Neuropeptide Y-like immunoreactivity in schizophrenia. Relationships with clinical measures

Differential depletion of GluN2A induces heterogeneous schizophrenia-related phenotypes in mice

BACKGROUND

Schizophrenia, a debilitating psychiatric disorder, displays considerable interindividual variation in clinical presentations. The ongoing debate revolves around whether this heterogeneity signifies a continuum of severity linked to a singular causative factor or a collection of distinct subtypes with unique origins. Within the realm of schizophrenia, the functional impairment of GluN2A, a subtype of the NMDA receptor, has been associated with an elevated risk. Despite GluN2A's expression across various neuronal types throughout the brain, its specific contributions to schizophrenia and its involvement in particular cell types or brain regions remain unexplored.

METHODS

We generated age-specific, cell type-specific or brain region-specific conditional knockout mice targeting GluN2A and conducted a comprehensive analysis using tests measuring phenotypes relevant to schizophrenia.

FINDINGS

Through the induction of germline ablation of GluN2A, we observed the emergence of numerous schizophrenia-associated abnormalities in adult mice. Intriguingly, GluN2A knockout performed at different ages, in specific cell types and within distinct brain regions, we observed overlapping yet distinct schizophrenia-related phenotypes in mice.

INTERPRETATION

Our interpretation suggests that the dysfunction of GluN2A is sufficient to evoke heterogeneous manifestations associated with schizophrenia, indicating that GluN2A stands as a prominent risk factor and a potential therapeutic target for schizophrenia.

FUNDING

This project received support from the Shanghai Municipal Science and Technology Major Project (Grant No. 2019SHZDZX02) awarded to Y.C. and the Natural Science Foundation of Shanghai (Grant No. 19ZR1468600 and 201409003800) awarded to G.Y.

Vascular-related biomarkers in psychosis: a systematic review and meta-analysis

Background

While the molecular underpinnings of vascular dysfunction in psychosis are under active investigation, their implications remain unclear due to inconsistent and sometimes sparse observations. We conducted a comprehensive meta-analysis to critically assess the alterations of vascular-related molecules in the cerebrospinal fluid (CSF) and blood of patients with psychotic disorders compared with healthy individuals.

Methods

Databases were searched from inception to February 23, 2023. Meta-analyses were performed using a random-effects model. Meta-regression and subgroup analyses were conducted to assess the effects of clinical correlates.

Results

We identified 93 eligible studies with 30 biomarkers investigated in the CSF and/or blood. Among the biomarkers examined, psychotic disorders were associated with elevated CSF-to-serum albumin ratio (standardized mean difference [SMD], 0.69; 95% confidence interval [CI], 0.35-1.02); blood S100B (SMD, 0.88; 95% CI, 0.59-1.17), matrix metalloproteinase-9 (MMP-9; SMD, 0.66; 95% CI, 0.46-0.86), and zonulin (SMD, 1.17; 95% CI, 0.04-2.30). The blood levels of S100B, MMP-9, nerve growth factor (NGF), vascular endothelial growth factor (VEGF), intercellular adhesion molecule 1 (ICAM-1), and vascular adhesion molecule 1 (VCAM-1) were altered in patient subgroups differing in demographic and clinical characteristics. Blood S100B level was positively correlated with age and duration of illness. Substantial between-study heterogeneity was observed in most molecules.

Conclusion

The alterations in certain vascular-related fluid markers in psychotic disorders suggest disturbances in normal vascular structures and functions. However, not all molecules examined displayed clear evidence of changes. While potential impacts of clinical factors, including the administered treatment, were identified, the exploration remained limited. Further studies are needed to investigate the diverse patterns of expression, and understand how these abnormalities reflect the pathophysiology of psychosis and the impact of clinical factors.

Biomarkers in the cerebrospinal fluid of patients with psychotic disorders compared to healthy controls: a systematic review and meta-analysis

Psychotic disorders are severe mental disorders with poorly understood etiology. Biomarkers in the cerebrospinal fluid (CSF) could provide etiological clues and diagnostic tools for psychosis; however, an unbiased overview of CSF alterations in individuals with psychotic disorders is lacking. The objective of this study was to summarize all quantifiable findings in CSF from individuals with psychotic disorders compared to healthy controls (HC). Studies published before January 25th, 2023 were identified searching PubMed, EMBASE, Cochrane Library, Web of Science, ClinicalTrials.gov, and PsycINFO. Screening, full-text review, data extraction, and risk of bias assessments were performed by two independent reviewers following PRISMA guidelines. Findings in patients and healthy controls were compared and summarized using random-effects analyses and assessment of publication bias, subgroup and sensitivity analyses were performed. 145 studies, covering 197 biomarkers, were included, of which 163 biomarkers have not previously been investigated in meta-analyses. All studies showed some degree of bias. 55 biomarkers measured in CSF were associated with psychosis and of these were 15 biomarkers measured in ≥2 studies. Patients showed increased levels of noradrenaline (standardized mean difference/SMD, 0.53; 95% confidence interval/CI, 0.16 to 0.90) and its metabolite 3-methoxy-4-hydroxyphenylglycol (SMD, 0.30; 95% CI: 0.05 to 0.55), the serotonin metabolite 5-hydroxyindoleacetic acid (SMD, 0.11; 95% CI: 0.01 to 0.21), the pro-inflammatory neurotransmitter kynurenic acid (SMD, 1.58; 95% CI: 0.34 to 2.81), its precursor kynurenine (SMD,0.99; 95% CI: 0.60 to 1.38), the cytokines interleukin-6 (SMD, 0.58; 95% CI: 0.39 to 0.77) and interleukin-8 (SMD, 0.43; 95% CI: 0.24 to 0.62), the endocannabinoid anandamide (SMD, 0.78; 95% CI: 0.53 to 1.02), albumin ratio (SMD, 0.40; 95% CI: 0.08 to 0.72), total protein (SMD, 0.29; 95% CI: 0.16 to 0.43), immunoglobulin ratio (SMD, 0.45; 95% CI: 0.06 to 0.85) and glucose (SMD, 0.48; 95% CI: 0.01 to 0.94). Neurotensin (SMD, -0.67; 95% CI: -0.89 to -0.46) and γ-aminobutyric acid (SMD, -0.29; 95% CI: -0.50 to -0.09) were decreased. Most biomarkers showed no significant differences, including the dopamine metabolites homovanillic acid and 3,4-dihydroxyphenylacetic acid. These findings suggest that dysregulation of the immune and adrenergic system as well as blood-brain barrier dysfunction are implicated in the pathophysiology of psychotic disorders.

Changes In Plasma NPY, IL-1β And Hypocretin In People Who Died By Suicide

PURPOSE

There is growing evidence showing that inflammatory cytokines and neuropeptides may be involved in the pathophysiology of suicidal behavior. However, studies have yielded contradictory data, and no biological markers that help predict suicide have been identified. This study aimed to identify biological patterns, such as NPY, IL-1β and hypocretin plasma levels, in people who died by suicide.

PATIENTS AND METHODS

Twenty-two people who died by suicide compared with 22 controls matched for age and sex were studied. In suicide and control subjects, we estimated the levels of NPY, IL-1β and hypocretin in plasma using enzyme-linked immunosorbent assay. The data are presented as the median (25th-75th percentile).

RESULTS

We found (1) a significant elevation in plasma NPY levels in suicide subjects versus control subjects (suicide: 11.38 (9.380-16.55); controls: 8.95 (7.590-10.93); P=0.013), and plasma NPY concentrations were approximately 62% higher in suicide subjects than those in control subjects; (2) a significant decrease in plasma IL-1β concentrations between suicide and control subjects (suicide: 121.1 (82.97-143.0); controls: 425.9 (233.1-835.3); P<0.001) as well as a decrease in IL-1β concentrations by almost 80%; and (3) no significant difference in plasma hypocretin levels between suicide and control subjects (suicide: 16.62 (13.62-25.77); controls: 21.63 (14.97-29.72); P=0.356).

CONCLUSION

Our results suggest that plasma NPY and IL-1β were related with suicide behavior rather than to suicide causes or suicide method. Specific combinations of plasma biomarkers may discriminate between types of suicidal behaviors and indicate increased risk for future suicide attempts.

Neuropeptide Y, social function and long-term outcome in schizophrenia

There is a lack of biomarkers in schizophrenia and the mechanisms underlying the observed deficits in social functioning are poorly understood. This cohort study aimed to explore whether neurotransmitter neuropeptide Y (NPY) in cerebrospinal fluid (CSF) from patients with schizophrenia is correlated to social function and clinical variables. A further aim was to determine whether baseline levels of NPY were associated with subsequent 3-year outcome. Fifty-six consecutively admitted patients with schizophrenia were included and underwent lumbar puncture and symptom ratings before antipsychotic treatment. NPY levels in CSF were determined by radioimmunoassay. Social function (Social Competence and Social Interest) was assessed by Nurses' Observation Scale for Inpatient Evaluation while psychiatric symptoms were rated using the Comprehensive Psychopathological Rating Scale. Three-year outcome was assessed with the Strauss-Carpenter Outcome Scale. Cross-sectional analysis showed a correlation between level of NPY and Social Competence at index admission (r(s)=0.37, p<0.05). The longitudinal analysis (i.e., at the 3-year follow-up) indicated that, for each standard deviation increase in baseline NPY, there was an increased risk of being unemployed (odds ratio [OR] 2.02, 95% confidence interval [CI] 1.07-3.82), having moderate or severe symptoms (OR 3.09, CI 1.30-7.32) or being hospitalized at least 6 months the previous year (OR 3.24, CI 1.09-9.64). However, NPY was not correlated to Social Interest or clinical variables at index admission. In conclusion, NPY levels in CSF are correlated to Social Competence and seem to predict some aspects of longitudinal outcome in schizophrenia.

Convergent lines of evidence support CAMKK2 as a schizophrenia susceptibility gene

Genes that are differentially expressed between schizophrenia patients and healthy controls may have key roles in the pathogenesis of schizophrenia. We analyzed two large-scale genome-wide expression studies, which examined changes in gene expression in schizophrenia patients and their matched controls. We found calcium/calmodulin (CAM)-dependent protein kinase kinase 2 (CAMKK2) is significantly downregulated in individuals with schizophrenia in both studies. To seek the potential genetic variants that may regulate the expression of CAMKK2, we investigated the association between single-nucleotide polymorphisms (SNPs) within CAMKK2 and the expression level of CAMKK2. We found one SNP, rs1063843, which is located in intron 17 of CAMKK2, is strongly associated with the expression level of CAMKK2 in human brains (P=1.1 × 10(-6)) and lymphoblastoid cell lines (the lowest P=8.4 × 10(-6)). We further investigated the association between rs1063843 and schizophrenia in multiple independent populations (a total of 130 623 subjects) and found rs1063843 is significantly associated with schizophrenia (P=5.17 × 10(-5)). Interestingly, we found the T allele of rs1063843, which is associated with lower expression level of CAMKK2, has a higher frequency in individuals with schizophrenia in all of the tested samples, suggesting rs1063843 may be a causal variant. We also found that rs1063843 is associated with cognitive function and personality in humans. In addition, protein-protein interaction (PPI) analysis revealed that CAMKK2 participates in a highly interconnected PPI network formed by top schizophrenia genes, which further supports the potential role of CAMKK2 in the pathogenesis of schizophrenia. Taken together, these converging lines of evidence strongly suggest that CAMKK2 may have pivotal roles in schizophrenia susceptibility.

Cerebrospinal fluid neuropeptide Y-like immunoreactivity correlates with impulsive aggression in human subjects

BACKGROUND

Neurochemical studies have pointed to a modulatory role in human aggression for a number of central neurotransmitters; some (e.g., serotonin) appear to play an inhibitory role, while others (e.g., vasopressin) appear to play a facilitator role in the modulation of aggression. While recent animal studies of neuropeptide Y (NPY) have suggested a facilitator role for central NPY in the modulation of aggression, no human studies of central NPY have yet been reported regarding aggression.

METHODS

Basal lumbar cerebrospinal fluid (CSF) was obtained from 60 physically healthy subjects with personality disorder (PD) (n=40) and from healthy volunteers (n=20). These samples were then assessed for CSF NPY-like immunoreactivity (NPY-LI) and other neurotransmitter-related species in CSF and correlated with measures of aggression and impulsivity.

RESULTS

Cerebrospinal fluid NPY-LI was higher in PD subjects compared with healthy volunteers and in subjects with intermittent explosive disorder compared with those without intermittent explosive disorder. In PD subjects, CSF NPY-LI was directly correlated with composite measures of aggression and impulsivity and a composite measure of impulsive aggression. Group differences in CSF NPY-LI concentration were accounted for by measures of impulsive aggression.

CONCLUSIONS

These data suggest a direct relationship between CSF NPY-immunoreactivity concentration and measures of impulsive aggression in human subjects. This adds to the complex picture of the central neuromodulatory role of impulsive aggression in human subjects.

No association between a functional polymorphism in the promoter region of the neuropeptide Y gene (-485C>T) and schizophrenia

It has been suggested that hypoactivity of neuropeptide Y (NPY) may be involved in the pathophysiology of schizophrenia. A post-mortem study revealed a decreased level of NPY in the brain of patients with schizophrenia. An increased level of NPY after antipsychotic treatment was also reported in animal brain and cerebrospinal fluid of patients. Previously Itokawa et al. reported a positive association between the functional -485C>T polymorphism in the NPY gene and schizophrenia in a Japanese population. The aim of this study is to replicate their positive findings in an independent Japanese case-control sample. Our sample includes 260 patients with schizophrenia (DSM-IV) and 196 control subjects. No significant differences in distribution of genotype or allele frequencies between patients and controls were observed. Our results suggest that the NPY -485C>T polymorphism may not confer susceptibility to schizophrenia, at least in our sample. Further studies in larger samples are warranted.

Behavioral profiling of NPY in aggression and neuropsychiatric diseases

The abundantly expressed neuropeptide Y (NPY) has potent effects on feeding, body weight, and blood pressure, and exhibits important functions in various behavioral domains such as motor activity and anxiety. The potent neurotransmitter exerts its biological effects through at least five G-protein coupled receptors termed Y(1), Y(2), Y(4), Y(5), and y(6). The behavioral profile of NPY function has been extensively studied using traditional pharmacological and classic genetic animal models. Based on these studies, variations in the profile of NPY and its receptors have been found. To limit the variability and inconsistencies in the behavioral profile of NPY and to clarify its effects on certain domains in further detail, it is important to design a rational standardized strategy for behavioral testing, using a complement of different well-established and reproducible tests. This strategy can minimize the risk that false positive or false negative results lead to a contradictory and inconsistent behavioral characterization of NPY function. Ideally, such screening should be composed of an initial monitoring of general health, sensory functions, and motor abilities, before specific behavioral domains such as anxiety or aggression are investigated using a multi-tiered phenotyping approach. In this review, we will focus on a brief description of the latest insights into the behavioral profile of NPY in the selective lesser investigated domains such as aggression and depression-schizophrenia-related behaviors. We will combine this information with possible strategies to evaluate the different specific phenotypes in more detail.

Involvement of neuropeptide systems in schizophrenia: human studies

Neuropeptides are heterogeneously distributed throughout the digestive, circulatory, and nervous systems and serve as neurotransmitters, neuromodulators, and hormones. Neuropeptides are phylogenetically conserved and have been demonstrated to regulate numerous behaviors. They have been hypothesized to be pathologically involved in several psychiatric disorders, including schizophrenia. On the basis of preclinical data, numerous studies have sought to examine the role of neuropeptide systems in schizophrenia. This chapter reviews the clinical data, linking alterations in neuropeptide systems to the etiology, pathophysiology, and treatment of schizophrenia. Data for the following neuropeptide systems are included: arginine-vasopressin, cholecystokinin (CCK), corticotropin-releasing factor (CRF), interleukins, neuregulin 1 (NRG1), neurotensin (NT), neuropeptide Y (NPY), opioids, secretin, somatostatin, tachykinins, thyrotropin-releasing hormone (TRH), and vasoactive intestinal peptide (VIP). Data from cerebrospinal fluid (CSF), postmortem and genetic studies, as well as clinical trials are described. Despite the inherent difficulties associated with human studies (including small sample size, variable duration of illness, medication status, the presence of comorbid psychiatric disorders, and diagnostic heterogeneity), several findings are noteworthy. Postmortem studies support disease-related alterations in several neuropeptide systems in the frontal and temporal cortices. The strongest genetic evidence supporting a role for neuropeptides in schizophrenia are those studies linking polymorphisms in NRG1 and the CCKA receptor with schizophrenia. Finally, the only compounds that act directly on neuropeptide systems that have demonstrated therapeutic efficacy in schizophrenia are neurokinin receptor antagonists. Clearly, additional investigation into the role of neuropeptide systems in the etiology, pathophysiology, and treatment of schizophrenia is warranted.

The “Yoking” of glutamatergic brain mechanisms involved in controlling brain neuronal excitability and psychosis to brain mechanisms involved in appetite regulation: a new hypothesis on the origin of psychosis

The authors speculate that the human primate evolved psychosis generating brain mechanisms in the service of certain feeding behaviors (i.e., appetite, foraging) during the course of evolution. Furthermore, these "psychosis generating brain mechanisms" may have grown directly out of brain mechanisms servicing appetite, of which neuropeptide Y (NPY) played an important role. A case is made for an NPY contribution to the pathophysiology of psychosis. We hypothesize that the psychomimetic effects of NPY extend to supporting certain "psychomotor" functions that might have been useful for obtaining food resources in "stressful environments" (potentially food resource rich/predator-competitor dangerous). The "psychomotor" functions proposed include helping the evolving ancestral human primate overcome behavioral inhibitions and fears related to venturing into "stressful environments" (potentially food resource rich/predator-competitor dangerous) after their home ranges had been stripped of resources, by providing feelings of decreased anxiety (anxiolysis), infatigability, and, perhaps, even grandiose delusions of physical ability and supernatural supports. We further speculate that it is this NPY mechanism that in part becomes dysregulated in idiopathic psychotic disorders such as schizophrenia. The NPY connection with psychosis could theoretically account for the possible associations between weight changes and antipsychotic response (e.g. [Acta Psychiatr. Scand. 100 (1999) 3] reported by others and body mass index and cocaine-induced psychosis by our group (i.e. [Israel J. Psychiatr. (2004), in submission]).

The relationship of changes in leptin, neuropeptide Y and reproductive hormones to antipsychotic induced weight gain

OBJECTIVES

Weight gain is an important side effect of antipsychotic (AP) treatment. Weight is regulated by multiple systems, including leptin, neuropeptide Y (NPY) and gonadal steroids. The aim was to investigate whether AP-induced weight gain was related to leptin and NPY abnormalities and whether these were associated with a disruption of gonadal steroid production.

METHODS

Twenty two female patients with schizophrenia receiving standard AP treatment were studied over a 3-month period. Plasma leptin, NPY, gonadal steroids and their regulators were measured along with weight and BMI.

RESULTS

Weight, leptin and testosterone levels increased over time. There were significant relationships between a change in oestrogen levels and both a change in NPY levels and a change in BMI. Change in BMI, weight and leptin all correlated strongly with a change in the testosterone/luteinizing hormone ratio.

CONCLUSIONS

AP treatment results in increase in weight over time and this increase is accompanied by increased leptin levels. AP-induced weight gain is also associated with disruption of the hypothalamic-pituitary-gonadal axis. Altered regulation of NPY, either through abnormal leptin control or serotonin blockade, is a possible explanation for the effects of AP medication on both weight and gonadal steroid levels.

Neuropeptides involved in the pathophysiology of schizophrenia and major depression

The present review summarizes the findings on the role of neuropeptides in the pathophysiology of schizophrenia and major depression. Several neuropeptides as vasopressin and endorphins in particular, beta-endorphin and gamma-type endorphins, cholecystokinin (CCK), neurotensin, somatostatin and Neuropeptide Y have been implicated in schizophrenia. During the last decade, however, few attempts to explore the significance of most of these and other neuropeptides in the pathophysiology of the disease or their therapeutic potential are found in the literature. An exception is neurotensin, which exerts neuroleptic-like effects in animal studies, while CSF, brain and blood studies are inconclusive. Things are different in major depression. Here much attention is paid to the endocrine abnormalities found in this disorder in particular the increased activity of the hypothalamic-pituitary-adrenal (HPA) axis. Neuropeptides as corticotropin-releasing hormone (CRH), vasopressin and corticosteroids are implicated in the symptomatology of this disorder. As a consequence much work is going on investigating the influence of CRH and corticosteroid antagonists or inhibitors of the synthesis of corticosteroids as potential therapeutic agents. This review emphasizes the role of vasopressin in the increased activity of the HPA axis in major depression and suggests exploration of the influence of the now available non-peptidergic vasopressin orally active V1 antagonists.

Effects of typical and atypical antipsychotics on neuropeptide Y in rat brain tissue and microdialysates from ventral striatum

The main goal of this study was to investigate effects of typical (haloperidol) and atypical (risperidone) antipsychotic drugs on brain regional neuropeptide Y (NPY)-like immunoreactivity (-LI) tissue concentrations and on release of NPY-LI in freely moving rats. An additional aim was to explore the effect of d-amphetamine on NPY-LI release following pretreatment with typical and atypical antipsychotics. During a 4-week period, male Wistar rats were fed chow to which vehicle, risperidone (1.15 mg/100 g food or 2.3 mg/100 g food), or haloperidol (1.15 mg/100 g food) were added. In one series of experiments, the animals were sacrificed on day 30 with focused microwave irradiation, the brain regions dissected and extracted for radioimmunoassay of NPY-LI. In another experimental series, probes were inserted into the ventral striatum. The perfusates were collected at 60-min intervals; NPY-LI was determined by radioimmunoassay. Haloperidol significantly increased NPY-LI in hypothalamus and the occipital cortex. In contrast, haloperidol decreased tissue levels of NPY-LI in striatum. Moreover, haloperidol and risperidone also significantly decreased extracellular NPY-LI concentrations in the ventral striatum. d-amphetamine (1.5 mg/kg) significantly increased extracellular NPY-LI in the vehicle group. Both haloperidol and risperidone pretreatments abolished the effect of d-amphetamine. The results show that d-amphetamine as well as haloperidol and risperidone selectively and specifically affect NPY-LI concentrations in brain tissue and microdialysates and that the effect of d-amphetamine is abolished by both typical and atypical antipsychotics.

Inhibition of amphetamine- and apomorphine-induced behavioural effects by neuropeptide Y Y(1) receptor antagonist BIBO 3304

Neuropeptide Y (NPY) has an important role in the regulation of stress responses and feeding behaviour. There is evidence that some effects elicited by NPY occur due to modulation of action of regular neurotransmitters. The main objective of the present study was to test behavioural effects of the novel neuropeptide Y (NPY) Y(1) receptor antagonist (R)-N-[[4-(aminocarbonylaminomethyl)-phenyl]methyl]-N(2)-(diphe nylacetyl)-argininamide trifluoroacetate (BIBO 3304) on dopamine-dependent behaviour. Intracerebroventricular administration of BIBO 3304 (1, 10, 50 nmol) had no effect on locomotor activity as measured by number of rearings and number of squares visited in an open field test in rats, but at 50 nmol dose defecation was significantly increased. BIBO 3304 (10 nmol) reduced amphetamine-induced increases in horizontal and vertical activity whereas its S-configurated enantiomer BIBO 3457 was inactive. In an open field test BIBO 3304 (10 nmol) inhibited purposeless running in rats sensitized to direct dopaminergic agonist apomorphine (0.5 mg/kg, s.c.). BIBO 3304 (10 nmol but not 1 nmol, i.c.v.) reduced fighting in apomorphine-induced aggression paradigm. Apomorphine-induced aggression was reduced by another, structurally similar, but less potent NPY Y(1) receptor antagonist BIBP 3226 (10 nmol, i.c.v.). A lower dose of BIBP 3226 (1 nmol, i.c.v.) was inactive. Concomitant administration of BIBO 3304 (10 nmol) with low doses of apomorphine (0.5 mg/kg s.c.) over the course of 10 days failed to prevent the development of apomorphine-induced aggressiveness. These data demonstrate that behavioural response to indirectly (amphetamine) and directly (apomorphine) acting dopaminergic stimulants is inhibited by NPY Y(1) receptor antagonists and suggest that NPY Y(1) receptor activation might be important in pathophysiology of disorders associated with hyperactivity of dopaminergic pathways, such as psychosis, schizophrenia and drug abuse. We propose that the effects of BIBO 3304 on amphetamine/apomorphine-induced locomotion and apomorphine-induced aggressiveness are due to modulation of postsynaptic dopaminergic responses rather than direct effects of NPY Y(1) receptor antagonists on dopamine or NPY release.

Effects of acute or long-term treatment with chlorpromazine, haloperidol or sulpiride on neuropeptide Y-like immunoreactivity concentrations in the nucleus accumbens of rat

The effects of acute, subchronic ( 14 days) or chronic (28 days) intraperitoneal (i.p.) administration of chlorpromazine (2 or 10 mg/kg), haloperidol (0.5 or 2 mg/kg) or sulpiride (50 or 100 mg/kg) on the neuropeptide Y (NPY) system in the rat nucleus accumbens were studied. NPY-like immunoreactivity (NPY-LI) decreased in a dose- and time-dependent manner, and was the lowest after haloperidol. NPY-LI levels increased 8 days after withdrawal of chronic drugs treatment. Acute administration of haloperidol reduced NPY mRNA, while Subchronic treatment did not change it. Subchronic i.p. administration of the dopamine D1-like antagonist SCH 23390 (1 mg/kg) reduced NPY-LI levels but the alpha1-adrenergic antagonist prazosin (0.2 mg/kg) had no effect. The effect of sulpiride coadministered with SCH 23390 was greater than that of SCH 23390 alone, while prazosin coadministered with sulpiride insignificantly reduced the effect of sulpiride. The dopamine D2/D3 agonist quinpirole given as a single injection (3 mg/kg) did not alter NPY-LI content by itself but antagonized the chlorpromazine-induced decrease and attenuated the haloperidol-induced decrease. Our findings indicate that the accumbens NPY system is markedly affected by the antipsychotics studied, and suggest that their effects may be in part mediated by blockade of D2-like (D2, D3) and D1 dopaminergic receptors.

The effects of acute phencyclidine treatment on neuropeptide Y (NPY) neuronal system in the rat arcuate nucleus studied by immunocytochemistry and in situ hybridization

Phencyclidine (PCP) is a dissociative drug and an antagonist of N-methyl-D-aspartate (NMDA) receptor. The effects of PCP treatment on neuropeptide Y (NPY) system in the arcuate nucleus of the rat hypothalamus were examined both by immunocytochemistry and in situ hybridization. In acute PCP-treated rats, the NPY-immunoreactive perikarya appeared in the arcuate nucleus but no perikarya were detected in controls, without colchicine pretreatment. The signals of NPY mRNA by in situ hybridization increased in the PCP-treated rats than those of controls. These results suggest that the NPY system in the arcuate nucleus might be partly controlled by glutamatergic neurons.

Neuropeptide Y-mediated enhancement of NMDA-stimulated [3H]dopamine release from rat prefrontal cortex is reversed by sigma1 receptor antagonists

Sigma (sigma) receptors are located in limbic areas, including the prefrontal cortex, where decreased dopamine levels have been linked to negative symptoms. Although the endogenous ligands for sigma receptors are unknown, neuropeptide Y (NPY) has been named as the potential endogenous agonist at these receptors. NPY enhanced NMDA-stimulated [3H]dopamine release in rat prefrontal cortex. This was in contrast to the inhibition produced by the sigma agonists (+)pentazocine and BD737. However, four sigma antagonists, including one which is sigma1 selective, that reverse (+)pentazocine- or BD737-mediated inhibition all reversed the NPY-mediated enhancement. In addition, PYX-1, a Y receptor antagonist, reversed both the (+)pentazocine- and BD737-mediated inhibition and the NPY-mediated enhancement of release. Peptide YY (PYY), [Leu31,Pro34]NPY and NPY(13-36) did not mimic the effect of NPY. Our findings are consistent with NPY acting as an endogenous ligand for a subtype of sigma receptor with characteristics different from Y1, Y2 and Y3 receptors but sensitive to PYX-1. These findings suggest a role for NPY, via sigma receptors, as a modulator of dopamine levels in the prefrontal cortex.

Phencyclidine alters regional concentrations of neuropeptide Y and peptide YY in rat brain

The psychotomimetic effects of Phencyclidine (PCP) often have a delayed onset and extend far from the time plasma drug levels reach their peak. PCP at a low dose is considered selective for actions on the N-methyl-D-aspartate-PCP receptor. We evaluated effects of PCP (2 and 10 mg/kg, IP) on regional content of neuropeptide Y (NPY)-like immunoreactivity (LI) and peptide YY (PYY)-LI, in the rat brain. Thirty minutes after administration of PCP, NPY-LI levels were significantly elevated in some limbic structures following both doses. A significant, widespread increase in NPY-LI levels was induced 2 hours after administration of the higher dose of PCP. On the contrary, NPY-LI was significantly decreased in a number of the regions 24 hours after PCP. The extent of reduction was less following the higher dose of PCP than following the lower dose. PCP did not cause a consistent effect on PYY-LI. The findings suggest that effects of PCP on brain NPY content might depend on the dose and the interval between administration of the drug and sacrifice.

CSF of neuroleptic-naive first-episode schizophrenic patients: levels of biogenic amines, substance P, and peptides derived from chromogranin A (GE-25) and secretogranin II (secretoneurin)

Lumbar cerebrospinal fluid (CSF) was collected from controls and neuroleptic-naive patients with their first acute schizophrenic episode. The CSF was analyzed for several biogenic amines and their metabolites [dopamine,dihydroxyphenylacetic acid (DOPAC), noradrenaline, 5-hydroxytryptamine (5-HT), 5-hydroxyindolacetic acid (5-HIAA)]. For these transmitters, which are stored and secreted from synaptic vesicles, there was no significant difference between controls and schizophrenic patients. As constituents of large dense-core vesicles substance P (SP) and GE-25 (derived from chromogranin A)-and secretoneurin (derived from secretogranin 11)-immunoreactivities were determined. SP-like immunoreactivity levels did not differ between controls and patients; however, GE-25 was elevated and especially the GE-25/secretoneurin ratio was significantly (p < .001) higher in patients. Characterization of the immunoreactivities by high-performance liquid chromatography did not reveal any difference between patients (n = 3) and controls in the processing of the two proproteins chromogranin A and secretogranin II. These data indicate that proteolytic processing of the two widespread constituents of large dense-core vesicles, i.e., chromogranin A and secretogranin II, is not altered in schizophrenic patients. The increase in the chromogranin A /secretoneurin ratio in schizophrenic patients deserves further investigation in order to elucidate its possible pathogenetic significance.

Increases in cortical neuropeptide Y and somatostatin concentrations following haloperidol-depot treatment in rats

The concentrations of neuropeptide Y (NPY) and somatostatin (SS) have been said to be altered in the brain and cerebrospinal fluid of schizophrenic patients. This alteration could result from the neuroleptic treatment. Therefore, it is of interest to evaluate effects of long-term treatment with neuroleptics on the peptide concentrations in the brain. Haloperidol (HPD) is one of the most frequently used neuroleptics for the treatment of schizophrenia. We determined regional brain levels of NPY and SS following HPD administration in the rat. A single intraperitoneal injection of HPD, at a dose of 1 mg/kg, did not affect peptide levels in the brain regions studied. Four weeks after an intramuscular deposit injection of HPD decanoate, 50 mg/kg, NPY concentrations were increased in a number of areas of the cerebral cortex. SS content was also significantly increased in the lateral prefrontal cortex and anterior cingulate cortex. Both peptide levels were decreased in the striatum. These results suggest that the reduction found in these peptides' levels in the cerebral cortex of the brain from schizophrenic patients may not be the consequence of HPD treatment and that these peptides' levels might be increased in the cerebral cortex of the brain of schizophrenic patients following the treatment with HPD.

Central nervous system pharmacology of neuropeptide Y

Neuropeptide Y (NPY) is a 36-amino acid peptide belonging to the pancreatic polypeptide family that has marked and diverse biological activity across species. NPY originally was isolated from mammalian brain tissue somewhat more than 10 years ago and, since that time, has been the subject of numerous scientific publications. NPY and its proposed three receptors (Y1, Y2 and Y3) are relatively abundant in and uniquely distributed throughout the brain and spinal cord. This review will highlight the results from a number of research-oriented studies that have examined how NPY is involved in CNS function and behavior, and how these studies may relate to the possible development of medicines, either NPY-like agonists or antagonists, directed towards the treatment of disorders such as anxiety, pain, hypertension, schizophrenia, memory dysfunction, abnormal eating behavior and depression.

Micropurification of two human cerebrospinal fluid proteins by high performance electrophoresis chromatography

Using C8 reversed-phase HPLC in conjunction with sodium dodecyl sulfate-polyacrylamide gel electrophoresis, we have fractionated proteins contained in human CSFs obtained from patients with schizophrenic disorders. When these proteins were electrophoretically blotted onto polyvinylidene difluoride membrane for direct N-terminal amino acid sequencing, several CSF proteins were identified; these included albumin, transferrin, apolipoprotein A-I, beta 2-microglobulin, and prealbumin. We have also identified two structurally related human CSF proteins designated cerebrin 28 (M(r) 28,000) and cerebrin 30 (M(r) 30,000) that have an N-terminal amino acid sequence of NH2-APPAQVSVQPNF and NH2-APEAQVSVQPLFXQ, respectively. Comparison of these sequences with existing database at Protein Identification Resource (R 32.0), GenBank (R 72.0), SWISS-PROT (R 22.0), and EMBL (R 31.0) indicated that they are unique proteins. These proteins were subsequently purified by high performance electrophoresis chromatography (HPEC) using an Applied Biosystems 230A HPEC system. A specific polyclonal antibody was prepared and an ELISA was established for cerebrin 30. It was noted that HPEC is a powerful tool to purify microgram quantities of proteins from human, rabbit, and rat CSFs. Using such a system, we have been able to micropurify as many as 10 proteins simultaneously in a single experiment because the elution of proteins occurred strictly according to their molecular weights. More importantly, we routinely obtained a recovery of > 90%. The potential use of this technology for micropurification of proteins was discussed.

Characterization of phencyclidine-induced effects on neuropeptide Y systems in the rat caudate-putamen

Multiple administrations of the psychotomimetic drug, phencyclidine-HCI (PCP), decreased striatal neuropeptide Y-like immunoreactivity (NPY-LI) levels in a dose-dependent manner. Single or multiple PCP administrations decreased striatal NPY levels after 10-12 h; levels returned to control 24 h after a single dose or 58 h after multiple doses. In contrast, no significant changes were seen in nigral NPY levels with either acute or multiple-dose PCP treatments. The role of monoamine, sigma or opioid receptors in PCP-induced striatal NPY changes was evaluated. When administered alone, the alpha 1-adrenergic antagonist, prazosin, the sigma antagonist, BMY 14802, and the dopamine D2 antagonist, sulpiride decreased striatal NPY levels; however, only prazosin and the dopamine D1 antagonist, SCH 23390, significantly attenuated PCP-induced changes. Administration of the gamma-aminobutyric acid transaminase (GABA-T) inhibitors, amino-oxyacetic acid (AOAA) or gamma-vinyl-GABA (GVG, vigabatrin, MDL 71,754) alone had no effect on striatal NPY-LI levels while administration of these indirect GABA agonists prior to or concurrently with PCP treatment completely blocked PCP-induced changes in striatal NPY-LI levels. The effect of the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist, MK-801, on striatal NPY-LI content resembled that of PCP and was also blocked by the two indirect GABA agonists. These data suggest that NPY systems are modulated by glutamatergic activity (specifically by the NMDA receptor) and that the interaction between these two transmitter systems is mediated by GABAergic mechanisms.

CSF chromogranin A-like immunoreactivity in schizophrenia: relationships with REM latency and slow wave sleep

Chromogranin A (CgA) is a calcium binding protein and a precursor of modulatory peptides in the brain. We measured CgA-like immunoreactivity (CgA-LI) in cerebrospinal fluid (CSF) in 15 male schizophrenic patients (diagnosed by DSM-III-R criteria) after 3 nights of polysomnography. Patients had been drug free for at least 33 days. Our earlier report that CSF CgA-LI in schizophrenic patients correlated significantly with negative symptoms and ventricle-brain ratios, which have been related to slow wave sleep, raised the possibility that CgA-LI might relate to slow wave sleep. CSF CgA-LI was significantly correlated with stage 4 sleep and rapid eye movement latency. Whether these positive relationships between CSF CgA-LI and electroencephalographic sleep measures are specific for schizophrenia awaits further study.

CSF chromogranin A-like immunoreactivity in schizophrenia. Assessment of clinical and biochemical relationships

Chromogranin A (CgA) is co-released with catecholamines and peptides and has a wide distribution in the brain. Chromogranin A provides a measure of tonic arousal. CSF CgA-like immunoreactivity (CgA-LI) was studied in 42 drug-free male schizophrenic patients. 33 of these patients were first studied during chronic haloperidol maintenance treatment. Withdrawal from haloperidol maintenance treatment was associated with a significant increase in CSF CgA-LI, particularly in the patients who did not relapse. Contrary to expectation CSF CgA-LI was higher in drug-free patients who slept longer the night before the lumbar puncture. Significant relationships were observed between CSF CgA-LI and CSF homovanillic acid, acetylcholinesterase, neuropeptide Y-LI and 5-hydroxy-indole acetic acid, but not with CSF norepinephrine or 3-methoxy-4-hydroxyphenylglycol. Ventricular brain ratios correlated negatively with CSF CgA-LI levels.