Y1 receptor activation is involved in the effect of exogenous neuropeptide Y on pup growth and the early termination of lactational diestrus in the postpartum rat

The effect of chronic administration of exogenous neuropeptide Y (NPY) and specific NPY receptor agonists and antagonists on reproductive function was examined in lactating rats. As previously demonstrated in our laboratory, chronic (7-day) intracerebroventricular (i.c.v.) NPY infusion (6 microg/day) from days 8-15 postpartum (pp) caused a significant decrease in milk production and an early termination of lactational diestrus. Similar application of the mixed Y1/Y4/Y5 receptor agonist (Leu31, Pro34) NPY (at 3, 6 and 9 microg/day) reproduced the effect of chronic NPY infusion on milk production in a dose-independent manner. Consistent with this effect, the potent Y1 antagonist/Y4 agonist, 1229U91, given concomitantly with NPY eliminated the decline in milk production. The Y2 receptor agonist, NPY13-36, had no effect on milk production at any of the doses used. Length of lactational diestrus was reduced following administration of the Y2 agonist at 18 microg/day but not at 9 microg or 27 microg/day whereas (Leu31, Pro34) NPY infusion had no effect on this parameter at any of the doses used. However, the group that was treated with NPY plus 1229U91 exhibited the usual length of lactational diestrus, indicating that there is at least some Y1 involvement in the effects of NPY on lactational infertility. To test the possibility that the effects of NPY infusion are mediated through changes in circulating prolactin and progesterone, plasma concentrations of these hormones were measured on day 15 pp in NPY-, (Leu31, Pro34) NPY- and vehicle-treated females. NPY-infused females had lower plasma prolactin concentrations than vehicle-infused dams but progesterone concentrations were similar across groups. Overall, these data indicate that chronic exogenous NPY-infusion in lactating females disrupts milk production and shortens lactational diestrus, most likely through reducing prolactin secretion, and that this effect is mediated via Y1 receptor activity.     

针刺对肥胖大鼠食欲调节因子神经肽Y与瘦素的作用研究

目的观察针刺对肥胖大鼠食欲调节因子神经肽Y(NPY)、瘦素(leptin)的影响,探讨针灸减肥的细胞分子机制。方法用放射免疫法检测外周血和下丘脑NPY、Leptin的含量,用RTPCR、NorthernBlot技术测定NPY、瘦素受体(OBR)基因表达水平,观察针刺治疗前后肥胖大鼠体质量、Lee’s指数和NPY、Leptin的含量及NPY、OBR基因表达水平的变化。结果肥胖大鼠的体质量、Lee’s指数和血清NPY、Leptin的含量及NPY基因表达明显高于正常大鼠,而下丘脑Leptin含量[(0.23±0.15)ng/mg]、OBR基因表达(0.13±0.02)明显低于正常大鼠[(0.51±0.13)ng/mg,(0.21±0.03)],针刺治疗后,针刺组大鼠的体质量、Lee’s指数和血清NPY、Leptin的含量及NPY基因表达显著下降,下丘脑Leptin含量[(0.58±0.08)ng/mg]、OBR基因表达(0.18±0.02)明显回升。结论针刺对肥胖机体外周血及中枢NPY、Leptin具有良性调整作用,同时可促进OBR基因表达和抑制NPY基因表达,这可能是针灸减肥的重要作用机制之一。     

环维黄杨星干预高血压大鼠脑组织NPY与超微结构的研究

目的观察中药单体环维黄杨星(CVB)对易卒中型肾血管性高血压大鼠(RHRSP)脑缺血-复流不同时间脑组织神经肽Y(NPY)表达与细胞超微结构的干预作用。方法采用环形银夹使SD大鼠的双侧肾动脉狭窄,制成RHRSP模型,再用线栓法制成一侧大脑中动脉闭塞(MCAO)脑缺血-复流实验组;观察CVB对脑缺血6h后再灌注6、72、168h不同时间点大鼠脑组织NPY表达、含水量、梗死面积百分率、行为学评分及细胞超微结构的干预作用(治疗组),并与生理盐水处理者(对照组)及假手术组对照。结果对照组脑缺血-复流6h后脑组织NPY、含水量与假手术组相比均明显升高,72h上升至高峰,脑梗死面积百分率亦急剧增加,168h开始下降,但仍高于假手术组。电镜显示,对照组脑缺血-复流上述不同时间分别出现不同程度神经元和血管壁的超微结构损害,脑缺血-复流72h后治疗组较对照组大鼠脑NPY、含水量及梗死面积显著降低,受损脑组织神经元和血管壁的超微结构亦明显改善。结论NPY可能参与了RHRSP急性缺血-复流性脑损伤病理过程,CVB对脑缺血脑损伤RHRSP大鼠NPY、水肿与超微结构有一定的干预作用。     

应用改进的大鼠应激模型证实海马CA3区神经元Nestin?NPY表达变化

 【目的】 应用改良的连续?恒定复合型应激大鼠模型,观察其血浆肾素活性(PRA)?血管紧张素Ⅱ(AngⅡ)水平和海马CA3区的Nestin?NPY表达? 【方法】 将雌性成鼠束缚并倒悬应激6 h/d,用放射免疫法测定急性应激(3 d)后血浆PRA?AngⅡ水平,用免疫组织化学方法观察应激3 d?21 d后CA3区锥体层细胞的Nestin?NPY表达变化? 【结果】 ①急性应激组血浆PRA和AngⅡ水平比正常对照组显著降低(P<0.01),尤以PRA水平的变化更明显?②急?慢性应激组海马CA3区的Nestin?NPY免疫阳性反应产物总面积(SA)和体视学光密度(IOD)值均较对照组低(P<0.01),急性组的组织损害比慢性组更严重?【结论】 本研究成功地构建了具有科学理论依据和实用价值的复合性应激大鼠模型,并利用此模型证实应激早期大鼠血浆PRA和AngⅡ水平有降低;观察急?慢性应激大鼠海马CA3区NPY和Nestin表达变化及其变化规律,结果提示NPY及其水解产物在应激所致海马神经元细胞骨架损害和谷氨酸释放过程中可能产生一定的影响?     

CCK-8 prevents the development of kindling and regulates the GABA and NPY expression in the hippocampus of pentylenetetrazole (PTZ)-treated adult rats

Neuronal loss and irreversible brain damage often cause the worsening of symptoms and the decreased efficacy of pharmacological treatment occurring in epileptic patients and animal models of kindling. Recently we reported that the neurotransmitter/neuromodulatory peptide Cholecystokinin-8 (CCK-8) is able to induce the structural and functional neuronal recovery of chemical- and surgical-induced lesions when i.p. injected in rodents. The present study therefore, was aimed at verifying the hypothesis that treatment with a CCK-8 dose having a neuroprotective action might affect brain alterations and the development of kindling in adult rats receiving the convulsant agent pentylenetetrazole (PTZ). Compared to rats receiving Saline prior to PTZ, which manifested clonic-tonic seizures (Class 5 behavioural change scale) after three weeks of treatment, rats pre-treated with CCK-8 showed an improvement of behavioural score exhibiting myoclonus and occasionally tonic seizures (Class 3/4). This decreased susceptibility to develop convulsions was associated with the recovery of PTZ-induced reduction of ChAT levels in forebrain and GABA/GAD expression in the hippocampus. Furthermore, NPY immunoreactivity distribution and NPY mRNA levels were also increased in the hippocampus of rats receiving CCK-8 injection before each PTZ treatment. These data indicate that CCK-8 possesses the ability to prevent and/or suppress the convulsant effects of PTZ by stimulating the synthesis of neurotransmitters/peptides involved in the inhibition of hippocampal hyper-excitability. Our findings suggest that CCK-8 may have anticonvulsant and neuroprotective properties that merit further investigation.     

Differential roles for neuropeptide Y Y1 and Y5 receptors in anxiety and sedation

Central administration of neuropeptide Y (NPY) causes both anxiolysis and sedation. Previous studies suggest that both effects are mediated via NPY Y1 receptors. However, most of these studies were carried out before the advent of specific NPY receptor ligands. Therefore, a potential role for other NPY receptors in anxiety and sedation remains a possibility. In the present study, we addressed this issue by testing the effects of intracerebroventricular (i.c.v.) injection of NPY as well as specific receptor agonists for the Y1 receptor ([D-His(26)]NPY), Y2 receptor (C2-NPY), and Y5 receptor ([cPP(1-7),NPY(19-23),Ala(31),Aib(32),Gln(34)]hPP) in the elevated plus maze and open field tests. As with NPY, the Y1 agonist had a dose-dependent anxiolytic-like effect in both behavioral tests. In contrast to NPY, which caused significant sedation in the open field test, the Y1 agonist was without sedative effect. The Y2 agonist showed neither anxiolytic-like nor sedative effects. The Y5 agonist showed anxiolytic-like activity in both behavioral tests and caused sedation in the same dose range as NPY in the open field test. These results indicate that anxiolytic-like effects of i.c.v.-administered NPY in rats are mediated via both Y1 and Y5 receptors, whereas sedation is mediated via Y5 receptors.     

Decreased cerebrospinal fluid neuropeptide Y (NPY) in patients with treatment refractory unipolar major depression: preliminary evidence for association with preproNPY gene polymorphism

Extensive animal studies suggest neuropeptide Y (NPY) to be involved in coping with a wide range of stressors, and that impaired central NPY signalling could be involved in the pathophysiology of anxiety and depression. Human studies of central NPY levels in depression have, however, been inconclusive. Here, we examined levels of NPY-like immunoreactivity (NPY-LI) in the cerebrospinal fluid (CSF) of medication-free subjects with treatment refractory unipolar depression. Patients were admitted to a research inpatient unit, examined under standardized conditions, and compared with a sample of volunteers in whom psychiatric morbidity was excluded. A robust suppression of NPY levels in patient CSF was found, while other putative CSF markers (monoamine metabolites, somatostatin) did not differ between the groups. We then explored whether this finding might be related to a recently described T1128C coding polymorphism which results in a Leu7-> Pro7 substitution of the signal peptide, and a previously not described T -399C polymorphism in the promoter region of the preproNPY gene. Preliminary evidence was found for an association of both markers with a diagnosis of depression, indicating the possibility of an underlying haplotype influencing the vulnerability for developing depressive illness. Our present findings are in line with an extensive animal literature, and further support the notion that impaired NPY function could contribute to depressive illness.     

Differences in basal levels of CREB and NPY in nucleus accumbens regions between C57BL/6 and DBA/2 mice differing in inborn alcohol drinking behavior

An increasing body of evidence suggests that genetic factors play a role in alcohol drinking behaviors. C57BL/6J (C57) mice innately consume larger amounts of alcohol compared to that consumed by DBA/2J (DBA) mice. Furthermore, alterations in cAMP-responsive element binding (CREB) protein function in the brain have been implicated in alcohol drinking behaviors. The present investigation examined innate expression and phosphorylation of CREB in various brain structures of C57 and DBA mice. It was found that CREB expression and phosphorylation was lower, specifically in the shell structure of the nucleus accumbens, in C57 mice compared to that in DBA mice. CREB expression and phosphorylation were similar in other brain regions such as the nucleus accumbens core and the cortical, amygdaloid, hippocampal, and striatal structures of C57 and DBA mice. The expression of a cAMP-inducible gene, neuropeptide Y (NPY), was also investigated in the nucleus accumbens region of C57 and DBA mice. It was found that in C57 mice, NPY protein levels were lower in the shell but not in the core structure of the nucleus accumbens compared to that in DBA mice. It was also found that C57 mice are not innately anxious, but they consume larger amounts of alcohol than do DBA mice. Because the shell structure of the nucleus accumbens has been implicated in reward mechanisms of alcohol, it is possible that lower CREB function in this brain structure may be in part associated with the excessive alcohol drinking behavior of C57 mice.     

Inhibitory effect of neuropeptide Y on morphine withdrawal is accompanied by reduced c-fos expression in specific brain regions

Neuropeptide Y (NPY) was previously shown in our laboratory to attenuate behavioral signs of morphine withdrawal. To further characterize the anti-withdrawal effect of NPY, the present study attempted to identify specific brain regions where NPY inhibits neuronal activity during withdrawal. Morphine dependence was induced in male Wistar rats by two daily subcutaneous injections of morphine at increasing doses, and the withdrawal syndrome was precipitated acutely by intraperitoneal administration of naloxone. Rats were pre-treated with an intracerebroventricular (icv) injection of NPY (12 nmol) or vehicle 30 min before the naloxone challenge. Withdrawal behavior was quantified using a point scoring technique based on motor- and non-motor-related signs. Brain areas involved in the attenuation of morphine withdrawal were delineated by radioactive in situ hybridization for the immediate early gene c-fos, which is a marker for neuronal activity. The present study confirmed the inhibitory effect of NPY on withdrawal behavior. Inhibition of behavioral signs of naloxone-precipitated morphine withdrawal was accompanied by significantly reduced c-fos expression in the locus coeruleus, lateral septal nucleus, ventral part of the periaqueductal grey, cingulate and frontal cortices, and septohippocampal nucleus. Our data suggest that neo- and allo-cortical areas as well as specific brainstem nuclei are involved in the anti-withdrawal effects of NPY.