催产素抑制外周刺激诱发的大鼠海马LTP及Fos蛋白表达

 目的 探讨催产素对外周刺激诱发的大鼠海马LTP及Fos蛋白表达的影响。方法 单刺激诱发海马CA1区场电位；强直刺激坐骨神经，诱发海马CA1区长时程增强场电位（LTP）。在强直刺激前于侧脑室内微量注入催产素(Oxytocin，OT)及催产素受体拮抗剂－Atosiban，观察其对LTP的影响。用免疫组化法检测海马Fos蛋白表达。结果 单刺激坐骨神经在海马CA1区诱发出潜伏期固定(171.9±33.1) ms且可重复出现的以正波为主的场电位，平均幅度(25.7±8.4) μV。强直刺激诱导LTP产生，催产素可抑制海马LTP的诱导，但预先注射Atosiban后，海马CA1区仍能出现LTP，但持续时间比对照组短。强直刺激前，海马内c-fos表达为阴性；强直刺激后，表达增强，催产素组表达则较弱，催产素加拮抗剂组也呈强阳性表达。结论 催产素抑制海马LTP的诱导，减弱c-fos的表达，而Atosiban对该效应有一定的抑制作用。提示催产素可能是通过其受体发挥作用的。     

快速老化小鼠海马脑片CA1区神经元放电特征模式研究

目的研究快速老化对记忆脑区海马CA1神经元电活动兴奋性的影响。方法应用脑片和细胞外记录技术,记录快速老化（sAM．P／8）组和正常对照组小鼠在海马脑片CA1区的锥体神经元自发放电序列,通过计算2组神经元自发放电频率和神经元放电间隔（ISI）研究快速老化对海马CA1区神经元兴奋性的影响。结果快速老化组小鼠海马CA1区神经元自发放电频率为（1．052±0．364）Hz（样本数n1=14）,正常对照组为4．416＋1．306Hz（样本数n1=22）,前者比后者显著降低（P〈0．05）;快速老化组ISI≥1s,占80．5％,正常对照组ISI均≤1S,其中95．6％≤0．5S,前者比后者显著延长。结论快速老化组小鼠海马脑片CA1区神经元的发放频率降低,ISI延长。提示快速老化对小鼠海马区神经元兴奋性电活动起到了明显的抑制作用。     

银杏内酯B对大鼠海马CA1区神经元自发放电的影响(英文)

为了研究银杏内酯B(Ginkgolide B,BN52021)对静息状态下的海马脑片神经元活动的影响。本研究应用细胞外记录单位放电技术观察了银杏内酯B对海马神经元电活动的影响,并分析了相关机制。结果显示:(1)在43个CA1区神经元放电单位给予银杏内酯B(0.1,1,10μmol/L)2min,有42个放电单位(97.67%)放电频率明显降低,且呈剂量依赖性;(2)预先用0.2mmol/L的L-glutamate(L-Glu)灌流海马脑片,10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(1μmol/L)2min,其癫痫样放电全部被抑制;(3)预先用L型钙通道开放剂BayK8644灌流8个海马脑片神经元,8个单位(100%)放电全部增加,在此基础上灌流银杏内酯B(1μmol/L)2min,7个放电单位(87.5%)放电频率明显减低;(4)在8个CA1区神经元,银杏内酯B(1μmol/L)对单位放电的抑制效应可被1mmol/L广泛钾通道阻断剂(tetraethylammonium,TEA)完全阻断。上述结果提示,银杏内酯B可抑制海马CA1区神经元的自发放电,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(delayed rectifier potassium channel,KDR)有关。银杏内酯B通过降低神经元的活动而发挥对中枢神经元的保护作用。     

侧脑室注射肾上腺髓质素激活去缓冲神经大鼠最后区神经元

目的观察侧脑室注射肾上腺髓质素(AM)对去缓冲神经大鼠最后区神经元自发放电和Fos蛋白表达的影响。方法应用细胞外记录的电生理学方法,观察雄性SD大鼠神经元自发放电活动;用免疫组化方法检测Fos蛋白的表达。结果侧脑室注射AM(1,3nmol/kg)诱发最后区出现大量Fos样免疫阳性神经元(Fos-LI),最后区神经元自发放电频率明显增加;降钙素基因相关肽受体拮抗剂CGRP8-37(30nmol/kg)可明显减弱AM的效应。结论AM对最后区神经元有直接兴奋作用,降钙素基因相关肽受体介导这一效应。     

催产素减轻新生大鼠海马神经元缺氧缺血性损伤

目的:探讨催产素(oxytocin)对新生大鼠缺氧缺血性损伤后海马CA1区神经元的作用及机制。方法:采用氧糖剥夺(OGD)制备体外缺氧缺血模型,取8只7~10日龄新生大鼠的急性分离脑片(6~8片/只)随机分为4组,即对照组、OGD 20 min组、OGD 40 min组和OGD+oxytocin组,进行TO-PRO-3染色实验观察催产素对神经元的作用。另取20只新生大鼠脑片随机分为4组,分别是OGD组、OGD+oxytocin组、OGD+d VOT(催产素受体阻断剂)+oxytocin组和OGD+bicuculline(GABAA受体阻断剂)+oxytocin组,用全细胞膜片钳记录不同药物作用下海马神经元缺氧去极化的出现时间。结果:TO-PRO-3染色结果显示海马CA1区神经元死亡数量随着氧糖剥夺时间延长而增加,催产素能显著减少OGD所致的死亡神经元数目(P0.05)。全细胞膜片钳记录结果显示,催产素可使缺氧去极化时间显著延长;d VOT及bicuculline可以消除这种效应。结论:催产素能减轻新生大鼠海马CA1区神经元缺氧缺血性损伤,其机制可能是通过结合催产素受体,增强抑制性神经传递,从而产生神经保护作用。     

麦角新碱对电针红藻氨酸所致大鼠海马痫样放电的作用

本实验通过侧脑室注射红藻氨酸(KA)致癫,观察电针大椎、腰俞,微电泳麦角新碱(Ms)对海马痫样放电和海马脑电的影响,初步分析5—HT与电针抑制癫痫的关系。结果表明:1.电针穴位能抑制海马痫样放电和脑电,而电针穴位同时微电泳Ms时,Ms能80％翻转电针中的作用,表明内源性5—HT和5—HT能神经元能被电针穴位     

平行绑定多电极技术研究大鼠基底核毁损对海马自发放电的影响

目的:研究应用平行绑定多电极细胞外记录技术探讨海人藻酸(KA)注射毁损Meynert基底核(NBM)后海马CA1区自发放电活动的改变。方法:雄性SD大鼠在水合氯醛麻醉和脑立体定位仪引导下,KA注射后破坏双侧NBM,一周后用改装的平行绑定多电极记录大鼠海马CA1区自发放电活动。结果:(1)与传统的细胞外单电极或多电极记录相比,本方法电极制备简单、灵活、造价低廉,细胞损伤小,可同时记录单个核团内多个神经元或相邻脑区多个神经元的活动,便于进一步对神经元环路活动进行分析。结合锋电位分类技术,可对单一通道获得的多个神经元活动进行甑别,大大提高实验精度和效率;(2)比较NBM毁损组和对照组核团放电发现:NBM毁损组大鼠CA1区自发放电频率明显减少,其中单个放电与爆发式(burst)放电类型的平均放电频率同时降低;NBM毁损组自发放电类型发生改变,burst数量增加,但burst内发放频率下降,burst间隔延长。结论:(1)平行绑定多电极技术简便、易行、灵活,结合多通道记录技术可为开展神经元环路活动研究提供有力工具;(2)NBM毁损可致大鼠海马CA1区自发放电频率减少和放电模式改变,提示NBM胆碱能系统参与海马环路的神经活动调控,NBM损伤所致海马自发放电活动的改变可能有助于解释阿尔茨海默病认知功能的下降。     

周围注射氯氨酮对皮下注射蜜蜂毒引起的猫脊髓广动力阈神经元长时程持续性放电增强的抑制效应(英文)

通过应用单细胞细胞外电生理记录 ,在乌拉坦 -氯醛糖合剂麻醉状态下 ,对在猫后爪局部注射单一剂量的氯氨酮对皮下注射蜜蜂毒引起的背角 WDR神经元放电增强的抑制作用进行了研究。在 WDR神经元周围感受野皮下注射蜜蜂毒可诱发出超过背景放电 1小时的单相持续性放电增强。在感受野中心蜜蜂毒注射部位用氯氨酮 ( 10 0 mmol/L,0 .1ml)局部预处理组 ( 3 .10± 0 .42放电数 /秒 ,n=5 )与盐水对照组 ( 7.61± 0 .17放电数 /秒 ,n=5 )相比对神经元的放电增强可大幅度地抑制 60 %。而且 ,用相同剂量的氯氨酮局部后处理组 ( 1.5 1± 0 .0 6放电数 /秒 ,n=5 )与盐水对照组 ( 7.76± 0 .15放电数 /秒 ,n=5 )相比 ,对神经元的放电增强可明显抑制 81%。不过 ,用相同剂量的氯氨酮在未经蜜蜂毒处理的对侧后爪相应区域皮下给药 ,对 WDR神经元放电增强不产生任何影响 ,提示局部注射氯氨酮的抑制效应并非是全身效应的结果。目前的结果提示 ,氯氨酮除了部分地通过阻断钠离子和电压敏感性钙通道的作用外 ,主要通过周围 NMDA受体发挥它的局部镇痛效应。     

COX-2抑制剂对幼鼠痫性发作海马神经元突触活动的影响

目的：观察环氧合酶-2（cyclooxygenase-2,COX-2）抑制剂硝基苯-甲磺酸（NS-398）对幼鼠痫样放电的作用及其对海马CA1锥体神经元突触电活动的影响,研究NS-398在幼鼠痫性发作中的作用。方法：用生后第14天龄SD大鼠制作海马组织脑切片,记录其CA1区锥体神经元场电位,以群峰电位（PS）个数和波幅作为指标来评价脑片放电的变化。给脑片用不同浓度青霉素,建立离体海马脑片痂样放电模型,在脑片灌流液中用不同浓度NS-398,观察对PS个数和波幅的影响。全细胞记录模式下,观察NS-398对海马CA1锥体神经元递质释放和突触活动的影响。分别记录自发性兴奋性突触后电流（sEPSC）和自发性抑制性突触后电流（sIPSC）,观察NS-398对其波幅和频率的影响。结果：NS-398浓度为10μmol／L时,对青霉素诱发的痼样放电没有多大的抑制效应;当浓度为20gmol／L时,有明显的抑制作用;为30μmol／L时抑制作用很强,明显降低PS的波幅和减少其频率。NS-398能明显抑制致痴大鼠海马锥体神经元sEPSC的频率,但是对其波幅及衰减时间没有明显的影响;同时NS-398能明显增强致痫大鼠海马脑片锥体神经元sIPSC的频率,明显延长sIPSC的衰减时间,对波幅影响不大。结论：COX-2抑制剂NS-398能减少sEPSC的放电和增强sIPSC的抑制功能,导致兴奋性神经递质的释放减少,降低神经元的兴奋性,从而抑制神经元异常放电。     

胆碱能药物对大鼠海马单位自发放电和伤害性放电的影响

在氨基甲酸乙酯和氯醛糖复合麻醉、箭毒制动和人工通气下,研究了侧脑室注射胆硷能激动剂和拮抗剂对大鼠背侧海马单位自发放电和伤害性放电的影响。结果显示:(1)侧脑室注射能增强或减弱学习记忆能力的M型或N型胆碱能受体激动剂后,海马单     

Somatostatin 28(1-14) immunoreactivity in primary afferent neurons of the rat spinal cord

Somatostatin 28(1-14) immunoreactivity is present in dorsal root ganglion cells and in the superficial laminae of the spinal cord in the rat. The distribution of somatostatin 28(1-14) immunoreactive varicosities in the dorsal horn corresponds well to the distribution of somatostatin 14 immunoreactive elements. Some dorsal root ganglion cells exhibit both somatostatin 14 and somatostatin 28(1-14) immunoreactivities.     

Increased oxytocinergic system activity in the cardiac muscle in spontaneously hypertensive SHR rats

IntroductionThe present study aimed to determine whether the presence of cardiac hypertrophy due to arterial hypertension is associated with a change in the activity of the oxytocinergic system in cardiomyocytes.Material and methodsThe experiments were performed on male, spontaneously hypertensive rats (SHR, n = 10) and normotensive Wistar-Kyoto rats (WKY, n = 12). Blood samples were collected from both SHR and WKY animals to asses plasma oxytocin (OT) concentration; the rats were sacrificed by decapitation. Samples of the left and right ventricles were harvested for the analysis of the OT and oxytocin receptor (OTR) protein by ELISA, and OT and OTR mRNA expression by RT-PCR. Immunohistopathological studies were performed to confirm the presence of OTR receptors in the cardiac muscle of the ventricles.ResultsPlasma OT concentration did not differ between SHR and WKY rats. In the SHR rats, the expression of OT mRNA and the OT protein level was higher in the left and the right ventricle, while OTR mRNA expression was significantly lower in both the left and the right ventricle. However, the level of OTR protein was higher only in the left ventricle of the SHR rats. The presence of OTR receptors was confirmed by immunohistochemical analysis in the muscle of the right and left ventricle.ConclusionsThe presence of arterial hypertension is associated with increased activity of the oxytocinergic system in the heart, especially in the area of the left ventricle. These findings support the important role of this system in the maintenance of cardiovascular homeostasis.     

The inhibitory effects of oxytocin on distal colonic contractile activity in rabbits are enhanced by ovarian steroids

Aims: To study the effects of oxytocin on isolated rabbit distal colon and the regulation of ovarian steroids by its action. Methods: Muscle strips parallel to either the circular or the longitudinal fibres were excised and suspended in tissue chambers containing 5 mL Krebs solution (37 °C) and bubbled continuously with 95% O₂ and 5% CO₂. The effects of oxytocin on isometric spontaneous contractile responses were recorded. The effects of atosiban, tetrodotoxin, Mg²⁺, progesterone and oestradiol on the oxytocin‐induced response were also examined. Results: Oxytocin (1, 10 and 100 nmol L^?1) dose dependently decreased the area under the contraction curve of distal colonic smooth muscle strips. The oxytocin receptor antagonist atosiban blocked the oxytocin (10 nmol L^?1)‐caused responses in a dose‐dependent manner. Tetrodotoxin (10 μmol L^?1) had no effect on the oxytocin‐induced response. Mg²⁺‐free Krebs solution attenuated the oxytocin‐induced response, but oestradiol (0.1 μmol L^?1) or progesterone (0.1 μmol L^?1) increased the oxytocin‐induced response. Conclusion: These results suggest that oxytocin inhibits the contractile motility of the distal colon, which is regulated by Mg²⁺ and ovarian steroids.     

Calcineurin/NFAT Pathway: A Novel Regulator of Parturition

Problem  The oxytocin (OT)–oxytocin receptor (OTR) system plays an important role in mammalian parturition. However, we found OTR-deficient (OTRKO) mice are fertile and deliver at term without birth defects, thus alternative pathways inducing parturition can be hypothesized.
Methods of study  We tested the gene expression profile of OTRKO mice using suppressive subtractive hybridization, and focused on the calcineurin/nuclear factor of activated T cells (NFAT) pathway. We examined the expression and localization of this pathway in mouse parturition.
Results  Calcineurin and NFATc1 were detected in the decidua of pregnant uteri at term using immunohistochemistry (IHC). We identified higher activation levels of NFATc1 in wild type (WT) than in OTRKO mice and increased calcineurin A and NFATc1 mRNA levels during pregnancy. Moreover, injection of FK506, the inhibitor of this pathway, prolonged the delivery of the first pup.
Conclusion  Our findings suggested that the calcineurin/NFAT pathway might play a substantial role in initiation of labor.     

Plasma levels of oxytocin after food deprivation and hypoglycaemia,and effects of 1–deamino-2–D-Tyr—(OEt)-4–Thr-8–Orn-oxytocin on blood glucose in rats

Björkstrand , E., Eriksson , M. & Uvnäs -Moberg , K. 1992. Plasma levels of oxytocin after food deprivation and hypoglycaemia, and effects of l-deamino-2–D-Tyr-(OEt)-l-Thr-8–Om-oxytocin on blood glucose in rats. Acta Physiol Scand 144 , 355–359. Received 1 March 1 991 , accepted 25 October 1991. ISSN 0001–6772. Department of Pharmacology, Karolinska Institute, Sweden. Oxytocin has been shown to influence insulin, glucagon and blood glucose levels in various experimental situations. The present study was performed in order to obtain support for a possible interaction of glucose and oxytocin under physiological conditions. We therefore studied whether or not short-term food deprivation (24 hours) affects basal oxytocin levels in male, female and lactating rats, since this is a situation when glucose is mobilized to prevent hypoglycaemia. Secondly, we studied whether oxytocin levels rise in a situation when blood glucose levels fall, i.e. following i.p. injection of insulin (20 U kg^-1). In order to explore the role of oxytocin more directly, we investigated whether i.p. injection of the oxytocin antagonist 1–deamino-2–D-Tyr-(OEt)-4–Thr-8–Orn-oxytocin affects blood glucose levels. Plasma levels of oxytocin, insulin and glucagon were measured with radioimmunoassay in samples obtained after decapitation. We found that oxytocin levels were significantly increased following short-term food deprivation in lactating rats. We also found that insulin-induced hypoglycaemia could elevate plasma levels of oxytocin in female and male rats. In addition, administration of an oxytocin antagonist cause a small, hut significant decrease in blood glucose levels after 30 min. These data imply that oxytocin may he one of several factors that take part in the control of blood glucose regulation.     

A Luminescent Label for the Immunoassay of Oxytocin

Abstract

Chemiluminescent labels have been shown to be interesting alternatives to radioisotope labels. Disadvantages of the latter are preparation of e.g. labelled protein/peptides every four to six weeks, and problems with storage and disposal. Amino-Butyl-Ethyl-Isoluminol(ABEI) was attached to the alpha-amino function of the N-terminal amino acid residue of oxytocin; this complex was used in immunoassays for oxytocin. This non-isotopic label did not require heating at 60°C for optimal light-signal development, a procedure usually required for chemiluminescent labels.

Standard curves were set up employing the ABEI-label on the one hand and ¹²⁵I-label on the other. Under identical conditions of final antibody concentration and amount of label, a comparison was made between the performance of the luminescent immunoassay (LIA) and that of the radioimmunoassay (RIA).

We conclude that the LIA systems resulted in standard curves of high precision; in comparison with RIA, the sensitivity of the LIA curves is not yet sufficient for the determination of oxytocin concentrations in e.g. human biological fuids.

Further improvements in sensitivity of the LIA systems are to be expected by selection of other luminescent labels or by the use of a more sensitive measuring device.     

Endocrinology: Pre-ovulatory oxytocin administration promotes the onset of the luteinizing hormone surge in human females

Luteinizing hormone (LH) secretion during the ovulatory cycleis believed to be predominantly regulated by gonadotrophin-releasinghormone. Investigations in animals have strongly suggested thatoxytocin also participates in LH control and the physiologicalevents controlling LH surge initiation. In the human female,however, there has been no evidence supporting oxytocin's involvementin the processes leading to ovulation. In this study the effectof a preovulatory infusion of oxytocin on the onset of the LHsurge was investigated in women aged 20–35 years who hadnatural ovulatory menstrual cycles of lengths between 25–35days. Vaginal ultrasound scanning monitored follicular growthduring the late follicular phase. When a follicle >>14mm in diameter was observed each woman was randomized into oneof two groups. One group (n = 8) received an oxytocin infusionof 256 mlU/min for 2 h, the other group (n = 8) received normalsaline. The women who were administered oxytocin at this latefollicular stage had an earlier onset of the LH surge than thosewho had received saline (P < 0.01). The results indicatethat oxytocin promotes the onset of the LH surge in humans.