神经肽Y与癫痫相关性的研究进展

现已公认,癫痫的发病主要是由于中枢神经系统兴奋性机制与抑制性机制失衡从而导致兴奋性异常增高所致。主要的兴奋性递质和抑制性递质分别是谷氨酸和γ-氨基丁酸（GABA）。在大脑新皮层和海马，产生内源性GABA的是一种中间神经元。在中枢神经系统中，有相当数量的不同类型的中间神经元是以它们各自所表达的一系列神经肽的不同而被区分，而中间神经元在调节中枢神经兴奋性的过程中，神经肽起着非常关键的作用。     

Increased neuropeptide Y secretion in the hypothalamic paraventricular nucleus of obese (fa/fa) Zucker rats

NPY is synthesized in the hypothalamic arcuate nucleus (ARC), and NPY injected into the paraventricular nucleus (PVN), the main site of NPY release, induces hyperphagia and reduces energy expenditure. Hypothalamic NPY and mRNA and NPY levels are increased in fatty Zucker rats, consistent with increased NPY release. This could explain the hyperphagia and reduced energy expenditure, which lead to obesity in the fatty Zucker rat. We have therefore compared NPY secretion in the PVN of conscious fatty and lean Zucker rats using push-pull sampling. The NPY secretory profile was consistently higher in fatty Zucker rats than in lean rats throughout the 3-h study period (P < 0.01), and mean NPY secretion over the whole 3 h was increased 2-fold in the fatty rats (P < 0.001). We conclude that fatty Zucker rats have increased NPY release in the PVN. This observation further supports the hypothesis that increased activity of the NPYergic ARC-PVN pathway may contribute to obesity in the fatty Zucker syndrome.     

The effect of neuropeptide Y on drinking in mice

Neuropeptide Y (NPY) when administered intracerebroventricularly is a potent stimulator of feeding and drinking in rats. In these studies we demonstrated that, in contrast, in mice NPY inhibits drinking induced by water deprivation and that associated with food intake. In addition, we found that mice failed to respond to the rat dipsogen angiotensin II. Old mice demonstrated hypodipsia compared to young mice and NPY failed to inhibit drinking in older mice. Monosodium glutamate (MSG) administered neonatally produces lesions of the arcuate nucleus, an area rich in NPY cell bodies. NPY inhibited drinking and enhanced feeding in MSG treated mice. NPY also significantly inhibited the intake of water flavored with 8% sucrose and 0.1% quinine. NPY failed to alter ingestion of 0.2% or 5% saline. These studies support the contention that marked species differences exist in the regulation of water intake between rats and mice.     

Circadian control during the day and night: Role of neuropeptide Y Y5 receptors in the suprachiasmatic nucleus

Circadian rhythms are reset by light during the night or by nonphotic stimuli during the day. Neuropeptide Y (NPY), which appears to mediate at least some nonphotic phase shifts by its actions in the suprachiasmatic nucleus (SCN), induces phase advances during the day and inhibits light-induced phase advances during the night. In this study, we used a highly selective Y5-like agonist to test whether activation of NPY Y5 receptors is sufficient to mimic NPY during the day and late night in Syrian hamsters. We also tested whether NPY in the early night reduces light-induced phase delays in a dose-dependent manner. Microinjection of a selective Y5 receptor agonist, (Ala(31), Aib(32))-NPY, into the SCN significantly inhibited light-induced phase advances during the late night, but did not induce phase advances during the day. In addition, concentrations of NPY ranging from 0.23 to 23 mM did not attenuate light-induced phase delays in the early night. These results suggest that activation of Y5-like receptors is sufficient to inhibit light-induced phase advances during the late night but is not sufficient to induce phase advances during the day. Furthermore, this study provided no evidence that NPY can inhibit light-induced phase shifts early in the night.     

Resistance to diet-induced obesity is associated with increased proopiomelanocortin mRNA and decreased neuropeptide Y mRNA in the hypothalamus

Mechanisms mediating genetic susceptibility to diet-induced obesity have not been completely elucidated. Elevated hypothalamic neuropeptide Y (NPY) and decreased hypothalamic proopiomelanocortin (POMC) are thought to promote the development and maintenance of obesity. To assess the potential role of hypothalamic neuropeptide gene expression in diet-induced obesity, the present study examined effects of a high-fat diet on hypothalamic NPY and POMC mRNA in three strains of mice that differ in susceptibility to develop diet-induced obesity. C57BL/6J, CBA, and A/J mice were fed either normal rodent chow or a high-fat diet for 14 weeks after which hypothalamic gene expression was measured. On the high-fat diet, C57BL/6J mice gained the most weight, whereas A/J mice gained the least weight. On the high-fat diet, NPY mRNA significantly decreased as body weight increased in CBA and A/J mice, but not in C57BL/6J mice. In addition, POMC mRNA significantly increased as body weight increased in A/J mice, but not in CBA and C57BL/6J mice. Since decreased NPY mRNA and increased POMC mRNA would presumably attenuate weight gain, these results suggest that a high-fat diet produces compensatory changes in hypothalamic gene expression in mice resistant to diet-induced obesity but not in mice susceptible to diet-induced obesity.     

Emotional behavior in aged neuropeptide Y (NPY) Y2 knockout mice

Neuropeptide Y (NPY) was shown to modulate anxiety- and depression-related behaviors in various animal models. Previous studies demonstrated that NPY Y₂ receptor knockout (KO) mice display an anxiolytic- and antidepressant-like phenotype compared with control animals. However, the long-term effect of the deletion of this receptor in aged animals is unknown. Thus, anxiety- and depression-related behaviors were investigated in 2-yr-old NPY Y₂ KO mice. Aged NPY Y₂ KO mice display an anxiolytic-like profile as assessed in the elevated plus-maze and open field, providing further support for a role for Y₂ receptors in anxiety-related behaviors. Furthermore, aged NPY Y₂ KO mice have significantly lower immobility scores in the forced swim test; supproting the role for this receptor in antidepressand-like behaviors. These data provide further evidence that modulators of the NPY Y₂ receptor subtype are drug targets for the treatment of anxiety and mood disorders in human subjects.     

Effect of neuropeptide Y Y2 receptor deletion on emotional stress‐induced neuronal activation in mice

In different behavioral paradigms including the elevated plus maze (EPM), it was observed previously that deletion of the neuropeptide Y Y2 receptor subtype results in potent suppression of anxiety‐related and stress‐related behaviors. To identify neurobiological correlates underlying this behavioral reactivtiy, expression of c‐Fos, an established early marker of neuronal activation, was examined in Y2 receptor knockout (Y2^−/−) vs. wildtype (WT) mice. Mice were placed on the open arm (OA) or closed arm (CA) of the EPM for 10 min and the effect on regional c‐Fos expression in the brain was investigated. The number of c‐Fos positive neurons was significantly increased in both WT and Y2^−/− lines after OA and CA exposure in 51 of 54 regions quantified. These regions included various cortical, limbic, thalamic, hypothalamic, and hindbrain regions. Genotype influenced c‐Fos responses to arm exposures in 6 of the 51 activated regions: the cingulate cortex, barrel field of the primary somatosensory cortex, nucleus accumbens, dorsal lateral septum, amygdala and lateral periaqueductal gray. These differences in neuronal activity responses to the novel environments were more pronounced after OA than after CA exposure. Mice lacking Y2 receptors exhibited reduced neuronal activation when compared to WT animals in response to the emotional stressors. Reduced neuronal excitability in the identified brain areas relevant to the processing of motivated, explorative as well as anxiety‐related behaviors is suggested to contribute to the reduced anxiety‐related behavior observed in Y2^−/− mice. Synapse 63:236–246, 2009. © 2008 Wiley‐Liss, Inc.     

Modulation of memory processing by neuropeptide Y

Neuropeptide Y (NPY) is a 36 amino acid peptide which occurs in high concentrations in the amygdala and the hippocampus. The studies reported here demonstrate that administration of porcine NPY into the third ventricle of the brain enhanced memory retention for T-maze footshock avoidance and step-down passive avoidance training in mice. Human NPY at 5 micrograms enhanced retention but the inactive free acid form for NPY did not. NPY at 5 micrograms administered subcutaneously did not enhance retention. Post-training administration of NPY produced a dose-dependent, inverted U-shaped dose-response curve for retention of both passive and active avoidance conditioning. NPY enhanced retention in a time-dependent manner. NPY was also found to alleviate the amnesia caused by anisomycin, a protein synthesis inhibitor, and scopolamine, an anticholinergic. Pre-test administration of NPY improved recall but did not affect acquisition. These data support the concept that NPY is a modulator of memory processes.     

Regulation of proopiomelanocortin gene expression by neuropeptide Y in the rat arcuate nucleus

In the arcuate nucleus which is richly innervated by both proopiomelanocortin (POMC) and neuropeptide Y (NPY) neurons, it has been shown that NPY fibers are in synaptic contact with POMC cell bodies. In order to determine whether NPY could influence POMC neuronal activity, we have studied the effects of NPY and some NPY analogs on POMC gene expression using quantitative in situ hybridization. The following peptides NPY, [Leu³¹, Pro³⁴]-NPY (a Y₁ receptor agonist), and NPY_13–36 (a Y₂ receptor agonist) were injected into the left lateral cerebral ventricle of adult male rats 4 h before being perfused for histological procedures. The intracerebroventricular injection of NPY and NPY_13–36 induced a significant decrease in the number of grains overlying the labelled neurons. On the other hand, the Y₁ receptor agonist [Leu31, Pro34]-NPY did not modify POMC mRNA levels. These data then strongly suggest that NPY negatively regulates the genetic expression of POMC neurons via the Y₂ NPY receptor subtype.     

Control of feeding and sexual behaviors by neuropeptide Y: physiological implications

Recent evidence suggests that a variety of hypothalamic neuropeptides may mediate interneuronal communication to coordinate diverse neuroendocrine and behavioral functions. In this work, we describe the effects of neuropeptide Y (NPY) on feeding and sexual behaviors. We observed that central administration of bolus NPY stimulated a robust, dose-related feeding response in satiated male and female rats. Continuous NPY receptor activation also evoked dose-related, intermittent feeding in a manner normally observed during nocturnal feeding. It appears that the paraventricular nucleus in the hypothalamus may be the primary site of NPY action because the anticipated reciprocal changes in NPY concentrations, in response to food deprivation followed by ad libitum food intake, occurred only in this site. Additional findings revealed that NPY-induced feeding may follow either substantial reduction or complete restraint of an inhibitory influence on feeding mediated by alpha 2-adrenoreceptor systems in satiated rats. Further, NPY was found to suppress male and female sexual behaviors. The suppressive effects on sexual behavior were apparent prior to or at the time of the onset of feeding after NPY administration. These observations may provide a neurochemical basis for clinical and animal studies on disorders of feeding associated with diminished reproductive functions.     

Direct excitatory effects of neuropeptide Y (NPY) on rat hippocampal neurones in vitro

Intracellular recordings from granule cells of the rat dentate gyrus show neuropeptide Y (NPY) applied by pressure ejection from pipettes containing 1.2-12 microM by pressures of less than 200 kPa for 1-5 s in duration to consistently evoke membrane depolarisations accompanied by a reduction in membrane resistance. The depolarisations were accompanied by an increase in excitability. Since the depolarisations evoked by NPY were not attenuated by either tetrodotoxin or kynurenic acid a direct excitatory action of NPY is postulated.     

神经肽Y及其受体在实验大鼠垂体腺瘤中的表达

目的研究神经肽Y(NPY)及其受体在实验大鼠垂体腺瘤中的表达,探索NPY在垂体腺瘤形成过程中的作用。方法雌性Wistar大鼠40只,通过腹腔注射雌激素的方法建立大鼠垂体腺瘤模型,在此基础上采用放射免疫法测定大鼠血浆NPY的浓度,应用免疫组化、免疫电镜和逆转录聚合酶链反应(RT-PCR)法分别研究大鼠垂体中NPY及其受体的表达。结果实验组大鼠垂体显著增大,血清泌乳素浓度明显增高;实验组大鼠血浆NPY浓度明显低于对照组;实验组大鼠垂体腺瘤中NPY及其Y1R和Y2R受体基因表达水平明显低于对照组;免疫电镜显示NPY阳性颗粒主要位于腺垂体细胞的内分泌颗粒中。结论实验组大鼠垂体腺瘤中NPY及其受体的表达下调可能与垂体腺瘤的形成有关。     

Multiple receptors for neuropeptide Y in the hippocampus: putative roles in seizures and cognition

Neuropeptide Y (NPY) is widely distributed throughout the central nervous system (CNS) and is one of the most conserved peptides in evolution, suggesting an important role in the regulation of basic physiological functions, including learning and memory. In addition, experimental studies have suggested that NPY, together with its receptors, may have a direct implication in several pathological disorders, including epilepsy/seizure. NPY-like immunoreactivity and NPY receptors have been shown to be present throughout the brain, but is concentrated in the hippocampus. The hippocampal formation has been repeatedly implicated in the modulation of cognition, as well as the pathogenesis of seizure. This review will concentrate on the hippocampal distribution of NPY, its receptors and the putative role played by this peptide in seizure, together with the regulation of cognitive function associated with learning and memory.     

癫痫动物模型脑中神经肽Y的动态含量变化及意义

目的:探讨匹罗卡品(PILO)诱发的癫痫大鼠模型脑组织中神经肽Y(Neuropeptide Y,NPY)含量的动态变化及意义,进一步明确NPY与癫痫的关系,为抗癫痫治疗,研制抗癫痫药物提供新途径。方法:健康成年雄性SD大鼠120只,随机分为两组:单纯腹腔注射匹罗卡品组(癫痫模型组);单纯腹腔注射生理盐水组(对照组);注射后根据Racine制定的标准判定是否有癫痫发作,并行脑电图检查,观察有无癫痫样波(棘波,尖波,棘慢波,尖慢波)发放。两组大鼠分别于给药后1h,3h,6h,24h,3d,7d,15d,30d,60d将大鼠麻醉,取出脑组织,对脑组织中的NPY含量进行测定。结果:癫痫模型组60只大鼠中,2只死于癫痫持续状态,其余大鼠可观察到边缘发作行为表现,脑电图有典型的癫痫样波发放,对照组无癫痫发作及癫痫样波发放。癫痫模型组脑NPY含量与对照组相比,差异有显著性P<0.05;癫痫模型组急性期(1h-7d)与慢性期(15d-60d)比较差异有显著性P<0.05,对照组差异无显著性;癫痫模型组与对照组脑中的NPY含量在12h,24h,15d,30d,60d.差异有显著性P<0.05或P<0.01,癫痫模型组脑中的NPY含量各组(各时间段)比较有差异有显著性P<0.05,对照组差异无显著性,癫痫模型组大鼠Ⅳ-Ⅴ级发作与Ⅱ-Ⅲ级发作,脑NPY含量比较,差异有显著性P<0.05。结论:1.神经肽Y与癫痫密切相关,癫痫发作后?     

Hypothalamic neuropeptide Y, its gene expression and receptor activity: relation to circulating corticosterone in adrenalectomized rats

Previous evidence has suggested a possible relationship between the adrenal steroid, corticosterone (CORT) and neuropeptide Y (NPY) in the brain. To provide a more systematic analysis of this interaction, the present study employed a variety of techniques, including in sity hybridization to measure NPY gene expression, radioimmunoassay to examine peptide levels and radioligand [¹²⁵I]peptide YY (PYY) binding for analysis of peptide receptors. The results show that adrenalectomy (ADX), which caused a decline in CORT to levels < 0.3 μg%, has generally little impact on the hypothalamic NPY projection system under normal, basal conditions. This includes peptide gene expression or content in the area of its cell bodies (arcuate nucleus, ARC), in addition to peptide binding at its receptor sites. While it also includes peptide content at most hypothalamic terminal sites, there are three notable exceptions, namely, the medial paraventricular (PVN) and dorsomedial nuclei and medial preoptic area, where NPY nerve terminals and glucocorticoid receptors are particularly dense and the decline in CORT through ADX markedly reduces NPY content. In contrast, evidence obtained from CORT replacement in ADX rats shows that this steroid has profound impact on all components of the hypothalamic NPY system. This peptide-steroid interaction is apparent at the level of the cell body (ARC), as well as at the nerve terminal or receptor site (PVN and ARC), where CORT levels > 10 μg% strongly potentiate NPY gene expression, peptide content and radioligand binding. These and other findings suggest that this CORT-NPY interaction in the hypothalamus occurs physiologically under conditions, e.g., at the onset of the active feeding cycle, when circulating CORT normally rises.     

Quantitative microdialysis of neuropeptide Y

The feasibility of using the difference method of quantitative microdialysis to measure neuropeptide Y (NPY) was evaluated in vitro and in vivo. The accuracy of this method was tested in vitro under steady-state conditions for 3 test solutions containing known concentrations of NPY. The estimated concentrations of NPY were 1.2 ± 0.6, 3.7 ± 0.9, and 15.1 ± 0.7 pg/μl (mean ± SEM) in agreement with the actual concentrations of NPY in the test solutions which were 1.1 ± 0.8, 4.6 ± 0.6, and 14.6 ± 0.5 pg/μl (mean ± SEM of solution samples), respectively. The responsiveness of the estimated NPY_ext measure to changes in the external concentration of NPY was also evaluated in vitro. An accurate estimate of NPY_ext was obtained within the first sampling period (within 15 min) after a 2–3-fold increase in the test solution concentration of NPY and within 2–3 sampling periods (15–45 min) in response to a 2–3-fold decrease in the test solution concentration of NPY. In vivo, the estimated basal concentration of NPY in dialysis samples from probes in the medial basal hypothalamus of anesthetized female rats (n = 4) was 4.0 ± 1.6 pg/μl and increased to 9.5 ± 0.3 pg/μl during K⁺ stimulation. Relative recovery was 22% in vivo under steady-state conditions and ranged from 14% to 30% during dynamic conditions. These results demonstrate that the difference method of quantitative microdialysis accurately estimates picomolar concentrations of NPY in vitro, and is sufficiently sensitive to detect basal and increasing concentrations of NPY in vivo.     

Anti-nociceptive effect of neuropeptide Y in periaqueductal grey in rats with inflammation

Experimental inflammation was induced by subcutaneous injection of carrageenan into the left hindpaw of rats. Intra-periaqueductal grey (PAG) injection of 0.02 or 0.1 nmol of neuropeptide Y (NPY), but not 0.004 nmol, induced significant increases in hindpaw withdrawal latency (HWL) to thermal and mechanical stimulation in rats with inflammation. Furthermore, the anti-nociceptive effect of NPY was blocked partly by following intra-PAG injection of the Y1 receptor antagonist NPY28-36. The results demonstrated that NPY plays an anti-nociceptive role in PAG in rats with inflammation, in which Y1 receptor is involved.     

Evidence of a physiological role for neuropeptide Y in ventromedial hypothalamic lesion-induced hyperphagia

We evaluated the role of neuropeptide Y (NPY), a potent endogenous orexigenic signal, in the ventromedial hypothalamic (VMH) lesion-induced hyperphagia in rats. To produce hyperphagia and excessive weight gain, adult female rats received bilateral electrolytic or sham lesions in the VMH. Concurrently, a permanent intracerebroventricular cannula was implanted in the third ventricle of the brain. After a recovery period, these rats were passively immunized against NPY to evaluate the role of endogenous NPY on hyperphagia. The results showed that intraventricular administration of NPY antibodies abolished the hyperphagia in VMH-lesioned rats. These revelations are in agreement with the notion that altered hypothalamic NPY release or action may underlie the hyperphagia and excessive weight gain seen in response to structural damage in the VMH.     

Methamphetamine stimulates the release of neuropeptide Y and noradrenaline from the paraventricular nucleus in rats

Effects of methamphetamine (MAP) on the extracellular neuropeptide Y (NPY) and noradrenaline (NA) levels were examined in the vicinity of the paraventricular nucleus (PVN) of freely moving rats by means of push-pull perfusion. The NA and NPY levels increased significantly in 30–60 min and reached the maximum level in 90–120 min after intraperitoneal administration of MAP. The effects were dose-dependent. The maximum levels were 1.6-fold of the pretreatment level for NPY and 7-fold for NA, respectively, when 5.0 mg/kg b.w. of methamphetamine was administered. It is concluded that MAP stimulates the releases of paraventricular NPY and NA, but the effect is more strong for NA than for NPY.     

The distribution of neuropeptide Y and brain-derived neurotrophic factor immunoreactivity in hippocampal formation of the monkey and rat

The distribution of neuropeptide Y (NPY) and Brain-Derived Neurotrophic Factor (BDNF) in the hippocampal formation of monkey and rat brains was studied immunohistochemically. The NPY-neuronal system is more highly developed in the monkey compared to that in the rat. The distribution of NPY-positive products was coincident with that of abundant BDNF-positive deposits. These observations suggest that the role of BDNF and the interaction of BDNF-NPY may differ between species.