中脑导水管周围灰质内微量注射神经肽γ减弱慢性神经痛大鼠对伤害性刺激的反应

探讨神经肽Y(neuropeptide Y,NPY)在SD大鼠中脑导水管周围灰质(periaqueductal grey,PAG)对伤害性刺激反应的作用。应用热板和机械压力实验法,以大鼠后爪缩爪反应潜伏期(paw withdrawal latency,PWL)为痛阈指标。观察PAG内微量注射NPY对PWLS的影响。PAG内注射0．05、0．1、0．2nmol NPY均显著地增加慢性神经痛大鼠的双侧PWLS,且呈量效关系。NPY引起的PWLs增加可被Y1受体拮抗剂和阿片受体拮抗剂所阻断。结果提示,在大鼠PAG微量注射NPY可产生明显的镇痛作用。     

大鼠中脑导水管周围灰质微量注射孤啡肽对痛和针刺镇痛的影响

孤啡肽是新近发现的神经肽,结构与内阿片肽相似,但作用明显不同。本文采用脑核团内微量注射方法,在大鼠电刺激甩尾测痛模型上,观察ＯＦＱ在中脑导水管周围灰质内对痛和针刺镇痛的影响。结果表明：ＰＡＧ内微量注射ＯＦＱ可使大鼠痛阈降低,并明显对抗针刺镇痛;另外还发现,ＯＦＱ在ＰＡＧ内还可以对抗μ受体激动剂羟甲芬太尼加强针刺镇痛的效应。     

褪黑素对大鼠中脑导水管周围灰质内阿片肽释放的影响

本文采用推挽灌流技术、放射免疫测定法,观察褪黑素（ｍｅｌａｔｏｎｉｎ,ＭＥＬ）对大鼠中脑导水管周围灰质（ＰＡＧ）推挽灌流液中β－内啡肽（β－Ｅｐ）、亮氨酸脑啡肽（Ｌ－ＥＫ）含量的影响,以探讨ＭＥＬ镇痛效应的中枢机制。结果显示,给药组大鼠腹腔注射（ｉｐ）ＭＥＬ１１０ｍｇ／ｋｇ后３０－５０ｍｉｎ,ＰＡＧ灌流液中β－Ｅｐ含量显著增加,而Ｌ－ＥＫ含量未见显著变化;在推挽灌流同时用５０℃热水刺激甩尾法测定痛     

导水管周围灰质参与电针对防御反应的抑制效应

在清醒家兔中,双侧损毁导水管周围灰质(PAG)的腹侧部或在双侧PAG腹侧部微量注射阿片受体拮抗剂纳洛酮,可明显阻断电针对刺激下丘脑背内侧区引起的防御反应的抑制效应。双侧损毁PAG腹侧部或在双侧PAG腹侧部微量注射纳洛酮,也都能减低直接兴奋弓状核区对防御反应的抑制作用的程度,在PAG 腹侧部微量注射阿片受体激动剂吗啡则可抑制刺激下丘脑引起的防御反应。以上实验结果提示,PAG 腹侧部的阿片受体可能参与电针抑制防御反应的机制。本文讨论了电针可能激活弓状核的内啡肽神经元并激活PAG 腹侧部的阿片受体而对防御反应发生抑制作用的可能性。     

电刺激猫中脑导水管周围灰质和中缝大核对脊髓背角神经元伤害性感受反应的抑制

1.在氯醛糖麻醉的猫上,观察了电刺激中脑导水管周围灰质(PAG)和中缝大核(NRM)对脊髓腰段背角神经元传入活动的影响。2.按照对刺激的反应型式,在背角记录到非伤害性低阈值传入、广动力范围、伤害性热敏以及高阈值传入诱发的自发放电抑制等四类神经元。3.刺激 PAG和 NRM对记录到的多数背角神经元皮肤传入反应有明显抑制效应,而对自发放电抑制性神经元产生去抑制。4.比较刺激两脑区的抑制效应:NRM 作用较PAG 强;PAG 活动对背角伤害性反应抑制的选择性较 NRM强;阿片肽拮抗剂-纳洛酮拮抗NRM刺激的抑制。5.这些结果提示PAG和NRM对脊髓的下行抑制,可能有一部分是通过不同神经机制实现的。     

导水管周围灰质微量注射阿片肽拮抗剂阻断甲醛致痛时脊髓背角P物质的变化

在大鼠脚掌注射福尔马林溶液后（２．５％,０．４ｍｌ）,在中脑导水管周围灰质内微量注射纳洛酮或β－内啡肽抗血清。用免疫组织化学方法结合计算机图像分析技术,观察到脊髓背角Ｐ物质样免疫阳性物质在福尔马林＋载液组的光密度（３．４２０８±０．４６２８）高于单纯载液组（１．５１８９±０．１４６５）,Ｐ＜０．０１;福尔马林＋纳洛酮组（１．８７０７±０．６６６４）与福尔马林＋β－内啡肽抗血清组（１．８５４７±０．７５３７）均明显低于福尔马林＋载液组,Ｐ＜０．０５;单纯注射纳洛酮或β－内啡肽抗血清组无明显变化。结果表明,导水管周围灰质内微量注射纳洛酮和β－内啡肽抗血清可以易化动物脚掌注射福尔马林引起的痛反应,并阻断脊髓背角Ｐ物质的增加。提示伤害性刺激可以引起中脑导水管周围灰质内β－内啡肽的释放,与相应的阿片受体作用,调制脊髓背角Ｐ物质的释放。     

大鼠中脑导水管周围灰质和束旁核联系途径的电生理分析

在48只清醒大鼠的中脑导水管周围灰质(PAG)记录到228个有自发放电的单位,检查了它们对束旁核(Pf)刺激和外周伤害性刺激和触刺激的反应,其中有76个单位对 pf 刺激有反应,反应型式有如下三类。8个单位在 Pf 刺激时出现逆行反应,潜伏期为3.18±0.57(SD)ms,传导速度相当于1.41m/s;这些单位的自发放电频率为1.1±0.45Hz,且不受夹尾或触尾刺激的影响。44个单位在 pf 刺激时出现顺行抑制;它们的自发放电频率为12.1±3.7(SD)Hz,且大多数单位(61.3%)在夹尾刺激时出现明显的增频反应,此反应亦可被 pf 刺激所抑制。24个单位在 pf 刺激时出现顺行兴奋;它们的自发放电频率为5.8±14(SD)Hz,对夹尾刺激表现增频或减频反应的单位数大致相等。对这些不同性质的 PAG 单位在中枢痛传递和痛感受的调制中所起的作用进行了讨论。     

中脑导水管周围灰质在侧脑室注入微量吗啡或纳洛酮所引起的镇痛或拮抗镇痛中的作用

本工作进一步探索中脑导水管周围灰质(PAG)在吗啡镇痛与纳洛酮拮抗吗啡镇痛中的作用。实验在清醒受限制的大鼠上进行,以电刺激鼠尾出现的甩尾和嘶叫为痛反应指标。结果表明:(1)侧脑室注射微量纳洛酮后,可使电刺激 PAG 或注射微量吗啡于 PAG 所引起的镇痛效应受到明显拮抗;(2)损毀 PAG 或注射微量纳洛酮于 PAG 后,可使由侧脑室注入微量吗啡所引起的镇痛效应显著减弱。由此可见 PAG 既是侧脑室注射吗啡镇痛作用的重要中枢部位,又是侧脑室注射纳洛酮拮抗吗啡镇痛的重要中枢部位。     

中脑导水管周围灰质内注射抗阿片肽血清对神经降压素增强电针镇痛的 …

本工作以钾离子透入引起大鼠甩尾反应作为痛反应指标,观察纳洛酮（ＮＸ）和抗阿片肽血清对大鼠中脑导水管周围灰质（ＰＡＧ）内微量注射神经降压素（ＮＴ）增强电针镇痛作用的影响。     

Up-regulation of neuropeptide Y levels and modulation of glutamate release through neuropeptide Y receptors in the hippocampus of kainate-induced epileptic rats

Kainate-induced epilepsy has been shown to be associated with increased levels of neuropeptide Y (NPY) in the rat hippocampus. However, there is no information on how increased levels of this peptide might modulate excitation in kainate-induced epilepsy. In this work, we investigated the modulation of glutamate release by NPY receptors in hippocampal synaptosomes isolated from epileptic rats. In the acute phase of epilepsy, a transient decrease in the efficiency of NPY and selective NPY receptor agonists in inhibiting glutamate release was observed. Moreover, in the chronic epileptic hippocampus, a decrease in the efficiency of NPY and the Y(2) receptor agonist, NPY13-36, was also found. Simultaneously, we observed that the epileptic hippocampus expresses higher levels of NPY, which may account for an increased basal inhibition of glutamate release. Consistently, the blockade of Y(2) receptors increased KCl-evoked glutamate release, and there was an increase in Y(2) receptor mRNA levels 30 days after kainic acid injection, suggesting a basal effect of NPY through Y(2) receptors. Taken together, these results indicate that an increased function of the NPY modulatory system in the epileptic hippocampus may contribute to basal inhibition of glutamate release and control hyperexcitability.     

Association of neuropeptide Y receptor Y5 polymorphisms with dyslipidemia in Mexican Americans

We examined the genetic association of neuropeptide Y receptor Y5 (NPY5R) single nucleotide polymorphisms (SNPs) with measures of the insulin resistance (metabolic) syndrome. We genotyped 10 NPY5R SNPs in 439 Mexican American individuals (age=43.3+/-17.3 years and BMI=30.0+/-6.7 kg/m2) distributed across 27 pedigrees from the San Antonio Family Diabetes Study and performed association analyses using the measured genotype approach as implemented in Sequential Oligogenic Linkage Analysis Routines (SOLAR). Minor alleles for five (rs11100493, rs12501691, P1, rs11100494, rs12512687) of the NPY5R SNPs were found to be significantly (p<0.05) associated with fasting plasma triglyceride concentrations and decreased high-density lipoprotein concentrations. In addition, the minor allele for SNP P2 was significantly associated (p=0.031) with a decreased homeostasis model assessment of beta-cell function (HOMA-%beta). Linkage disequilibrium between SNP pairs indicated one haplotype block of five SNPs (rs11100493, rs12501691, P1, rs11100494, rs12512687) that were highly correlated (r2>0.98). These preliminary results provide evidence for association of SNPs in the NPY5R gene with dyslipidemia (elevated triglyceride concentrations and reduced high-density lipoprotein levels) in our Mexican American population.     

Effect of neuropeptide Y microinjected into the hypothalamus on ethanol consumption

Guide cannula were implanted in rats aimed at the paraventricular nucleus (PVN) of the hypothalamus for microinjection of neuropeptide Y (NPY), D-NPY_27–36, or vehicle. In the Wistar rat, there was no significant effect on the consumption of ethanol. In Myers’ high ethanol preferring (mHEP) rats, D-NPY_27–36 caused a significant 54% decrease in ethanol consumption from baseline, but the response was not different from vehicle. NPY-induced feeding in satiated Wistar rats, was blocked by a Y₁ receptor antagonist, D-NPY_27–36. D-NPY_27–36 decreased 78% feeding in food-deprived rats. Thus, neither the Wistar nor the mHEP rat perceives ethanol as a source of calories comparable to food.     

Circulating neuropeptide Y in dog plasma consists of multiple peptide fragments

Neuropeptide Y-like immunoreactivity (NPY-LI) in dog plasma was characterized and quantified using three extraction methods (Sep-Pak:acetonitrile, HCl:ethanol, and ethanol). Sep-Pak extraction yields the best recovery and preserves the integrity of the peptide. Oxidized NPY is not generated during blood collection. Using two antisera of different specificities, at least three peptide forms in normal dog arterial and venous plasma were detected. A peptide with retention times similar to oxidized NPY or peptide YY is the major component of plasma NPY-LI under basal conditions, but NPY(1–36) predominates during sympathetic stimulation. The mature peptide in dog plasma is similar to human NPY. The antiserum ABII provides a more accurate measure of circulating NPY(1–36) and its oxidized form. The antiserum ABI is useful for detecting NPY-like fragments.     

神经肽Y对心室肌细胞离子通道的影响

采用全细胞膜片钳技术观察神经肽Y(neuropeptide Y,NPY)对心室肌细胞离子通道的影响。结果如下：(1)NPY浓度在1．0～100nmol/L范围内剂量依赖性抑制大鼠心室肌细胞I_(Ca-L),IC_(50)值为1．86nmol/L。NPY对I_(Ca-L)的I-V曲线的最大峰值电位、激活和失活电位均无显著影响。NPY对去甲肾上腺素(norepinephrine,NE)增加的I_(Ca-L)有显著抑制作用。(2)NPY对人鼠心室肌细胞I_(Na/Ca)有显著抑制作用。10nmol/L NPY使前向I__(Na/Ca)由(0．27±0．11)pA/pF减小为(0．06±0．01)pA/pF;反向I__(Na/Ca)由(0．45±0．12)pA/pF降为(0．27±0．09)pA/pF(P＜0．05,n=4)。(3)NPY对大鼠心室肌细胞I_(to)有显著增强作用。10 nmol/L NPY使I_(to)由(12．5±0．70)pA/pF增加至(14．7±0．59)pA/pF(P＜0．05,n=4)。(4)10nmol/L NPY对大鼠心室肌细胞I_(Na)没有显著影响。(5)10nmol/L NPY对豚鼠心室肌细胞I_K无明显影响。研究结果证实,NPY抑制大鼠心室肌细胞I_(Ca-L)和I_(Na/Ca),增强I_(to)对I_Na和豚鼠心审肌细胞I_K没有显著作用,表明NPY对上述主要离子通道的效应与NE的效应相拮抗。     

Modulation of neuropeptide Y and Y1 receptor expression in the amygdala by fluctuations in the brain content of neuroactive steroids during ethanol drinking discontinuation in Y1R/LacZ transgenic mice

Previous studies have shown that GABAergic neuroactive steroids increase Y₁ receptor (Y₁R) gene expression in the amygdala of Y ₁ R / LacZ transgenic mice, harbouring the murine Y₁R gene promoter linked to a LacZ reporter gene. As ethanol is known to increase GABAergic neuroactive steroids, we investigated the relationship between fluctuations in the brain content of neuroactive steroids induced by chronic voluntary ethanol consumption or ethanol discontinuation and both the level of neuropeptide Y (NPY) immunoreactivity and Y₁R gene expression in the amygdala of Y ₁ R / LacZ transgenic mice. Ethanol discontinuation (48 h) after voluntary consumption of consecutive solutions of 3%, 6%, 10% and 20% (v/v) ethanol over 4 weeks produced an anxiety-like behaviour as measured by elevated plus maze. Voluntary ethanol intake increased the cerebrocortical concentration of the progesterone metabolite 3α-hydroxy-5α-pregnan-20-one (3α,5α-TH PROG) that returned to control level 48 h after discontinuation of ethanol intake. Ethanol discontinuation significantly decreased NPY immunoreactivity and concomitantly increased Y ₁ R / LacZ transgene expression in the amygdala, whereas chronic ethanol intake failed to affect these parameters. The 5α-reductase inhibitor finasteride prevented both the increase in the cerebrocortical concentration of 3α,5α-TH PROG apparent after 4 weeks of ethanol intake and the changes in NPY immunoreactivity and transgene expression induced by ethanol discontinuation. Data suggest that 3α,5α-TH PROG plays an important role in the changes in NPY–Y₁R signalling in the amygdala during ethanol discontinuation.     

Adaptive responses in hypothalamic neuropeptide Y in the face of prolonged high-fat feeding in the rat

While a dysregulation in neuropeptide Y (NPY) signaling has been described in rodent models of obesity, few studies have investigated the time-course of changes in NPY content and responsiveness during development of diet-induced obesity. Therefore we investigated the effect of differing lengths (2-17 weeks) of high-fat diet on hypothalamic NPY peptide content, release and NPY-induced hyperphagia. Male Sprague-Dawley rats (211 +/- 3 g) were fed either a high-fat diet (30% fat) or laboratory chow (5% fat). Animals were implanted with intracerebroventricular cannulae to investigate feeding responses to NPY (0.5 nmol, 1 nmol) after 4 or 12 weeks of diet. At the earlier stage of obesity, NPY-induced hyperphagia was not altered; however, animals maintained on the high-fat diet for the longer duration were hyper-responsive to NPY, compared to chow-fed control rats (p < 0.05). Overall, hypothalamic NPY peptide content tended to be decreased from 9 to 17 weeks of diet (p < 0.05). Total hypothalamic NPY content was negatively correlated with plasma leptin concentration (p < 0.05), suggesting the hypothalamic NPY system remains responsive to leptin's inhibitory signal. In addition, hypothalamic NPY overflow was significantly reduced in high-fat fed animals (p < 0.05). Together these results suggest a reduction in hypothalamic NPY activity in high-fat fed animals, perhaps in an attempt to restore energy balance.     

Interrupting activator protein-1 signaling in conscious rats can modify neuropeptide Y gene expression and feeding behavior of phenylpropanolamine

The mechanism for phenylpropanolamine (PPA)-induced anorexia has been attributed to its inhibitory action on hypothalamic neuropeptide Y (NPY), an orexigenic agent abundant in the brain. However, molecular mechanisms behind this effect are not well known. In this study, we investigated whether activator protein-1 (AP-1) signaling was involved. Rats were daily treated with PPA for 4 days. Changes in hypothalamic NPY, c- fos , c- jun , superoxide dismutase (SOD)-1, and SOD-2 mRNA contents were measured and compared. Results showed that c- fos and c- jun mRNA levels were increased following PPA treatment, which were relevant to a reduction in NPY mRNA level. To further determine if c- fos /c- jun genes were involved in PPA anorexia, infusions of antisense oligonucleotide into cerebroventricle were performed before daily PPA treatment in freely moving rats. Results showed that either c- fos or c- jun knock down could block PPA anorexia and restore NPY mRNA content to normal level. It is suggested that AP-1 signaling may participate in the central regulation of PPA-mediated appetite suppression via the modulation of NPY gene expression. Moreover, this modulation might be partly because of the neuroprotective effect of AP-1 since SOD gene was activated during PPA treatment.