室旁神经元尼氏小体较对照组明显减少.结论在严格控制实验动物及实验条件前提下,采用立体定向技术损毁下丘脑室旁核建立尿崩症动物模型的方法是可行的.     

下丘脑室旁核在调节水、钠代谢神经网络中的作用

下丘脑是调节自主神经系统的最重要的中枢神经结构,它包括对摄食、水电解质平衡、体温、睡眠、情绪、感觉、性行为、垂体激素释放、昼夜节律调节等多种功能的影响。而下丘脑室旁核(paraventricular nucleus,PVN)是其中重要的核团之一,参与以上多种功能调节。目前对下丘脑及PVN的研究成果颇多,但由于其神经网络关系复杂,存在从分子水平到大体神经解剖结构之间连续或不连续的整合关系,还需长期创新性的探索以揭示其奥秘。     

局灶脑缺血鼠下丘脑室旁核促肾上腺皮质素释放激素的表达

目的探讨脑缺血对下丘脑垂体肾上腺轴的影响。方法动态观察局灶脑缺血鼠下丘脑室旁核（ＰＶＮ）促肾上腺皮质素释放激素（ＣＲＨ）的变化，采用免疫组化方法显示ＰＶＮＣＲＨ的表达。结果正常对照组鼠下丘脑ＰＶＮ有少量ＣＲＨ的表达，脑缺血２天内下丘脑ＰＶＮ无ＣＲＨ的表达，脑缺血第三天后ＣＲＨ的表达明显增多，且一直持续到脑缺血的第八周，而假手术组４周基本恢复正常。结论脑缺血后下丘脑ＰＶＮ的ＣＲＨ分泌细胞立即被激活；长期脑缺血使ＣＲＨ分泌细胞的活动增强。     

下丘脑室旁核神经元亚群在应激反应中的作用与机制

下丘脑室旁核由多种类型神经元构成,是启动并调节应激反应的关键核团之一。在应激源的作用下,下丘脑室旁核神经元释放多种激素至垂体门脉系统或神经垂体,启动应激反应,并在生殖稳态、电解质平衡以及血压调节中发挥关键作用。本文综述了下丘脑室旁核的不同神经元亚群在应激中的作用与研究进展,旨在为应激的机制研究和药物研发提供新的思路。     

银杏内酯B对大鼠下丘脑室旁核神经元自发放电的影响

目的 研究银杏内酯B(GinkgolideB,BN52021)对静息状态下的下丘脑脑片室旁核神经元自发放电活动的影响.方法 应用细胞外记录单位放电技术.结果 (1)在27个下丘脑室旁核神经元放电单位给予银杏内酯B(0.1,1,10μmol/L)2分钟,有26个放电单位(96.30%)放电频率明显降低,且呈剂量依赖性;(2)预先用0.2 mmol/L的L-glutamate(L-Glu)灌流下丘脑脑片,8个放电单位放电频率明显增加,表现为癫痫样放电,在此基础上灌流银杏内酯B(1 μmol/L)2分钟,其癫痫样放电全部被抑制;(3)预先用L型钙通道开放剂BayK 8644灌流8个下丘脑脑片,8个放电单位(100%)全部放电增加,在此基础上灌流银杏内酯B(1μmol/L)2分钟,8个放电单位(100%)放电频率明显减低(4)在8个下丘脑室旁核神经元放电单位上,银杏内酯B(1 μmol/L)的抑制效应可被广泛钾通道阻断剂(tetraethylammonium,TEA)1 mmol/L完全阻断.结论 银杏内酯B(GinkgolideB,BN52021)可抑制下丘脑室旁核神经元自发放电,并可抑制由L-glutamate诱发的神经元放电.提示银杏内酯B对心血管中枢神经元通过降低其活动而具有一定程度的保护作用,这种作用可能与银杏内酯B抑制L型钙通道有关,而且可能与延迟整流型钾通道(delayedrectifier potassium channel,K<,DR>)有关.     

损毁大鼠下丘脑室旁核后AVP和ANP的关系

目的借助立体定向技术尝试建立因下丘脑室旁核损伤引起的中枢性尿崩症动物模型.在此基础上探讨下丘脑室旁核调节水钠代谢的机制.方法SD大鼠在立体定向仪引导下,试验组向下丘脑室旁核(PVN)注射海人藻酸,以达到损毁目的;对照组则注射人工脑脊液,取血检测血管加压素(AVP)和心钠素(ANP)水平.对比分析尿量,研究PVN损伤后AVP和ANP在体内的变化.结果下丘脑PVN损毁后试验组大鼠尿量为(1.26±0.34)ml,明显多于对照组(0.78±0.16)ml;检测血浆AVP和ANP含量分别为:试验组(3.91±0.48)pg/ml、(332±27.48)pg/ml:对照组(8.05±0.78)pg/ml、(291±31.66)pg/ml.结论下丘脑PVN损毁后血浆AVP水平降低,而ANP水平反而升高,该结果可能是下丘脑损伤后机体水钠代谢紊乱的深层原因,即具体表现为肾脏排水排钠增加.     

迷走神经切断对胃肠道给予大鼠伤寒杆菌诱发的下丘脑室旁核和视上核Fos表达的影响

为研究迷走神经在自然感染状态下向脑传递免疫信息的作用。应用免疫组织化学方法,观察了切断隔下迷走神经对大鼠消化道内给予鼠伤寒杆菌刺激诱发的下丘脑室旁核和视上核的Fos表达变化的影响。结果发现,接受细菌刺激的动物与仅给予生理盐水的动物相比,回肠和肠系膜淋巴结有明显炎症存在,室旁结果发现,接受细菌刺激的动物与仅给予生理盐水的动物相比,回肠和肠系膜淋巴结有明显炎症存在,室旁核外侧部和视上核背侧部的Fos阳性细胞数增加;膈下迷走神经切断后,手术 细菌组与假手术 细菌组相比,室旁核的外侧部和视上核背部Fos表达减少。因此迷走神经途径在自然感染性免疫应答过程中,特别是在其早期阶段可能是传递腹腔免疫信息的重要途径之一。     

Differentiated cardiovascular afferent regulation of locus coeruleus neurons and sympathetic nerves

The activity of brain norepinephrine (NE) neurons in the locus coeruleus (LC) and peripheral sympathetic nerve activity (NE-SNA) in the splanchnic/renal nerve were recorded simultaneously during alterations of arterial blood pressure and circulating blood volume. Utilizing this experimental procedure we have previously found that both central and peripheral NE neurons are inhibited during blood pressure elevation. Furthermore, both neuronal systems were found to be inhibited during blood volume load, an effect apparently mediated by vagal afferents. In the present study both brain NE-LC activity and NE-SNA were increased during blood volume depletion. However, during prolonged hemorrhage the initial excitation of NE-SNA was followed by a marked inhibition. In contrast, the increase in NE-LC activity remained throughout the volume depletion period. The responses of central and peripheral NE neurons during hemorrhage were abolished in animals subjected to bilateral cervical vagotomy. Nitroprusside- or phenylephrine-induced blood pressure variations were associated with reciprocal changes in both central and peripheral NE neuronal activity. The NE-LC responses to blood pressure variations were abolished after bilateral vagotomy. NE-SNA responses, on the other hand, persisted after bilateral vagotomy. Our present and previous findings show that brain NE-LC neurons, similarly to peripheral NE neurons in the splanchnic/renal nerve, are regulated by tonically active cardiovascular afferents. Whereas peripheral NE-SNA is regulated by both arterial (high pressure) baroreceptors and cardiac volume (low pressure) receptors, the NE-LC neurons seem exclusively regulated by cardiac volume (low pressure) receptors.     

Locus coeruleus neurons and sympathetic nerves: Activation by cutaneous sensory afferents

The effects of mechanical and thermal cutaneous sensory stimulation on the activity of central norepinephrine (NE) neurons in the locus coeruleus (LC) and on peripheral sympathetic nerve activity (NE-SNA) in a renal branch of the splanchnic nerve were studied, using electrophysiological techniques in the anesthetized rat. Noxious, mechanical sensory stimulation caused a parallel and virtually identical change in central NE-LC activity and peripheral NE-SNA and both neuronal systems showed a biphasic excitation-inhibition response. Both non-noxious and noxious thermal sensory stimulation above 36 degrees C caused a parallel increase in NE-LC firing rate and NE-SNA, changes that were accompanied by increases in arterial blood pressure and heart rate. The increases in central and peripheral NE neuronal activity were linearly correlated. However, the two neuronal systems differed in their ability to adapt during prolonged noxious thermal stimulation. NE-LC neurons adapted completely and returned to baseline firing rate within 5 min during ongoing noxious thermal stimulation. In contrast, an increase in NE-SNA remained throughout the stimulation period. In recent studies in this laboratory, blood volume depletion was found associated with a marked NE-LC activation. In contrast to the present results during prolonged noxious stimulation, there was no attenuation of the NE-LC activation during prolonged hemorrhage. Taken in conjunction, these data indicate a discriminatory capacity of the NE-LC system in monitoring sensory or autonomic stimuli. Thus, only those stimuli of imperative importance for the animal were found to be associated with continuing robust NE-LC discharge.     

An investigation into the mechanism of cardiovascular responses elicited by electrical stimulation of locus coeruleus and subcoeruleus in the cat

Electrical stimulation of locus coeruleus (LC) and subcoeruleus (SC) elicited an increase in heart rate (HR) and blood pressure (BP). Adrenergic neurone blockade in the posterior hypothalamus with guanethidine and also bilateral adrenalectomy completely blocked the LC stimulation induced cardiovascular responses. The cardiovascular responses elicited by electrical stimulation of SC were, however, unaffected by the former and only partially inhibited by the latter. It is suggested that the LC stimulation-evoked rise in HR and BP is mediated by catecholamine release from the adrenal medulla due to an activation of the hypothalamic-adrenal axis. The cardiovascular responses elicited by stimulation of SC are mainly due to activation of the sympathetic preganglionic neurones and are further augmented by the adrenal catecholamine release.     

Central Oxytocin Mediates Stress-Induced Tachycardia

To address the role of oxytocin in the control of cardiovascular reactivity, we examined the effect of central injection of oxytocin, vasopressin and mixed base antisense oligodeoxynucleotides on stress-induced cardiovascular and endocrine changes. Antisense oligomers were injected into the paraventricular nucleus (PVN), 4 h prior to the stress test. The oxytocin antisense abolished the tachycardia produced by 5 min of shaker stress. The blood pressure and plasma oxytocin responses were not different between the groups. PVN levels of OT were reduced in the oxytocin antisense-treated group while brain stem levels were increased. These results demonstrate the importance of a specific peptide system, the PVN/oxytocin axis, in stress-induced tachycardia. Further, the data illustrate the effectiveness of short-term treatment with antisense oligomers on physiological responses.     

Nucleus locus coeruleus: A morphometric golgi study in rats of three age groups

Using Rapid Golgi and Nissl techniques, 3 major cell types: fusiform, multipolar and avoid shaped cells were identified in the nucleus locus coeruleus of male rats. Each cell type was described and quantitated as to age-related changes between 30 and 90 and between 90 and 220 days of age. The orientation and dendritic architecture of each type of cell in the locus coeruleus and relationship of these cells to blood vessels in the locus coeruleus and to surrounding structures is also described. One hundred neurons per age group were measured as to their maximal linear extent and the number of spines on the somal surfaces were counted. Dendritic number, linear extent, diameter and number of spines along a 50 μm segment near the mid-point of dendritic extensions in an equal number of primary and secondary dendrites were quantified for each age group and comparisons of these parameters between each cell group were made. Axons of each cell type were defined as to their origin and general orientation and trajectory. Axon collaterals of multipolar cells were shown to be recurrent in type projecting back onto the dendrites and soma of multipolar cells. One of the most striking findings was that between 30 and 90 days there were significant decreases in spine density on both primary and secondary dendrites in all three cell types in the locus coeruleus. This was followed by significant increases in spine density on both primary and secondary dendrites between 90 and 220 days in each of the 3 cell types. It is of interest that these age-related cell changes in spine density in the nucleus locus coeruleus are exactly out-of-phase with those of the nucleus raphe dorsalis.     

Participation of the nucleus locus coeruleus in DOCA-salt hypertensive rats

The locus coeruleus was subjected to biphasic electrical stimulation, and a group of deoxycorticosterone acetate (DOCA)-salt hypertensive rats revealed a greater pressor response than a group of normotensive control rats. The pressor threshold current (i.e. minimum current to raise the arterial pressure by 10 mm Hg) of DOCA-salt hypertensive rats was also lower. The threshold current was low even in the prehypertensive stage of DOCA-salt treated rats. During arterial pressure fall, the pressurethreshold current lowered only in normotensive rats and neither group underwent a change during pressure rise. These data indicated that the locus coeruleus had a pressor role and it had been accelerated in DOCA-salt treated rats before hypertension was evident. Following bilateral electrical lesions of the locus coeruleus no significant differences were observed in the arterial pressure changes, while vascular reactivity to norepinephrine did not differ between the two groups. The results suggest that the locus coeruleus may be involved in the development of hypertension but may not be important in the maintenance of it.     

Role of N‐methyl‐D‐aspartate and non‐N‐methyl‐D‐aspartate receptors in the cardiovascular effects of L‐glutamate microinjection into the hypothalamic paraventricular nucleus of unanesthetized rats

We report on the cardiovascular effects of L‐glutamate (L‐glu) microinjection into the hypothalamic paraventricular nucleus (PVN) as well as the mechanisms involved in their mediation. L‐glu microinjection into the PVN caused dose‐related pressor and tachycardiac responses in unanesthetized rats. These responses were blocked by intravenous (i.v.) pretreatment with the ganglion blocker pentolinium (PE; 5 mg/kg), suggesting sympathetic mediation. Responses to L‐glu were not affected by local microinjection of the selective non‐NMDA receptor antagonist NBQX (2 nmol) or by local microinjection of the selective NMDA receptor antagonist LY235959 (LY; 2 nmol). However, the tachycardiac response was changed to a bradycardiac response after treatment with LY235959, suggesting that NMDA receptors are involved in the L‐glu heart rate response. Local pretreatment with LY235959 associated with systemic PE or dTyr(CH₂)₅(Me)AVP (50 μg/kg) respectively potentiated or blocked the response to L‐glu, suggesting that L‐glu responses observed after LY235959 are vasopressin mediated. The increased pressor and bradycardiac responses observed after LY + PE was blocked by subsequent i.v. treatment with the V₁‐vasopressin receptor antagonist dTyr(CH₂)₅(Me)AVP, suggesting vasopressin mediation. The pressor and bradycardiac response to L‐glu microinjection into the PVN observed in animals pretreated with LY + PE was progressively inhibited and even blocked by additional pretreatment with increasing doses of NBQX (2, 10, and 20 nmol) microinjected into the PVN, suggesting its mediation by local non‐NMDA receptors. In conclusion, results suggest the existence of two glutamatergic pressor pathways in the PVN: one sympathetic pathway that is mediated by NMDA receptors and a vasopressinergic pathway that is mediated by non‐NMDA receptors. © 2009 Wiley‐Liss, Inc.     

Evidence against specificity of electrical stimulation of the nucleus locus coeruleus in activating the sympathetic nervous system in the rat

Electrical stimulation of the central nucleus locus coeruleus (LC) was previously shown to increase activity of the peripheral sympathetic nervous system (SNS) as measured by increases in plasma levels of the norepinephrine (NE) metabolite 3-methoxy-4-hydroxyphenthyleneglycol (MHPG) in the rat⁵. Four experimental approaches were designed to test the specificity of the LC cell group in activating the SNS in the stimulation paradigm. Varying the stimulation current amplitude, varying the site of stimulating electrode placement, and electrolytic lesions of the LC yielded results consistent with the hypothesis that the site of SNS activation was within the anatomical region of the LC cell group. Neurochemical lesioning with intraventricular 6-hydroxydopamine, however, did not effectively block the plasma MHPG increase observed after stimulation of the LC region. The possibility that non-noradrenergic cells, fibers of passage, or terminals in the LC region of the midbrain may be responsible for SNS activation when the LC is electrically stimulated is discussed. These studies are pertinent to all studies of LC function which employ electrical stimulation of the LC nucleus, including investigations of the role of the LC in social behavior, intracranial self-stimulation, and blood pressure regulation.