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.     

3H]-BIBP3226 and [3H]-NPY binding to intact SK-N-MC cells and CHO cells expressing the human Y1 receptor

We have studied the binding of [3H]-NPY and the newly developed non-peptide Y1 receptor antagonist [3H]-BIBP3226 to intact SK-N-MC cells and CHO-K1 cells transfected with the human NPY Y1 receptor gene i.e. CHO-Y1 cells. Whereas the association and dissociation of the specific [3H]-NPY binding was slow, the binding kinetics of [3H]-BIBP3226 binding was very rapid. Saturation binding of both radioligands reveal the presence of an apparently homogeneous population of high affinity binding sites in both cell lines. The corresponding equilibrium dissociation constants are similar for the two cell lines and are close to those obtained from previous competition binding experiments. The specific binding of both radioligands was completely and with high affinity displaced by BIBP3226 and its inactive (S)-enantiomer BIBP3435 was much less potent. Whilst the NPY Y1 agonists NPY, PYY and [Leu31-Pro34]-NPY completely and potently displaced [3H]-NPY binding, they could only displace 70 to 80% of the [3H]-BIBP3226 binding sites in CHO-Y1 and SK-N-MC cells. A possible explanation can be that only part of the receptors are G-protein coupled. In agreement pertussis toxin was found to reduce high affinity [3H]-NPY binding sites in CHO-Y1 cells whereas [3H]-BIBP3226 binding parameters remained unchanged.     

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.     

Metabolic responses of postmenopausal women to supplemental dietary boron and aluminum during usual and low magnesium intake: boron, calcium, and magnesium absorption and retention and blood mineral concentrations

The regulation by neuropeptide Y of alpha2-adrenoceptors in the nucleus tractus solitarii was evaluated in the adult normotensive Wistar Kyoto rat and the adult spontaneously hypertensive rat. The microinjection of a submaximal dose of l-noradrenaline (800 pmol in 50 nl) alone into the nucleus tractus solitarii produced a significant reduction in the mean arterial blood pressure in either strain. The threshold dose (1 pmol in 50 nl) of neuropeptide Y(1-36) for the vasodepressor response in the Wistar Kyoto rat was five times higher than that (0.2 pmol in 50 nl) in the spontaneously hypertensive rat. Furthermore, neuropeptide Y(1-36) at 0.2 pmol in 50 nl could significantly counteract the vasodepressor response to l-noradrenaline (800 pmol in 50 nl) in the spontaneously hypertensive rat, but not in the Wistar Kyoto rat, in which 1 pmol in 50 nl of neuropeptide Y(1-36) must be employed to counteract the vasodepressor response to l-noradrenaline (800 pmol in 50 nl), although the vasodepressor responses are of a similar magnitude. The in situ hybridization and quantitative receptor autoradiographical experiments showed that the alpha2A-adrenoceptor messenger RNA levels and the B(max) value of the alpha2-adrenoceptor agonist [3H]p-aminoclonidine binding sites measured in the nucleus tractus solitarii of the spontaneously hypertensive rat were substantially lower than those in the Wistar Kyoto rat. The quantitative receptor autoradiographical results were consistent with the cardiovascular results and showed that in the spontaneously hypertensive rat, neuropeptide Y(1-36) at 1 nM led to a significant increase in the K(d) value of [3H]p-aminoclonidine binding sites. In the Wistar Kyoto rat, neuropeptide Y(1-36) produced this effect only at 10 nM. The present study provides evidence for an increase of the potency of neuropeptide Y(1-36) to antagonistically modulate alpha2-adrenoceptors in the nucleus tractus solitarii of the spontaneously hypertensive rat. This enhanced antagonistic action may partly be related to a reduction in the number of alpha2A-adrenoceptors in the nucleus tractus solitarii of the spontaneously hypertensive rat, since a decrease has been observed in the alpha2A-adrenoceptor messenger RNA levels and the alpha2-adrenoceptor binding sites in the spontaneously hypertensive rat. This increased potency of neuropeptide Y(1-36) to antagonize alpha2-adrenoceptor function in the nucleus tractus solitarii of the spontaneously hypertensive rat may contribute to the development of high blood pressure in this hypertensive strain.     

Neuropeptide Y Y1-receptor stimulation is required for physiological amplification of preovulatory luteinizing hormone surges

Neuropeptide Y (NPY) has been shown to potentiate the actions of LHRH during the generation of preovulatory LH surges. It is not yet known, however, if activation of a specific subtype of NPY receptors in the anterior pituitary gland is an obligatory event in the stimulation of spontaneous LH surges. A battery of NPY receptor agonists, as well as the specific NPY Y1 receptor antagonist BIBP3226, were used to assess the role of Y1 receptors in the amplification of LH surges. In Exp 1, the potencies of a number of NPY agonists in facilitating LHRH-induced LH surges were assessed in pentobarbital (PB)-blocked, proestrous rats. The rank-ordered potencies of these compounds were determined to be PYY = [Leu31Pro34]NPY > NPY > hPP = rPP = NPY(13-36), which most closely reproduces the known rank-ordered affinties of these compounds for the Y1 receptor. In Exp 2, a Y1 subtype- specific antagonist, BIBP3226, was administered to unanesthetized, proestrous rats to assess the involvement of the Y1 receptor in the stimulation of spontaneous LH surges. The BIBP3226 compound strongly attenuated the endogenous proestrous LH surge, reducing the integrated value of LH secretion during the proestrous surge by more than 70%. In Exp 3, we assessed the ability of the Y1 receptor antagonist to block exogenous NPY effects on LHRH-induced LH surges. Treatment with BIBP3226 was found to completely prevent NPY amplification of LHRH-induced LH surges in pentobarbital-blocked, proestrous rats, thus confirming a pituitary locus of action of the drug. Taken together, these data clearly demonstrate that activation of neuropeptide Y receptors of the Y1 subtype is required for the physiological amplification of the spontaneous preovulatory LH surge in rats.     

Prejunctional neuropeptide Y receptors in human kidney and atrium

The aim of our study was to characterize functionally prejunctional neuropeptide Y (NPY) receptors in human and rabbit renal cortex, as well as in human right atrium. Segments of human atrial appendages and of human and rabbit renal cortex were preincubated with [3H]noradrenaline, superfused with Krebs-Henseleit solution and stimulated electrically in superfusion chambers. The stimulation-induced outflow of radioactivity was taken as an index of endogenous noradrenaline release. The effects of subtype-selective NPY analogs on the stimulation-induced noradrenaline release were studied. NPY, its endogenous analog, peptide YY, and its C-terminal fragment, NPY13-36, but not its analog, [Leu31,Pro34]NPY, concentration dependently (1-100 nM) inhibited [3H]noradrenaline release in all tissues studied. NPY-induced inhibition of [3H]noradrenaline release in human and rabbit kidney was abolished by pretreatment with pertussis toxin. We conclude that prejunctional inhibition of noradrenaline release in human heart and human and rabbit kidney occurs through NPY receptors of the Y2 subtype, which appear to couple to a pertussis toxin-sensitive G protein.     

Nonpeptide peptidomimetic antagonists of the neuropeptide Y receptor: benextramine analogs with selectivity for the peripheral Y2 receptor

We synthesized a new series of benextramine analogs as neuropeptide Y (NPY) functional group mimetics and tested them for N-[propionyl-3H]NPY ([3]NPY) displacement activity in rat brain membrane homogenates and for NPY receptor antagonist activity in the rat femoral artery. The tetraamine, carbon analog N,N'-bis[6-[N-(2-naphthylmethyl)amino]hexyl]-1,6-hexanediamine (15) was equipotent with benextramine (based on comparison of the relevant IC50's) in a rat brain [3H]NPY displacement assay, suggesting that the disulfide is not a necessary feature of benextramine's [3H]NPY displacement activity, although this analog maintained selectivity for the benextramine-sensitive binding site population. The bis(N,N-dialkylguanyl) disulfide and carbon analogs 14a-c were 3-4 times more potent than their respective controls in displacing [3H]NPY from rat brain membrane homogenates with IC50's ranging from 15 to 18 microM and maintained selectivity for the benextramine-sensitive, Y1 binding site population. However, the activity of the carbon analog N,N'-bis[6-[N-(2-naphthylmethyl)amino]hexyl]-N,N'-(1,6- hexanediyl)diguanidine tetrahydrochloride (14b) showed a different profile in a femoral artery vasoconstriction assay; at 1.0 nM, this analog shifted the concentration-effect curve of the Y2-selective agonist NPY13-36 to the right (pA2 = 9.2; Kd = 0.63 nM) without a significant change in the maximum effect, while even at 1.0 mM it had no effect on the vasoconstrictive activity of the Y1-selective agonist [Leu31,Pro34]NPY. Thus, the bis(N,N-dialkylguanidine) analogs of benextramine are selective, competitive antagonists of the postsynaptic NPY receptor in the femoral artery.     

125I]Leu31, Pro34-PYY is a high affinity radioligand for rat PP1/Y4 and Y1 receptors: evidence for heterogeneity in pancreatic polypeptide receptors

Cloned receptors for the PP-fold peptides are subdivided into Y1, Y2, PP1/Y4, Y5 and Y6. NPY and PYY have similar affinity for Y1, Y2, Y5 and Y6 receptors while PP has highest affinity for PP1. Pro34-substituted analogs of NPY and PYY have selectivity for Y1 and Y1-like receptors over Y2 receptors. In the present study, we found the putative Y1-selective radioligand, [125I]Leu31, Pro34-PYY, also binds with high affinity to the rat PP1 receptor in cell lines expressing the receptor. However, in rat brain sections, [125I]Leu31, Pro34-PYY does not appear to bind to the interpeduncular nucleus, a brain region containing a high density of [125I]-bPP binding sites. Therefore, it appears there is additional heterogeneity in receptors recognizing PP.     

Presence of Helicobacter species DNA in Swedish water

Neuropeptide Y (NPY) alters behavioral activity and innate immune functions of rats within minutes of intracerebroventricular (i.c.v.) application. Using combinations of the Y1-5a,b(6) agonist NPY, the Y1,3,5 agonist [Leu31-Pro34]NPY (LP-NPY), and the selective Y1 antagonist BIBP3226 (BIBP), we investigated whether the NPY-Y1 receptor (Y1R) subtype regulates NPY-induced behavioral and immunological effects at 15 min after i.c.v. application. Administration of both NPY and LP-NPY decreased rearing activity in the open field and suppressed granulocyte function in the blood. These effects were blocked by BIBP pre-treatment. In contrast to the blood, NPY and BIBP+NPY treatments stimulated granulocyte function within the splenic compartment. In addition, a blood leukophilia composed of granulocytes and NK cells was induced by NPY only. We conclude that the tested early effects of NPY are mediated by either the Y1R (rearing, blood granulocyte function), or a non-Y1R (splenic granulocyte function), or by a combined receptor activation (leukocyte mobilization). Furthermore, the immunological effects of NPY demonstrate compartment specificity.     

The ligand binding site of NPY at the rat Y1 receptor investigated by site-directed mutagenesis and molecular modeling

The ligand binding site of neuropeptide Y (NPY) at the rat Y1 (rY1,) receptor was investigated by construction of mutant receptors and [3H]NPY binding studies. Expression levels of mutant receptors that did not bind [3H]NPY were examined by an immunological method. The single mutations Asp85Asn, Asp85Ala, Asp85Glu and Asp103Ala completely abolished [3H]NPY binding without impairing the membrane expression. The single mutation Asp286Ala completely abolished [3H]NPY binding. Similarly, the double mutation Leu34Arg/Asp199Ala totally abrogated the binding of [3H]NPY, whereas the single mutations Leu34Arg and Asp199Ala decreased the binding of [3H]NPY 2.7- and 5.2-fold, respectively. The mutants Leu34Glu, Pro35His as well as Asp193Ala only slightly affected [3H]NPY binding. A receptor with a deletion of the segment Asn2-Glu20 or with simultaneous mutations of the three putative N-terminal glycosylation sites, displayed no detectable [3H]NPY binding, due to abolished expression of the receptor at the cell surface. Taken together, these results suggest that amino acids in the N-terminal part as well as in the first and second extracellular loops are important for binding of NPY, and that Asp85 in transmembrane helix 2 is pivotal to a proper functioning of the receptor. Moreover, these studies suggest that the putative glycosylation sites in the N-terminal part are crucial for correct expression of the rY1 receptor at the cell surface.     

Inhibition of glucose stimulated insulin secretion by neuropeptide Y is mediated via the Y1 receptor and inhibition of adenylyl cyclase in RIN 5AH rat insulinoma cells

Neuropeptide Y (NPY) has been shown to inhibit insulin secretion from the islets of Langerhans. We show that insulin secretion in the insulinoma cell line RIN 5AH is inhibited by NPY. 125I-Peptide YY (PYY) saturation and competition-binding studies using NPY fragments and analogues on membranes prepared from this cell line show the presence of a single class of NPY receptor with a Y1 receptor subtype-like profile. Inhibition of insulin secretion in this cell line by NPY fragments and analogues also shows a Y1 receptor-like profile. Both receptor binding and inhibition of insulin secretion showed the same orders of potency with NPY > [Pro34]-NPY > NPY 3-36 > NPY 13-36. The Y1 receptor antagonist, BIBP 3226, blocks NPY inhibition of insulin secretion from, and inhibits 125I-PYY binding to, RIN 5AH cells. Northern blot analysis using a Y1-receptor specific probe shows that NPY Y1 receptors are expressed by RIN 5AH cells. Y5 receptors are not expressed in this cell line. Neuropeptide Y inhibition of insulin secretion is blocked by incubation with pertussis toxin, implying that the effect is via a G-protein (Gi or Go) coupled receptor. Neuropeptide Y inhibits the activation of adenylyl cyclase by isoprenaline in RIN 5AH cell lysates, and the stimulation of cAMP by glucagon-like peptide-1 (7-36) amide (GLP-1). It also blocks insulin secretion stimulated by GLP-1, but not by dibutyryl cyclic AMP. Hence, we suggest that NPY inhibits insulin secretion from RIN 5AH cells via a Y1 receptor linked through Gi to the inhibition of adenylyl cyclase.     

Neuropeptide Y Y1 receptors in the rat forebrain: autoradiographic demonstration of [125I][Leu31,Pro34]-NPY binding sites and neurons expressing Y1 receptor mRNA

Using the specific monoiodinated NPY analog [Leu31,Pro34]-NPY we have localized NPY binding sites of the Y1 type in forebrain areas of the rat. The resulting receptor autoradiograms were compared with the regional distribution and cellular localization of the mRNA encoding Y1 receptor as demonstrated by in situ hybridization histochemistry. High densities of Y1 binding sites were present in the cerebral cortex, the claustrum, the thalamus and the medical mammillary nucleus, while moderate densities of Y1 binding sites were observed in the amygdalahippocampal complex. Lower binding densities were observed in septal nuclei, most hypothalamic nuclei and the circumventricular organs. High levels of Y1 mRNA were observed in the granula cell layer of the hippocampal dentate gyrus, several thalamic nuclei and the hypothalamic arcuate nucleus, while moderate levels of Y1 mRNA were seen in the frontoparietal cortex, several thalamic nuclei, the hippocampal pyramidal layers, the subiculum, the olfactory tubercle, the claustrum and a number of hypothalamic nuclei. Using the hypothalamic arcuate nucleus as an example, the distribution of immunoreactive NPY, Y1 mRNA and Y1 binding sites was compared, and possible implications of Y1 mediated actions within this nucleus are discussed. The present study further enlightens the anatomical distribution of NPY binding sites of the Y1 type within the central nervous system of the rat, and extends the understanding of central actions of NPY mediated via this type of receptor.     

Neuropeptide Y stimulates bile secretion via Y1 receptor in the left dorsal vagal complex in rats

Neuropeptide Y (NPY) injected into the cerebrospinal fluid and the left dorsal vagal complex enhances bile acid-independent and bicarbonate-dependent bile secretion through vagal muscarinic pathways in animal models. NPY binds to and activates six different receptor subtypes, and NPY Y1 and Y2 receptors are distributed in the dorsal vagal complex. We sought to determine which NPY receptor subtypes are involved in central stimulation of bile secretion by examining the effect of microinjection of specific NPY receptor agonists into the dorsal vagal complex. The bile duct was cannulated in urethane-anesthetized and bile acid-compensated rats. After measuring basal secretion, NPY, peptide YY (PYY), [Leu31, Pro34]NPY, NPY(13-36), or NPY(3-36) was microinjected into the either right or left dorsal vagal complex and bile secretion was observed for 100 minutes. Hepatic branch vagotomy was performed 2 hours before the peptide injection. Microinjection of NPY and PYY (8 pmol) into the left dorsal vagal complex increased bile secretion. [Leu31, Pro34]NPY microinjected into the left dorsal vagal complex also dose-dependently (1-8 pmol) stimulated bile acid-independent and bicarbonate-dependent bile secretion. Microinjection of NPY(13-36) into the left dorsal vagal complex did not stimulate and NPY(3-36) dose-dependently inhibited bile secretion. Stimulation of bile secretion by [Leu31, Pro34]NPY was abolished by hepatic branch vagotomy. NPY acts in the left dorsal vagal complex to stimulate bile acid-independent and bicarbonate-dependent bile secretion via Y1 receptor subtype.     

Differential modulation of NMDA-stimulated [3H]dopamine release from rat striatum by neuropeptide Y and sigma receptor ligands

Although the identity of the endogenous ligands for sigma (sigma) receptors is unknown, neuropeptide Y (NPY) has been named as a possible candidate for a natural transmitter at these receptors. Using a superfusion system, we compared the effect of NPY on NMDA-stimulated [3H]dopamine release in rat striatum to that of the sigma agonists (+)-pentazocine and BD737. In contrast to (+)-pentazocine- or BD737-mediated inhibition of release, NPY enhanced release. However, the same sigma antagonists (BD1008, DuP734, haloperidol and DTG) that reverse (+)-pentazocine- or BD737-mediated inhibition, as well as a Y receptor antagonist, PYX-1, all reversed the enhancement. PYX-1 also reversed the (+)-pentazocine- and BD737-mediated inhibition of release. Peptide YY (PYY) and [Leu31,Pro34]NPY did not mimic the effect of NPY. NPY13-36 enhanced release to the same extent as NPY but the effect was not reversed by sigma antagonists. Our findings are consistent with the potential role of NPY as an endogenous ligand for a subtype of sigma receptor with characteristics different from Y1, Y2 and Y3 receptors but sensitive to PYX-1.     

Neuropeptide Y and the calcitonin gene-related peptide attenuate learning impairments induced by MK-801 via a sigma receptor-related mechanism

It has been shown recently that low doses of sigma (sigma) receptor ligands like 1,3-di-(2-tolyl)guanidine (DTG), (+)N-allylnormetazocine [(+)SKF 10,047] and (+)pentazocine can antagonize learning impairments induced by dizocilpine (MK-801), a non-competitive antagonist at the NMDA receptor channel. This antagonism has been proposed to involve sigma receptor sites since it is blocked by the administration of purported sigma antagonists such as NE-100 and BMY-14802. It has also been demonstrated that peptides of the neuropeptide Y (NPY) and calcitonin gene-related peptide (CGRP) families modulate, in vivo, sigma labelling and electrophysiological effects in the hippocampal formation. Accordingly, we investigated if NPY- and CGRP-related peptides modulate cognitive processes by interacting with sigma sites in mice. In order to test this hypothesis, a step-down passive avoidance task was used. Interestingly, similarly to various sigma agonists, NPY, peptide YY (PYY) and the Y1 agonist [Leu31Pro34]NPY (but not NPY[13-36], a purported Y2 agonist), as well as hCGRPalpha and the purported CGRP2 agonist [Cys(ACM)2-7]hCGRPalpha (but not CGRP[8-37], a CGRP1 receptor antagonist), significantly attenuated learning impairments induced by MK-801. Furthermore, the effects of NPY, [Leu31Pro34]NPY, hCGRPalpha and [Cys(ACM)2-7]hCGRPalpha were blocked by the administration of the sigma antagonist, BMY-14802. The present data suggest that NPY- and CGRP-related peptides can indirectly interact in vivo with sigma receptors to modulate cognitive processes associated with NMDA receptor function.     

Altered neuropeptide Y Y1 responses in mesenteric arteries in rats with congestive heart failure

The aim of the present study was to elucidate if the potentiating effect of neuropeptide Y on various vasoactive agents in vitro is (1) altered in mesenteric arteries from rats with congestive heart failure and (2) mediated by the neuropeptide Y Y1 receptor. The direct vascular effects of neuropeptide Y and its modulating effects on the contractions induced by endothelin-1-, noradrenaline-, 5-hydroxytryptamine (5-HT)-, U46619-(9,11-dideoxy-11alpha, 9alpha-epoxymethano-prostaglandin F2alpha) and ATP, and acetylcholine-induced dilatations were studied in the presence and absence of the neuropeptide Y Y1 antagonist, BIBP3226 (BIBP3226?(R)-N2-(diphenylacetyl)-N-[(4-hydroxyphenyl)methyl ]-D-arginine-amide?). Neuropeptide Y, per se, had no vasoactive effect in the arteries. The potency of endothelin-1 was significantly decreased in congestive heart failure rats. Neuropeptide Y and neuropeptide Y-(13-36) potentiated the endothelin-1-induced contraction in congestive heart failure mesenteric arteries. In 20% of the congestive heart failure rats, sarafotoxin 6c induced a contraction of 31+/-4%. Neuropeptide Y also potentiated U46619- and noradrenaline-induced contractions but not 5-HT-induced contractions in congestive heart failure arteries. In sham-operated animals neuropeptide Y potentiated noradrenaline- and 5-HT-induced contractions. These potentiations were inhibited by BIBP3226. Acetylcholine induced an equipotent relaxation in both groups which was unaffected by neuropeptide Y. In conclusion, neuropeptide Y responses are altered in congestive heart failure rats. The potentiating effect differs between vasoactive substances. Neuropeptide Y Y1 and non-neuropeptide Y1 receptors are involved.     

NPY Y1 receptors in the dorsal periaqueductal gray matter regulate anxiety in the social interaction test

We have reported previously that the NPY Y1 receptor antagonist BIBP3226 applied into the dorsal periaqueductal gray matter (DPAG) has an anxiogenic-like effect in the elevated plus-maze test in rats. In the present study the effects of neuropeptide Y (NPY) Y1 receptor antagonists BIBP3226 (500 pmol) and 1229U91 (formerly also GR231118, GW1229 and EXBP68, 100 and 500 pmol) administered into the DPAG were investigated in the social interaction test in rats. BIBP3226 and 1229U91 (both 500 pmol) significantly decreased the time spent in active social interaction. These results provide additional evidence that NPY-ergic neurotransmission in the DPAG may be involved in the modulation of anxiety-related behaviour and suggest that endogenous NPY, released under stressful conditions in the DPAG, relieves anxiety via the NPY Y1 receptors. This is the first report demonstrating the effect of NPY receptor active agent on social behaviour.     

Alternative splicing of Pax6 in bovine eye and evolutionary conservation of intron sequences

There are now six recognized neuropeptide Y (NPY) receptor subtypes (Y1-Y4 and two recently cloned distinct receptors labeled Y5), of which Y1 and one of the Y5's have been suggested could mediate the effect of NPY on feeding. The fragments NPY(2-36) and NPY(3-36), which bind Y1 only poorly, were injected intracerebroventricularly (icv) and found to have similar dose-response relationships to NPY in the stimulation of feeding. However NPY (13-36), which stimulates both Y2 and Y5, caused no increase in food intake, even at high doses. Maximal stimulation with the classical Y1 agonist [Pro34]-NPY produced only 50% of the maximum effect of NPY itself despite fully inhibiting adenylyl cyclase activity in vitro in a Y1 system. The novel fragment [Pro34]-NPY(3-36) is as effective at stimulating food intake as the classical Y1 analogue [Pro34]-NPY but bound to the Y1 receptor with only 1/20th of the affinity of NPY and failed to inhibit adenylyl cyclase through this receptor. [Pro34]-NPY(3-36) is therefore a relatively appetite-selective ligand. Coadministration of high dose NPY(13-36) and [Pro34]NPY did not enhance feeding compared with [Pro34]-NPY alone. In addition, the NPY Y1 receptor antagonist BIBP-3226, which does not bind Y2, Y4, or Y5 receptors, significantly reduced NPY induced feeding. These results indicate that the feeding effect of icv NPY involves a novel receptor and that it is functionally distinct from the recognized receptor subtypes.     

Distinction of consolidative bronchioloalveolar carcinoma from pneumonia: do CT criteria work?

In the present study, the effects of intracerebroventricular (ICV) NPY, [Leu31, Pro34]NPY and NPY13-36 have been evaluated with respect to anxiety in mice in the elevated plus maze. NPY had opposing effects on behavior, depending on the doses used. NPY decreased the normal preference for the closed arms of the maze at 0.7 nmol, indicating an anxiolytic effect; however, at 7 pmol NPY further increased the preference for the closed arm, indicating an anxiogenic effect. [Leu31, Pro34]NPY, a Y1-type receptor agonist, significantly reduced the preference for the closed arms at 70 pmol. NPY13-36, a Y2-type receptor agonist, significantly intensified the preference at 20 pmol. It has been demonstrated that NPY produces not only an anxiolytic effect via Y1-type receptors, but also an anxiogenic effect via Y2-type receptors. The time course of these NPY actions are quite different and the anxiogenic effect was observed only shortly after ICV NPY injection.