The epidemiology, prevalence and hospital outcomes of infants with gastroschisis.

OBJECTIVE: The purpose of this study is to evaluate recent trends in prevalence of gastroschisis among infants admitted for neonatal intensive care in the United States. STUDY DESIGN: Retrospective review of a de-identified patient data. The current study extends our observations through the end of 2007 to 2015. RESULTS: During the study period (1 January 1997 to 12 December 2015), there were 1 158 755 total discharges; 6023 (5.2/1000) had gastroschisis and 1885 (1.6/1000) had an omphalocele. Between 1997 and 2008, the reported rate of gastroschisis increased from 2.9 to 6.4/1000 discharges. From 2008 to 2011, the values have slowly decreased from 6.4 to 4.7/1000 discharges and since 2011 have been stable. The largest drop in the prevalence was in mothers who were <20 years old. In contrast, the reported rate of omphalocele was stable at 1 to 2/1000 discharges. CONCLUSION: The prevalence of gastroschisis increased from 1997 to 2008, and then declined thereafter.

Impact of duration of rupture of membranes on outcomes of premature infants.

OBJECTIVE: The primary aim of the study was to determine how the risk of adverse outcomes was related to the duration of the latency period and gestational age at birth following preterm premature rupture of the fetal membranes (PPROM). STUDY DESIGN: Retrospective review of infants discharged from 330 neonatal intensive care units. We defined four subgroups based on gestational age: 23 to 25, 26 to 28, 29 to 31 and 32 to 34 weeks. Each gestational age group was evaluated by duration of ROM: <24 h, 1 to 7 days, 8 to 14 days, 15 to 21 days, 21 to 28 days and >28 days and compared with a referent group (PPROM of >24 h but <7 days). RESULT: In all, 239 808 non-anomalous infants 23 to 34 weeks' gestational age were identified; 37 233 (15.5%) had rupture of membranes (ROM) >24 h. Compared with a reference group (PPROM of >24 h but <7 days), the risk of mortality for PPROM of 8 to 14, 15 to 21 and 21 to 28 days varied depending on gestational age at birth. Only PPROM >28 days was consistently associated with increased mortality and decreased likelihood of survival without morbidity in all gestational age subgroups. CONCLUSION: PPROM for >28 days is associated with an increased risk of death and morbidity.

Factors associated with mortality in neonates with gastroschisis.

PURPOSE: The ongoing epidemic of gastroschisis has created multiple challenges and continues to raise questions concerning the optimal management of these high-risk patients. Although the overall survival rate has increased over the past 3 decades, morbidity and mortality remain significant. The purpose of this study was to analyze the main factors associated with mortality in neonates admitted to an intensive care unit for the management of this abdominal wall defect. METHODS: This study is a retrospective review of a large de-identified neonatal intensive care dataset encompassing 284 institutions in 32 states and Puerto Rico, from 1/1/1997 to 1/1/2010. Of the 629 440 neonates in the dataset, a total of 3 456 newborns were diagnosed with gastroschisis (5.5/1 000 hospital discharges). Of these, 685 were transferred to other centers and data was missing on 22, leaving 2 749 infants available for analysis. RESULTS: Out of these 2 749 infants of whom we knew the outcome, 115 (4.2%) died. Multivariate logistic regression showed that the factors independently associated with an increased risk of death were male gender, immature gestational age, low birth weight, low 5 min Apgar Score, the need for vasopressors during the first week after birth and the need for high levels of oxygen support. The presence of associated anomalies, vaginal delivery, treatment with surfactant and the need for ventilator support on the day of birth were not independent risk factors associated with an increased mortality. CONCLUSION: Premature delivery and low birth weight are the most important factors associated with an increased risk of mortality. Cesarean section does not appear to reduce the risk.

Elevation in plasma creatinine and renal failure in premature neonates without major anomalies: terminology, occurrence and factors associated with increased risk.

OBJECTIVE: The goal of this study was to describe the changes in plasma creatinine levels that occur in prematurely born neonates, to better understand the use of the terms 'renal dysfunction' and 'renal failure' among premature neonates, as well as to evaluate the demographic and outcome characteristics associated with renal problems in preterm neonates who have no major congenital anomalies. STUDY DESIGN: Retrospective review of the Pediatrix neonatal intensive care patient clinical data warehouse. RESULT: The study cohort consisted of neonates born with an estimated gestational age of ≤ 30 completed weeks in whom there was no report of any major anomalies (n=66,526). In this group of 66,526 neonates, there were 64,030 (96.2%) with no report of renal dysfunction or failure, 1239 (1.9%) in whom there was a diagnosis of renal dysfunction and 1257 infants (1.9%) with a diagnosis of renal failure. The clinical circumstances most strongly associated with a diagnosis of renal dysfunction and/or renal failures were low gestational age and birth weight. In addition, multivariate analysis showed that the factors associated with an increased risk of renal problems were vasopressor use during the first 7 days after birth, grade 3 or 4 intraventricular hemorrhage, a patent ductus arteriosus, necrotizing enterocolitis, male gender, the use of indomethacin, a positive blood culture during the first 7 days after birth, the use of high-frequency ventilation in the first 2 days after birth, non-White race and prolonged exposure to antibiotics. Mortality was higher in patients with renal problems than in neonates without renal problems (39.1 vs 10.2%, P<0.01) and higher in neonates with renal failure than in neonates with renal dysfunction (57.6 vs 20.1%, P<0.01). CONCLUSION: Renal dysfunction and/or failure are common diagnoses, especially in extremely premature neonates and there are potentially modifiable factors that increase the risk of renal problems.

The changing pattern of inhaled nitric oxide use in the neonatal intensive care unit.

OBJECTIVE: The purpose of this study was to evaluate the demographic characteristics and outcomes of neonates who were admitted to a neonatal intensive care unit and treated with inhaled nitric oxide (iNO) during the years 2000-08. The goal of studying this group of neonates was to evaluate how iNO use has evolved in infants and to estimate the frequency of off-label use of this drug in this population. STUDY DESIGN: Retrospective review of the Pediatrix Clinical Data Warehouse de-identified data set. Pediatrix Medical Group provides intensive care services in 244 hospitals in 32 states and Puerto Rico. Nine (3.7%) centers provide extracorporeal membrane oxygenation. RESULT: There were 494 255 neonates in the data set; 4316 (0.9%) were treated with iNO. The use of iNO increased from 154 of 32 967 patients in 2000 to 921 of 75 911 patients in 2008; a 2.6-fold increase (0.47 to 1.23%). There were 155 872 infants <34 weeks estimated gestational age discharged between 1 January 2000 and 31 December 2008; 1656 (1.1%) were treated with iNO. Since approval in 2000, the reported use of iNO in neonates <34 weeks increased from 0.3 to 1.8% in 2008; a sixfold increase in the reported use of iNO. The biggest increase occurred in infants between 23 and 26 weeks' gestational age (0.8 to 6.6%). In contrast, the increase in iNO use among neonates born ≥34 weeks has only increased from 0.5 to 1%. CONCLUSION: The use of iNO has increased and the greatest increase has been the off-label use among preterm neonates.

New insights into spontaneous intestinal perforation using a national data set: (2) two populations of patients with perforations.

BACKGROUND: Spontaneous intestinal perforation (SIP) is increasingly common in the premature infant and has been demonstrated to be associated with early postnatal administration of glucocorticoids and indomethacin. Before survival of the extremely low birth weight (ELBW) infant, SIP was thought to be a rare, congenitally acquired disease sporadically affecting the muscularis of the distal intestine. These disparate views of etiology have not been previously reconciled in the literature. OBJECTIVES: (1) To establish a cohort of SIP patients in a national data set. (2) To use timing of diagnosis as a unique data element and thereby differentiate between SIP cases which are susceptible to postnatal risk factors versus those occurring at or immediately after birth (and therefore not exposed to postnatal risk factors). METHODS: A large identified national data set was used to retrospectively look at timing of diagnosis and then the cohort was divided into postnatal treatment groups for further subanalyses. This analysis resulted in the division of the cohort into early and late diagnosis SIP subcohorts. These were then queried retrospectively by univariate analysis to look for differences in demographics between the two (using a P-value < 0.05). RESULTS: There were 633 patients with SIP evaluated in this data set. The early SIP cohort (0-3 days) was made up of 116 infants with a median BW of 1.401 kg, whereas the late cohort (4-14 days) held 386 infants with a median BW of 775 g. Infants with early SIP were significantly more likely to: be male, have higher Apgar scores, have not received antenatal steroids, surfactant or required mechanical ventilation. CONCLUSIONS: Two populations of infants acquire SIP: ELBW infants acquire SIP on average between 7 and 10 days of life after exposure to indomethacin and glucocorticoids (either endogenous or exogenous), and infants with early SIP (0-3 days) who are significantly less likely to have been exposed to postnatal risk factors and are less premature.

New insights into spontaneous intestinal perforation using a national data set: (1) SIP is associated with early indomethacin exposure.

BACKGROUND: Spontaneous intestinal perforation (SIP) is increasingly common in the premature infant and is associated with significant morbidity. Indomethacin use has been implicated as a co-risk factor for SIP when combined with glucocorticoids, but previous evidence argued against indomethacin being an independent risk factor when used prophylactically. OBJECTIVES: (1) To establish a homogeneous cohort of SIP patients in a national data set and to contrast them to patients with surgical necrotizing enterocolitis (NEC). (2) To test the hypothesis that early post-natal indomethacin is independently associated with SIP. METHODS: A large de-identified data set was retrospectively queried by diagnosis, and then multiple antenatal and post-natal variables were tested by both univariate and multivariate analysis to identify associations with SIP. Sub-analyses were also performed to look at the timing of drug administration. RESULTS: There were 2105 patients evaluated in the data set. Patients were divided into matched controls (n = 581), those with SIP without report of NEC (n = 633) and those with NEC requiring surgery (n = 891). Infants with SIP were more likely to have a patent ductus arteriosus and more likely to be treated with vasopressors than either control or NEC patients. Compared to infants with NEC, patients with SIP were smaller, less mature and required more support. SIP was also diagnosed earlier than NEC (median of 7 vs 15 days). Patients with SIP were more likely to be treated with indomethacin, hydrocortisone or both on days of life 0-3 than controls. CONCLUSIONS: (1) Surgical NEC and SIP have significant differences in presentation, demographics and morbidity. (2) A detailed look at drug timing revealed that early post-natal indomethacin is independently associated with SIP.

Expression of a novel neuropeptide Y receptor subtype involved in food intake: an in situ hybridization study of Y5 mRNA distribution in rat brain.

Our group has reported on the cloning of a novel rat neuropeptide Y (NPY) receptor involved in NPY-induced food intake, the Y5 receptor. The distribution in rat brain of the mRNA encoding this receptor has been determined by in situ hybridization histochemistry, using radiolabeled oligonucleotide probes. Control experiments were carried out in cell lines transfected with either rat Y1 or rat Y5 cDNAs. With the exception of the cerebellum, only the antisense probes yielded hybridization signal in rat brain tissue sections. A number of brain regions contained hybridization signals indicative of Y5 mRNA localization. Chief among these were various hypothalamic nuclei, including the medial preoptic nucleus, the supraoptic nucleus, the paraventricular nucleus, and the lateral hypothalamus. Other regions with substantial hybridization signals included the midline thalamus, parts of the amygdala and hippocampus, and some midbrain and brain-stem nuclei. In general a low density of Y5 mRNA was observed in most cortical structures, with the exception of the cingulate and retrosplenial cortices, each of which contained a moderate abundance of Y5 hybridization signal. The distribution of this receptor mRNA is consistent with a role for the Y5 receptor in food intake and also suggests involvement in other processes mediated by NPY.

Design, synthesis and SAR of a series of 2-substituted 4-amino-quinazoline neuropeptide Y Y5 receptor antagonists.

The design of a novel series of NPY-Y5 receptor antagonists is described. Key elements for the design were the identification of weak Y5 hits from a Y1 program, results from a combinatorial approach and database mining. This led to the discovery of the quinazoline 4 and the aryl-sulphonamide moiety as major components of the pharmacophore for Y5 affinity. The synthesis and SAR towards CGP71683A is described.

Low-dose nitric oxide therapy for persistent pulmonary hypertension of the newborn. Clinical Inhaled Nitric Oxide Research Group.

BACKGROUND: Inhaled nitric oxide improves gas exchange in neonates, but the efficacy of low-dose inhaled nitric oxide in reducing the need for extracorporeal membrane oxygenation has not been established. METHODS: We conducted a clinical trial to determine whether low-dose inhaled nitric oxide would reduce the use of extracorporeal membrane oxygenation in neonates with pulmonary hypertension who were born after 34 weeks' gestation, were 4 days old or younger, required assisted ventilation, and had hypoxemic respiratory failure as defined by an oxygenation index of 25 or higher. The neonates who received nitric oxide were treated with 20 ppm for a maximum of 24 hours, followed by 5 ppm for no more than 96 hours. The primary end point of the study was the use of extracorporeal membrane oxygenation. RESULTS: Of 248 neonates enrolled, 126 were randomly assigned to the nitric oxide group and 122 to the control group. Extracorporeal membrane oxygenation was used in 78 neonates in the control group (64 percent) and in 48 neonates in the nitric oxide group (38 percent) (P=0.001). The 30-day mortality rate in the two groups was similar (8 percent in the control group and 7 percent in the nitric oxide group). Chronic lung disease developed less often in neonates treated with nitric oxide than in those in the control group (7 percent vs. 20 percent, P=0.02). The efficacy of nitric oxide was independent of the base-line oxygenation index and the primary pulmonary diagnosis. CONCLUSIONS: Inhaled nitric oxide reduces the extent to which extracorporeal membrane oxygenation is needed in neonates with hypoxemic respiratory failure and pulmonary hypertension.

Galanin receptor subtypes.

The neuropeptide galanin, which is widely expressed in brain and peripheral tissues, exerts a broad range of physiological effects. Pharmacological studies using peptide analogues have led to speculation about multiple galanin receptor subtypes. Since 1994, a total of three G-protein-coupled receptor (GPCR) subtypes for galanin have been cloned (GAL1, gal2 and gal3). Potent, selective antagonists are yet to be found for any of the cloned receptors. Major challenges in this field include linking the receptor clones with each of the known physiological actions of galanin and evaluating the evidence for additional galanin receptor subtypes.

Food intake in free-feeding and energy-deprived lean rats is mediated by the neuropeptide Y5 receptor.

The new neuropeptide Y (NPY) Y5 receptor antagonist CGP 71683A displayed high affinity for the cloned rat NPY Y5 subtype, but > 1, 000-fold lower affinity for the cloned rat NPY Y1, Y2, and Y4 subtypes. In LMTK cells transfected with the human NPY Y5 receptor, CGP 71683A was without intrinsic activity and antagonized NPY-induced Ca2+ transients. CGP 71683A was given intraperitoneally (dose range 1-100 mg/kg) to a series of animal models of high hypothalamic NPY levels. In lean satiated rats CGP 71683A significantly antagonized the increase in food intake induced by intracerebroventricular injection of NPY. In 24-h fasted and streptozotocin diabetic rats CGP 71683A dose-dependently inhibited food intake. During the dark phase, CGP 71683A dose-dependently inhibited food intake in free-feeding lean rats without affecting the normal pattern of food intake or inducing taste aversion. In free-feeding lean rats, intraperitoneal administration of CGP 71683A for 28 d inhibited food intake dose-dependently with a maximum reduction observed on days 3 and 4. Despite the return of food intake to control levels, body weight and the peripheral fat mass remained significantly reduced. The data demonstrate that the NPY Y5 receptor subtype plays a role in NPY-induced food intake, but also suggest that, with chronic blockade, counterregulatory mechanisms are induced to restore appetite.

Clinically significant gastroesophageal reflux in the at-risk premature neonate: relation to cognitive scores, days in the NICU, and total hospital charges.

OBJECTIVE: The principal objective of this retrospective, cohort study was to determine if clinically significant gastroesophageal reflux (GER) would impair the long-term cognitive and motor development of preterm infants. An additional objective was to determine the effects of clinically significant GER on the length of hospital stay and total hospital charges in preterm infants. STUDY DESIGN: The design was a retrospective, cohort study of 66 preterm infants, followed in the Neonatal Developmental Follow-Up Clinic of The Children's Hospital in Greenville, SC. Thirty-three premature infants with clinically significant GER met the following study criteria: birth dates, 1988 through 1994; lack of gastrointestinal anatomic defects; and lack of acute neurologic injury (defined as no intraventricular hemorrhage greater than Papile's grade I, no periventricular leukomalacia, no seizures, and no history of birth asphyxia). Clinically significant GER was defined as GER associated with moderate to severe apnea (n=29) or GER associated with moderate to severe feeding intolerance (n=4). The study patients were matched as closely as possible with 33 control premature infants for sex (except when twins were used), ethnicity, social risk, gestational age, birth weight, and Apgar scores at 1 and 5 minutes. Social risk was categorized using Hack's Social Risk Scale. Important covariates included apnea, home monitoring, and nasal continuous positive airway pressure. RESULTS: Neurodevelopmental test scores from 7 months of age through 2 years of age did not show any significant differences between premature infants with clinically significant GER and premature infants with no evidence of clinically significant GER. Total hospital charges were statistically different for the clinically significant GER infants and the nonclinically significant GER infants (median $112,916 versus median $63,928, p=0.01). Total neonatal intensive care unit length of stay measures were statistically different between the two groups (median 53 days versus median 40.5 days, p=0.01). CONCLUSION: Even though clinically significant GER may pose a substantial medical risk in premature infants, the long-term cognitive consequences appear to be negligible. Nevertheless, those premature infants with clinically significant GER do consume significantly more hospital resources than matched controls. Early diagnosis and intervention may possibly lessen the impact of medical costs and reduce length of hospital stay.

Molecular biology and pharmacology of multiple NPY Y5 receptor species homologs.

NPY is a 36-amino acid peptide which exerts its physiological effects through the activation of a family of G-protein coupled receptors. In vivo and in vitro characterization of the recently cloned rat Y5 receptor suggests that it is a primary mediator of NPY-induced feeding (Gerald et al., Nature 1996;382:168-171). We now report the molecular cloning and pharmacological characterization of the human, dog and mouse homologs of the Y5 receptor. With the exception of a 21 amino acid repeat in the amino terminus of the mouse Y5 receptor, the sequence of the four species homologs appear to be highly conserved, with 88% to 97% amino acid identities between any two species. Similarly, the pharmacological profiles of the four species homologs as determined in porcine 125I-PYY binding assays show a great deal of conservation, with the following rank order of affinity: human or porcine NPY, PYY, [Leu31,Pro34]NPY, NPY(2-36), human PP > human [D-Trp32]NPY > rat PP, C2-NPY. Northern blot analysis reveals that the Y5 receptor is widely distributed in the human brain, with the strongest signals detected in the cortex, putamen and caudate nucleus. The chromosomal localization of the human Y5 receptor, previously shown to be overlapping and in the opposite orientation to the Y1 receptor, is determined to be 4q31, the same locus as previously demonstrated for the human Y1 receptor (Herzog et al., J Biol Chem 1993;268:6703-6707), suggesting that these receptors may be coregulated. These Y5 species homologs along with corresponding animal models may be useful in the search for novel therapeutics in the treatment of obesity and related feeding disorders.

Cloned human and rat galanin GALR3 receptors. Pharmacology and activation of G-protein inwardly rectifying K+ channels.

The neuropeptide galanin has been implicated in the regulation of processes such as nociception, cognition, feeding behavior, and hormone secretion. Multiple galanin receptors are predicted to mediate its effects, but only two functionally coupled receptors have been reported. We now report the cloning of a third galanin receptor distinct from GALR1 and GALR2. The receptor, termed GALR3, was isolated from a rat hypothalamus cDNA library by both expression and homology cloning approaches. The rat GALR3 receptor cDNA can encode a protein of 370 amino acids with 35% and 52% identity to GALR1 and GALR2, respectively. Localization of mRNA by solution hybridization/RNase protection demonstrates that the GALR3 transcript is widely distributed, but expressed at low abundance, with the highest levels in the hypothalamus and pituitary. We also isolated the gene encoding the human homologue of GALR3. The human GALR3 receptor is 90% identical to rat GALR3 and contains 368 amino acids. Binding of porcine 125I-galanin to stably expressed rat and human GALR3 receptors is saturable (rat KD = 0.98 nM and human KD = 2.23 nM) and displaceable by galanin peptides and analogues in the following rank order: rat galanin, porcine galanin approximately M32, M35 approximately porcine galanin-(-7 to +29), galantide, human galanin > M40, galanin-(1-16) > [D-Trp2]galanin-(1-29), galanin-(3-29). This profile resembles that of the rat GALR1 and GALR2 receptors with the notable exception that human galanin, galanin-(1-16), and M40 show lower affinity at GALR3. In Xenopus oocytes, activation of rat and human GALR3 receptors co-expressed with potassium channel subunits GIRK1 and GIRK4 resulted in inward K+ currents characteristic of Gi/Go-coupled receptors. These data confirm the functional efficacy of GALR3 receptors and further suggest that GALR3 signaling pathways resemble those of GALR1 in that both can activate potassium channels linked to the regulation of neurotransmitter release.

Molecular biology and pharmacology of galanin receptors.

Galanin was first isolated 15 years ago. Diversity of galanin receptors has been suspected from the study of native tissues and functional responses to galanin and galanin-like peptides in vitro and in vivo. The recent application of molecular biologic techniques to clone galanin receptors has extended this diversity. So far, three galanin receptor subtypes, GALR1, GALR2, and GALR3, have been cloned from both human and rat. Their molecular structure, pharmacologic profiles, tissue distribution, and signal transduction properties have been partially elucidated.

Cloning and characterization of the human galanin GALR2 receptor.

We present the molecular cloning and characterization of the human galanin receptor, hGALR2. hGALR2 shares 85%, 39%, and 57% amino acid identities to rGALR2, hGALR1, and hGALR3, respectively. hGALR2, along with rGALR2, can be distinguished from the other cloned galanin receptors by a tolerance for both N-terminal extension and C-terminal deletion of galanin, as well as by a primary signaling mechanism involving phosphatidyl inositol hydrolysis and calcium mobilization. By RT-PCR, GALR2 mRNA was abundant in human hippocampus, hypothalamus, heart, kidney, liver, and small intestine. A weak GALR2 mRNA signal was detected in human retina, and no signal was detected in cerebral cortex, lung, spleen, stomach, or pituitary.

Expression cloning of a rat hypothalamic galanin receptor coupled to phosphoinositide turnover.

The neuropeptide galanin is widely distributed throughout the central and peripheral nervous systems and participates in the regulation of processes such as nociception, cognition, feeding behavior, and insulin secretion. Multiple galanin receptors are predicted to underlie its physiological effects. We now report the isolation by expression cloning of a rat galanin receptor cDNA distinct from GALR1. The receptor, termed GALR2, was isolated from a rat hypothalamus cDNA library using a 125I-porcine galanin (125I-pGAL) binding assay. The GALR2 cDNA encoded a protein of 372 amino acids exhibiting 38% amino acid identity with rat GALR1. Binding of 125I-pGAL to transiently expressed GALR2 receptors was saturable (KD = 0.15 nM) and displaceable by galanin peptides and analogues in rank order: porcine galanin approximately M32 approximately M35 approximately M40 >/= galanin-(1-16) approximately M15 approximately [D-Trp2]galanin-(1-29) > C7 >> galanin-(3-29). This profile resembles that of the rat GALR1 receptor with the notable exception that [D-Trp2]galanin exhibited significant selectivity for GALR2 over GALR1. Activation of GALR2 receptors with porcine galanin and other galanin analogues increased inositol phospholipid turnover and intracellular calcium levels in stably transfected Chinese hamster ovary cells and generated calcium-activated chloride currents in Xenopus oocytes, suggesting that the rat GALR2 receptor is primarily coupled to the activation of phospholipase C.

Distribution of the neuropeptide Y Y2 receptor mRNA in rat central nervous system.

Our group has recently reported the expression cloning of the human neuropeptide Y Y2 receptor DNA and subsequently the cloning of the rat homologue. These studies have made it possible to localize the mRNA encoding this NPY receptor subtype in rat tissues. We have, thus, carried out in situ hybridization studies, using radiolabeled oligonucleotide probes to the rat Y2 receptor mRNA, to determine the distribution of Y2 mRNA in rat brain and limited peripheral ganglia. Probe specificity was confirmed by testing antisense and sense probes in transfected cells. In rat brain, hybridization signals obtained with the antisense probes were discrete and were restricted to neuronal profiles in specific subregions of the cortex, hippocampus, amygdala, thalamus, hypothalamus, mesencephalon and pons. Among the regions exhibiting the most intense labeling were the CA3 region of the hippocampus, the arcuate nucleus of the hypothalamus and layer 3 of the piriform cortex. Other regions containing labeled neurons included the medial amygdala, the centromedial thalamic nucleus, the dorsal raphe, the dorsal motor nucleus of the vagus and the trigeminal ganglion. The present results indicate that the mRNA encoding the Y2 receptor is discretely localized in the rat brain and that the distribution is generally consistent with previous radioligand-binding studies. This study should help clarify the relationship between the Y2 receptor distribution and functional studies of NPY receptor subtype classification and provides further evidence for the involvement of the Y2 receptor in multiple physiological processes.

Modeling the G-protein-coupled neuropeptide Y Y1 receptor agonist and antagonist binding sites.

Neuropeptide Y (NPY) receptors belong to the G-protein-coupled receptor (GPCR) superfamily and mediate several physiological responses, such as blood pressure, food intake, sedation and memory retention. To understand the interactions between the NPY Y1 receptor subtype and its ligands, computer modeling was applied to the natural peptide agonist, NPY and a small molecule antagonist, BIBP3226. An agonist and antagonist binding domain was elucidated using mutagenesis data for the Y1 receptor as well as for other GPCR families. The agonist and antagonist ligands which were investigated appear to share common residues for their interaction within the transmembrane regions of the Y1 receptor structure, including Gln120, Asn283 and His306. This is in contrast to findings with tachykinin receptors where the binding domains of the non-peptide antagonists have very little in common with the binding domains of the agonist, substance-P. In addition, a hydrogen bond between the hydroxyl group of Tyr36 of NPY and the side chain of Gln219, an interaction that is absent in the model complex between Y1 and the antagonist BIBP3226, is proposed as one of the potential interactions necessary for receptor activation.