Upregulation Of Neuropeptide Y Research Articles

Administration of neuropeptide Y into the rat nucleus accumbens shell, but not core, attenuates the motivational impairment from systemic dopamine receptor antagonism by α-flupenthixol

Previous research has demonstrated that dopamine and Neuropeptide Y (NPY) promote motivated behavior, and there is evidence to suggest that they interact within neural circuitry involved in motivation. NPY and dopamine both modulate appetitive motivation towards food through direct actions in the nucleus accumbens (NAc), although how they interact in this region to promote motivation is presently unclear. In this study, we sought to further elucidate the relationship between NAc NPY and dopamine and their effects on motivated behavior. Specifically, we examined whether NAc injections of NPY might reverse behavioral deficits caused by reduced dopamine signaling due to systemic dopamine receptor antagonism. Appetitive motivation was measured using a progressive ratio-2 paradigm. Male Sprague Dawley rats were treated with systemic injections of the dopamine antagonist, α-flupenthixol or a saline vehicle. Two hours following injections, they were administered infusions of NPY (at 0, 156, or 235 pmol) into either the NAc shell (n = 12) or the NAc core (n = 10) and were placed in operant chambers. In both groups, α-flupenthixol impaired performance on the PR-2 task. NPY receptor stimulation of the NAc shell significantly increased both breakpoint and active lever presses during the PR-2 task, and dose-dependently increased responding following systemic dopamine receptor blockade. NPY did not affect appetitive motivation when injected into the NAc core. These data demonstrate that NPY in the NAc shell can improve motivational impairments that result from dopamine antagonism, and that these effects are site specific. These results also suggest that upregulation of NPY in neurodegenerative diseases may possibly buffer early motivational deficits caused by dopamine depletion in Parkinson’s and Huntington’s disease patients, both of which show increased NPY expression after disease onset.

Upregulation of neuropeptide Y in cardiac sympathetic nerves induces stress (Takotsubo) cardiomyopathy.

Substantial emotional or physical stress may lead to an imbalance in the brain, resulting in stress cardiomyopathy (SC) and transient left ventricular (LV) apical ballooning. Even though these conditions are severe, their precise underlying mechanisms remain unclear. Appropriate animal models are needed to elucidate the precise mechanisms. In this study, we established a new animal model of epilepsy-induced SC. The SC model showed an increased expression of the acute phase reaction protein, c-Fos, in the paraventricular hypothalamic nucleus (PVN), which is the sympathetic nerve center of the brain. Furthermore, we observed a significant upregulation of neuropeptide Y (NPY) expression in the left stellate ganglion (SG) and cardiac sympathetic nerves. NPY showed neither positive nor negative inotropic and chronotropic effects. On the contrary, NPY could interrupt β-adrenergic signaling in cardiomyocytes when exposure to NPY precedes exposure to noradrenaline. Moreover, its elimination in the left SG via siRNA treatment tended to reduce the incidence of SC. Thus, our results indicated that upstream sympathetic activation induced significant upregulation of NPY in the left SG and cardiac sympathetic nerves, resulting in cardiac dysfunctions like SC.

Abstract 5168: The dual regulatory role of Neuropeptide Y in colon cancer

Abstract Introduction: Colon cancer is the third most common cancer and affects approximately one million people every year. Patients with inflammatory bowel diseases (IBDs) have a higher risk of developing colon cancer. The neuropeptides, particularly neuropeptide Y (NPY) which is a 36-amino acid neuropeptide found in the brain, the autonomic nervous system and different peripheral tissues including the colon is associated with the development and progression of IBD. Objective: The objective of this study was to determine the role of NPY in colon cancer and establish NPY and its receptors as new targets for colon cancer. Methods: Immunohistochemical analysis was performed to detect the expression of NPY in colon cancer. Colon cancer (CT26) bearing mice were treated with both NPY Y1 receptor (Y1R) (BIBO 3304) or Y2 receptor (Y2R) (BIIE0246) specific antagonists and the effect on tumor growth and progression was studied. In vitro tumor and endothelial cell proliferation assays and colonic endothelial cell (CEC) migration and tubule forming assays were also conducted. Results and Conclusion: Our results show that there is significant upregulation of NPY in colon cancer and NPY is profusely secreted by colonic epithelial cells. Treatment of CT26 tumor bearing mice with both Y1R and Y2R antagonists resulted in significant reduction of tumor growth. Treatment with Y1R antagonist was associated with reduced number of proliferative cells in tumor tissues, while Y2R antagonist treated tumor tissues showed significant reduction in angiogenesis (micro vessel density). However, tumor cell apoptosis was significantly increased in both the treated groups compared to vehicle treated control group. Our in vitro results showed that treatment with NPY (100nM) significantly increased CT26 tumor cell as well as CEC proliferation compared to respective untreated control cells. However, when CT26 tumor cells were previously treated with Y1R antagonist (1μM) the effect of NPY was abrogated. Y2R antagonist (1μM) prior treated tumor cells didn't show any significant reduction in NPY induced tumor cell proliferation. On the contrary, when CEC were prior treated with Y2R antagonist, NPY mediated CEC proliferation was abrogated. Prior treatment with Y1R antagonist had no effect on this function of NPY. NPY also promoted migration and tube formation capabilities of CEC. Prior treatment with Y2R antagonist also significantly decreased these NPY mediated functions of CEC. Y1 antagonist had no effect on CEC. Our results thus show that NPY by acting through Y1 receptors, which are predominantly expressed by tumor cells, controls the proliferation and growth of the cancer cells. Also, NPY by acting through Y2 receptors that are mostly expressed by the endothelial cells controls the functions of these cells present in the tumor microenvironment. This to our knowledge is the first report about the dual regulatory role of NPY in colon cancer by which it controls both the tumor cells as well as the endothelial cells in the surrounding microenvironment. Citation Format: Sandeep Goswami, Debanjan Chakroborty, Sujit Basu, Wendy Frankel, Chandrani Sarkar. The dual regulatory role of Neuropeptide Y in colon cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5168.

Neuropeptide Y Acts Directly on Cartilage Homeostasis and Exacerbates Progression of Osteoarthritis Through NPY2R.

Neuropeptide Y (NPY) is known to regulate bone homeostasis; however, its functional role as a risk factor during osteoarthritis (OA) remains elusive. In this study, we aim to investigate the direct effect of NPY on degradation of cartilage and progression of OA and explore the molecular events involved. NPY was overexpressed in human OA cartilage accompanied with increased expression of NPY1 receptor (NPY1R) and NPY2 receptor (NPY2R). Stressors such as cold exposure resulted in the peripheral release of NPY from sympathetic nerves, which in turn promoted upregulation of NPY and NPY2R in articular cartilage in vivo. Intra-articular administration of NPY significantly promoted chondrocyte hypertrophy and cartilage matrix degradation, with a higher OARSI score than that of control mice, whereas inhibition of NPY2R but not NPY1R with its specific antagonist remarkably ameliorated NPY-mediated effects. Moreover, NPY activated mTORC1 pathway in articular chondrocytes, whereas the administration of rapamycin (an mTORC1 inhibitor) in vitro abrogated NPY-mediated effects. Mechanistically, mTORC1 downstream kinase S6K1 interacted with and phosphorylated SMAD1/5/8 and promoted SMAD4 nuclear translocation, resulting in upregulation of Runx2 expression to promote chondrocyte hypertrophy and cartilage degradation. In conclusion, our findings provided the direct evidence and the crucial role of NPY in cartilage homeostasis. © 2020 American Society for Bone and Mineral Research.

Effect of inducible nitric oxide synthase and neuropeptide Y in plasma and placentas from intrahepatic cholestasis of pregnancy.

To analyze inducible nitric oxide synthase (iNOS) and neuropeptide Y (NPY) expression in maternal plasma and placentas of human with intrahepatic cholestasis of pregnancy (ICP). The plasma and placentas were collected from 35 women with normal pregnancies and 33 women with ICP. Enzyme-linked immunosorbent assays were used to investigate maternal plasma iNOS and NPY levels. The mRNA levels and cell-specific localization of iNOS and NPY were determined by quantitative PCR, Western Blotting and immunohistochemical analysis in placentas. In human placentas, it revealed iNOS and NPY were mainly localized in syncytiotrophoblast, cytotrophoblastin and vascular endothelium cells using immunohistochemistry analysis. iNOS protein and mRNA expression in ICP maternal plasma and placental tissue were significantly lower than in control groups (P <0.01). In maternal plasma and placentas tissue from ICP patients, a marked up-regulation of NPY protein and mRNA expression were observed (P <0.01). iNOS and NPY may play a role in the effect of maternal cholestasis on the placenta. The down-regulation of iNOS and up-regulation of NPY in ICP may influence the blood flow of the utero-placental-fetal unit, which may play a significant role in poor fetoplacental vascular perfusion, acute hypoxia and adverse pregnancy outcomes.

NPY up-regulation in the tadpole brain of Euphlyctis cyanophlyctis during osmotic stress

Most of the amphibians breed in temporary ponds vulnerable to occasional desiccation, thus, leaving their larvae exposed to stressful fluctuations in various environmental parameters including salinity. These animals possess a well suited central adaptive mechanism to adapt to these alterations. Neuropeptide Y (NPY), a 36 amino acid neurotransmitter, has been reported to antagonize various neuropsychological consequences of stress within the mammalian brain. Osmotic regulation of NPY in the hypothalamo-neurohypophysial pathway of mammalian brain is also known. Although the molecule possesses an extensive distribution in the brain of amphibians, its functional association is not well understood. We have investigated the endogenous response of NPY-ergic system to osmotically stressful conditions in the brain of Indian skipper frog-Euphlyctis cyanophlyctis tadpoles. Using Immunohistochemistry, we observed an up-regulation of NPY immunoreactivity (NPY-ir) in the brain of tadpoles exposed to stressful salt concentrations. A significant increase of NPY-ir occurred in the pallium and septum regions of telencephalon; preoptic area, epithalamic, thalamic and hypothalamic parts of diencephalon. Most of the regions are implicated in the modulation of stress and anxiety related brain functions and have also been shown to respond to the salinity stress in mammals. In addition, NPY producing neurons in pre-optic and hypothalamic parts show a close co-existence with the vasopressin-ergic neurons. Thus, our study suggests a possible role of NPY in stabilizing the neuro-endocrinological consequences of osmotic stress in an amphibian brain.

A potential anti-allodynic mechanism of GDNF following L5 spinal nerve ligation; Mitigation of NPY up-regulation in the touch sense pathway

Intrathecal delivery of glial cell line-derived neurotrophic factor (GDNF) reverses mechanical allodynia after 5th lumbar (L5) spinal nerve ligation (SNL). However, the molecular mechanism behind this process is not fully understood. Following sciatic nerve injury, primary afferent neurons in the injured dorsal root ganglion (DRG) begin to express neuropeptide Y (NPY) that is absent in normal DRG. The aim of the current study was to determine the relationship of this de novo expression of NPY and the anti-allodynic effect of GDNF. Following L5 SNL, 73% of neurons began to express NPY mRNA in the ipsilateral L5 DRG and robust NPY-immunoreactive fibers appeared in the ipsilateral GN where the touch-sense mediating A-fiber primary afferents from the hindpaw terminate. Seven-daylong intrathecal infusion of GDNF at the L5 DRG level, starting on day three when mechanical allodynia had fully developed, reversed once-established these changes. The GN neurons normally expressed NPY Y1 receptor, but not Y2, Y4, or Y5 receptors, and L5 SNL did not change the expression pattern. Bolus intracisternal injection of BIBP3226, a Y1 receptor antagonist, dose-dependently reversed mechanical allodynia. We demonstrated that GDNF reversed once-established mechanical allodynia as well as NPY induction in the touch-sense processing pathway. NPY could facilitate touch-sense processing by Y1 receptor in the gracile nucleus after peripheral nerve injury. GDNF may exert anti-allodynic effects through mitigation of this NPY up-regulation. The effectiveness of delayed treatment further indicates the therapeutic potential of GDNF on neuropathic pain.

Pancreatic islet neuropeptide Y overexpression has minimal effect on islet morphology and β-cell adaptation to high-fat diet.

Neuropeptide Y (NPY) is highly expressed in the hypothalamus, where it regulates feeding and energy homeostasis. Interestingly, NPY and its receptors are also expressed in peripheral tissues with roles in metabolism, including pancreatic islets. In islets, NPY is known to suppress insulin secretion acutely. In addition, the role of NPY in β-cell de-differentiation has been postulated recently. Therefore, we studied transgenic mice expressing NPY under rat insulin promoter (TG) to determine the effects of chronic up-regulation of NPY on islet morphology and function. NPY levels were 25 times higher in islets of TG mice compared with wild-type (WT) littermates, whereas no differences in NPY expression were noted in the brains of TG and WT mice. Islet NPY secretion was 2.3-fold higher in TG compared with WT mice. There were no significant changes in body weight, glucose tolerance, or insulin sensitivity in TG mice fed regular rodent diet or high-fat diet (HF). Islet β-cell area was comparable between TG and WT mice both on regular rodent and HF diets, indicating that NPY overexpression is insufficient to alter β-cell maturation or the compensatory increase of β-cell area on HF. One abnormality noted was that the glucose-stimulated insulin secretion in islets isolated from TG was reduced compared with those from WT mice on HF diet. Overall, an increase in islet NPY level has little impact on islet function and is insufficient to affect glucose homeostasis in mice.

Abstract 5354: Neuropeptide Y as a prognostic marker of colorectal cancer

Abstract Introduction: Colorectal cancer affects a large population not only in the United States but worldwide and is one of the major causes of mortality due to cancer. Among the numerous risk factors that might lead to the incidence and development of this disease, inflammatory bowel diseases (IBD) have been identified as a very prominent factor and patients are at much higher risk of developing colorectal cancer in their lifetime. Objective/Hypothesis: As chronic inflammation leads to colorectal cancer and among the various neuromediators, the neuropeptides, particularly neuropeptide Y (NPY) is associated with the development and progression of IBD and as NPY has the potential to augment inflammation and angiogenesis through its Y2 receptor we hypothesize that NPY is an important regulator of the process of development of colorectal cancer (CRC). Results: Our results show that the expression of both NPY its Y2 receptor is upregulated in an axozymethane / dextran sodium sulphate (AOM/DSS) induced mouse model of inflammatory CRC. Upregulation of NPY in AOM/DSS induced CRC in mice is associated with increased angiogenesis. NPY Y2 receptors are expressed in these angiogenic vessels. Furthermore, this upregulation of NPY and Y2 receptor is also related to higher expression of the inflammatory cytokine, TNF-α, that has been shown to promote progression of carcinogenesis in AOM/DSS induced CRC mouse models. Our in vitro studies show that NPY can promote angiogenic potential of human umbilical vein endothelial cells (migration and permeability) through Y2 receptors present in these cells. Conclusion: We here show for the first time that NPY might be associated with the progression of inflammatory colorectal cancer and hence may serve as a prognostic marker of the disease. Citation Format: Chandrani Sarkar, Debanjan Chakroborty. Neuropeptide Y as a prognostic marker of colorectal cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 5354. doi:10.1158/1538-7445.AM2014-5354

Therapeutic concentrations of valproate but not amitriptyline increase neuropeptide Y (NPY) expression in the human SH-SY5Y neuroblastoma cell line

Neuropeptide Y (NPY) is a peptide found in the brain and autonomic nervous system, which is associated with anxiety, depression, epilepsy, learning and memory, sleep, obesity and circadian rhythms. NPY has recently gained much attention as an endogenous antiepileptic and antidepressant agent, as drugs with antiepileptic and/or mood-stabilizing properties may exert their action by increasing NPY concentrations, which in turn can reduce anxiety and depression levels, dampen seizures or increase seizure threshold.We have used human neuroblastoma SH-SY5Y cells to investigate the effect of valproate (VPA) and amitriptyline (AMI) on NPY expression at therapeutic plasma concentrations of 0.6mM and 630nM, respectively. In addition, 12-O-tetradecanoylphorbol-13-acetate (TPA) known to differentiate SH-SY5Y cells into a neuronal phenotype and to increase NPY expression through activation of protein kinase C (PKC) was applied as a positive control (16nM). Cell viability after drug treatment was tested with a 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. NPY expression was measured using immunofluorescence and quantitative RT-PCR (qRT-PCR). Results from immunocytochemistry have shown NPY levels to be significantly increased following a 72h but not 24h VPA treatment. A further increase in expression was observed with simultaneous VPA and TPA treatment, suggesting that the two agents may increase NPY expression through different mechanisms. The increase in NPY mRNA by VPA and TPA was confirmed with qRT-PCR after 72h. In contrast, AMI had no effect on NPY expression in SH-SY5Y cells.Together, the data point to an elevation of human NPY mRNA and peptide levels by therapeutic concentrations of VPA following chronic treatment. Thus, upregulation of NPY may have an impact in anti-cancer treatment of neuroblastomas with VPA, and antagonizing hypothalamic NPY effects may help to ameliorate VPA-induced weight gain and obesity without interfering with the desired central effects of VPA.

Of Mice and Men: Neuropeptide Y and Its Receptors Are Associated with Atherosclerotic Lesion Burden and Vulnerability

Neuropeptide Y (NPY), a sympathetic and platelet-derived vascular mitogen and angiogenic factor, has been implicated in atherosclerosis in animal and human genetic studies. Here we evaluate its association with human and murine atherosclerosis, and assess the role of platelet-derived NPY in lesion vulnerability. NPY immunoreactivity (NPY-ir) was measured in the platelet-poor and platelet-rich (PRP) plasmas, and NPY receptors (mitogenic Y1R and angiogenic Y2 and Y5Rs), CD26/DPPIV (a protease forming Y2/Y5-selective agonist), CD31-positive vascularity, and lesion morphology assessed by histo- and immunocyto-chemistry-in patients with peripheral artery disease (PAD) and healthy volunteers, and in lard-fed ApoE-/- mice. NPY and NPY-R immunostaining was greater in lesions from PAD patients compared to normal vessels of healthy volunteers (p < 0.001), and localized to smooth muscle cells, macrophages, and adventitial/neovascular endothelial cells. CD26/DPPIV staining co-localized with CD31-positive endothelial cells only in atherosclerotic lesions. NPY-ir in PRP (but not plasma) and vascular immunostaining was higher (p < 0.05 and 0.001, respectively) in men (not women) with PAD compared to healthy subjects. A similar gender specificity was observed in mice. PRP NPY-ir levels correlated with lesion area (p = 0.03), necrotic core area, and the necrotic core-to-lesion area ratio (p < 0.01) in male, but not female, mice. Also males with neovascularized lesions had higher PRP NPY-ir levels than those lacking lesion microvessels (p < 0.05). NPY and its Rs are up-regulated in human and murine atherosclerotic lesions suggesting pathogenic role. DPPIV expression by microvascular endothelium in atherosclerotic tissue may shift NPY's affinity toward angiogenic Y2/Y5Rs, and thus enhance angiogenesis and lesion vulnerability. Remarkably, plaque neovascularization was associated with increased NPY-ir in PRP in males but not females, suggesting that platelet NPY may be a novel mediator/marker of lesion vulnerability particularly in males, for reasons that remain to be determined. Both animal and human data suggest that NPY is an important contributor to, and platelet NPY-ir a marker of, atherosclerotic lesion burden and vulnerability but only in males, perhaps due to androgen-dependent up-regulation of NPY, previously shown in rats.

Neuronal plasticity in animal models and the epileptic human hippocampus

Prolonged status epilepticus in humans as in experimental animals can initiate the development of temporal lobe epilepsy (TLE) (Kapur, 1999). Therefore, application of potent convulsant substances such as kainic acid or pilocarpine in rats induces acute status epilepticus that, after a silent period of 1–2 weeks, is followed by spontaneous convulsions. The status epilepticus is characterized by severe limbic seizures and sequelae of neuropathologic signs including opening of the blood–brain barrier, local brain edema, bleeding into the brain, and activation of microglia and astrocytes followed by neurodegeneration in the hippocampus, amygdala, entorhinal cortex, and other brain areas (Sperk et al., 1983; Du et al., 1993; Rizzi et al., 2003). Induced by the seizure activity, neurotransmitters such as γ-aminobutyric acid (GABA), glutamate, or amine transmitters are released from their stores and mechanisms of their resynthesis are strongly activated (Sperk et al., 1983). In addition, pronounced changes in the expression of multiple functionally important proteins have been found in brains of experimental animals and humans (Herdegen et al., 1993; Sperk, 1994; McNamara, 1999; Morimoto et al., 2004).

Modification of classical neurochemical markers in identified primary afferent neurons with Aβ‐, Aδ‐, and C‐fibers after chronic constriction injury in mice

It is functionally important to differentiate between primary afferent neurons with A-fibers, which are nociceptive or nonnociceptive, and C-fibers, which are mainly nociceptive. Neurochemical markers such as neurofilament 200 (NF200), substance P (SP), and isolectin B4 (IB4) have been useful to distinguish between A- and C-fiber neurons. However, the expression patterns of these markers change after peripheral nerve injury, so that it is not clear whether they still distinguish between fiber types in models of neuropathic pain. We identified neurons with Abeta-, Adelta-, and C-fibers by their conduction velocity (corrected for utilization time) in dorsal root ganglia taken from mice after a chronic constriction injury (CCI) of the sciatic nerve and control mice, and later stained them for IB4, SP, calcitonin gene-related peptide (CGRP), NF200, and neuropeptide Y (NPY). NF200 remained a good marker for A-fiber neurons, and IB4 and SP remained good markers for C-fiber neurons after CCI. NPY was absent in controls but was expressed in A-fiber neurons after CCI. After CCI, a group of C-fiber neurons emerged that expressed none of the tested markers. The size distribution of the markers was investigated in larger samples of unidentified dorsal root ganglion neurons and, together with the results from the identified neurons, provided only limited evidence for the expression of SP in Abeta-fiber neurons after CCI. The extent of up-regulation of NPY showed a strong inverse correlation with the degree of heat hyperalgesia.

Activation of transcription factor c- jun in dorsal root ganglia induces VIP and NPY upregulation and contributes to the pathogenesis of neuropathic pain

Vasoactive intestinal peptide (VIP) and neuropeptide Y (NPY) in dorsal root ganglia (DRGs) are known to be upregulated and to contribute to the mechanisms of neuropathic pain following peripheral nerve injury. Moreover, transcription factor c-Jun regulates the expressions of both VIP and NPY in cultured DRG neurons. To elucidate the role of c-Jun in the induction of neuropathic pain hypersensitivity, we examined whether activated c-Jun affects pain behavior and the expressions of VIP and NPY following chronic constriction injury (CCI) of rat sciatic nerve. Intrathecal treatment with c- jun antisense oligodeoxynucleotides (AS-ODN) significantly reduced mechanical allodynia, but not thermal hyperalgesia following CCI. In addition, c- jun AS-ODN also suppressed the remarkable elevations of VIP and NPY mRNAs and the percentages of phosphorylated c-Jun-, VIP-, and NPY-immunoreactive neurons observed in DRGs following CCI. These results show that the activation of c-Jun in DRGs induces VIP and NPY upregulation and contributes to the pathogenesis of neuropathic pain following CCI.

Goldblatt hypertension is reduced by transgenic overexpression of neuropeptide Y in the rat

Neuropeptide Y (NPY) is expressed in the sympathetic nervous system and the peptide has been implicated in the central regulation of blood pressure (BP). The hypertension in the Goldblatt one-kidney one-clip (1K1C) model is predominantly due to sodium and fluid retentions and enhanced sympathetic nervous activity. This experiment was designed to determine if NPY is involved in the development of 1K1C hypertension in the rat. Sprague Dawley transgenic male rats (NTG) overexpressing NPY under its natural promoter and non-transgenic littermates (CTR) were used. BP was measured by telemetry. After baseline (3 days) BP recording, the rats were subjected to 1K1C or sham surgery and telemetric recordings of BP and HR were continued for 3 weeks. Baseline BP was lower in the NTG group (by 6.5 mmHg, p<0.05). 1K1C (but not sham treatment) increased BP gradually in both groups; however the BP of the transgenic rats was significantly lower than that of the control (113.8 ±0.8 vs 135.7 ±0.2 mmHg, NTG vs CTR, respectively). During the treatment HR was not changed in the CTR but it was reduced in the NTG subjects (by 16 bpm, p<0.05). Thus, increased NPY signaling reduced the development of 1K1C hypertension. The mechanism of the hypotensive effect of NPY upregulation may involve central inhibition of the sympathetic outflow, an increase in sodium excretion, or increase of the baroreflex responsiveness. These results indicate that NPY is an antihypertensive neurotransmitter of the autonomic nervous system and that genetic deficiencies in NPY signaling may underlie the etiology of some forms of hypertension. Support: HL 57921.

Effect of a graded single constriction of the rat sciatic nerve on pain behavior and expression of immunoreactive NPY and NPY Y1 receptor in DRG neurons and spinal cord

In the present study, the rat sciatic nerve was constricted to varying degrees using only one ligature with a very thin polyethylene sheath placed between nerve and ligature thread. Complete nerve transection was studied for comparison. With a 40–80% constriction of the nerve we observed allodynia to a similar extent as in the so-called Bennett model based on four loose ligatures. We also monitored changes in the expression of neuropeptide Y (NPY) and the NPY Y1 receptor (Y1R) in the lumbar 4–5 dorsal root ganglia (DRG) and dorsal horn and found upregulation of NPY and downregulation of the Y1R in DRG neurons after injury. These results indicate that similar peptide and receptor changes occur in this model as after axotomy and in other nerve injury models, although the immunohistochemical and behavioral changes seem to be dependent on the degree of constriction of the nerve. Thus, it seems relevant to monitor the degree of constriction when evaluating pain and other post-injury events. The possibility that some of the changes in NPY-ergic neurotransmission are related to the generation of allodynia is discussed; as well as the possibility to use this mononeuropathic model based on a single ligature nerve constriction (SLNC) as a complementary approach to other widely used pain models.

Responsiveness to peripherally administered melanocortins in lean and obese mice.

To elucidate mechanisms of melanocortin action, we investigated the effects of a melanocortin receptor agonist (melanotetan II [MTII]) in lean C57BL/6J and obese (DIO, ob/ob, UCP1-DTA) mice. MTII administration (100 microg q.i.d. i.p.) for 24 h results in similar weight loss but a more pronounced decrease of food intake in DIO mice. After 4 and 8 days of MTII treatment, however, the reduction in both food intake and body weight is more pronounced in DIO mice than in lean mice. MTII administration for 24 h prevents food deprivation-induced alterations in hypothalamic neuropeptide Y (NPY) and liver adiponectin receptor 1 and adiponectin receptor 2 mRNA expression, but does not alter hypothalamic mRNA expression of melanocortin 4 receptor or adiponectin serum and mRNA expression levels. NPY and agouti gene-related protein (AgRP) mRNA expression after 8 days of MTII is increased to levels comparable to pair-fed mice. In summary, 1) MTII is an effective treatment for obesity and related metabolic defects in leptin-resistant (DIO, UCP1-DTA) and leptin-sensitive (ob/ob) mouse models of obesity; 2) the effects of MTII on food intake and body weight are more pronounced in DIO mice than in lean mice; 3) the tachyphylactic effect after prolonged MTII administration appears to be, at least in part, caused by a compensatory upregulation of NPY and AgRP mRNA levels, whereas decreasing leptin levels may play a very minor role in mediating tachyphylaxis; and 4) alterations in adiponectin receptor mRNA expression after fasting or MTII treatment may contribute to altered insulin sensitivity and needs to be studied further.

Neuronal and glial pathological changes during epileptogenesis in the mouse pilocarpine model

The rodent pilocarpine model of epilepsy exhibits hippocampal sclerosis and spontaneous seizures and thus resembles human temporal lobe epilepsy. Use of the many available mouse mutants to study this epilepsy model would benefit from a detailed neuropathology study. To identify new features of epileptogenesis, we characterized glial and neuronal pathologies after pilocarpine-induced status epilepticus (SE) in CF1 and C57BL/6 mice focusing on the hippocampus. All CF1 mice showed spontaneous seizures by 17–27 days after SE. By 6 h there was virtually complete loss of hilar neurons, but the extent of pyramidal cell death varied considerably among mice. In the mossy fiber pathway, neuropeptide Y (NPY) was persistently upregulated beginning 1 day after SE; NPY immunoreactivity in the supragranular layer after 31 days indicated mossy fiber sprouting. β2 microglobulin-positive activated microglia, normally absent in brains without SE, became abundant over 3–31 days in regions of neuronal loss, including the hippocampus and the amygdala. Astrogliosis developed after 10 days in damaged areas. Amyloid precursor protein immunoreactivity in the thalamus at 10 days suggested delayed axonal degeneration. The mortality after pilocarpine injection was very high in C57BL/6 mice from Jackson Laboratories but not those from Charles River, suggesting that mutant mice in the C57BL/6(JAX) strain will be difficult to study in the pilocarpine model, although their neuropathology was similar to CF1 mice. Major neuropathological changes not previously studied in the rodent pilocarpine model include widespread microglial activation, delayed thalamic axonal death, and persistent NPY upregulation in mossy fibers, together revealing extensive and persistent glial as well as neuronal pathology.

Neuropeptide Y.

Neuropeptide Y.

A role for NPY overexpression in the dorsomedial hypothalamus in hyperphagia and obesity of OLETF rats.

Otsuka Long-Evans Tokushima Fatty (OLETF) rats lacking CCK-A receptors are hyperphagic, obese, and diabetic. We have previously demonstrated that these rats have a peripheral satiety deficit resulting in increased meal size. To examine the potential role of hypothalamic pathways in the hyperphagia and obesity of OLETF rats, we compared patterns of hypothalamic neuropeptide Y (NPY), proopiomelanocortin (POMC), and leptin receptor mRNA expression in ad libitum-fed Long-Evans Tokushima (LETO) and OLETF rats and food-restricted OLETF rats that were pair-fed to the intake of LETO controls. Pair feeding OLETF rats prevented their increased body weight and elevated levels of plasma insulin and leptin and normalized their elevated POMC and decreased NPY mRNA expression in the arcuate nucleus. In contrast, NPY expression was upregulated in the dorsomedial hypothalamus (DMH) in pair-fed OLETF rats. A similar DMH NPY overexpression was evident in 5-wk-old preobese OLETF rats. These findings suggest a role for DMH NPY upregulation in the etiology of OLETF hyperphagia and obesity.