Evidence for neuropeptide Y mediation of eating produced by food deprivation and for a variant of the Y1 receptor mediating this peptide's effect.

Neuropeptide Y (NPY) elicits eating when injected directly into the paraventricular nucleus (PVN) or perifornical hypothalamus (PFH). To identify the essential regions of the NPY molecule and the relative contributions of Y1 and Y2 receptors, the eating stimulatory potency of NPY was compared to that of its fragments, analogues, and agonists when injected into the PVN or PFH of satiated rats. Additionally, antisera to NPY was injected into the cerebral ventricles (ICV) to determine whether passive immunization suppresses the eating produced by mild food deprivation. Tests with NPY fragments revealed that NPY(2-36) was surprisingly potent, nearly three times more so than intact NPY. In contrast, fragments with further N-terminal deletions were progressively less effective or ineffective, as was the free acid form of NPY. Collectively, this suggests that both N- and C-terminal regions of NPY participate in the stimulation of eating. Tests with agonists revealed that the putative Y1 agonist [Pro34]NPY elicited a strong dose-dependent feeding response, while the putative Y2 agonist, C2-NPY, had only a small effect at the highest doses. Although this suggests mediation by Y1 receptors, the uncharacteristically high potency of NPY(2-36) may additionally suggest that the receptor subtype underlying feeding is distinct from that mediating other responses. Additional results revealed that ICV injection of antisera to NPY, which should inactivate endogenous NPY, produced a concentration-dependent suppression of eating induced by mild food deprivation. This finding, along with published work demonstrating enhanced levels of hypothalamic NPY in food-deprived rats, suggests that endogenous NPY mediates the eating produced by deprivation.     

Vasoactive intestinal peptide (VIP): an amnestic neuropeptide

Vasoactive intestinal peptide (VIP) is a neuropeptide present in high concentrations in the hippocampus. The studies reported here demonstrate that VIP administered into the third ventricle of the brain caused amnesia in mice trained on a left-right footshock avoidance task in a T-maze. VIP resulted in amnesia when administered directly into the rostral portion of the hippocampus at a 10-fold lower dose than was needed to produce amnesia when VIP was administered intracerebroventricularly. When VIP was administered 24 hr after training, it failed to impair retention measured a week later. VIP receptor antagonist ([4-Cl-D-Phe6,Leu17]VIP) enhanced retention when administered into the rostral portion of the hippocampus, suggesting that VIP plays a physiological role in memory modulation. VIP receptor antagonist administered 24 hr after training did not facilitate retention. To gain some insight as to how VIP may be affecting memory processing, we determined if some memory-improving compounds showed a selective ability to block amnesia induced by VIP. The amnestic effect of VIP was blocked by peripheral administration of the memory-enhancing agents, arecoline, naloxone and ST 587 (a noradrenergic receptor agonist) but not by cholecystokinin octapeptide. Central administration of arecoline, but not neuropeptide Y, blocked the amnestic effect of VIP. It is concluded that VIP is a potent amnestic peptide.     

Characterization of NPY receptor subtypes Y2 and Y7 in rainbow trout Oncorhynchus mykiss

We report the cloning and pharmacological characterization of two neuropeptide Y (NPY) receptor subtypes, Y2 and Y7, in rainbow trout (Oncorhynchus mykiss). These subtypes are approximately 50% identical to each other and belong to the Y2 subfamily of NPY receptors. The binding properties of the receptors were investigated after expression in human HEK-293 EBNA cells. Both receptors bound the three zebrafish peptides NPY, PYYa, and PYYb, as well as porcine NPY and PYY, with affinities in the nanomolar range that are similar to mammalian Y2. The affinity of the truncated porcine NPY fragments, NPY 13-36 and NPY 18-36 was markedly lower compared to mammalian and chicken Y2. This suggests that mammalian and chicken Y2 are unique among NPY receptors in their ability to bind truncated peptide fragments. The antagonist BIIE0246, developed for mammalian Y2, did not bind either of the two rainbow trout receptors. Our results support the proposed expansion of this gene family by duplications before the gnathostome radiation. They also reveal appreciable differences in the repertoire and characteristics of NPY receptors between fish and tetrapods stressing the importance of lineage-specific gene loss as well as sequence divergence after duplication.     

Effects of neuropeptide Y on food intake and brain biogenic amines in the rainbow trout (Oncorhynchus mykiss)

Neuropeptide Y (NPY) is one of the most potent stimulants of food intake in mammals, but very little is known about NPY actions in fish. The present study investigated the role of NPY in food intake in the rainbow trout (Oncorhynchus mykiss). Food intake was monitored at different times after intracerebroventricular administration of porcine NPY (4 or 8 microg). Both doses significantly increased food intake at 2 and 3 h, and this effect was dose-dependent. However, 50 h after administration of NPY, food intake was significantly lower than in control fish, and cumulative food intake had returned to levels similar to those seen in the control group. The NPY antagonist (D-Tyr27,36, D-Thr32)-NPY (10 microg) inhibited food intake 2 h after icv administration, but did not block the orexigenic effect of NPY when administered jointly with 4 microg NPY. To identify the NPY receptor subtypes involved in the effects of NPY on food intake, we studied the effects of the Y1 receptor agonist (Leu31, Pro34)-NPY (4 microg), the Y2 receptor agonist NPY(3-36) (4 microg), and the highly specific Y5 receptor agonist (cPP(1-7), NPY19-23, Ala31, Aib32, Gln34)-hPP (4 microg). Short-term (2 h) food intake was moderately stimulated by the Y1 agonist, more strongly stimulated by the Y2 agonist, and unaffected by the Y5 agonist. We found that administration of NPY (8 microg icv) had no effect on aminergic systems in several brain regions 2 and 50 h after NPY administration. These results indicate that NPY stimulates feeding in the rainbow trout, and suggest that this effect is cooperatively mediated by Y2- and Y1-like NPY receptors, not by Y5-like receptors.     

Y2 receptors for neuropeptide Y in the nucleus of the solitary tract mediate depressor responses.

In anesthetized, spontaneously breathing rats, microinjections of selective agonists of neuropeptide Y (NPY) receptor subtypes were made into the medial region of the caudal nucleus of the solitary tract (NTS) at the level of the area postrema. This region of the rat NTS exhibits very high densities of NPY binding sites. Microinjections of the long C-terminal NPY fragment, NPY(13-36), a selective agonist at Y2 receptors, into the caudal NTS elicited pronounced, dose-related reductions in blood pressure and respiratory minute volume. Moreover, the specific pattern of cardiorespiratory responses elicited by NPY(13-36) was remarkably similar, over approximately the same dosage range, with the cardiorespiratory response pattern elicited by intact NPY. In contrast to the potent NTS-mediated responses evoked by NPY(13-36), similar microinjections conducted with either NPY(26-36), an inactive C-terminal NPY fragment, or [Leu31,Pro34]NPY, a NPY analog with specific agonist properties at Y1 receptors, into the same caudal NTS sites did not appreciably affect cardiorespiratory parameters even at 10-20-fold higher dosages. The present results with selective agonists for NPY receptor subtypes suggest that the depressor responses and reductions in minute volume elicited by microinjections of intact NPY and NPY(13-36) were mediated by Y2 receptors in the caudal NTS, likely distributed at presynaptic sites in the medial region of the subpostremal NTS.     

Increased brain neuropeptide Y1 and Y2 receptor binding in NPY knock out mice does not result in increased receptor function

The brain neuropeptide Neuropeptide Y (NPY) is an important modulator of a number of centrally mediated processes including feeding, anxiety-like behaviors, blood pressure and others. NPY produces its effects through at least four functional G-protein coupled receptors termed Y1, Y2, Y4 and Y5. In the brain, the Y1 and Y2 receptor subtypes are the predominant receptor population. To better understand the roles of NPY, genetically modified mice lacking NPY were produced but lacked the expected phenotypes. These mice have previously been reported to have a marked increase in Y2 receptor binding. In the present study, we found an upregulation of both Y1 and Y2 receptor binding and extended these findings to the female. These increases were as large as 10-fold or greater in many brain regions. To assess functional coupling of the receptors, we performed agonist-induced [(35)S]GTPgammaS autoradiography. In the mouse brain, the Y1/Y4/Y5 agonist Leu(31),Pro(34)-NPY increased [(35)S]GTPgammaS binding with a regional distribution consistent with that produced when labeling adjacent sections with [(125)I]-Leu(31),Pro(34)-PYY. In a few brain regions, minor increases were noted in the agonist-induced binding when comparing knock out mice to wild type. The Y2 agonist C2-NPY stimulated [(35)S]GTPgammaS binding in numerous brain areas with a regional distribution similar to the binding observed with [(125)I]-PYY3-36. Again, no major increases were noted in the functional activation of Y2 receptors between knock out and wild type mice. Therefore, the increased Y1 and Y2 binding observed in the NPY knock out mice does not represent an increase in NPY receptor mediated signaling and is likely due to an increase in spare (uncoupled) receptors.     

Interactions between orexin A, NPY and galanin in the control of food intake of the goldfish, Carassius auratus

The neuropeptides orexin A (OXA), neuropeptide Y (NPY) and galanin (GAL) have been shown to play a role in the regulation of food intake in mammals. They also significantly stimulate feeding in goldfish. In order to assess the interactions between these peptides in the control of feeding in goldfish, we investigated the effects of central injection of specific receptor antagonists for NPY (BIBP 3226) and GAL (M40) on OXA-induced feeding and the effects of desensitization of orexin receptors on NPY- and GAL-induced feeding. We investigated the effects of BIBP 3226 on GAL-induced feeding and the effects of M40 on NPY-induced feeding. We also examined the effects of coinjection of each pair of neuropeptides on feeding behavior. Injections of 10 ng/g OXA, 5 ng/g NPY and 10 ng/g GAL each induced an increase in feeding. Fish treated with 5 ng/g BIBP or 20 ng/g M40 had food consumption similar to saline controls. BIBP at 5 ng/g significantly reduced NPY- and OXA-induced feeding. Injections of 20 ng/g M40 significantly decreased GAL-induced feeding, but had no effect on OXA-induced feeding. Blocking of orexin receptors by treatment with high doses of OXA (100 ng/g) resulted in a decrease in both NPY- and GAL-induced feeding. Coinjection with 0.5 ng/g OXA and either 0.5 ng/g NPY or 0.5 ng/g GAL resulted in a food intake higher than that observed in saline control fish and in fish treated with NPY or GAL alone at 0.5 ng/g. NPY mRNA expression was increased in the telencephalon and in the hypothalamus compared to saline-treated fish, following injection of OXA. These results indicate that both NPY and GAL are at least, in part, dependent on coaction with OXA for the stimulation of food intake and feeding behavior in goldfish. In addition, the effects of OXA are mediated, in part, by the NPY pathway. This suggests a functional interdependence between these three peptidergic systems in the control of energy balance in goldfish.     

Effects of systemic pancreastatin on memory retention

Pancreastatin, a peptide isolated from the pancreas, was shown to enhance memory retention after peripheral administration in mice when administration following T-maze footshock avoidance training. The effect of pancreastatin on memory retention, one week after training, was time dependent showing enhancement of retention when pancreastatin was administered 0 and 30 min but not 60 min after training. Pancreastatin reversed the amnesia produced by scopolamine. The pancreastatin fragment (33-49) also enhanced memory. Pancreastatin did not increase glucose in vivo. We conclude that peripherally administered pancreastatin modulates memory processing.     

Bis(31/31')[[Cys(31), Nva(34)]NPY(27-36)-NH(2)]: a neuropeptide Y (NPY) Y(5) receptor selective agonist with a latent stimulatory effect on food intake in rats

The actions of neuropeptide Y (NPY) are mediated by at least six G-protein coupled receptors denoted as Y(1), Y(2), Y(3), Y(4), Y(5), and y(6). Investigations using receptor selective ligands and receptor knock-out mice suggest that NPY effects on feeding are mediated by both Y(1) and Y(5) receptors. We have previously shown that Cys-dimers of NPY C-terminal peptides exhibit Y(1) selectivity relative to Y(2) receptors. Re-investigation of their selectivity with respect to the newly cloned receptors, has identified bis(31/31') [[Cys(31), Nva(34)]NPY(27-36)-NH(2)] (BWX-46) as a Y(5) receptor selective agonist. BWX-46 selectively bound Y(5) receptors, and inhibited cAMP synthesis by Y(5) cells with potencies comparable to that of NPY. Moreover, BWX-46 (10 microM) exhibited no significant effect on the cAMP synthesis by Y(1), Y(2), and Y(4) cells. Thus, BWX-46 constitutes the lowest molecular weight Y(5) selective agonist reported to date. Intrahypothalamic (i.h.t)-injection of 30 and 40 microg of BWX-46 stimulated the food intake by rats in a gradual manner, reaching maximal level 8 h after injection. This response was similar to that exhibited by other Y(5) selective agonists, but differed from that of NPY, which exhibited a rapid orexigenic stimulus within 1 h. It is suggested that the differences in the orexigenic stimuli of NPY and Y(5) agonists may be due to their differences in the signal transduction mechanisms.     

Cardiorespiratory responses to intracerebroventricular injection of neuropeptide Y in anaesthetised dogs.

Cardiovascular and respiratory effects of intracerebroventricular (icv) administration of neuropeptide Y (NPY) and separate, preferential agonists for NPY Y1 and Y2 receptors were observed in anaesthetised dogs. Central injections of NPY resulted in significant cardiac slowing and decreases in arterial pressure. These cardiovascular effects were blocked by central injection of the NPY Y1- preferring antagonist 1229U91. Central injection of NPY did not have a significant effect on ventilation, but the NPY Y1 antagonist 1229U91 administered alone caused a significant increase in ventilation. The NPY Y1-receptor agonist [Leu31Pro34] NPY significantly decreased ventilation while the NPY Y2 receptor agonist N-acetyl [Leu28Leu31] NPY 24--36 significantly increased it. A similar inverse relationship was seen with respect to blood pressure, with the NPY Y1-receptor agonist [Leu31Pro34] NPY significantly decreasing blood pressure, while the NPY Y2 receptor agonist N-acetyl [Leu28Leu31] NPY 24-36 significantly increased it. These findings suggest a role for NPY Y1 receptors in pathways mediating decreases in ventilation and blood pressure, and for NPY Y2 receptors in those mediating increased ventilation and blood pressure.     

Centrally administered neuropeptide Y delays gastric emptying via Y2 receptors in rats

It has been shown that centrally administered neuropeptide Y (NPY) delays gastric emptying. To determine the receptor subtypes of NPY mediating the inhibitory effects on gastric emptying, effects of intracerebroventricular injection of NPY, [Leu31,Pro34]NPY (a Y1 agonist) and NPY-(3-36) (a Y2 agonist) on solid gastric emptying and postprandial antropyloric motility were studied in conscious rats. Intracerebroventricular injection of NPY and NPY-(3-36), but not [Leu31,Pro34] NPY, delayed solid gastric emptying in a dose-dependent manner (0.03-3 nmol). After the feeding (40 min), contractions with low frequency and high amplitude of the antrum were frequently observed, and the peak contraction of the antrum occurred most often 3-6 s before the peak contraction of the pylorus. Intracerebroventricular injection of NPY and NPY-(3-36) (3 nmol), but not [Leu31,Pro34]NPY, significantly reduced antral contractions and the number of antropyloric coordination events. It is suggested that centrally administered NPY impairs postprandial antral contractions and antropyloric coordination via Y2 receptors, resulting in delayed gastric emptying.     

Energy Metabolic Profile of Mice after Chronic Activation of Central NPY Y1, Y2, or Y5 Receptors**

Objective: Neuropeptide Y (NPY), a 36‐amino acid peptide with orexigenic properties, is expressed abundantly in the central nervous system and binds to several NPY receptor subtypes. This study examines the roles of the NPY Y1, Y2, and Y5 receptor(s) in energy homeostasis. Research Methods and Procedures: We administered intracerebroventricular NPY (3 μg/d) or selective peptide agonists for the Y1, Y2, and Y5 receptor subtypes to C57Bl/6 mice for 6 days by mini‐osmotic pumps to assess the role of each receptor subtype in NPY‐induced obesity. Energy expenditure (EE) and respiratory quotient (RQ) were studied using indirect calorimetry. Adiposity was measured by DXA scanning and fat pad dissection. Insulin sensitivity was tested by whole‐blood glucose measurement after an insulin challenge. Results: Central administration of the selective Y1 agonist, Y5 agonist, or NPY for 6 days in mice significantly increased body weight, adiposity, and RQ, with significant hyperphagia in the Y5 agonist‐ and NPY‐treated groups but not in the Y1 agonist‐treated group. The NPY, Y1, or Y5 agonist‐treated mice had little change in total EE during ad libitum and pair‐feeding conditions. Conversely, selective activation of the Y2 receptor reduced feeding and resulted in a significant, but transient, weight loss. Discussion: Central activation of both Y1 and Y5 receptors increases RQ and adiposity, whereas only Y5 receptor activation reduces energy expended per energy ingested. Selective activation of Y2 autoreceptors leads to hypophagia and transient weight loss, with little effect on total EE. Our study indicates that all three NPY receptor subtypes may play a role in regulating energy homeostasis in mice.     

Inhibitory and stimulatory effects of neuropeptide Y(17-36) on rat cardiac adenylate cyclase activity. Structure-function studies.

Neuropeptide Y (NPY) inhibits cardiac adenylate cyclase activity by interacting with specific receptors coupled to a pertussis toxin-sensitive G protein. Structure-activity studies revealed that only C-terminal fragments can exhibit an NPY-like inhibitory effect on 125I-NPY binding and adenylate cyclase activity of rat cardiac ventricular membranes. Although NPY(17-36) inhibited 125I-NPY binding with high potency, it produced a biphasic effect on basal (GTP, 10 and 100 microM or guanosine 5'-gamma-O-(thio)triphosphate (GTP gamma S, 10 microM) adenylate cyclase activity. Low concentrations (less than 1 nM) of NPY(17-36) inhibited the adenylate cyclase activity whereas high concentrations (greater than 1 nM) reversed this action. GTP gamma S (100 microM) reversed the biphasic effect of NPY(17-36). NPY(17-36) exhibited only a stimulatory effect in the membranes from pertussis toxin-treated rats and an inhibitory effect with membranes from cholera toxin-treated rats. Low concentrations (less than 1 nM) of NPY(17-36) inhibited isoproterenol-stimulated adenylate cyclase activity whereas high doses (greater than 1 nM) reversed this activity. The cardiac NPY receptor antagonist, NPY(18-36) (1 microM), completely blocked the biphasic effect of NPY(17-36) on isoproterenol-stimulated activity. The inhibitory dose-response curve of NPY on isoproterenol-stimulated adenylate cyclase activity was shifted parallel to the right by NPY(17-36) (1 microM), suggesting that it is an antagonist of NPY at high concentrations. N-alpha-acetylated and C-terminally deamidated analogs of NPY(17-36) had no effect on the adenylate cyclase activity. [im-DNP-His26] NPY exhibited a more pronounced biphasic effect whereas N-alpha-myristoyl-NPY(17-36) elicited only a stimulatory effect. These investigations suggest that: 1) the inhibitory and stimulatory effects of NPY(17-36) are mediated by high affinity NPY receptors coupled to a pertussis toxin-sensitive G protein and a distinct population of low affinity receptors coupled to a cholera toxin-sensitive G protein, respectively; and 2) the stimulatory effect of NPY(17-36) is dissociable.     

Critical role of dipeptidyl peptidase IV in neuropeptide Y-mediated endothelial cell migration in response to wounding

Recently, we have discovered that neuropeptide Y (NPY), a sympathetic neurotransmitter, is also present in human umbilical endothelial cells (HUVECs), and is potently chemotactic and angiogenic by acting on one or several of Y1-Y5 receptors. In HUVECs, NPY is co-localized with dipeptidyl peptidase IV (DPPIV) which cleaves Tyr(1)-Pro(2) from NPY(1-36) to form NPY(3-36) resulting in the formation of a non-Y1 receptor agonist, which remains angiogenic. Presently we studied the effects of DPPIV's blockade using monoclonal antibodies (mAbs) on migration of HUVECs in response to NPY(1-36) or NPY(3-36) following cell wounding. Both peptides caused similar dose-dependent increases in cell migration (+80% at 0.1 nM) 12 h after wounding. DPPIV mAbs, E19 and E26, significantly reduced HUVEC's migration below that of the untreated cells, and blocked responses to NPY(1-36) but not NPY(3-36). Enhanced expression of DPPIV was found in the migrating cells and in cells with their protrusions at the edge of the wound (immunostaining and Western blot). Thus, DPPIV's expression is stimulated by endothelial wounding and its enzymatic activity is required for NPY-mediated chemotaxis. Furthermore, this suggests that non-Y1 receptors activated by NPY(3-36) (Y2, Y3 and/or Y5) mediate angiogenic effects of NPY.     

Neuropeptide Y inhibits estrous behavior and stimulates feeding via separate receptors in Syrian hamsters

Central injections of neuropeptide Y (NPY) increase food intake in Syrian hamsters; however, the effect of NPY on sexual behavior in hamsters is not known nor are the receptor subtypes involved in feeding and sexual behaviors. We demonstrate that NPY inhibits lordosis duration in a dose-related fashion after lateral ventricular injection in ovariectomized, steroid-primed Syrian hamsters. Under the same conditions, we compared the effect of two receptor-differentiating agonists derived from peptide YY (PYY), PYY-(3-36) and [Leu(31),Pro(34)]PYY, on lordosis duration and food intake. PYY-(3-36) produced a 91% reduction in lordosis duration at 0.24 nmol. [Leu(31),Pro(34)]PYY was less potent, producing a reduction in lordosis duration (66%) only at 2.4 nmol. These results suggest NPY effects on estrous behavior are principally mediated by Y2 receptors. PYY-(3-36) and [Leu(31),Pro(34)]PYY stimulated comparable dose-related increases in total food intake (2 h), suggesting Y5 receptors are involved in feeding. The significance of different NPY receptor subtypes controlling estrous and feeding behavior is highlighted by results on expression of Fos immunoreactivity (Fos-IR) elicited by either PYY-(3-36) or [Leu(31),Pro(34)]PYY at a dose of each that differentiated between the two behaviors. Some differences were seen in the distribution of Fos-IR produced by the two peptides. Overall, however, the patterns of expression were similar. Our behavioral and anatomic results suggest that NPY-containing pathways controlling estrous and feeding behavior innervate similar nuclei, with the divergence in pathways controlling the separate behaviors characterized by linkage to different NPY receptor subtypes.     

Neuropeptide Y: a new mediator linking sympathetic nerves,blood vessels and immune system?

Neuropeptide Y (NPY(1-36)), a sympathetic cotransmitter and neurohormone, has pleiotropic activities ranging from the control of obesity to anxiolysis and cardiovascular function. Its actions are mediated by multiple Gi/o-coupled receptors (Y1-Y5) and modulated by dipeptidyl peptidase IV (DPPIV/cd26), which inactivates NPY's Y1-agonistic activity but generates the Y2 and Y5-agonist, NPY(3-36). Released by sympathetic activity, NPY is a major mediator of stress, responsible for prolonged vasoconstriction via Y1 receptors. Y1 receptors also mediate NPY's potent vascular growth-promoting activity leading in vivo in rodents to neointima formation. This and the association of a polymorphism of the NPY signal peptide with increased lipidemia and carotid artery thickening in humans strongly suggest NPY's role in atherosclerosis. NPY and DPPIV/cd26 are also coexpressed in the endothelium, where the peptide activates angiogenesis. A similar system exists in immune cells, where NPY and DPPIV/cd26 are coactivated and involved in the modulation of cytokine release and immune cell functions. Thus, NPY, both a messenger and a modulator for all three systems, is poised to play an important regulatory role facilitating interactions among sympathetic, vascular and immune systems in diverse pathophysiological conditions such as hypertension, atherosclerosis and stress-related alterations of immunity.     

Cloning and characterization of Rhesus monkey neuropeptide Y receptor subtypes

Neuropeptide Y (NPY) is a 36 amino acid peptide that is abundant in the brain and peripheral nervous system. NPY has a variety of effects when administered into the brain including a pronounced feeding effect, anxiolysis, regulation of neuroendocrine axes and inhibition of neurotransmitter release. These effects are mediated by up to 6 G protein coupled receptors designated Y1, Y2, Y3, Y4, Y5 and y6. To better understand the phylogeny and pharmacology of NPY in non-human primates, we have cloned and expressed the NPY Y1, Y2 and Y5 receptor subtypes from the Rhesus monkey. No cDNA sequence encoding a Y4 receptor was found suggesting substantial sequence differences when compared to the human sequence. Comparison of these sequences with those from human indicated strong sequence conservation of Y1, Y2 and Y5 between the two species. The displacement of (125)I-PYY binding to the Rhesus monkey and human receptors by various peptides was compared to evaluate the pharmacology of the two species. Similar pharmacologies were noted across the species at the various receptor subtypes. These results indicate the Rhesus monkey and human NPY receptor subtypes have a close amino acid sequence conservation and that the peptide recognition domains are conserved as well.     

Differential regulation of neuropeptide Y receptors in the brains of NPY knock-out mice

To study the effect of NPY deletion on the regulation of its receptors in the NPY knockout (NPY KO) mice, the expression and binding of NPY receptors were investigated by in situ hybridization and receptor autoradiography using (125)I-[Leu(31),Pro(34)]PYY and (125)I-PYY(3-36) as radioligands. A 6-fold increase in Y2 receptor mRNA was observed in the CA1 region of the hippocampus in NPY KO mice, but a significant change could not be detected for Y1, Y4, Y5 and y6 receptors. Receptor binding reveals a 60-400% increase of Y2 receptor binding in multiple brain areas. A similar increase in Y1 receptor binding was seen only in the hypothalamus. These results demonstrate the NPY receptor expression is altered in mice deficient for its natural ligand.     

石杉碱甲对电休克大鼠记忆、ARCmRNA及蛋白表达的影响

目的：研究石杉碱甲对电休克模型大鼠记忆和海马活性调节的细胞骨架联合基因（Activity-regulatedcytoskeletal—associatedgene,ARC）表达的影响。方法：大鼠随机分为假电休克对照组和电休克组,再随机分为生理盐水对照组（CS组、ES组）和石杉碱甲组（CH组、EH组）。第l-17天行生理盐水或石杉碱甲灌胃;第8—17天给予假电痉挛刺激或电痉挛刺激;第18天水迷宫定位航线实验;然后各组大鼠随机分成两组,一组取海马用RT．PCR检测ARCmRNA表达,Westem--blot法检测ARC蛋白表达水平,一组于48小时后行水迷宫空间位置探寻实验。结果：电休克导致大鼠显著记忆障碍,ARCmRNA、ARC蛋白表达水平较假电休克对照组显著下降;而石杉碱甲干预的电休克大鼠记忆保持较好,ARCmRNA、ARC蛋白表达水平显著高于生理盐水干预的电休克大鼠,与假电休克大鼠相比无显著性差异。结论：石杉碱甲能减轻电休克模型大鼠记忆损害,其机制可能与海马ARC的表达增加有关。     

Role of neuropeptide Y Y(2) receptors in modulation of cardiac parasympathetic neurotransmission.

The aim of the study was to clarify the role of the Y(2) receptor in regulation of vagal control of the heart, using Y(2)((-/-)) receptor-knockout mice. Adult Y(2)((+/+),(-/-)) mice (50% C57BL/6-50% 129/SvJ background) were anaesthetised and artificially ventilated. Arterial blood pressure and pulse interval was recorded and both vagus nerves were cut. The cardiac end of the right vagus nerve was stimulated supra-maximally every 30 s (7 V, 2-2.5 Hz, 5 s). Neuropeptide Y (NPY) and a Y(2) receptor agonist, N-acetyl [Leu(28, 31)]NPY 24-36, were injected intravenously in both groups of mice. N-acetyl [Leu(28, 31)] NPY 24-36 was also administered to control mice in the presence of a Y(2) receptor antagonist, BIIE0246. Stimulation of the vagus nerve increased pulse interval (PI) by approximately 100 ms. NPY and N-acetyl [Leu(28, 31)] NPY 24-36 attenuated the increase in PI evoked by vagal stimulation in control mice only. The attenuation was reduced in the presence of BIIE0246. The results presented here show in Y(2)((-/-)) receptor-knockout mice that NPY and N-acetyl [Leu(28, 31)] NPY 24-36 have no effect on PI evoked by vagal stimulation. These findings demonstrate that NPY attenuates parasympathetic activity to the heart via the Y(2) receptor.