Distribution of neuropeptide Y-like immunoreactive fibers in the cat thalamus

Neuropeptide Y-like immunoreactivity was studied in the thalamus of the cat using an indirect immunoperoxidase method. The densest network of immunoreactive fibers was observed in the nucleus (n.) paraventricularis anterior. In the anterior, intralaminar and midline thalamic nuclei, as well as in the n. geniculatum medialis, n. geniculatum lateralis, n. habenularis lateralis, n. medialis dorsalis, n. lateralis posterior and n. pulvinar a low density of neuropeptide Y-like immunoreactive fibers was observed. Neuropeptide Y-like fibers were totally absent in the n. ventralis lateralis, n. ventralis medialis, n. ventralis postero-medialis and n. ventralis postero-lateralis. In addition, neuropeptide Y-like perikarya were found in the n. parafascicularis, n. suprageniculatus, n. geniculatum lateralis ventralis, n. medialis dorsalis and n. lateralis posterior.     

Localization and characterization of neuropeptide Y-like peptides in the brain and islet organ of the anglerfish (Lophius americanus)

Summary Results from a previous report demonstrate that more than one molecular form of neuropeptide Y-like peptide may be present in the islet organ of the anglerfish (Lophius americanus). Most of the neuropeptide Y-like immunoreactive material was anglerfish peptide YG, which is expressed in a subset of islet cells, whereas an additional neuropeptide Y-like peptide(s) was localized in islet nerves. To learn more about the neuropeptide Y-like peptides in islet nerves, we have employed immunohistochemical and biochemical methods to compare peptides found in anglerfish islets and brain. Using antisera that selectively react with either mammalian forms of neuropeptide Y or with anglerfish peptide YG, subsets of neurons were found in the brain that labelled with only one or the other of the antisera. In separate sections, other neurons that were labelled with either antiserum exhibited similar morphologies. Peptides from brains and islets were subjected to gel filtration and reverse-phase high performance liquid chromatography. Radioimmunoassays employing either the neuropeptide Y or peptide YG antisera were used to examine chromatographic eluates. Immunoreactive peptides having retention times of human neuropeptide Y and porcine neuropeptide Y were identified in extracts of both brain and islets. This indicates that peptides structurally similar to both of these peptides from the neuropeptide Y-pancreatic polypeptide family are expressed in neurons of anglerfish brain and nerve fibers of anglerfish islets. The predominant form of neuropeptide Y-like peptide in islets was anglerfish peptide YG. Neuropeptide Y-immunoreactive peptides from islet extracts that had chromatographic retention times identical to human neuropeptide Y and porcine neuropeptide Y were present in much smaller quantities. These results are consistent with the hypothesis that peptides having significant sequence homology with human neuropeptide Y and porcine neuropeptide Y are present in the nerve fibers that permeate the islet.     

Neuropeptide Y-like immunoreactivity in neuritic plaques of Alzheimer's disease

Alzheimer's disease, a form of senile dementia, is characterized by the presence of neuritic plaques and neurofibrillary tangles throughout the cortex and hippocampus. This study demonstrates the presence of neuropeptide Y-like immunoreactivity within 10-20% of neuritic plaques. Neuropeptide Y is a 36 amino acid peptide which is distributed unevenly throughout the brain and has an interneuronal location.     

Distribution of peptidyl-glycine alpha-amidating monooxygenase immunoreactivity in the brain,pituitary and islet organ of the anglerfish (Lophius americanus)

Peptidyl-glycine alpha-amidating monooxygenase (PAM; EC 1.14.17.3) is an enzyme that catalyzes conversion of glycine-extended peptides to alpha-amidated bioactive peptides. Two peptides that are processed at their carboxyl-termini by this enzyme are neuropeptide Y and anglerfish peptide Y, both of which possess a C-terminal glycine that is used as a substrate for amidation. Results from previous reports have demonstrated that neuropeptide Y-like and anglerfish peptide Y-like immunoreactivities are present in the brain of anglerfish (Lophius americanus). Furthermore, neuropeptide Y-like peptides, namely anglerfish peptide Y and anglerfish peptide YG (the homologues of pancreatic polypeptide) are present in the islet organ of this species. Neuropeptide Y has also been localized in the anterior, intermediated and posterior lobes of the pituitary gland in a variety of species. In order to learn more about the distribution of the enzyme responsible for alpha amidation of these peptides in the brain and pituitary and to specifically investigate the relationship of this enzyme to peptide synthesizing endocrine cells of the anglerfish islet, we performed an immunohistochemical study using several antisera generated against different peptide sequences of the enzyme. PAM antisera labeled cells in the islet organ, pituitary and brain, and fibers in the brain and pituitary gland. The PAM staining pattern in the brain was remarkably similar to the distribution of neuropeptide Y immunoreactivity reported previously. Clusters of cells adjacent to vessels in the anterior pituitary displayed punctate PAM immunoreactivity while varicose fibers were observed in the pituitary stalk and neurohypophysis. Endocrine cells of the islet organ were differentially labeled with different PAM antisera. Comparison of the staining patterns of insulin, glucagon, and anglerfish peptide Y in the islet organ to PAM immunoreactivity suggests a distribution of forms of PAM enzyme in insulin and anglerfish peptide Y-containing cells, but no overlap with glucagon-producing cells. The results also indicate that PAM immunoreactivity is widely distributed in the brain, pituitary and islet organ of anglerfish in cells that contain peptides that require presence of a C-terminal glycine for amidation.     

Distribution and colocalization of neuropeptide Y- and tyrosine hydroxylase-like immunoreactivity in the guinea-pig heart

Summary The localization and distribution of neuropeptide Y-like immunoreactivity in the guinea-pig heart were studied by use of immunohistochemical methods. A widespread distribution of immunoreactive processes was observed in all regions of the heart. They occur either singly or together with several other immunoreactive processes and are most often aligned parallel to the myocardial bundles. A dense network of processes is present in the region of both the sinuatrial and atrioventricular nodes and single fibers are occasionally observed to be closely associated with nodal ganglion cells. Positive cell bodies were not seen within the heart. All small, medium and large coronary vessels are surrounded by a dense network of immunoreactive processes. A rich innervation at the media-adventitia junction of the aorta, pulmonary trunk, superior and inferior vena cava was also observed. Comparison of adjacent sections stained with antisera directed to avian pancreatic polypeptide, carboxyl-terminal hexapeptide of pancreatic polypeptide or neuropeptide Y demonstrated a very similar immunoreactive pattern, suggesting that these antisera are reacting with the same or a closely related substance. Likewise, the same immunoreactive patterns were observed in adjacent sections incubated in antiserum to neuropeptide Y or tyrosine hydroxylase, and analysis of elution-restained sections demonstrated that the same processes contain both neuropeptide Y- and tyrosine hydroxylase-like immunoreactivity. Neuropeptide Y- and tyrosine hydroxylase-like immunoreactivity was reduced by the same magnitude after treatment with the sympathetic neurotoxin 6-hydroxydopamine, but it was not affected by the primary sensory neurotoxin capsaicin. Furthermore, the pattern of neuropeptide Y- and tyrosine hydroxylase-like immunoreactivity did not match the staining patterns observed with antisera to vasoactive intestinal polypeptide or substance P or with the acetylcholinesterase staining pattern. In conclusion, neuropeptide Y-like immunoreactivity in the heart and great vessels coexists with that for catecholamines and is likely to originate from sympathetic ganglia.     

Demonstration of a neuropeptide Y-like immunoreactivity in human phaeochromocytoma extracts

Using a porcine neuropeptide Y directed radioimmunoassay it was shown that acid extracts of human phaeochromocytoma tumour tissue contained a neuropeptide Y-like peptide. Further fractionation and purification of this immunoreactivity showed that this human neuropeptide Y-like immunoreactivity was closely similar in molecular size and separation characteristics to porcine neuropeptide Y. The possible contribution of neuropeptide Y to the hypertension characterizing human phaeochromocytoma is discussed.     

Developmental study of neuropeptide Y-like immunoreactivity in the neurohypophysis and intermediate lobe of the rhesus monkey (Macaca mulatta)

Summary The purpose of this study was to examine the development and distribution of neuropeptide Y-immunoreactive fibers in the neurohypophysis of the rhesus monkey (Macaca mulatta) throughout life and the relationship of these fibers to the hypothalamo-hypophyseal portal vasculature. In rhesus monkeys, which varied in age from fetal life to 34 years, neuropeptide Y-immunoreactive fibers were present at all ages examined. In adult monkeys, varicose neuropeptide Y-labeled fibers were concentrated in the upper infundibular stem in association with capillary loops of the portal vasculature and the long portal vessels. Other fibers travelled down the infundibular stem and were distributed at the junction of the lower infundibular stem and infundibular process in the vicinity of the short portal vessels. In the infundibular process, neuropeptide Y-immunoreactive fibers were concentrated along the border of the intermediate lobe. Other stained fibers were sparsely distributed in the infundibular process and were often associated with small vessels. Neuropeptide Y-immunoreactivity was also located in a few fibers and cells of the intermediate lobe. Very few labeled fibers were seen in the fetal neurohypophysis, but their number increased gradually during the first postnatal year. At two years of age, a high density of stained fibers was observed, especially in the infundibular process. The number of axons in the infundibular process was lower at 12 years and continued to decline until 34 years of age. Neuropeptide Y may modulate hormone release at these sites and may also be released directly into vessels in the infundibular process. The close association of neuropeptide Y-labeled fibers with capillaries of the portal vasculature strongly suggests that neuropeptide Y is released into the portal blood of monkeys throughout life and may influence hormone secretion from the anterior pituitary gland.     

Neuropeptide Y-like immunoreactivity in perivascular nerve fibres of the guinea-pig

The distribution of perivascular nerve fibres displaying neuropeptide Y-like immunoreactivity was studied in the guinea-pig. Generally, neuropeptide Y fibres were numerous around arteries and moderate in number around veins. In the heart, immunoreactive fibres were numerous in the auricles and the atria (epi- and endocardium) whereas the ventricles had a more scarce supply. The coronary vessels were richly supplied with fibres. Around large elastic and muscular arteries the fibres formed well developed plexuses. Small arteries in the respiratory tract, the gastrointestinal tract and the genito-urinary tract received a particularly rich supply. In the liver, spleen and kidney only few perivascular fibres were seen. Since immunoreactive fibres around blood vessels disappeared upon surgical or chemical sympathectomy, and sequential immunostaining with antisera against dopamine-beta-hydroxylase (a marker for adrenergic neurons) and against neuropeptide Y revealed their co-existence, it is concluded that neuropeptide Y fibres around blood vessels are sympathetic and adrenergic.     

A comparative study of neuropeptides in the intestine of two stomachless teleosts (Poecilia reticulata,Leuciscus idus melanotus) under conditions of feeding and starvation

Summary Endocrine cells containing bombesin-, enkephalin-, gastrin/CCK-, 5-HT-, and substance P-like material were demonstrated in the alimentary tract of Poecilia reticulata and Leuciscus idus melanotus. Endocrine cells with neuropeptide-Y-like immunoreactivity were found only in P. reticulata, those with VIP-like immunoreactivity only in L. idus melanotus. Gut nerves showing bombesin-, G/CCK-5-HT-, neurotensin-, substance P-and VIP-like immunoreactivity were observed in both species investigated, enkephalin- and neuropeptide Y-like immunoreactivity in P. reticulata alone. The distribution and amount of endocrine cells and nerves along the gut as visualized with the appropriate antisera varied in both teleosts. Histologically, the intestinal tract of these stomachless fish can be divided into three regions. A large number of endocrine cells with VIP-like immunoreactivity was noted in the rectum of L. idus melanotus. Endocrine cells containing bombesin-, enkepha-lin- and substance P-like material were found only in intestinal parts I and II in L. idus melanotus. Neuropeptide Y-like immunoreactivity was absent from intestinal part I of P. reticulata. The influence of starvation on the immunoreactivity of nerves and enteroendocrine cells in the teleost intestine was examined. After a starvation period of more than 6 weeks, no alterations were observed either in the appearance or amount of nerve and endocrine cell immunoreactivity.     

Nerve growth factor receptor-like immunoreactivity in primary and permanent canine tooth pulps of the cat

Summary The distribution of nerve growth factor receptor (NGF receptor)-like immunoreactivity in pulps of developing primary and mature permanent cat canine teeth was examined, by use of a monoclonal antibody against NGF receptor detected by fluorescence immunohistochemistry and pre-embedding immunocytochemical light- and electron microscopy. Both primary and permanent pulps contained a vast number of NGF receptor-like immunoreactive nerves. Immunolabelling appeared to be localized both to axons and Schwann cells. In addition, many blood vessel walls in immature primary tooth pulps showed NGF receptor-like immunoreactivity, in contrast to permanent pulps where blood vessels rarely were NGF receptor-immunoreactive. Double-labelling immunofluorescence experiments revealed that in the permanent pulp a majority of the NGF receptor-positive nerves also showed calcitonin gene-related peptide (CGRP)-like immunoreactivity, and many showed substance P-like immunoreactivity. However, nerve fibers with neuropeptide Y-like immunoreactivity lacked NGF receptor-like immunoreactivity. In developing primary tooth pulps fewer NGF receptor-positive nerves were CGRP-like immunoreactive or substance P-like immunoreactive, as compared to the permanent pulp. Neuropeptide Y-like immunoreactive nerve fibers were not detected in the primary tooth pulp. The results suggest a role for nerve growth factor in both developing and mature sensory nerves of the tooth pulp.     

PBAN/pyrokinin神经肽类及其基因的研究进展

昆虫在其生长发育过程中,如胚胎发育、蜕皮变态、滞育、迁飞、代谢、生殖等都离不开神经肽的调控。信息素合成激活肽(pheromone biosynthesis activating neuropeptide,PBAN)和Pyrokinin神经肽是C端具有五肽FXPRL(X=S,V,T,G等)(苯丙-X-脯-精-亮氨酸)序列的一类神经肽,在昆虫的生长发育中起重要的生理功能,如性信息素的合成、控制表皮色素、促进胚胎滞育和刺激内脏肌肉收缩等重要的生理功能。因此近几年对PBAN/pyrokinin神经肽的鉴定、加工、作用和降解方式的研究成为研究的热点,为研制高效、低毒、专一性强、无公害的杀虫剂提供了思路。介绍了PBAN/pyrokinin神经肽类及其基因的研究进展,并对PBAN/pyrokinin神经肽在害虫防治中的应用进行了展望。     

Pharmacological characterisation of neuropeptide F (NPF)-induced effects on the motility of Mesocestoides corti (syn. Mesocestoides vogae) larvae

Neuropeptide F is the most abundant neuropeptide in parasitic flatworms and is analogous to vertebrate neuropeptide Y. This paper examines the effects of neuropeptide F on tetrathyridia of the cestode Mesocestoides vogae and provides preliminary data on the signalling mechanisms employed. Neuropeptide F (>/=10 microM) had profound excitatory effects on larval motility in vitro. The effects were insensitive to high concentrations (1 mM) of the anaesthetic procaine hydrochloride suggesting extraneuronal sites of action. Neuropeptide F activity was not significantly blocked by a FMRFamide-related peptide analog (GNFFRdFamide) that was found to inhibit GNFFRFamide-induced excitation indicating the occurrence of distinct neuropeptide F and FMRFamide-related peptide receptors. Larval treatment with guanosine 5'-O-(2-thiodiphosphate) trilithium salt prior to the addition of neuropeptide F completely abolished the excitatory effects indicating the involvement of G-proteins and a G-protein coupled receptor in neuropeptide F activity. Addition of guanosine 5'-O-(2-thiodiphosphate) following neuropeptide F had limited inhibitory effects consistent with the activation of a signalling cascade by the neuropeptide. With respect to Ca(2+) involvement in neuropeptide F-induced excitation of M. vogae larvae, the L-type Ca(2+)-channel blockers verapamil and nifedipine both abolished neuropeptide F activity as did high Mg(+) concentrations and drugs which blocked sarcoplasmic reticulum Ca(2+)-activated Ca(2+)-channels (ryanodine) and sarcoplasmic reticulum Ca(2+) pumps (cyclopiazonic acid). Therefore, both extracellular and intracellular Ca(2+) is important for neuropeptide F excitation in M. vogae. With respect to second messengers, the protein kinase C inhibitor chelerythrine chloride and the adenylate cyclase inhibitor MDL-2330A both abolished neuropeptide F-induced excitation. The involvement of a signalling pathway that involves protein kinase C was further supported by the fact that phorbol-12-myristate-13-acetate, known to directly activate protein kinase C, had direct excitatory effects on larval motility. Although neuropeptide F is structurally analogous to neuropeptide Y, its mode-of-action in flatworms appears quite distinct from the common signalling mechanism seen in vertebrates.     

The distribution and colocalization of neuropeptides in perivascular nerves innervating the large arteries and veins of the snake,Elaphe obsoleta

Summary Single- and dual-labelling immunohistochemistry were used to determine the distribution and coexistence of neuropeptides in perivascular nerves of the large arteries and veins of the snake, Elaphe obsoleta, using antibodies for vasoactive intestinal polypeptide, substance P, calcitonin gene-related peptide, neuropeptide Y, galanin, somatostatin, and leu-enkephalin. Blood vessels were sampled from four regions along the body of the snake: region 1, arteries and veins anterior to the heart; region 2, central vasculature 5 cm anterior and 10 cm posterior to the heart; region 3, arteries and veins in a 30-cm region posterior to the liver; and region 4, dorsal aorta and renal arteries, renal and intestinal veins, 5–30 cm cephalad of the vent. A moderate to dense distribution of vasoactive intestinal polypeptide-like immunoreactive fibres was found in most arteries and veins of regions 1–3, but fibres were absent from the vessels of region 4. The majority of vasoactive intestinal polypeptide-like immunoreactive fibres contained colocalized substance P-like immunoreactivity, and these fibres were unaffected by either capsaicin or 6-hydroxydopamine (6-OHDA) pretreatment. In the anterior section of the snake, the vagal trunks contained many cell bodies with colocalized vasoactive intestinal polypeptide and substance P-like immunoreactivity. It is suggested that the vasoactive intestinal polypeptide/substance P-like immunoreactive cell bodies and fibres are parasympathetic postganglionic nerves. Neuropeptide Y-like immunoreactive fibres were observed in all arteries and veins, being most dense in regions 3 and 4. The majority of these fibres also contained colocalized galanin-like immunoreactivity, and were absent in tissues from 6-OHDA pretreated snakes, suggesting that neuropeptide Y and galanin are colocalized in adrenergic nerves. A small number of neuropeptide Y-like immunoreactive fibres contained vasoactive intestinal polypeptide but not galanin, and were unaffected by 6-OHDA treatment. All calcitonin gene-related peptide-like immunoreactive fibres contained colocalized substance P-like immunoreactivity, and these fibres were observed in all vessels, being particularly dense in the carotid artery and jugular veins. All calcitonin gene-related peptide/substance P-like immunoreactive fibres appeared damaged after capsaicin treatment suggesting they represent fibres from afferent sensory neurons. A sparse plexus of somatostatin-like immunoreactive fibres was observed in the vessels only from region 4. No enkephalin-like immunoreactive fibres were found in any blood vessels from any region. This study provides morphological evidence to suggest that there is considerable functional specialization within the components of the rat snake peripheral autonomic system controlling the circulation, in particular the regulation of venous capacitance.     

Increases of neuropeptide Y-like immunoreactivity in plasma during insulin-induced hypoglycemia in man

Neuropeptide Y-like immunoreactivity (NPY-LI) in plasma during insulin-induced hypoglycemia was measured in 4 healthy male volunteers. Plasma NPY-LI increased from 167 +/- 11 pg/ml to 247 +/- 25 pg/ml 30 min after the administration of insulin (0.1 U/kg body weight IV), reached the maximum (296 +/- 6 pg/ml) 45 min after the insulin, and then decreased. These results suggest that NPY is released into the systemic circulation during insulin-induced hypoglycemia in man.     

Cloning, expression and growth promoting action of Red tilapia (Oreochromis sp.) neuropeptide Y

Neuropeptide Y, a 36 amino acid peptide abundantly expressed in the brain, is the most potent orexigenic factor known to date in mammals. It has been shown to be one of the most conserved neuropeptides in vertebrate evolution. It seems that neuropeptide Y functions, in addition to sequence conservation, are also well conserved in fish. In the present study, we cloned and reported the cDNA sequence coding for tilapia 36 aminoacid neuropeptide Y. We express the tilapia neuropeptide Y gene in Escherichia coli driven by T7 promoter. The recombinant neuropeptide Y was purified up to 80% by affinity chromatography. We developed both, a food intake and a growth performance experiment to evaluate the effects of neuropeptide Y administration. Juvenile tilapia receiving recombinant neuropeptide Y (1 microg/g of body weight) by intraperitoneal injection increased food intake compared to controls (p < 0.05). Similarly, in the growth performance experiment, we observed an increase in body weight (p < 0.05) of tilapia fry receiving the same dose of the peptide. Neuropeptide Y treatment had no significant effect on hepatosomatic index and muscle moisture content. On the other hand, muscle protein content was increased in treated animals. These results demonstrate that administration of biologically active E. coli-derived neuropeptide Y resulted in a growth promoting action in fish.     

Projection pathways,co-existence of peptides and synaptic organization of nerve fibers in the inferior mesenteric ganglion of the guinea-pig

Summary The presence of immunoreactive enkephalin, dynorphin, vasoactive intestinal polypeptide, cholecystokinin, substance P and neuropeptide Y in nerve fibers that project to the guinea-pig inferior mesenteric ganglion was analysed, after different denervation and ligation procedures. A quantitative analysis demonstrates that enkephalin- and substance P fibers reach the ganglion mainly via lumbar splanchnic and partly via intermesenteric nerves. Dynorphin-, vasoactive intestinal polypeptide- and cholecystokinin fibers reach the ganglion mainly via colonic and partly via hypogastric or intermesenteric nerves. Neuropeptide Y fibers enter via intermesenteric, lumbar splanchnic and hypogastric nerves and pass through the ganglion. Analysis of serial 0.5 m sections tends to confirm co-existence: of dynorphin, vasoactive intestinal polypeptide and cholecystokinin in fibers projecting from the colon; of dynorphin with substance P in the lumbar splanchnic nerves; and of neuropeptide Y with substance P in the hypogastric and colonic fibers. Synaptic contacts, predominantly axodendritic, onto the ganglion cells from enkephalin-, vasoactive intestinal polypeptide-, and substance P-containing terminals were revealed by electron microscopy. Enkephalin-immunoreactive axon varicosities are filled with small, clear vesicles with a few large, cored vesicles and form asymmetric synapses; dynorphin-, vasoactive intestinal polypeptide- and cholecystokinin-immunoreactive axon varicosities are rich in large, dense-cored vesicles and form symmetric synapses.     

Purification and characterization of human neuropeptide Y from adrenal-medullary phaeochromocytoma tissue.

Human neuropeptide Y was isolated from acid extracts of adrenal-medullary phaeochromocytoma tissue. After (NH4)2SO4 fractionation, the neuropeptide Y-like immunoreactivity was purified from the resolubilized 80%-saturation-(NH4)2SO4 peptide-rich precipitate, by gel filtration, cation-exchange chromatography and reverse-phase high-pressure liquid chromatography. Amino acid analysis of the peptide revealed a composition almost identical with that of the pig peptide, the exception being the loss of one leucine residue and its replacement with methionine. Tryptic digestion of the peptide and subsequent amino acid analysis of the fragments further confirmed the identity of the peptide. Carboxypeptidase Y digestion of the (1-19)-peptide tryptic fragment has shown the methionine to be located at position 17 in human neuropeptide Y.     

Immunocytochemical localization of neuropeptide Y (NPY) in the human hypothalamus

Summary In order to study the distribution of neuropeptide Y-like immunoreactivity in the human hypothalamus, an immunocytochemical localization of this peptide was performed. Using antibodies developed against synthetic porcine neuropeptide Y (NPY), we have been able to localize immunoreactivity in neuronal cell bodies located exclusively in the infundibular nucleus. Immunostained fibers were found in several regions in the hypothalamus with a high concentration in the periventricular areas. Fibers were also found in the neurovascular zone of the median eminence, the pituitary stalk and the posterior pituitary. These results suggest that immunoreactive material related to porcine NPY is present in the human hypothalamus, with a distribution similar to that observed in the rat.     

Differential activation of "social" and "solitary" variants of the Caenorhabditis elegans G protein-coupled receptor NPR-1 by its cognate ligand AF9

Natural variations of wild Caenorhabditis elegans isolates having either Phe-215 or Val-215 in NPR-1, a putative orphan neuropeptide Y-like G protein-coupled receptor, result in either "social" or "solitary" feeding behaviors (de Bono, M., and Bargmann, C. I. (1998) Cell 94, 679-689). We identified a nematode peptide, GLGPRPLRF-NH2 (AF9), as a ligand activating the cloned NPR-1 receptor heterologously expressed in mammalian cells. Shifting cell culture temperatures from 37 to 28 degrees C, implemented 24 h after transfections, was essential for detectable functional expression of NPR-1. AF9 treatments linked both cloned receptor variants to activation of Gi/Go proteins and cAMP inhibition, thus allowing for classification of NPR-1 as an inhibitory G protein-coupled receptor. The Val-215 receptor isoform displayed higher binding and functional activity than its Phe-215 counterpart. This finding parallels the in vivo observation of a more potent repression of social feeding by the npr-1 gene encoding the Val-215 form of the receptor, resulting in dispersing (solitary) animals. Since neuropeptide Y shows no sequence homology to AF9 and was functionally inactive at the cloned NPR-1, we propose to rename NPR-1 and refer to it as an AF9 receptor, AF9-R1.