大鼠头端延髓腹外侧区神经元对电刺激中脑导水管周围灰质背侧部及腹外侧部的反应（英文）

观察了大鼠延髓头端腹外侧区（rostralventrolateralmedulla，RVLM）神经元电活动对电刺激中脑导水管周围灰质背侧部及腹外侧部（dorsalandventrolateralperiaqueductalgraymatter，dPAG和vPAG）的反应。在139个神经元中,有92个被刺激dPAG兴奋；125个神经元中，有72个被刺激vPAG抑制。相当数量的神经元接受dPAG和vPAG的汇聚影响。刺激vPAG可减弱刺激dPAG在RVLM引起的兴奋反应。在检测的36个神经元中，有24个因具有压力敏感性并投射至脊髓而被认为是心血管神经元。这些结果与RVLM的心血管活动整合功能有关。     

L—NA对大鼠学习记忆的影响及NO、SS相关性研究

目的 探讨一氧化氮（NO）和生长抑素（SS）在学习记忆过程中的作用及相互作用。方法 大鼠海马微量注射一氧化氮合酶（NOS）抑制剂N-ω硝基－L精氨酸（N-ω－Nitro-L-Arginine,L-NA) 后采用Y型电迷宫观察大鼠学习记忆能力的改变,以硝酸还原酶法测定海马NO含量,以放射免疫法测定海马SS含量,并进行学习记忆能力、NO含量和SS含量相关性分析。结果 海马微量注射L－NA组大鼠与生理盐水对照组和正常对照组比较,海马中NO、SS含量明显下降（P＜0．01）。Y型电迷宫测定次数明显增加（P＜0．01）,L－NA组大鼠海马NO水平和SS水平呈显著正相关,NO、SS水平均与Y型电迷宫测试次数呈显著负相关。结论 海马中NO、SS水平的正常是机体实现正常学习和记忆过程的重要因素;NO可能通过调节SS的合成和释放,共同促进学习和记忆过程。     

脑室注射L—精氨酸抑制授乳大鼠射乳反射

为判断中枢一氧化氮（ＮＯ）对射乳反射的影响，以乳内压变化为指标，观察了脑室注射ＮＯ供体Ｌ－精氨酸对授乳大鼠反射性与诱发性射乳的影响。结果发现，Ｌ－精氨酸对吸吮刺激所诱导的反射性射乳具有明显的抑制性作用。提示，中枢ＮＯ确实对射乳反射中枢具有抑制性作用。     

丘脑中央下核和顶盖前区前核分别参与介导强电针和弱电针的 …

在大鼠以强电刺激外周感受野诱发的脊髓背角ＷＤＲ和ＮＳ神经元的晚串放电（Ｃ－反应）作为伤害感受性反应，观察了双侧丘脑中央下核（Ｓｍ）或顶盖前区前核（ＡＰｔＮ）内微量注射局麻药利多卡因对不同强度电针引起的镇痛效应的影响。结果表明：双侧Ｓｍ局麻可明显减弱强电针对Ｃ－反应的抑制效应，但对弱电针的抑制效应无明显影响，双侧ＡＰｔＮ局麻可明显减弱弱电针对Ｃ－反应的抑制效应，但以强电针的抑制效应无明显影响，结果提     

红核在大脑皮质下行调控脊髓伤害感受性传递中的作用

以电刺激外周感受野诱发的大鼠脊髓背角WDR和NS神经元的晚串放电（C-反应）为指标，以串脉中刺激对侧大脑脚（CP）作为条件刺激，在C-反应受到明显抑制的神经元。分别观察了电解损毁红核（RN）和RN内注射兴奋性氨基酸的受体拮抗剂对刺激CP的下行抑制作用的影响。结果发现：损毁同侧RN后，刺激CP对C反应的抑制作用明显减弱，而损毁同侧RN背侧结构，对侧RN及假损毁RN均无此效应；RN内微量注射兴奋性氨基酸受体拮抗剂AP5和DNQX均可减弱刺激CP对C-反应的抑制。提示RN至少部分参与大脑皮质对脊髓伤害感受性传递的下行抑制作用。且以同侧RN为主；在与痛觉调制有关的皮质-RN通路中既有NMDA受体又有非NMDA受体的参与。     

中枢神经系统一氧化氮对大鼠的痛觉调制作用

以钾离子透入引起大鼠甩尾的电流强度(mA)作为痛反应指标,采用侧脑室微量注射L-精氨酸(L-Arg)、亚甲基蓝(MB)等,观察大鼠痛阈的变化,分析探讨中枢神经系统中一氧化氮(NO)对大鼠痛觉的调制作用.结果显示:大鼠侧脑室微量注射NO前体及供体物质L-Arg和硝普钠(SNP)均引起明显的痛敏效应.微量注射MB和L-NAME后大鼠痛阈升高非常显著.侧脑室微量注射MB和L-Arg混合液后,大鼠痛阈较单纯注射MB组表现出明显降低的趋势,但与L-Arg组相比大鼠痛阈升高明显.提示:提高中枢内NO水平具有明显的痛敏效应,而降低中枢神经系统NO水平表现显著镇痛作用.中枢神经系统NO对大鼠痛觉的调制作用至少部分是通过NO-cGMP途径实现的.     

一氧化氮对大鼠学习功能的影响

为探讨一氧化氮（NO）在学习过程中的可能作用，采用荧光分光光度法检测隔-海马通路损伤的大鼠以及海马微量注射一氧化氮合酶（NOS）抑制剂NG-硝基-L-精氨酸（NNLA）大鼠的海马和大脑皮层及外周血中NO含量的变化，并采用水迷宫和跳台试验同时观察大鼠学习能力的改变，结果表明隔-海马通路损伤或海马微量注射NNLA大鼠，海马中NO含量均明显下降并出现学习功能障碍，提示NO在学习过程中起重要作用。     

中枢神经系统一氧化氮对大鼠的痛觉调制作用

以钾离子透入引起大鼠甩尾的电流强度（ｍＡ）作为痛反应指标,采用侧脑室微量注射Ｌ－精氨酸（Ｌ－Ａｒｇ）、亚甲基蓝（ＭＢ）等,大鼠痛阈的变化,分析探讨中枢神经系统中一氧化氮（ＮＯ）对大鼠痛觉的调制作用,结果显示：大鼠侧脑室微量注射ＮＯ前体及供体物质Ｌ－Ａｒｇ和硝普钠（ＳＮＰ）均引起明显的痛敏效应。微量注射ＭＢ和Ｌ－ＮＡＭＥ后大鼠痛阈升高非常显著。侧脑室微量注射ＭＢ和Ｌ－Ａｒｇ混合液后,大鼠痛阈较单纯注     

下丘脑外侧区胃泌素神经元对大鼠胃缺血—再灌注损伤的作用

目的：观察下丘脑外侧区（lateral hypothalamic area,LHA)对胃缺血－再灌注损伤（gastric ischemia-reperfusion injury,GI-RI)的影响，并对LHA的调控通路进行了初步分析。方法：采用夹闭大鼠腹腔动脉30min，松开动脉夹血流复灌60min的GI－RI模型，用电和化学刺激，电损毁和核团微量注射等方法。结果：（1）电或化学刺激LHA均显著加重GI－RI；（2）背侧迷走复合体（dorsal vagal complex,DVC)内微量注射五肽胃泌素后，对GI－RI的效应与电刺激一致；（3）电解损毁双侧DVC或DVC内微量注射胃泌素受体阻断剂丙谷胺均可取消电刺激LHA加重GI－RI的作用。（4）切断膈下迷走神经后电刺激LHA，GI－RI则减轻。结论：LHA具有加重大鼠GI－RI的作用；LHA的这种作用可能是因电或化学刺激后，激活了其中的胃泌素能神经元，经其下行投射纤维释放胃泌素作用于DVC神经元上的胃泌素受体，并通过迷走神经介导，从而影响GI－RI。     

丘脑中央下核和顶盖前区前核分别参与介导强电针和弱电针的镇痛效应

在大鼠以强电刺激外周感受野诱发的脊髓背角ＷＤＲ和ＮＳ神经元的晚串放电（Ｃ－反应）作为伤害感受性反应,观察了双侧丘脑中央下核（Ｓｍ）或顶盖前区前核（ＡＰｔＮ）内微量注射局麻药利多卡因对不同强度电针引起的镇痛效应的影响。结果表明：双侧Ｓｍ局麻可明显减弱强电针对Ｃ－反应的抑制效应,但对弱电针的抑制效应无明显影响;双侧ＡＰｔＮ局麻可明显减弱弱电针对Ｃ－反应的抑制效应,但对强电针的抑制效应无明显影响。结果提示,不同强度的电针刺激可能由粗细不同的纤维传入,通过不同的中枢机制产生镇痛作用。Ｓｍ参与介导强电针兴奋细纤维产生的镇痛作用;ＡＰｔＮ则参与介导弱电针兴奋粗纤维产生的镇痛作用。     

Electroacupuncture induces c-Fos expression in the rostral ventrolateral medulla and periaqueductal gray in cats: relation to opioid containing neurons

Our previous studies have shown that electroacupuncture (EA) at the Neiguan-Jianshi (P5-P6) acupoints inhibits sympathetic outflow and attenuates excitatory visceral cardiovascular reflexes through enkephalin- or beta-endorphin-related opioid receptors in the rostral ventrolateral medulla (rVLM). It is not known whether EA at these acupoints activates neurons containing enkephalin or beta-endorphin in the rVLM as well as in the periaqueductal gray (PAG) that are involved in EA-mediated central neural regulation of sympathetic activity. The present study evaluated activated neurons in the rVLM and PAG by detecting c-Fos immunoreactivity, and identified the relationship between c-Fos nuclei and neuronal structures containing enkephalin or beta-endorphin in these regions. To enhance the detection of cell bodies containing enkephalin or beta-endorphin, colchicine (90-100 microg/kg) was injected into the subarachnoid space in anesthetized cats 28-30 h prior to EA or the sham-operated control for EA. Following bilateral barodenervation and cervical vagotomy, EA (1-4 mA, 2 Hz, 0.5 ms) was performed at the P5-P6 acupoints (overlying median nerve; n=7) for 30 min. Identical procedures, with the exception of electrical stimulation, were carried out in five control animals. EA decreased blood pressure (BP) in four of seven cats (5-15 mm Hg) while the sham procedure for EA produced no responses. Perikarya containing enkephalin were found in the rVLM and rarely in the PAG, while no cell bodies labeled with beta-endorphin were identified in either region. Compared to animals in the control group, more c-Fos immunoreactivity, located principally in close proximity to fibers containing enkephalin or beta-endorphin, was observed in the rVLM and ventrolateral PAG (vlPAG) in EA-treated cats. Moreover, neurons double-labeled with c-Fos and enkephalin in the rVLM were significantly increased in cats following EA stimulation (P<0.05). These data indicate that EA at the P5-P6 acupoints activates neurons in the rVLM and vlPAG. These activated neurons contain enkephalin in the rVLM, and most likely interact with nerve fibers containing enkephalin or beta-endorphin in both the rVLM and vlPAG. The results from this study provide the first anatomical evidence showing that EA at the P5-P6 acupoints has the potential to influence neuronal structures (perikarya, axons and/or dendrites) containing enkephalin or beta-endorphin in specific regions of the brain stem. These neurons likely form the substrate for EA's influence on sympathoexcitatory cardiovascular reflexes.     

Conditioned place aversion organized in the dorsal periaqueductal gray recruits the laterodorsal nucleus of the thalamus and the basolateral amygdala

The amygdala-ventral periaqueductal gray circuit is crucial for the expression of contextual conditioned fear. However, little is known about the neural circuits activated when the stimulation of the dorsal periaqueductal gray (dPAG) is used as unconditioned stimulus (US) in conditioned fear paradigms. The present paper examines the Fos-protein distribution in the brain of rats submitted to a conditioned place aversion (CPA) paradigm using the dPAG chemical stimulation with semicarbazide (SMC), an inhibitor of the GABA synthesizing enzyme, as US and the quadrant of an arena where the drug was injected as the paired neutral stimulus. Our results show that CPA associated with SMC injections caused a significant Fos labeling in the laterodorsal nucleus of the thalamus (LD), basolateral nucleus of amygdala (BLA) and in the dorsomedial PAG (dmPAG). This pattern of brain activation is clearly different from the neural substrates of the classical fear conditioning reported in the literature. Moreover, this paper shows that CPA with the use of chemical stimulation of the dPAG could be used as an experimental model of panic disorder with agoraphobia in the extent that panic attacks repeatedly associated with specific contexts may turn in this condition in the clinics. This condition activates the BLA probably through the LD. Besides, it indicates that the dPAG can be the link between amygdala and the brainstem motor regions that controls CPA when dPAG stimulation is used as US instead of footshocks. From this evidence we suggest that a loop dPAG-LD-BLA-dPAG is activated during the panic disorder with agoraphobia.     

The dorsal periaqueductal and basolateral amygdala are necessary for the expression of conditioned place avoidance induced by semicarbazide stimulation of the dorsal periaqueductal region

The amygdala is critically involved in the regulation of unconditioned and conditioned reactions to threatening stimuli. It has been suggested that a neural circuit responsible for the production of defensive behavior elicited by the dorsal periaqueductal gray (dPAG) stimulation may project through ascending fibers to forebrain structures such as the basolateral complex of the amygdala (BLA). The present study evaluates the involvement of the dPAG and BLA in the mediation of unconditioned and conditioned responses organized in the dPAG using the open field and the conditioned place aversion (CPA) tests. In both tests, the intra-dPAG injections of semicarbazide (SEM), an inhibitor of the GABA synthesizing enzyme, was used as unconditioned stimulus (US). Using the open field test, we examine the effects of BLA inactivation with the GABA-(A) receptor agonist muscimol (MUS) on the unconditioned fear. We also investigated, through the CPA test, the effects of BLA and/or dPAG inactivation with MUS on the acquisition and the expression of the fear conditioned response. Our results showed that intra-BLA injections of MUS did not change the unconditioned fear elicited by dPAG injections of SEM. As for the CPA test, intra-BLA and intra-dPAG injections of MUS impaired the expression of CPA behavior induced by SEM injections into the dPAG. However, this inactivation of BLA did not impair the acquisition of the CPA behavior induced by injections of SEM into the dPAG. Altogether, these findings suggest that BLA does not participate in the mediation of unconditioned fear induced by dPAG chemical stimulation or in the acquisition of CPA in which aversive stimulation of the dPAG was used as US. In contrast, our results indicate that the activation of the dPAG and BLA is essential to the expression of the conditioned aversive response.     

Fear state induced by ethanol withdrawal may be due to the sensitization of the neural substrates of aversion in the dPAG

The neural substrate underlying the aversive effects induced by ethanol abstinence is still unclear. One candidate for such effects is the dorsal periaqueductal gray (dPAG), a core structure of the brain aversion system. The main aim of this study is to examine the role of the dPAG as a possible locus of the aversive effects following abrupt alcohol withdrawal. To this end, rats were subjected to an oral ethanol self-administration procedure, in which animals were offered 6-8% (v/v) ethanol solution for a period of 21 days followed by an abrupt discontinuation of the treatment on the two subsequent days. Control animals received control dietary fluid for similar periods of time. The effects of ethanol withdrawal were examined in the elevated plus-maze (EPM) (Exp. I), on the prepulse inhibition of startle to loud sounds (Exp. II) and on the freezing and escape responses induced by electrical stimulation of the dPAG (Exp. III). In Experiment III, rats were implanted with an electrode aimed at the dPAG and the number and duration of ultrasonic vocalizations (USVs) were also recorded in the rats that received dPAG stimulation at freezing and escape thresholds. Data obtained showed that ethanol withdrawal elicited significant "anxiety-like" behaviors, as revealed by the decrease in the number of entries into and time spent onto the open arms of the EPM. Startle reflex and prepulse inhibition remained unchanged in withdrawn animals. In addition, discontinuation from the chronic ethanol regimen caused a reduction in the stimulation thresholds for freezing and escape and in the number and duration of USVs. Together, these effects have been interpreted in the frame of a high fear state elicited by activation of the dPAG. These findings are indicative that ethanol withdrawal sensitizes the substrates of fear at the level of this midbrain structure.     

Stimulation of the ventrolateral medulla inhibits the baroreceptor input to the nucleus tractus solitarius

Extracellular recording experiments were done in urethane- and chloralose-anaesthetized, paralyzed and artificially ventilated rabbits. Thirty-one baroreceptor-sensitive neurones were identified in the region of the nucleus tractus solitarius (NTS) by their excitatory responses to stimulation of the ipsilateral aortic nerve. A conditioning stimulus delivered to the ipsilateral or contralateral rostral ventrolateral medulla (rVLM) inhibited the excitatory responses of 80.0% (19 out of 24) neurones to an aortic test stimulus as early as 3 ms and extending as long as 400 ms after conditioning. The same inhibitory effect was also observed by application of excitant amino acid DL-homocysteic acid (0.2 M, 100 nl) into the ipsi- or contralateral rVLM area in 6 units. In 5 units inhibited by rVLM stimulation, evoked discharges were inhibited by prolonged electrical stimulation of the superficial peroneal nerve (SP) with low intensity and low frequency (0.1-0.3 mA and 5-10 Hz). These results provide the electrophysiological evidence for the suppressing effect of the rVLM on the excitatory responses of NTS neurones to baroreceptor afferent stimulation.     

Respiratory responses elicited by rostral versus caudal dorsal periaqueductal gray stimulation in rats

The periaqueductal gray (PAG) is a central neural region essential for defense behavior and coordination of accompanying autonomic responses. Activation of rostral versus caudal dorsal (dPAG) regions mediates different cardiovascular response patterns. Stimulation of the dPAG also elicits increased respiratory activity, however, it is unknown if there is a regional difference in dPAG modulation of respiratory pattern. The present study was undertaken to identify whether activation of rostral vs caudal dPAG modulates respiration differently. In anesthetized, spontaneously breathing rats, chemical and electrical stimulation in rostral and caudal dPAG evoked an increased respiratory frequency (f(R)) with significant shortening of both inspiratory (Ti) and expiratory time (Te). Stimulation in the dPAG also evoked significant increases in electromyography activity of the diaphragm (dEMG), arterial pressure, and heart rate. Caudal dPAG stimulation evoked a greater increase in f(R) due to a significantly greater decrease in Ti and Te than the rostral dPAG. Caudal dPAG stimulation also evoked a greater increase in baseline dEMG activity and elicited a significantly greater increase in dEMG amplitude above baseline than rostral dPAG. There was a rostro-caudal difference in the post-stimulus respiratory recovery response, with the caudal dPAG eliciting a longer sustained effect. No regional differences were identified in the arterial blood pressure and heart rate during dPAG stimulation. The results demonstrate that the magnitude of the respiratory response during and immediately after activation of the caudal dPAG is greater than during rostral dPAG stimulation.     

Possible involvement of nitric oxide in the central salt-loading-induced cardiovascular responses in conscious rats

The objective of this study was to elucidate the possible involvement of nitric oxide (NO) in the cardiovascular responses induced by central salt loading. Direct perfusion of the hypothalamic paraventricular nucleus (PVN) region with hypertonic saline (0.3 or 0.45 M) was performed in conscious rats by using an in vivo brain microdialysis technique. The extracellular concentration of NO metabolites in the PVN region was measured, as were the blood pressure (BP) and heart rate (HR). Perfusion of 0.45 M saline increased the BP, HR, and NO metabolite levels in the PVN region; however, perfusion of 0.3 M saline enhanced only the level of NO metabolites but did not induce changes in the BP and HR. Next, we determined whether the NO was involved in the cardiovascular responses induced by hypertonic saline. 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 perfusion of 0.45 M saline, while direct infusion of 3-morpholinosyndnonimine (SIN-1, a NO donor) in the PVN region induced increases in the BP and HR. These results suggest that local perfusion of the PVN region with hypertonic saline elicits a local release of NO, which may be carried out by activating nitric oxide synthase to produce cardiovascular responses.     

Blockade of GABAA receptors in the region of the anterior basolateral amygdala of rats elicits increases in heart rate and blood pressure

Stimulation of the amygdala in rats is known to elicit increases in heart rate (HR) and blood pressure (BP) as well as locomotor activity associated with emotional arousal. The present study was conducted to localize and characterize the role of the GABA system of the amygdala in regulating these cardiovascular responses. Male Sprague-Dawley rats with arterial catheters placed for physiological measurements were implanted with chronic microinjection cannulae in the anterior basolateral (BLA) and central (Ce) amygdaloid nuclei under pentobarbital anesthesia. After recovering, rats were microinjected bilaterally with saline (250 nl) and bicuculline methiodide (BMI, 5-25 ng/250 nl), a selective GABAA antagonist. Microinjection of BMI in the BLA caused significant increases in HR and BP as well as locomotor stimulation while saline had no effect. The cardiovascular response to BMI was blocked by pentobarbital anesthesia. Microinjection of equimolar concentrations of (+)-baclofen HCl (GABAB agonist), phaclofen (GABAB antagonist), or strychnine (glycine antagonist) into the BLA or BMI into the Ce had no significant cardiovascular effects. The cardiovascular effects of BMI injection in the BLA does not appear to be secondary to generalized seizure activity. These results suggest that endogenous GABA, acting on GABAA receptors in the region of the BLA, may be involved in cardiovascular regulation.     

l-Allylglycine dissociates the neural substrates of fear in the periaqueductal gray of rats

The dorsal (dPAG) and ventral (vPAG) regions of the periaqueductal gray are well known to contain the neural substrates of fear and anxiety. Chemical or electrical stimulation of the dPAG induces freezing, followed by a robust behavioral reaction that has been considered an animal model of panic attack. In contrast, the vPAG is part of a neural system, in which immobility is the usual response to its stimulation. The defense reaction induced by the stimulation of either region is accompanied by antinociception. Although GABAergic mechanisms are known to exert tonic inhibitory control on the neural substrates of fear in the dPAG, the role of these mechanisms in the vPAG is still unclear. The present study examined defensive behaviors and antinociception induced by microinjections of an inhibitor of γ-aminobutyric acid synthesis, l-allylglycine (l-AG; 1, 3, and 5 μg/0.2 μl), into either the dPAG or vPAG of rats subjected to the open field and tail-flick tests. Passive or tense immobility was the predominant behavior after l-AG (1 or 3 μg) microinjection into the vPAG and dPAG, respectively, which was replaced with intense hyperactivity, including jumps or rearings, after injections of a higher dose (5 μg/0.2 μl) into the dPAG or vPAG. Moreover, whereas intra-dPAG injection of 3 μg l-AG produced intense antinociception, only weak antinociception was induced by intra-vPAG injections of 5 μg l-AG. These findings suggest that GABA mechanisms are involved in the mediation of antinociception and behavioral inhibition to aversive stimulation of the vPAG and exert powerful control over the neural substrates of fear in the dPAG to prevent a full-blown defense reaction possibly associated with panic disorder.