Marked decrease of neuropeptide Y Y2 receptor binding sites in the hippocampus in murine prion disease

Using autoradiographic binding methodology with monoiodinated peptide YY together with the agonists neuropeptide Y (NPY) and NPY (13-36), as well as in situ hybridization with oligonucleotide probes complementary to the NPY Y2 receptor (Y2-R) mRNA, we have studied whether or not intracerebral prion inoculation affects Y2-Rs in male CD-1 mice. Monoiodinated peptide YY binding, mainly representing Y2-Rs, was down-regulated by 85% in the CA1 strata oriens and radiatum and by 50-65% in the CA3 stratum oriens 110-140 days postinoculation. In the CA3 stratum radiatum, where the mossy fibers from the dentate granule cells project, there was a significant decrease in PYY binding at 110-120 days. Y2-R mRNA, moderately expressed both in the CA1 and CA3 pyramidal cell layers and the granule cell layer in the dentate gyrus, showed a slight, but not significant, decrease in CA3 neurons 130 days postinoculation. The results indicate that the accumulation of the scrapie prion protein in the CA1-3 region strongly inhibits NPY binding at the Y2-Rs, which, however, is only marginally due to reduced Y2-R mRNA expression. The loss of the ability of NPY to bind to inhibitory Y2-Rs may cause dysfunction of hippocampal circuits and may contribute to the clinical symptoms in mouse scrapie.     

Characterization of endogenous neuropeptide Y in rat hippocampus and its metabolism by nanospray mass spectrometry

Neuropeptide Y (NPY) is a 36-residue-long neuropeptide which has been implicated in the regulation of feeding behavior and modulation of the circadian rhythm. We identified the primary structure of the endogenous NPY-immunoreactive material in the rat hippocampus using a combination of chromatographic techniques and nanospray mass spectrometry. The major component in the brain tissue corresponded to the authentic amidated form of NPY(1-36). The fate of NPY in the central nervous system was studied by subjecting pure peptide to the protease(s) present in hippocampal synaptosomes to reveal potential cleavage site(s). NPY was efficiently metabolized with a single cleavage between Leu30-Ile31. Thus, processing of NPY resulted in formation of the C-terminally truncated fragment NPY(1-30) and its counterpart NPY(31-36). The enzyme revealed properties of aspartic protease, being blocked by pepstatin and having a pH optimum between 4 and 5. The data clarify the structure of NPY and its inactivation pathway in the brain, which is different from that found in the periphery, and may have important consequences in vivo.     

Characterization of the neuropeptide Y5 receptor in the human hypothalamus: a lack of correlation between Y5 mRNA levels and binding sites

Neuropeptide Y (NPY) is a 36-amino-acid peptide that appears to play a central role in the control of feeding behavior. Recently, a cDNA encoding a novel NPY receptor subtype (Y5) was cloned from the rat and human hypothalamus, and shown to have a pharmacology consistent with NPY-induced feeding. We have subsequently cloned this cDNA from human hypothalamus and stably expressed it in CHO cells. Consistent with earlier reports, hY5 has a high affinity for NPY, [Leu31, Pro34]NPY, and NPY(3-36), but low affinity for larger C-terminal deletions of NPY and BIBP3226. High levels of hY5 mRNA were found in the human testis, brain, spleen and pancreas, with lower levels in several other tissues. In the human brain, hY5 mRNA levels were typically higher than hY2, but lower in comparison to hY1 receptor mRNA. To quantify the relative amounts of hY1, hY2 and hY5 mRNA in the human hypothalamus, we employed competitive RT-PCR. Interestingly, the relative amount of hY5 mRNA was substantially higher than either hY1 or hY2. However, pharmacological characterization of NPY binding sites in human hypothalamus membranes revealed predominantly the hY2 subtype. These data establish that while hY5 mRNA levels are very high in the human hypothalamus, conventional radioligand binding techniques do not detect hY5-like binding site. Whether hY5-like binding sites exist in the other human tissues that express hY5 mRNA (and what function hY5 has in those tissues) awaits future investigation.     

Characterization of the rat myometrial contractile response to neuropeptide Y

The in vitro contractile effect of neuropeptide Y (NPY) on rat myometrial strips was for the first time demonstrated and characterised, and the EC50 value estimated to be 267 +/- 87 nM. This effect is presumably mediated by the NPY1 receptor being responsible for postsynaptic effects throughout the peripherial nervous system, thus indicating a direct uterotonic effect of NPY. Further, the effect was demonstrated to the dependent on extracellular Ca2+. Short-term exposures to NPY markedly desensitized the tissue affecting subsequent responses to NPY as well as to oxytocin (OT). This desensitization was time and concentration-dependent, but lasted less than three hours. However, long-term infusions of NPY for 5 days increased to response to both NPY and OT. Long-term infusions of OT caused a marked decrease of the NPY response, and it is concluded that common pathways for up and down regulation of the myometrial responsiveness to several peptide hormones may exist.     

Trimethyltin intoxication induces marked changes in neuropeptide expression in the rat hippocampus

Stenosis of vessels proximal to the renal artery is an unusual cause of allograft ischemia. We report four patients who had such 'suprarenal' arterial stenoses leading to graft dysfunction that was reversed with revascularization. We additionally review the existing literature on this entity, outline the etiologies of such stenoses, as well as discuss the surgical and non-surgical therapeutic options in patients with this uncommon cause of allograft dysfunction.     

Stimulation of neuropeptide Y overflow in the rat paraventricular nucleus by corticotropin-releasing factor

Neuropeptide Y (NPY) and corticotropin-releasing factor (CRF) are present at high concentrations in the hypothalamus where they mediate important endocrine and autonomic functions. Morphological and physiological studies have suggested an interaction between these peptides, and opposing actions of CRF and NPY have been reported on feeding and other behaviors. This study investigated the effect of CRF on NPY release in vivo, measured by push-pull techniques, in the anesthetized rat. Push-pull probes implanted into the paraventricular nucleus of the hypothalamus (PVN) were perfused with modified Ringer solution containing bovine serum albumin at 15 microl/min, and the perfusate was lyophilized prior to NPY radioimmunoassay. NPY overflow from the rat PVN was increased threefold by perfusion of a depolarizing concentration of potassium (50 mmol/L KCl). When CRF was administered into the PVN via the push-pull cannula at 1 or 5 microg/ml, dose-dependent increases in NPY overflow of two- and fivefold were observed (p < 0.05). These increases were abolished by prior intracerebroventricular (i.c.v.) administration of the CRF antagonist [D-Phe12,Nle(21,38),C(alpha)MeLeu32]CRF (12-41) at 1 or 5 microg/microl, respectively. NPY overflow returned promptly to resting levels following CRF administration. In contrast, when CRF was administered by i.c.v. bolus at a similar total dose (2 microg), no significant effect on NPY overflow was observed. These data provide in vivo evidence for an interaction between CRF and NPY at the level of the PVN.     

Appetitive memory restoration after electroconvulsive shock in the rat.

Previous studies have demonstrated that noncontingent aversive stimulation can produce recovery from amnesia induced by electroconvulsive shock (ECS) for passive avoidance training. The present 2 experiments with a total of 120 male albino Sprague-Dawley rats examined the stimulus characteristics necessary to restore appetitive memory after ECS. In a 1-trial appetitive task, posttraining ECS proved to be an effective amnestic agent. Memory was restored by (a) 1 60-sec exposure to the appetitive reinforcer outside of the training situation and (b) 3 135-sec exposures to the training apparatus in the absence of the reinforcer. These results indicate that the "reminder effect" is not a consequence of generalization of learning that occurs during the reminder treatment. Data suggest that stimuli specific to the training situation are potential agents for reversing experimental amnesia. It is concluded that this class of recovery agents is better characterized as reminders than as stressors. A mechanism for recovery from experimental amnesia is proposed. (17 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Distinct changes in peptide YY binding to, and mRNA levels of, Y1 and Y2 receptors in the rat hippocampus associated with kindling epileptogenesis

Electrical kindling of the rat dorsal hippocampus induced significant changes in the binding of 125I-peptide YY to Y1 and Y2 subtypes of neuropeptide Y receptors and in their mRNA levels in the area dentata as assessed by quantitative receptor autoradiography and in situ hybridization histochemistry. Binding to Y1 receptor sites decreased by 50% (p < 0.05) in the molecular layer of the stimulated dentate gyrus, 2 days after preconvulsive stage 2 and 1 week or 1 month after generalized stage 5 seizures compared with sham-stimulated rats. Binding to Y2 receptor sites increased bilaterally by 36-87% (p < 0.05) in the hilus at stage 2 and 1 week or 1 month after stage 5. No significant changes were observed after one afterdischarge or in the other hippocampal subfields or in the cortex. Y1 receptor mRNA signal decreased bilaterally by 50-64% (p < 0.01) in the granule cell layer, 6 h but not 24 h after stages 2 and 5. The Y2 receptor mRNA signal was enhanced by 283% (p < 0.01) in the stimulated granule cell layer 24 h after stage 2. At 6 and 24 h after stage 5, mRNA levels were increased both ipsilaterally (283 and 360%, respectively; p < 0.01) and contralaterally (190 and 260%, respectively; p < 0.05). No significant changes in level of either mRNA was found following one afterdischarge. These modifications, and the enhanced neuropeptide Y release previously shown in the hippocampus, suggest that kindling is associated with lasting changes in neuropeptide Y-mediated neurotransmission.     

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/microliter (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/microliter (mean +/- SEM of solution samples), respectively. The responsiveness of the estimated NPYext measure to changes in the external concentration of NPY was also evaluated in vitro. An accurate estimate of NPYext 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/microliters and increased to 9.5 +/- 0.3 pg/microliter 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.     

Inhibition of stimulated cyclic AMP production by multiple neuropeptide Y receptors in the rat brainstem

Neuropeptide Y (NPY) has been shown to modulate blood pressure, heart rate and to inhibit the baroreceptor reflex at the level of nucleus tractus solitarius (NTS). The aim of this study was to examine effects of NPY and its related peptides on forskolin (1 microM)-stimulated cyclic AMP production in slices of the rat NTS. Each peptide was present at 0.3 microM. Pretreatment with NPY inhibited the stimulated increase in cyclic AMP levels in slices of rat NTS. Also [Pro34]NPY, an analog, which activates Y1, Y3 (and Y5) receptors inhibited the stimulated increase in cyclic AMP levels. However, pretreatment with the Y1 receptor-selective antagonist BIBP3226 (3 microM) did not affect the [Pro34]NPY-evoked inhibition of cyclic AMP levels. In addition, [Leu31,Pro34]NPY, an Y1 (and PP1/Y4 and Y5) receptor agonist did not inhibit the stimulated increase in cyclic AMP production. Also the Y2 receptor-selective agonist C2-NPY inhibited the stimulated elevation of cyclic AMP levels, while peptide YY, which does not recognize Y3 receptors did not significantly affect the stimulated cyclic AMP production. In conclusion, it seems that Y2 and Y3 receptors are coupled to inhibition of adenylate cyclase activity in the rat NTS.     

Role of the Y5 neuropeptide Y receptor in feeding and obesity

Removal of a plate from the distal femur creates a risk of fracture through the screw holes. This is a particular concern when a total knee arthroplasty is present because supracondylar fracture may occur with minimal trauma. A patient who presents after prior plating of a distal femur fracture with osteoporosis, retained hardware associated with pain, and gonarthrosis severe enough to warrant total knee arthroplasty is often difficult to manage. Prophylactic intramedullary rodding is a well-accepted method of treating pathologic stress risers in the femur. An intramedullary rod can be inserted into the femur at the time of total knee arthroplasty. This method permits simultaneous plate removal and total knee arthroplasty while protecting the femur from postoperative fracture.     

Zinc deficiency increases hypothalamic neuropeptide Y and neuropeptide Y mRNA levels and does not block neuropeptide Y-induced feeding in rats

Zinc deficiency reduces intake and produces an unusual approximately 3.5-d cycle of intake in rats. The mechanism underlying the anorexia and cycling has not yet been defined; current hypotheses suggest that alterations in amino acid metabolism and neurotransmitter concentrations may be a part of this anorexia. Recent reports indicate that appetite-stimulating neuropeptide Y (NPY) may be elevated during zinc deficiency. This suggests that a resistance to NPY may exist during zinc deficiency because NPY levels are high, yet appetite is low. The purpose of this study was to measure NPY peptide and mRNA concentrations during zinc deficiency in specific nuclei of the hypothalamus in which peptide and mRNA for NPY are known to be associated with appetite, and also to determine whether zinc-deficient rats are responsive to central infusions of NPY. Both NPY peptide levels in the paraventricular nucleus and NPY mRNA levels in the arcuate nucleus were higher (P < 0.05) in zinc-deficient rats than in zinc-adequate rats. When rats were administered exogenous NPY to the paraventricular nucleus, both zinc-deficient and zinc-adequate rats responded similarly by increasing food intake. These results suggest that NPY is elevated during zinc deficiency in an attempt to restore normal food intake levels, rather than being reduced and thereby contributing to the anorexia associated with zinc deficiency. During zinc deficiency, NPY receptors are able to bind NPY and initiate an orexigenic response.     

Modulation of neuropeptide Y overflow by leptin in the rat hypothalamus, cerebral cortex and medulla

This study examined whether leptin can exert inhibitory actions on brain NPY overflow in Sprague-Dawley and in lean and obese Zucker rats, and tested the site-specificity of the effect. Slices of rat hypothalamus, cerebral cortex and medulla oblongata were perfused with modified Krebs buffer containing either leptin or KCl. Depolarization of tissues with 40 mM KCl elicited a significant doubling of NPY overflow in all brain regions tested. At 1 microM, leptin significantly reduced NPY overflow only in the rat hypothalamus, while at 3 microM, leptin reduced NPY overflow from all regions. However, no effect of 1 microM leptin was observed in the hypothalamus of obese Zucker rats: this insensitivity to leptin is in keeping with their genetic defect. In conclusion, the inhibitory effect of leptin on hypothalamic NPY overflow provides further evidence for important modulatory actions between these two feeding mediators. Moreover, the effect of leptin observed in the cerebral cortex and medulla oblongata supports a role of leptin in brain regions other than the hypothalamus.     

Distribution of a novel hypothalamic neuropeptide Y receptor gene and it''s absence in rat

The alteration in calcium transport in the liver of rats with streptozocin(STZ)-diabetic state was investigated. STZ (6 mg/100 g body weight) was subcutaneously administered in rats, and 1 or 2 weeks later they were sacrificed by bleeding. STZ administration caused a remarkable elevation of serum glucose concentration. Liver calcium content was significantly increased by STZ administration. Hepatic plasma membrane (Ca2+-Mg2+)-ATPase activity was markedly elevated by STZ administration. This increase was completely abolished by the presence of staurosporine (10(-7)-10(-5) M), an inhibitor of protein kinase C, in the enzyme reaction mixture, suggesting an involvement of protein kinase C signalling. Moreover, the STZ-induced increase in liver plasma membrane (Ca2+-Mg2+)-ATPase activity was significantly raised by the presence of okadaic acid (10(-5) and 10(-4) M). Meanwhile, the STZ-increased (Ca2+-Mg2+)-ATPase activity was not appreciably altered by the presence of anti-regucalcin IgG in the reaction mixture, indicating that the activatory protein regucalcin does not participate in the elevation of the enzyme activity. The present study demonstrates that STZ-induced diabetes causes the increase in hepatic plasma membrane (Ca2+-Mg2+)-ATPase activity of rats.     

Imaging of the super high affinity binding sites for [3H]Ro15-4513 in rat hippocampus: comparison between in vitro and in vivo binding

Using fluorescence optical and electron spin resonance spectroscopy, we have investigated the production of superoxide by bovine endothelial nitric oxide synthase (NOS). In contrast to neuronal NOS, the heme moiety is identified as the exclusive source of superoxide production by endothelial NOS. Thus, calmodulin-mediated enzyme regulation affects production of nitric oxide and superoxide simultaneously and inseparably. The balance between the nitric oxide/superoxide reaction pathways may be shifted by addition of exogenous heme-specific agents, such as tetrahydrobiopterin. Our results have direct relevance for the pathophysiology of atherosclerosis.     

Solution structure of human neuropeptide Y

The three-dimensional structure of synthetic human neuropeptide Y in aqueous solution at pH 3.2 and 37 degrees C was determined from two-dimensional 1H NMR data recorded at 600 MHz. A restraint set consisting of 440 interproton distance restraints inferred from NOEs and 11 backbone and 4 side-chain dihedral angle restraints derived from spin-spin coupling constants was used as input for distance geometry calculations on DIANA and simulated annealing and restrained energy minimization in X-PLOR. The final set of 26 structures is well defined in the region of residues 11-36, with a mean pairwise rmsd of 0.51 A for the backbone heavy atoms (N, C alpha and C) and 1.34 A for all heavy atoms. Residues 13-36 form an amphipathic alpha-helix. The N-terminal 10 residues are poorly defined relative to the helical region, although some elements of local structure are apparent. At least one of the three prolines in the N-terminal region co-exists in both cis and trans conformations. An additional set of 24 distances was interpreted as intermolecular distances within a dimer. A combination of distance geometry and restrained simulated annealing yielded a model of the dimer having antiparallel packing of two helical units, whose hydrophobic faces form a well-defined core. Sedimentation equilibrium experiments confirm the observation that neuropeptide Y associates to form dimers and higher aggregates under the conditions of the NMR experiments. Our results therefore support the structural features reported for porcine neuropeptide Y [Cowley, D.J. et al. (1992) Eur. J. Biochem., 205, 1099-1106] rather than the 'aPP' fold described previously for human neuropeptide Y [Darbon, H. et al. (1992) Eur. J. Biochem., 209, 765-771].     

Melatonin binding sites in the harderian gland of the rat and Syrian hamster

Specific melatonin binding sites in the harderian gland of both rat and Syrian hamster were studied using [125I]melatonin. In both species, binding of [125I]melatonin by harderian gland membranes exhibited properties such as dependence on time, temperature, membrane concentration, saturability, and high specificity. Only one class of high-affinity binding sites was found with a Kd of 0.19 and 6.47 nM for the rat and Syrian hamster, respectively. The binding capacity in the rat harderian gland was 4.00 fmol/mg protein; in the Syrian hamster it was 7.58 fmol/mg protein. In the rat, no sex differences were found in the binding of the tracer to the membranes. However, in the Syrian hamster, binding of [125I]melatonin by the harderian gland was twice higher in the female than in the male. No changes were found in the Kd values (6.47 vs. 6.94 nM), while binding capacity was significantly increased in the female (13.50 fmol/mg protein) when compared to the male hamster (7.58 fmol/mg protein). Binding of [125I]melatonin by the harderian gland of male hamsters was modified by castration but not by melatonin treatment. Castration induced an increase of binding up to the level of females. However, chronic melatonin administration did not alter the [125I]melatonin binding in either intact or gonadectomized male hamsters. Binding studies also showed diurnal variations. There was a diurnal rhythm of [125I]melatonin binding by Syrian hamster harderian glands with the peak at the end of the light period and the trough late in the dark period. This rhythm in the binding is observed in both male and female hamsters, although binding in females was always higher than that in males.(ABSTRACT TRUNCATED AT 250 WORDS)     

Centrally administered neuropeptide Y (NPY) inhibits gastric emptying and intestinal transit in the rat

OBJECTIVE: The aim was to investigate the phasic characteristics of normal human left coronary artery flow and velocity profiles across the vessel. METHODS: The phasic characteristics of flow in the human left anterior descending coronary artery, the centreline flow velocities, and the velocity profiles were measured in 10 patients during corrective surgery for atrial septal defect after closure of the defect. None of these patients had any detectable coronary artery stenosis or left ventricular hypertrophy. Measurements were made with a 20 MHz 80 channel pulsed Doppler velocimeter. RESULTS: The velocity waveform displayed a diastolic-predominant pattern with a systolic to diastolic velocity ratio of 0.29(SD 0.17). Reverse flow was observed in early systole in five patients and in mid to late systole in six patients. The values of peak Reynolds number, unsteadiness parameter, and pulsatility index were 504(198), 2.5(0.6), and 5.9(4.4) respectively. The velocity profiles during diastole showed considerable variability in shape, ranging from symmetrical to skewed to M shaped patterns. The peak wall shear rate was 765(250) s-1 on the epicardial wall of the vessel and 712(301) s-1 on the myocardial wall; the difference was not statistically significant. CONCLUSIONS: The velocity waveform displayed a diastolic-predominant pattern. Considerable variability in shape of the velocity profile was found and was perhaps due to the time evolution of the velocity profile within the diastolic time period.     

Modulation of [3H]dopamine release by neuropeptide Y in rat striatal slices

Polycythemia vera (PV) is associated with a high incidence of thrombosis. The association of apparent and secondary polycythemia with thrombosis is not clear. It was suggested that activation of the coagulation system contributes to thrombus formation in PV. However, the mechanism of activation is unknown. Monocytes generate a potent tissue factor (TF) upon stimulation with various substances, which is involved in thrombus formation in various disorders. Therefore, we studied the possibility that the factor is involved in the activation of coagulation and thrombus formation also in PV. Unstimulated peripheral blood mononuclear cells (PBMC) from each of the different types of polycythemia expressed weak TF activity (2 U) and antigen (41.4 to 52.9 pg/ml), which were similar to normal controls. Following stimulation with endotoxin, PBMC from normal controls and from apparent and secondary polycythemia showed a 3.9- to 4.5-fold increase in TF, while cells from PV showed a 21-fold increase (P<0.001). Similar levels were generated by PBMC after treatment of PV and at the spent phase. TF was generated by monocytes but not by lymphocytes. Plasma prothrombin fragment1+2 (F1+2) levels, assayed at the same time, were significantly higher in PV (2.46 nm) compared to normals and apparent and secondary polycythemia (0.22 to 0.32 nm), and were in a significant correlation with monocyte TF activity and antigen levels (r = 0.77, 0.87). The high levels of F1+2 confirm that the coagulation system is activated in PV. The increased capacity of monocytes to generate TF may be responsible for the activation of the coagulation system and thrombus formation. The hypercoagulability state that is induced by this mechanism suggests that long-life oral anticoagulation should be considered once thrombosis has been developed in PV.