Involvement of hippocampal neuropeptide Y in mediating the chronic actions of lithium, electroconvulsive stimulation and citalopram

Neuropeptide Y (NPY) has been considered to be involved in the pathogenesis of affective disorders, and chronic treatment with lithium or electroconvulsive stimuli (ECS) has been shown to increase mRNA and peptide levels of NPY in rat brain tissue. Consequently, parameters reflective of NPYergic neurotransmission were studied in the hippocampus of rats following chronic treatment with lithium, ECS or the selective serotonin re-uptake inhibitor (SSRI), citalopram. Lithium (28 days, diet) and ECS (10 days, once daily) treatments caused a marked increase in levels of preproNPY mRNA in the CA1 area and dentate gyrus (DG). This increase was accompanied by an increase in extracellular levels of NPY in the dorsal hippocampus of freely moving rats as determined by microdialysis, suggesting that lithium and ECS treatments lead to an increased biosynthesis and release of NPY in this area. (125)I-peptide YY (PYY) binding was reduced by 40 and 60% respectively in the DG following the same treatments, showing that the increased release is accompanied by a down-regulation of corresponding binding sites. In contrast, citalopram (10 mg/kg i.p., twice daily for 28 days) caused a 100% increase in (125)I-PYY binding in CA, CA3 and DG while levels of preproNPY mRNA and extracellular NPY in the hippocampus were unaffected. The results indicate that various agents and stimuli exerting antidepressant effects in humans, such as chronic lithium, ECS and citalopram all increase NPYergic neurotransmission in the hippocampus by distinct modes of action. Moreover, NPY (6 microg) given intracerebroventricularly (i.c.v.) induced an antidepressant-like effect in the forced swim test. It is hypothesised that the increase in NPYergic neurotransmission may be associated with the mechanism of action of various antidepressant treatments in the alleviation of depression.     

Electroconvulsive stimuli selectively affect behavior and neuropeptide Y (NPY) and NPY Y(1) receptor gene expressions in hippocampus and hypothalamus of Flinders Sensitive Line rat model of depression.

Previously we reported that basal neuropeptide Y (NPY)-like immunoreactivity-(LI) in hippocampus of the "depressed" Flinders Sensitive Line (FSL) rats was lower compared to the control Flinders Resistant Line (FRL) and that electroconvulsive stimuli (ECS) raise NPY-LI in discrete brain regions. Here we studied NPY mRNA expression, NPY Y(1) receptor (Y(1)) mRNA expression and binding sites, and behavior under basal conditions (Sham) and after repeated ECS. Baseline NPY and Y(1) mRNAs in the CA1-2 regions and dentate gyrus were lower while the Y(1) binding was higher in the FSL. ECS had larger effects on both NPY and behavior in the FSL rats. ECS increased NPY mRNA in the CA1-2, dentate gyrus and hypothalamus in FSL, but only in the dentate gyrus in FRL. ECS also increased Y(1) mRNA in the CA1-2, dentate gyrus and the parietal cortex in both strains, while in the hypothalamus the increase was observed only in the FSL rats. Consistently with Y(1) mRNA increase, Y(1) binding was downregulated in the corresponding regions. ECS decreased FSL immobility in the Porsolt swim test. These findings suggest that NPY is involved in depressive disorder and that antidepressant effects of ECS may in part be mediated through NPY.     

Chronic benzodiazepine administration alters hippocampal CA1 neuron excitability: NMDA receptor function and expression(1)

Rats are tolerant to benzodiazepine (BZ) anticonvulsant actions two days after ending one-week administration of the BZ, flurazepam (FZP). Concurrently, GABA(A) receptor-mediated inhibition is reduced and AMPA receptor-mediated excitation is selectively enhanced in CA1 pyramidal neurons in hippocampal slices. In the present study, the effects of chronic FZP exposure on NMDA receptor (NMDAR) currents were examined in CA1 pyramidal neurons in hippocampal slices and following acute dissociation. In CA1 neurons from chronic FZP-treated rats, evoked NMDAR EPSC amplitude was significantly decreased (52%) in slices, and the maximal current amplitude of NMDA-induced currents in dissociated neurons was also significantly reduced (58%). Evoked NMDAR EPSCs were not altered following acute desalkyl-FZP treatment. Using in situ hybridization and immunohistochemical techniques, a selective reduction in NR2B subunit mRNA and protein expression was detected in the CA1 and CA2 regions following FZP treatment. However, total hippocampal NMDAR number, as assessed by autoradiography with the NMDAR antagonist, [(3)H]MK-801, was unchanged by FZP treatment. These findings suggest that reduced NMDAR-mediated currents associated with chronic BZ treatment may be related to reduced NR2B subunit-containing NMDARs in the CA1 and CA2 regions. Altered NMDAR function and expression after chronic BZ exposure may contribute to BZ anticonvulsant tolerance or dependence.     

Neuropeptide Y expression in mouse hippocampus and its role in neuronal excitotoxicity

Aim: To investigate neuropeptide Y (NPY) expression in mouse hippocampus within early stages of kainic acid (KA) treatment and to understand its role in neuronal excitotoxicity. Methods: NPY expression in the hippocampus within early stages of KA intraperitoneal (ip) treatment was detected by immunohistochemistry (IHC) and in situ hybridization (ISH) methods. The role of NPY and Y5, Y2 receptors in excitotoxicity was analyzed by terminal deoxynucleotidyl transferase-mediated UTP nick end-labeling (TUNEL) assay. Results: Using IHC assay, in granule cell layer of the dentate gyrus (DG), NPY positive signals appeared 4 h after KA injection, reached the peak at 8 h and leveled off at 16 and 24 h. In CA3, no positive signal was found within the first 4 h after KA injection, but strong signal appeared at 16 and 24 h. No noticeable signal was detected in CA1 at all time points after KA injection. Using the ISH method, positive signals were detected at 4, 8, and 16 h in CA3, CA1, and hilus. In DG, much stronger ISH signals were detected at 4 h, but leveled off at 8 and 16 h. TUNEL analysis showed that intracerebroventricularly (icv) infusion of NPY and Y5, Y2 receptor agonists within 8 h after KA insult with proper dose could remarkably rescue pyramidal neurons in CA3 and CAI from apoptosis. Conclusion: NPY is an important anti-epileptic agent. The preceding elevated expression of NPY in granule cell layer of DG after KA injection might partially explain its different excitotoxicity-induced apoptotic responses in comparison with the pyramidal neurons from CA3 and CA1 regions. NPY can not only reduce neuronal excitability but also prevent excitotoxicity-induced neuronal apoptosis in a time-and doserelated way by activation of Y5 and Y2 receptors.     

The effect of intrahippocampal injection of group II and III metobotropic glutamate receptor agonists on anxiety; the role of neuropeptide Y.

Earlier studies conducted by our group and by other authors indicated that metabotropic glutamatergic receptor (mGluR) ligands might have anxiolytic activity and that amygdalar neuropeptide Y (NPY) neurons were engaged in that effect. Apart from the amygdala, the hippocampus, another limbic structure, also seems to be engaged in regulation of anxiety. It is rich in mGluRs and contains numerous NPY interneurons. In the present study, we investigated the anxiolytic activity of group II and III mGluR agonists after injection into the hippocampus, and attempted to establish whether hippocampal NPY neurons and receptors were engaged in the observed effects. Male Wistar rats were bilaterally microinjected with the group II mGluR agonist (2S,1'S,2'S)-2-(carboxycyclopropyl)glycine (L-CCG-I), group III mGluR agonist O-Phospho-L-serine (L-SOP), NPY, the Y1 receptor antagonist BIBO 3304, and the Y2 receptor antagonist BIIE 0246 into the CA1 or dentate area (DG). The effect of those compounds on anxiety was tested in the elevated plus-maze. Moreover, the effects of L-CCG-I and L-SOP on the expression of NPYmRNA in the hippocampus were studied using in situ hybridization method. It was found that a significant anxiolytic effect was induced by L-SOP injection into the CA1 region or by L-CCG-I injection into the DG. The former effect was inhibited by BIBO 3304, the latter by BIIE 0246. NPY itself showed antianxiety action after injection into both structures. In the CA1 area, the effect of NPY was prevented by BIBO 3304, whereas in the DG by BIIE 0246. Both the mGluR agonists L-CCG-I and L-SOP induced a potent increase in NPYmRNA expression in the DG region of the hippocampal formation. The obtained results indicate that group II and III mGluR agonists, L-CCG-I and L-SOP, as well as NPY display anxiolytic activity in the hippocampus, but act differently in the CA1 and DG. It was observed that group III mGluRs and Y1 receptors were engaged in the response in the CA1 area, whereas group II mGluRs and Y2 receptors played a pivotal role in the DG region.     

Functional interaction between neuropeptide Y receptors and modulation of calcium channels in the rat hippocampus

We investigated the functional interaction between neuropeptide Y (NPY) receptors using nerve terminals and cultured rat hippocampal neurons, and we evaluated the involvement of voltage-gated Ca(2+) channels (VGCCs) in NPY receptors-induced inhibition of Ca(2+) influx and glutamate release. The KCl-evoked release of glutamate from hippocampal synaptosomes was inhibited by 1 microM NPY and this effect was insensitive to either BIBP3226 (Y1 receptor antagonist) or L-152,804 (Y5 receptor antagonist), but was sensitive to BIIE0246 (Y2 receptor antagonist). We could also pharmacologically dissect the NPY receptors activity by using Y1, Y2 and Y5 receptor agonists ([Leu(31),Pro(34)]NPY, NPY13-36, NPY (19-23)-(Gly(1),Ser(3),Gln(4),Thr(6),Ala(31),Aib(32),Gln(34))-pancreatic polypeptide (PP), respectively), and in all the cases we observed that these agonists could inhibited the KCl-induced release of glutamate. However, the selective and specific co-activation of both Y1 and Y2 or Y2 and Y5 receptors resulted in non-additive inhibition, and this effect was prevented in the presence of the Y2 antagonist, but was insensitive to the Y1 or Y5 receptor antagonist. Moreover, as we previously showed for Y1 receptors, we also observed that the activation of Y5 receptors inhibited the glutamate release in the dentate gyrus and CA3 subregion, without significant effect in the CA1 subregion of the hippocampus. The same qualitative results were obtained when we investigated the role of NPY Y1 and Y2 receptors in modulating the changes in [Ca(2+)](i) due to KCl depolarisation in cultured hippocampal neurons. The inhibitory effect of nitrendipine (L-type VGCC blocker) or omega-conotoxin GVIA (omega-CgTx; N-type VGCC blocker) was not potentiated by the simultaneous activation of Y1 or Y2 receptors. Moreover, the exocytotic release of glutamate was inhibited by omega-agatoxin IVA (omega-Aga; P-/Q-type VGCC blocker), and this VGCC blocker did not potentiate Y1, Y2 or Y5 receptor-mediated inhibition of glutamate release. Also, the effect of ionomycin in inducing the exocytotic release of glutamate from hippocampal synaptosomes was insensitive to the activation of NPY receptors. In the present paper, we identified a role for NPY Y1, Y2 and Y5 receptors in modulating the exocytotic release of glutamate and the [Ca(2+)](i) changes in the rat hippocampus. In conditions of co-activation, there appears to exist a physiological cross-talk between Y1 and Y2 and also between Y2 and Y5 receptors, in which Y2 receptors play a predominant role. Moreover, we also show that Y1 and Y2 receptors exert their inhibitory action by directly modulating L-, N-, and P-/Q-type VGCCs, whereas the inhibition of glutamate release mediated by the Y5 receptors seems to involve P-/Q-type VGCCs.     

吗啡依赖性大鼠海马CA1区NPY细胞阳性表达

目的 观察吗啡依赖性大鼠海马区NPY细胞的变化.方法 用皮下注射吗啡法建立雄性大鼠吗啡依赖模型.用免疫组织化学和图像分析方法观察大鼠CA1区NPY细胞的变化.结果 吗啡依赖性大鼠海马CA1区NPY细胞免疫反应减弱(p＜0.01).结论 NPY细胞减少与吗啡依赖性的发生、发展.     

Blockade of neuropeptide Y(2) receptors and suppression of NPY's anti-epileptic actions in the rat hippocampal slice by BIIE0246

Neuropeptide Y (NPY) has been shown to suppress synaptic excitation in rat hippocampus by a presynaptic action. The Y(2) (Y(2)R) and the Y(5) (Y(5)R) receptors have both been implicated in this action. We used the non-peptide, Y(2)R-selective antagonist, BIIE0246, to test the hypothesis that the Y(2)R mediates both the presynaptic inhibitory and anti-epileptic actions of NPY in rat hippocampus in vitro. NPY and the Y(2)R-selective agonist, [ahx(5-24)]NPY, both inhibited the population excitatory postsynaptic potential (pEPSP) evoked in area CA1 by stratum radiatum stimulation in a concentration-dependent manner. BIIE0246 suppressed the inhibitory effects of both agonists, suppressing the maximal inhibition without causing a change in the agonist EC(50), in a manner inconsistent with competitive antagonism. BIIE0246 washed out from hippocampal slices extremely slowly. Application of agonist at high concentrations (1 - 3 microM) for prolonged periods did not alter the rate of washout, but did partially overcome the antagonism, inconsistent with an insurmountable antagonism by BIIE0246. In the stimulus train-induced bursting (STIB) model of ictal activity in hippocampal slices, both NPY and [ahx(5-24)]NPY inhibited primary afterdischarge (1 degrees AD) activity. BIIE0246 (100 nM) completely suppressed the actions of NPY and [ahx(5-24)]NPY in this model. In contrast, the potent Y(5)R-selective agonist, Ala(31)Aib(32)NPY, affected neither 1 degrees AD activity in the presence of BIIE0246, nor, by itself, even the pEPSP in CA1. BIIE0246 potently suppresses NPY actions in rat hippocampus, suggesting a dominant role for Y(2)R there. The apparently insurmountable antagonism observed may result from the lipophilic nature of the antagonist.     

The effects of chronic administration of morphine on the levels of brain and adrenal catecholamines and neuropeptide Y in rats.

1. Monoamine turnover and neuropeptide Y (NPY) levels were investigated in the central and peripheral nervous systems in adult male rats chronically treated with morphine. 2. The well-recognized biochemical alterations (serotoninergic turnover increased in the hypothalamus, hippocampus and striatum; dopaminergic turnover increased in the striatum and cortex; adrenaline levels decreased in the adrenal glands) were observed. 3. In addition, we observed a significant decrease of the NPY levels in the hypothalamus, the striatum and the adrenal glands. The observed changes were not reflected in plasma. 4. Our results contribute to the evidence that brain and adrenal monoamines and NPY could be involved in the mechanism of morphine tolerance and/or dependence.     

神经肽Y对海人酸致痫大鼠中GABAB受体的影响

目的 探讨重组腺相关病毒载体神经肽Y(rAAV2/1-NPY-EGF-P)干预前后海人酸致痫大鼠海马中GABABR表达的变化.方法 将36只雄性Wistar大鼠随机分为三组:KA组(海人酸致痫大鼠组)、NPY组(神经肽Y干预组)及NS组(对照组).KA组大鼠海马CA3区注射海人酸,完成慢性模型,造模成功后不注射病毒;NPY组大鼠海马CA3区注射海人酸,完成慢性模型,造模成功后向脑室注射10μL滴度为5×10u vg/mL的神经肽Y进行基因转染;NS组海马CA3区注射等量的0.9％NaCl.三组大鼠各12只,在基因转染后2周、4周分别取6只观察其发作行为学变化,并采用RT-PCR检测GABABR的表达,以GAPDH为标准参照基因,以之定量分析基因表达的RQ值(相对定量值).结果 通过RT-PCR发现,KA组、NPY组及NS组、海马组织均有GABABR表达.KA组GABABR的基因表达较NS组呈下降趋势(P＜0.05),NPY组GABABR的基因表达呈上升趋势,差异有统计学意义(P＜0.05).结论 KA组中GABABR的表达明显下降,NPY组中GABABR的表达呈上升趋势.说明GABABR基因表达的降低可能是导致癫痫发生、发展的重要因素.NPY可能通过改变抑制性神经递质的GAB-ABR的表达来达到调控癫痫发作的目的.     

Neuroprotective effect of NPY on kainate neurotoxicity in the hippocampus

Previous studies showed that neuropeptide Y (NPY) inhibited hippocampal epileptiform activity and that endogenous NPY might have neuroprotective effects. Therefore, in the present study, the effect of NPY microinjected intrahippocampally on the kainate-induced lesion and changes in NPY immunoreactivity (-IR) were investigated in rat hippocampus. Male Wistar rats, chronically cannulated, were unilaterally injected with kainic acid (KA) 2.5 nmol/1 microl, or additionally with NPY (470 pmol/1 microl) 30 min before or 30 min after KA injection, into the CA1 or dentate gyrus (DG) area of the hippocampus. Seven days later, their brains were taken out and analyzed histologically to estimate the lesion extent, and immunohistochemically to assess NPY-IR. It was found that KA induced extensive degeneration of CA pyramidal neurons and NPY-IR interneurons in the injected hippocampus. Simultaneously, NPY immunoreactivity appeared in mossy fibres and some granular cells in the contralateral hippocampus. NPY given 30 min after the KA injection into CA1 region, induced significant diminution of the lesion extent in the CA pyramidal layer (diminution by 61%). No significant effect was found when NPY was given 30 min before KA or when rats were microinjected into the DG area. The obtained results indicate neuroprotective action of NPY in some models of the kainate-induced hippocampal degeneration.     

海马 GDNFmRNA的表达参与大鼠吗啡戒断反应

目的：观察吗啡戒断大鼠侧脑室胶质细胞源性神经营养因子（glial cell derived neurotrophic factor，GDNF）反义寡脱氧核苷酸注射后对海马GDNFmRNA表达的影响。方法：SD大鼠侧脑室立体定位，皮下注射吗啡建立吗啡依赖大鼠模型，侧脑室微注射GDNF有义和反义寡脱氧核苷酸，纳洛酮催促戒断，应用原位杂交方法检测海马GDNFmRNA的表达。结果：侧脑室注射GDNF反义寡脱氧核苷酸能显著抑制大鼠吗啡戒断症状评分（n=t,p〈0．05）。吗啡依赖大鼠海马CA2区GDNFmRNA表达较对照组显著增加（n=3，P〈0．05），CA1和CA3区变化不明显；吗啡依赖大鼠纳洛酮（4mg／kg，岫催促戒断后海马CA1、CA2和CA3区GDNFmRNA表达较依赖组有增加趋势，但均没有显著差异心=3，P〉0．05）；吗啡依赖大鼠纳洛酮激发前24h侧脑室注射GDNF反义寡脱氧核苷酸能显著抑制吗啡依赖大鼠依赖和戒断后CA2区GDNFmRNA表达的增加（n=3，p〈0．05），而CA1和CA3区与戒断组大鼠相应区域相比没有差异；吗啡依赖大鼠纳洛酮激发前24h侧脑室注射GDNF有义寡脱氧核苷酸与戒断组大鼠相比海马CA1、CA2和CA3区GDNFmRNA表达均没有显著性差异（n=3，P〉0．05）。结论：在转录水平，海马CA2区GDNF表达的变化在吗啡依赖和戒断中可能起重要作用。     

Absence of tolerance to the excitatory effects of benzodiazepines: clonazepam-evoked shaking behavior in the rat.

Select benzodiazepine (BDZ) agonists, such as clonazepam, evoke wet-dog shakes (WDS) in the rat, a behavior which may be influenced by serotonergic drugs. To further study the role of serotonin (5-HT) and BDZ receptors in BDZ-induced WDS, we injected adult rats daily for 21 days with clonazepam and measured WDS and 5-HT1, 5-HT2, and BDZ receptors. Clonazepam 5 mg/kg upregulated 5-HT1 and 5-HT2 receptors in frontal cortex, but not in brainstem or spinal cord, compared to vehicle controls, without a change in BDZ receptors. A 10 mg/kg dose of the same drugs, however, did not alter 5-HT receptors. Chronic treatment with clonazepam failed to decrease clonazepam-induced WDS, resulting instead in a significant increase. The increase was prevented by chronic cotreatment with the 5-HT2 antagonist ketanserin, which significantly down-regulated 5-HT2 and BDZ sites. In vitro, clonazepam did not inhibit radioligand binding at 5-HT1 or 5-HT2 receptors in frontal cortex, brainstem, or spinal cord. Lack of tolerance to WDS evoked by clonazepam suggests different mechanisms for the excitatory and inhibitory effects of BDZs. The dose-independent effects of chronic clonazepam administration on 5-HT receptors are not mediated by activity of clonazepam at 5-HT receptor recognition sites.     

Running has differential effects on NPY, opiates, and cell proliferation in an animal model of depression and controls.

Physical activity has documented beneficial effect in treatment of depression. Recently, we found an antidepressant-like effect of running in an animal model of depression, the Flinders Sensitive Line (FSL) and demonstrated that it was associated with increased hippocampal cell proliferation. In this study, we analyzed levels of mRNAs encoding the neuropeptide Y (NPY) and the opioid peptides dynorphin and enkephalin in hippocampus and correlated these to cell proliferation in the FSL and in the 'nondepressed' Flinders Resistant Line (FRL) strain, with/without access to running wheels. Running increased NPY mRNA in dentate gyrus and the CA4 region in FSL, but not in FRL rats. NPY mRNA increase was correlated to increased cell proliferation in the subgranular zone of dentate gyrus. Baseline dynorphin and enkephalin mRNA levels in the dentate gyrus were lower in the FSL compared to the FRL strain. Running had no effect on dynorphin and enkephalin mRNAs in the FSL strain but it decreased dynorphin mRNA, and there was a trend to increased enkephalin mRNA in the FRL rats. Thus, it would appear that the CNS effects of running are different in 'depressed' and control animals; modification of NPY, a peptide associated with depression and anxiety, in depressed animals, vs effects on opioids, associated with the reward systems, in healthy controls. Our data support the hypothesis that NPY neurotransmission in hippocampus is malfunctioning in depression and that antidepressive treatment, in this case wheel running, will normalize it. In addition, we also show that the increased NPY after running is correlated to increased cell proliferation, which is associated with an antidepressive-like effect.     

NPY presynaptic actions are reduced in the hypothalamic mpPVN of obese (fa/fa), but not lean, Zucker rats in vitro

1. Neuropeptide Y (NPY) profoundly enhances feeding when injected intracerebroventricularly, or directly into hypothalamic nuclei, such as the paraventricular nucleus (PVN). Paradoxically, NPY has a reduced action on feeding in obese Zucker rats relative to lean Zucker rats, although the obese rats have much higher levels of hypothalamic NPY expression. GABAergic inputs to a subpopulation of medial parvocellular PVN (mpPVN) neurons are sensitive to NPY. Here, we tested the hypothesis that the blunted eating response to NPY observed in obese Zucker rats will be reflected in a reduced NPY action at mpPVN GABAergic synapses. 2. 'Blind' whole-cell patch-clamp recordings made from mpPVN neurons in acute brain slices of lean and obese Zucker rats revealed GABAergic inhibitory postsynaptic currents (IPSC) responses which were inhibited by NPY. While the maximum response in the obese Zucker rats was significantly less than in lean Zucker or Sprague-Dawley rats, there was no difference in the EC(50). 3.Experiments using blocking concentrations of Y(1)- or Y(5)-receptor antagonists revealed no differences between lean and obese Zucker rats in the contributions of either of these receptors to the total NPY response in mpPVN. 4. NPY is less effective at the mpPVN GABA synapse in obese than in lean Zucker rats. This is not associated with a change in the proportion of Y(1) or Y(5) receptors mediating the NPY response, and is consistent with the downregulation of NPY receptors or a reduction in receptor-effector coupling, and with the reduced sensitivity of obese rats to NPY.     

Receptor subtypes Y1 and Y5 mediate neuropeptide Y induced feeding in the guinea-pig

1. Neuropeptide Y (NPY) is one of the most potent stimulants of food intake. It has been debated which receptor subtype mediates this response. Initially Y(1) was proposed, but later Y(5) was announced as a 'feeding' receptor in rats and mice. Very little is known regarding other mammals. The present study attempts to characterize the role of NPY in feeding behaviour in the distantly related guinea-pig. When infused intracerebroventricularly, NPY dose-dependently increased food intake. 2. PYY, (Leu(31),Pro(34))NPY and NPY(2 - 36) stimulated feeding, whereas NPY(13 - 36) had no effect. These data suggest that either Y(1) or Y(5) receptors or both may mediate NPY induced food intake in guinea-pigs. 3. The Y(1) receptor antagonists, BIBO 3304 and H 409/22 displayed nanomolar affinity for the Y(1) receptor (K(i) values 1.1+/-0.2 nM and 5.6+/-0.9 nM, respectively), but low affinity for the Y(2) or Y(5) receptors. When guinea-pigs were pretreated with BIBO 3304 and H 409/22, the response to NPY was inhibited. 4. The Y(5) antagonist, CGP 71683A had high affinity for the Y(5) receptor (K(i) 1.3+/-0.05 nM) without having any significant activities at the Y(1) and Y(2) receptors. When CGP 71683A was infused into brain ventricles, the feeding response to NPY was attenuated. 5. The present study shows that NPY stimulates feeding in guinea-pigs through Y(1) and Y(5) receptors. As the guinea-pig is very distantly related to the rat and mouse, this suggests that both Y(1) and Y(5) receptors may mediate NPY-induced hyperphagia also in other orders of mammals.     

地卓西平对吗啡依赖大鼠部分脑区前脑啡肽基因表达的影响

目的:研究谷氨酸受体拮抗剂地卓西平对吗啡依赖大鼠部分脑区前脑啡肽(PENK)基因转录水平的影响.方法:18只雄性Sprague-Dawley大鼠随机等分吗啡组、干预组及对照组,每组6只.吗啡组大鼠腹腔注射吗啡,起始剂量5 mg/kg,2次/d,逐日递增5 mg,至第10天为50 mg/kg;干预组大鼠每次注射吗啡前30分钟腹腔注射地卓西平0.075 mg/kg;对照组按平行对照原则注射同体积的生理盐水.末次注射后3 h取脑并冰冻切片,留取中脑腹侧被盖区(VTA)、伏隔核(NAc)、中脑导水管灰质(PAG)、杏仁核(AMG)、海马CA1区(HIPCA1)的切片.利用原位杂交及图像分析技术检测各脑区PENK mRNA的水平(吸光度A值).结果:与对照组相比,吗啡组大鼠各脑区A值均明显降低,干预组大鼠在除AMG外的其它被检脑区也明显降低;与吗啡组相比,干预组大鼠VTA、NAc、AMG、HIPCA1区A值升高.结论:吗啡依赖大鼠多个脑区PENK基因表达明显下调,合并使用地卓西平可在一定程度上拮抗PENK基因表达的下调.     

MPEP, mGlu5 receptor antagonist, regulates NPYmRNA expression in hippocampal and amygdalar neurons

Our earlier studies showed that the metabotropic glutamate receptor 5 (mGluR5) antagonist, MPEP, could regulate neuropeptide Y (NPY) neurons in the amygdala, influencing both peptide expression and its antianxiety effects. Two brain structures are particularly engaged in a regulation of anxiety, namely the amygdala and also the hippocampus. They both belong to the limbic system and contain NPY neurons and mGlu5 receptors. Therefore, in the present study, we examined the effect of MPEP on NPY and NPYmRNA expression in the amygdala and the hippocampus of the rat brain. NPY expression was studied by immunohistochemical method, and radioimmunoassay, and the NPY synthesis was examined using NPYmRNA in situ hybridization. Immunohistochemical localization of mGluR5 was also carried out. It was found that MPEP given 3 times every 8 h potently decreased NPYmRNA expression 30 min after the last dose in both those structures (to 8-20% of the control level). After single MPEP treatment, we did not observe any changes in NPYmRNA level in the hippocampus, and its decrease in the amygdala 6 h after MPEP administration. The obtained results suggest a positive regulatory control of NPY synthesis by mGlu5 receptors in hippocampal and amygdalar neurons.     

Selective enhancement of AMPA receptor-mediated function in hippocampal CA1 neurons from chronic benzodiazepine-treated rats

Two days following one-week administration of the benzodiazepine, flurazepam (FZP), rats exhibit anticonvulsant tolerance in vivo, while reduced GABA(A) receptor-mediated inhibition and enhanced EPSP amplitude are present in CA1 pyramidal neurons in vitro. AMPA receptor (AMPAR)-mediated synaptic transmission in FZP-treated rats was examined using electrophysiological techniques in in vitro hippocampal slices. In CA1 pyramidal neurons from FZP-treated rats, the miniature excitatory postsynaptic current (mEPSC) amplitude was significantly increased (33%) without change in frequency, rise time or decay time. Moreover, mEPSC amplitude was not elevated in dentate granule neurons following 1-week FZP treatment or in CA1 pyramidal neurons following acute desalkyl-FZP treatment. Regulation of AMPAR number was assessed by quantitative autoradiography with the AMPAR antagonist, [(3)H]Ro48-8587. Specific binding was significantly increased in stratum pyramidale of hippocampal areas CA1 and CA2 and in proximal dendritic fields of CA1 pyramidal neurons. Regulation of AMPAR subunit proteins was examined using immunological techniques. Neither abundance nor distribution of GluR1-3 subunit proteins was different in the CA1 region following FZP treatment. These findings suggest that enhanced AMPAR currents, mediated at least in part by increased AMPAR number, may contribute to BZ anticonvulsant tolerance. Furthermore, these studies suggest an interaction between GABAergic and glutamatergic systems in the CA1 region which may provide novel therapeutic strategies for restoring BZ effectiveness.     

Neuropeptide Y induced attenuation of catecholamine synthesis in the rat mesenteric arterial bed

The effect of neuropeptide Y (NPY) on the basal and nerve stimulation-induced increase in norepinephrine synthesis was studied in the isolated and perfused mesenteric arterial bed of the rat. Tyrosine hydroxylation, the rate-limiting step in catecholamine (CA) biosynthesis, was assessed by measuring the accumulation of DOPA in the perfusate/superfusate overflow after perfusion of the mesenteric arterial bed with the decarboxylase inhibitor m-hydroxybenzyl hydralazine (NSD-1015). Treatment with NDS-1015 resulted in a time-dependent increase in DOPA production and nerve stimulation (8 Hz, supramaximal voltage, 2 ms duration) increased DOPA production even further. NPY 1 to 100 nM was observed to produce a concentration-dependent attenuation in both the basal and nerve stimulation-induced increase in DOPA formation.To come to an understanding of the NPY receptor subtype mediating the inhibition of CA synthesis, the rank order of potency of a series of NPY analogs with varying selectivity for NPY receptor subtypes including intestinal polypeptide (PYY), PYY 13-36, Leu36 Pro34 NPY, human pancreatic polypeptide (h-PP), and rat pancreatic polypeptide (r-PP) were determined. In addition, the effect of various selective NPY antagonists on the inhibitory effect of NPY was also examined. These included the Y1 antagonist BIB03304, the Y2 antagonist BIIE0246, and the Y5 antagonist CGP71683. The IC50's for NPY, PYY, PYY13-36, Leu31 Pro34 NPY, and hPP in inhibiting CA synthesis were 5, 7, 15, 30, and 33 nM respectively. rPP failed to inhibit CA synthesis. All 3 of the NPY antagonists produced attenuation of the NPY-induced inhibition of CA synthesis, but it took a combination of all 3 to completely block the effect of a maximal inhibitory concentration of NPY.These results demonstrate that NPY inhibits CA synthesis in the perfused mesenteric arterial bed and can do so by activation of a variety of receptors including the Y1, Y2, and Y5.