Embryonic expression of vasoactive intestinal peptide (VIP) and VIP receptor genes

Overexpression of VIPR2 in mice results in microencephaly with paradoxical increased white matter volume

Large scale studies in populations of European and Han Chinese ancestry found a series of rare gain-of-function microduplications in VIPR2, encoding VPAC2, a receptor that binds vasoactive intestinal peptide and pituitary adenylate cyclase-activating polypeptide with high affinity, that were associated with an up to 13-fold increased risk for schizophrenia. To address how VPAC2 receptor overactivity might affect brain development, we used a well-characterized Nestin-Cre mouse strain and a knock-in approach to overexpress human VPAC2 in the central nervous system. Mice that overexpressed VPAC2 were found to exhibit a significant reduction in brain weight. Magnetic resonance imaging analysis confirmed a decrease in brain size, a specific reduction in the hippocampus grey matter volume and a paradoxical increase in whole-brain white matter volume. Sex-specific changes in behavior such as impaired prepulse inhibition and contextual fear memory were observed in VPAC2 overexpressing mice. The data indicate that the VPAC2 receptor may play a critical role in brain morphogenesis and suggest that overactive VPAC2 signaling during development plays a mechanistic role in some forms of schizophrenia.

Identification of VIPR2 rare and common variants in the Chinese Han population with schizophrenia

Introduction

Schizophrenia is a severe and chronic psychiatric disorder with hereditary risk up to 80% as previous studies indicated. Several researches have demonstrated a significant association between schizophrenia and microduplications that overlap the vasoactive intestinal peptide receptor 2 gene (VIPR2).

Methods

To further investigate potential causal VIPR2 gene variants, all exons and un-translated portions of the VIPR2 gene were sequenced using amplicon targeted resequencing in 1804 Chinese Han patients with schizophrenia and 996 healthy counterparts in the present study.

Results

Nineteen rare non-synonymous mutations and 1 frameshift deletion was identified for schizophrenia, among which 5 variants have never been reported so far. Frequencies of rare non-synonymous mutations were significantly different between the two groups. Specifically, the non-synonymous mutation rs78564798 (P_allele = 0.006) as well as two rare variations in the VIPR2 gene's introns (rs372544903, P_allele = 0.026 and a novel mutation, chr7:159034078, GRCh38, P_allele = 0.048) were significantly associated with schizophrenia.

Discussion

Our findings add new evidence that the functional and probable causative variants of VIPR2 gene may play an important role in susceptibility to schizophrenia. Further studies on validations of VIPR2's function in the etiology of schizophrenia are warranted.

Generation of KS-133 as a Novel Bicyclic Peptide with a Potent and Selective VIPR2 Antagonist Activity that Counteracts Cognitive Decline in a Mouse Model of Psychiatric Disorders

Worldwide, more than 20 million people suffer from schizophrenia, but effective and definitive new therapeutic drugs/treatments have not been established. Vasoactive intestinal peptide receptor 2 (VIPR2) might be an attractive drug target for the treatment of schizophrenia because both preclinical and clinical studies have demonstrated a strong link between high expression/overactivation of VIPR2 and schizophrenia. Nevertheless, VIPR2-targeting drugs are not yet available. VIPR2 is a class-B G protein-coupled receptor that possesses high structural homology to its subtypes, vasoactive intestinal peptide receptor 1 (VIPR1) and pituitary adenylate cyclase-activating polypeptide type-1 receptor (PAC1). These biological and structural properties have made it difficult to discover small molecule drugs against VIPR2. In 2018, cyclic peptide VIpep-3, a VIPR2-selective antagonist, was reported. The aim of this study was to generate a VIpep-3 derivative for in vivo experiments. After amino acid substitution and structure optimization, we successfully generated KS-133 with 1) a VIPR2-selective and potent antagonistic activity, 2) at least 24 h of stability in plasma, and 3) in vivo pharmacological efficacies in a mouse model of psychiatric disorders through early postnatal activation of VIPR2. To the best of our knowledge, this is the first report of a VIPR2-selective antagonistic peptide that counteracts cognitive decline, a central feature of schizophrenia. KS-133 may contribute to studies and development of novel schizophrenia therapeutic drugs that target VIPR2.

Probing the VIPR2 Microduplication Linkage to Schizophrenia in Animal and Cellular Models

Pituitary adenylate cyclase-activating polypeptide (PACAP, gene name ADCYAP1) is a multifunctional neuropeptide involved in brain development and synaptic plasticity. With respect to PACAP function, most attention has been given to that mediated by its specific receptor PAC1 (ADCYAP1R1). However, PACAP also binds tightly to the high affinity receptors for vasoactive intestinal peptide (VIP, VIP), called VPAC1 and VPAC2 (VIPR1 and VIPR2, respectively). Depending on innervation patterns, PACAP can thus interact physiologically with any of these receptors. VPAC2 receptors, the focus of this review, are known to have a pivotal role in regulating circadian rhythms and to affect multiple other processes in the brain, including those involved in fear cognition. Accumulating evidence in human genetics indicates that microduplications at 7q36.3, containing VIPR2 gene, are linked to schizophrenia and possibly autism spectrum disorder. Although detailed molecular mechanisms have not been fully elucidated, recent studies in animal models suggest that overactivation of the VPAC2 receptor disrupts cortical circuit maturation. The VIPR2 linkage can thus be potentially explained by inappropriate control of receptor signaling at a time when neural circuits involved in cognition and social behavior are being established. Alternatively, or in addition, VPAC2 receptor overactivity may disrupt ongoing synaptic plasticity during processes of learning and memory. Finally, in vitro data indicate that PACAP and VIP have differential activities on the maturation of neurons via their distinct signaling pathways. Thus perturbations in the balance of VPAC2, VPAC1, and PAC1 receptors and their ligands may have important consequences in brain development and plasticity.

[Pathophysiological implication of the VPAC2 receptor in psychiatric disorders]

The advent of the genomic era has led to the discovery of linkages of several genes and pathways to schizophrenia and autism spectrum disorder (ASD) that may serve as new biomarkers or therapeutic targets for these diseases. Two large-scale genetic studies published early in 2011 provided evidence that functional microduplications at 7q36.3, containing VIPR2, are a risk factor for schizophrenia. 7q36.3 microduplications were also reported to be significantly increased in ASD. VIPR2 encodes VPAC2, a seven transmembrane heterotrimeric G protein-coupled receptor that binds two homologous neuropeptides with high affinity, PACAP and VIP. These clinical studies demonstrate a VIPR2 genetic linkage to schizophrenia and ASD and should lead to novel insights into the etiology of these mental health disorders. However, the mechanism by which overactive VPAC2 signaling may lead to schizophrenia and ASD is unknown. In the present review, we will describe recent advances in the genetics of schizophrenia and attempt to discuss the pathophysiological role of altered VPAC2 signaling in psychiatric disorders.

Reductions in synaptic proteins and selective alteration of prepulse inhibition in male C57BL/6 mice after postnatal administration of a VIP receptor (VIPR2) agonist

RATIONALE

An abundance of genetic and epidemiologic evidence as well as longitudinal neuroimaging data point to developmental origins for schizophrenia and other mental health disorders. Recent clinical studies indicate that microduplications of VIPR2, encoding the vasoactive intestinal peptide (VIP) receptor VPAC2, confer significant risk for schizophrenia and autism spectrum disorder. Lymphocytes from patients with these mutations exhibited higher VIPR2 gene expression and VIP responsiveness (cAMP induction), but mechanisms by which overactive VPAC2 signaling may lead to these psychiatric disorders are unknown.

OBJECTIVES

We subcutaneously administered the highly selective VPAC2 receptor agonist Ro 25-1553 to C57BL/6 mice from postnatal day 1 (P1) to P14 to determine if overactivation of VPAC2 receptor signaling during postnatal brain maturation affects synaptogenesis and selected behaviors.

RESULTS

Western blot analyses on P21 revealed significant reductions of synaptophysin and postsynaptic density protein 95 (PSD-95) in the prefrontal cortex, but not in the hippocampus in Ro 25-1553-treated mice. The same postnatally restricted treatment resulted in a disruption in prepulse inhibition of the acoustic startle measured in adult mice. No effects were observed in open-field locomotor activity, sociability in the three-chamber social interaction test, or fear conditioning or extinction.

CONCLUSION

Overactivation of the VPAC2 receptor in the postnatal mouse results in a reduction in synaptic proteins in the prefrontal cortex and selective alterations in prepulse inhibition. These findings suggest that the VIPR2-linkage to mental health disorders may be due in part to overactive VPAC2 receptor signaling during a critical time of synaptic maturation.

Role of G protein-coupled vasoactive intestinal peptide receptors in HIV integration

The pathogenesis of HIV infection is closely linked to the replication of the virus in vivo. Even though the progress in anti-HIV-1 chemotherapy in the past several years has been dramatic, the efficient protection against HIV-1 infection still remains one of the most important global challenges. The complete blockage of AIDS progression appears to be difficult with current treatment due to the rapid occurrence of viral drug-resistance, increasing cost and the likelihood of adverse side effects. Furthermore, although originally regarded with high hope, development of a suitable vaccine appears to be years away. The purpose of this article is to describe previous findings regarding a potentially important role of the vasoactive intestinal peptide/pituitary adenylate cyclase-activating polypeptide (VPAC) family of G protein-coupled receptors in HIV-1 infection, to provide evidence for the involvement of these receptors in providing signals that can control the integration of the virus into the host DNA and to report new findings that support a role for VPAC receptors in the facilitation of HIV integration.

Select cognitive deficits in vasoactive intestinal peptide deficient mice

Background

The neuropeptide vasoactive intestinal peptide (VIP) is widely distributed in the adult central nervous system where this peptide functions to regulate synaptic transmission and neural excitability. The expression of VIP and its receptors in brain regions implicated in learning and memory functions, including the hippocampus, cortex, and amygdala, raise the possibility that this peptide may function to modulate learned behaviors. Among other actions, the loss of VIP has a profound effect on circadian timing and may specifically influence the temporal regulation of learning and memory functions.

Results

In the present study, we utilized transgenic VIP-deficient mice and the contextual fear conditioning paradigm to explore the impact of the loss of this peptide on a learned behavior. We found that VIP-deficient mice exhibited normal shock-evoked freezing behavior and increases in corticosterone. Similarly, these mutant mice exhibited no deficits in the acquisition or recall of the fear-conditioned behavior when tested 24-hours after training. The VIP-deficient mice exhibited a significant reduction in recall when tested 48-hours or longer after training. Surprisingly, we found that the VIP-deficient mice continued to express circadian rhythms in the recall of the training even in those individual mice whose wheel running wheel activity was arrhythmic. One mechanistic explanation is suggested by the finding that daily rhythms in the expression of the clock gene Period2 continue in the hippocampus of VIP-deficient mice.

Conclusion

Together these data suggest that the neuropeptide VIP regulates the recall of at least one learned behavior but does not impact the circadian regulation of this behavior.

Deficits in social behavior and reversal learning are more prevalent in male offspring of VIP deficient female mice

Blockage of vasoactive intestinal peptide (VIP) receptors during early embryogenesis in the mouse has been shown to result in developmental delays in neonates, and social behavior deficits selectively in adult male offspring. Offspring of VIP deficient mothers (VIP +/-) also exhibited developmental delays, and reductions in maternal affiliation and play behavior. In the current study, comparisons among the offspring of VIP deficient mothers (VIP +/-) mated to VIP +/- males with the offspring of wild type (WT) mothers mated to VIP +/- males allowed assessment of the contributions of both maternal and offspring VIP genotype to general health measures, social behavior, fear conditioning, and spatial learning and memory in the water maze. These comparisons revealed few differences in general health among offspring of WT and VIP deficient mothers, and all offspring exhibited normal responses in fear conditioning and in the acquisition phase of spatial discrimination in the water maze. WT mothers produced offspring that were normal in all tests; the reduced VIP in their VIP +/- offspring apparently did not contribute to any defects in the measures under study. However, regardless of their own VIP genotype, all male offspring of VIP deficient mothers exhibited severe deficits in social approach behavior and reversal learning. The deficits in these behaviors in the female offspring of VIP deficient mothers were less severe than in their male littermates, and the extent of their impairment was related to their own VIP genotype. This study has shown that intrauterine conditions had a greater influence on behavioral outcome than did genetic inheritance. In addition, the greater prevalence of deficits in social behavior and the resistance to change seen in reversal learning in the male offspring of VIP deficient mothers indicate a potential usefulness of the VIP knockout mouse in furthering the understanding of neurodevelopmental disorders such as autism.

Regardless of genotype, offspring of VIP-deficient female mice exhibit developmental delays and deficits in social behavior

Pharmacological studies indicate that vasoactive intestinal peptide (VIP) may be necessary for normal embryonic development in the mouse. For example, VIP antagonist treatment before embryonic day 11 resulted in developmental delays, growth restriction, modified adult brain chemistry and reduced social behavior. Here, developmental milestones, growth, and social behaviors of neonates of VIP-deficient mothers (VIP +/-) mated to VIP +/- males were compared with the offspring of wild type mothers (VIP +/+) mated to VIP +/+ and +/- males, to assess the contributions of both maternal and offspring VIP genotype. Regardless of their own genotype, all offsprings of VIP-deficient mothers exhibited developmental delays. No delays were seen in the offspring of wild type mothers, regardless of their own genotype. Body weights were significantly reduced in offspring of VIP-deficient mothers, with VIP null (-/-) the most affected. Regardless of genotype, all offspring of VIP-deficient mothers expressed reduced maternal affiliation compared with wild type offspring of wild type mothers; +/- offspring of wild type mothers did not differ in maternal affiliation from their wild type littermates. Play behavior was significantly reduced in all offsprings of VIP-deficient mothers. Maternal behavior did not differ between wild type and VIP-deficient mothers, and cross-fostering of litters did not change offspring development, indicating that offspring deficits were induced prenatally. This study illustrated that the VIP status of a pregnant mouse had a greater influence on the growth, development and behavior of her offspring than the VIP genotype of the offspring themselves. Deficiencies were apparent in +/+, +/- and -/- offspring born to VIP-deficient mothers; no deficiencies were apparent in +/- offspring born to normal mothers. These results underscore the significant contribution of the uterine environment to normal development and indicate a potential usefulness of the VIP knockout mouse in furthering the understanding of neurodevelopmental disorders with social behavior deficits such as autism.

Blockage of VIP during mouse embryogenesis modifies adult behavior and results in permanent changes in brain chemistry

Vasoactive intestinal peptide (VIP) regulates growth and development during the early postimplantation period of mouse embryogenesis. Blockage of VIP with a VIP antagonist during this period results in growth restriction, microcephaly, and developmental delays. Similar treatment of neonatal rodents also causes developmental delays and impaired diurnal rhythms, and the adult brains of these animals exhibit neuronal dystrophy and increased VIP binding. These data suggest that blockage of VIP during the development of the nervous system can result in permanent changes to the brain. In the current study, pregnant mice were treated with a VIP antagonist during embryonic days 8 through 10. The adult male offspring were examined in tests of novelty, paired activity, and social recognition. Brain tissue was examined for several measures of chemistry and gene expression of VIP and related compounds. Glial cells from the cortex of treated newborn mice were plated with neurons and examined for VIP binding and their ability to enhance neuronal survival. Treated adult male mice exhibited increased anxiety-like behavior and deficits in social behavior. Brain tissue exhibited regionally specific changes in VIP chemistry and a trend toward increased gene expression of VIP and related compounds that reached statistical significance in the VIP receptor, VPAC-1, in the female cortex. When compared to control astrocytes, astrocytes from treated cerebral cortex produced further increases in neuronal survival with excess synaptic connections and reduced VIP binding. In conclusion, impaired VIP activity during mouse embryogenesis resulted in permanent changes to both adult brain chemistry/cell biology and behavior with aspects of autism-like social deficits.

Neonatal mice of the Down syndrome model, Ts65Dn, exhibit upregulated VIP measures and reduced responsiveness of cortical astrocytes to VIP stimulation

The Ts65Dn segmental mouse model of Down syndrome (DS) possesses a triplication of the section of chromosome 16 that is most homologous to the human chromosome 21 that is trisomic in DS. This model exhibits many of the characteristics of DS including small size, developmental delays, and a decline of cholinergic systems and cognitive function with age. Recent studies have shown that vasoactive intestinal peptide (VIP) systems are upregulated in aged Ts65Dn mice and that VIP dysregulation during embryogenesis is followed by the hypotonia and developmental delays as seen in both DS and in Ts65Dn mice. Additionally, astrocytes from aged Ts65Dn brains do not respond to VIP stimulation to release survival-promoting substances. To determine if VIP dysregulation is age-related in Ts65Dn mice, the current study examined VIP and VIP receptors (VPAC-1 and VPAC-2) in postnatal day 8 Ts65Dn mice. VIP and VPAC-1 expression was significantly increased in the brains of trisomic mice compared with wild-type mice. VIP-binding sites were also significantly increased in several brain areas of young Ts65Dn mice, especially in the cortex, caudate/putamen, and hippocampus. Further, in vitro treatment of normal neurons with conditioned medium from VIP-stimulated Ts65Dn astrocytes from neonatal mice did not enhance neuronal survival. This study indicates that VIP anomalies are present in neonatal Ts65Dn mice, a defect occurs in the signal transduction mechanism of the VPAC-1 VIP receptor, cortical astrocytes from neonatal brains are dysfunctional, and further, that VIP dysregulation may play a significant role in DS.

Vasoactive intestinal peptide antagonist treatment during mouse embryogenesis impairs social behavior and cognitive function of adult male offspring

Vasoactive intestinal peptide (VIP) is a regulator of rodent embryogenesis during the period of neural tube closure. VIP enhanced growth in whole cultured mouse embryos; treatment with a VIP antagonist during embryogenesis inhibited growth and development. VIP antagonist treatment during embryogenesis also had permanent effects on adult brain chemistry and impaired social recognition behavior in adult male mice. The neurological deficits of autism appear to be initiated during neural tube closure and social behavior deficits are among the key characteristics of this disorder that is more common in males and is frequently accompanied by mental retardation. The current study examined the blockage of VIP during embryogenesis as a model for the behavioral deficits of autism. Treatment of pregnant mice with a VIP antagonist during embryonic days 8 through 10 had no apparent effect on the general health or sensory or motor capabilities of adult offspring. However, male offspring exhibited reduced sociability in the social approach task and deficits in cognitive function, as assessed through cued and contextual fear conditioning. Female offspring did not show these deficiencies. These results suggest that this paradigm has usefulness as a mouse model for aspects of autism as it selectively impairs male offspring who exhibit the reduced social behavior and cognitive dysfunction seen in autism. Furthermore, the study indicates that the foundations of some aspects of social behavior are laid down early in mouse embryogenesis, are regulated in a sex specific manner and that interference with embryonic regulators such as VIP can have permanent effects on adult social behavior.

Cerebellar cortical-layer-specific control of neuronal migration by pituitary adenylate cyclase-activating polypeptide

Migration of immature neurons is essential for forming the cortical layers and nuclei. Impairment of migration results in aberrant neuronal cytoarchitecture, which leads to various neurological disorders. Neurons alter the mode, tempo and rate of migration when they translocate through different cortical layers, but little is known about the mechanisms underlying this process. Here we show that endogenous pituitary adenylate cyclase-activating polypeptide (PACAP) has short-term and cortical-layer-specific effects on granule cell migration in the early postnatal mouse cerebellum. Application of exogenous PACAP significantly slowed the migration of isolated granule cells and shortened the leading process in the microexplant cultures of the postnatal day (P)0-3 cerebella. Interestingly, in the cerebellar slices of P10 mice, application of exogenous PACAP significantly inhibited granule cell migration in the external granular layer (EGL) and molecular layer (ML), but failed to alter the movement in the Purkinje cell layer (PCL) and internal granular layer (IGL). In contrast, application of PACAP antagonist accelerated granule cell migration in the PCL, but did not change the movement in the EGL, ML and IGL. Inhibition of the cAMP signaling and the activity of phospholipase C significantly reduced the effects of exogenous PACAP on granule cell migration. The PACAP action on granule cell migration was transient, and lasted for approximately 2 h. The duration of PACAP action on granule cell migration was determined by the desensitization of its receptors and prolonged by inhibiting the protein kinase C. Endogenous PACAP was present sporadically in the bottom of the ML, intensively in the PCL, and throughout the IGL. Collectively, these results indicated that PACAP acts on granule cell migration as "a brake (stop signal) for cell movement." Furthermore, these results suggest that endogenous PACAP slows granule cell migration when the cells enter the PACAP-rich PCL, and 2 h later the desensitization of PACAP receptors allows the cells to accelerate the rate of migration and to actively move within the PACAP-rich IGL. Therefore, endogenous PACAP may provide a cue that regulates granule cell migration in a cerebellar cortical-layer-specific manner.

Noncompensation in peptide/receptor gene expression and distinct behavioral phenotypes in VIP- and PACAP-deficient mice

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) are closely related neurotrophic peptides of the secretin/glucagon family. The two peptides are derived from a common ancestral gene and share many functional attributes in neuronal development/regeneration which occur not only from overlapping receptor subtype signaling but also through common mechanisms regulating their expression. Although PACAP or VIP null mice have been generated for study, it is unclear whether the expression of the complementary peptide or their receptor systems are altered in a compensatory manner during nervous system development. By radioimmunoassay and quantitative PCR measurements, we first show that PACAP and VIP have very different temporal patterns of expression in developing postnatal mouse brain. In wild-type animals, PACAP transcript and peptide levels increased rapidly 2- and 5-fold, respectively, within 1 week of age. These levels at 1 week of age were maintained through adulthood. VIP transcript and peptide levels, by contrast, increased 25- and 50-fold, respectively, over a later time course. In parallel studies of development, there were no apparent compensatory increases in brain VIP expression in the PACAP knockout animals, PACAP expression in the VIP-deficient animals, or receptor mRNA levels in either genotype. To the contrary, there was evidence for developmental delays in the expression of peptide and receptor transcripts in the knockout animals. A series of behavioral and neurological tests demonstrated differences between the knockout genotypes, revealing some functional distinctions between the two genes. These results suggest that the PACAP and VIP have evolved to possess distinct biological activities and intimate that the respective knockout phenotypes represent deficits unmitigated by the actions of the complementary related peptide.

Characterization of novel splice variants of the PAC1 receptor in human neuroblastoma cells: consequences for signaling by VIP and PACAP

Expression of VPAC and PAC1 receptor isoforms was determined in six neuroblastoma cell lines as well as in human embryonic and adult brain using reverse transcriptase PCR and quantitative PCR. PAC1 receptor splice variants missing a 21 amino acid sequence in the amino terminal domain were found to be the major receptor variants in the neuroblastoma cell lines and also were highly expressed in embryonic brain compared to adult brain. In four of the neuroblastoma cell lines, VIP and PACAP stimulated cyclic AMP production with different potencies and levels of maximal stimulation. High potency and greatest maximal stimulation of cyclic AMP for each peptide were recorded in SH-SY5Y cells, indicating the presence of high affinity VIP and PACAP receptors. Further characterization of specific VPAC and PAC1 receptor isoforms was carried out in the SH-SY5Y cell line, where along with known PAC1 receptor splice variants and the VPAC2 receptor, a number of novel PAC1 receptor splice variants were identified. The comparatively low level expression of the VPAC2 receptor along with the poor responsiveness of SH-SY5Y cells to the VPAC2 receptor-specific agonist Ro 25-1553 indicated that this receptor did not contribute significantly to the observed VIP responses. When the individual PAC1 receptor isoforms were expressed in COS 7 cells, the ability of VIP to activate cyclic AMP production was increased more than 50-fold at the majority of the PAC1 receptor variants lacking the 21 amino acid amino terminal domain sequence compared to those with the complete domain. Smaller changes were seen in the potency of PACAP-38. Similar trends were seen with inositol phosphate responses, where in each case agonist potencies were lower than for cyclic AMP production. The results of this study show that the combination of different amino terminal and intracellular loop 3 splicing variants in the PAC1 receptor dictates the ability of agonists, particularly VIP, to activate signaling pathways. VIP has considerably greater potency at most PAC1 receptors with the short amino terminal domain, and these therefore may mediate physiological effects of both VIP and PACAP. Furthermore, there may be a phenotypic switch in the expression of different PAC1 receptor amino terminal splice variants between embryonic and mature nervous system, indicating that regulation of this event may have an important role in VIP/PACAP function, particularly in the developing nervous system.

Pituitary adenylate cyclase-activating polypeptide promotes differentiation of mouse neural stem cells into astrocytes

We have found that pituitary adenylate cyclase-activating polypeptide (PACAP) employed at the physiological concentrations induces the differentiation of mouse neural stem cells into astrocytes. The differentiation process was not affected by cAMP analogues such as dibutylic cAMP (db-cAMP) or 8Br-cAMP or by the specific competitive inhibitor of protein kinase A, Rp-adenosine-3',5'-cyclic monophosphothioate triethylamine salt (Rp-cAMP). Expression of the PACAP receptor (PAC1) in neural stem cells was detected by both RT-PCR and immunoblot using an affinity-purified antibody. The PACAP selective antagonist, PACAP(6-38), had an inhibitory effect on the PACAP-induced differentiation of neural stem cells into astrocytes. These results indicate that PACAP acts on the PAC1 receptor on the plasma membrane of mouse neural stem cells, with the signal then transmitted intracellularly via a PAC1-coupled G protein, does not involve Gs. This signaling mechanism may thus play a crucial role in the differentiation of neural stem cells into astrocytes.

VIP and PACAP induce selective neuronal differentiation of mouse embryonic stem cells

The capacity of embryonic stem cells (ES cells) to differentiate into neuronal cells represents a potential source for neuronal replacement and a model for studying factors controlling early stages of neuronal differentiation. Various molecules have been used to induce such differentiation but so far neuropeptides acting via functional G-protein-coupled receptors (GPCRs) have not been investigated. Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are neuropeptides expressed in early development which affect neuronal precursor proliferation and neuronal differentiation. VIP and PACAP share two common receptors (VPAC1 and VPAC2 receptors) while only PACAP binds with high affinity to PAC1 receptors. The aim of the study was to determine whether VIP and PACAP could produce functional neuronal differentiation of ES cells. Mouse ES cells were allowed to aggregate in embryoid bodies (EBs) in the presence or not of VIP and PACAP for 1 week. VIP and PACAP potently increased the proportion of EB-derived cells expressing specifically a neuronal phenotype shown by immunocytochemistry and neurite outgrowth without altering glial cell number. Binding and RT-PCR analyses demonstrated the presence of VPAC2 and PAC1 receptors on ES cells. Accordingly, both peptides increased cyclic AMP and intracellular calcium. In contrast, EB-derived cells only expressed a functional PAC1 receptor, suggesting a switch in GPCR phenotype during ES cell differentiation. These original data demonstrate that functional GPCRs for VIP and PACAP are present on ES cells and that these neuropeptides may induce their differentiation into a neuronal phenotype. It opens an exciting new field for neuropeptide regulation of tissue ontogenesis.

PACAP activates PKA, PKC and Ca(2+) signaling cascades in rat neuroepithelial cells

Several studies have reported that the PAC(1) receptor (PAC1-R), the specific receptor for PACAP, is expressed at early developmental stages. Here, we describe that the cytosolic Ca(2+) concentration ([Ca(2+)](i)) was increased by PACAP, but not VIP, in a concentration range from 10(-12) to 10(-8) M via the PAC(1)-R in isolated single cells from the rat neural fold. This activation of the cells by PACAP was mimicked by agonists and inhibited by antagonists of the cAMP/PKA and PLC/PKC cascades. These data indicate that PACAP/PAC(1)-R is linked to [Ca(2+)](i) signaling via two G-protein-coupled protein kinase pathways and may thereby play an important role in early neurodevelopment.

A study of novel polymorphisms in the upstream region of vasoactive intestinal peptide receptor type 2 gene in autism

We investigated the vasoactive intestinal peptide receptor type 2 (VIPR2) gene as a candidate gene for autism. We searched for mutations in the VIPR2 gene in autistic individuals, and 10 novel polymorphisms were identified. Three polymorphisms in the upstream region were studied in detail, and there was no significant difference in the frequencies between the autistic group (n = 14) and unrelated controls (n = 52). The distribution of the genotypes in two of the three polymorphisms differed somewhat between autistic subjects with gastrointestinal problems and those without. Moreover, there was a trend showing a correlation between the genotypes for the third polymorphism and the severity of stereotypical behavior as ranked by the Gilliam Autism Rating Scale. These preliminary results suggest that VIPR2 may have a role in gastrointestinal symptoms and stereotypical behaviors in autism, although a larger collection of samples suitable for transmission disequilibrium tests is necessary to validate the results.

Organization of vasoactive intestinal peptide-like immunoreactive system in the brain, olfactory organ and retina of the zebrafish, Danio rerio, during development

The localization of vasoactive intestinal peptide (VIP)-like immunoreactivity was investigated in the brain, olfactory system and retina of the zebrafish, Danio rerio, during development and in juvenile specimens, by using the indirect immunofluorescence and the peroxidase-antiperoxidase methods. In 24 h post fertilization (hpf) embryos, VIP-like immunoreactive cells were present in the olfactory pit, the retina, and several regions of the brain, including the dorsal telencephalon, the diencephalon, the tegmentum of the mesencephalon, the caudal rhombencephalon and the anterior pituitary. In 48 hpf embryos, additional VIP-like immunoreactive cell bodies were found in the ventral telencephalon, whereas in the diencephalon VIP-like immunopositive cells were more concentrated within the ventro-caudal hypothalamus. During the 7 day larval period, a dense plexus of VIP-like immunoreactive fibers first appeared in the olfactory bulbs. In 15-day-old larvae, two new groups of positive cells were observed in the periventricular preoptic nucleus and in the dorsal rhombencephalon. In 1 month/2 months old animals, VIP-like immunoreactive elements were confined to the olfactory organ, the olfactory bulbs, the periventricular preoptic nucleus and the pituitary, pars distalis. At 3 months stage, a large number of cells was observed in the periventricular preoptic nucleus. Western immunoblot analysis confirmed that VIP-like peptides, with molecular weight similar to that of synthetic VIP, are present early during the development of zebrafish. These results show that VIP-like immunoreactive structures appear early during ontogeny both in the olfactory pit, retina and brain. Transient expression of positive cells was found in the retina, telencephalon, diencephalon and brainstem. The location of VIP-like immunoreactivity indicates that, during development, VIP could be involved in several neuromodulatory functions, including the processing of visual and olfactory informations, as well as growth or survival promotion activities. The presence of VIP-like immunopositive cells in the pituitary, pars distalis, suggest that, during development, VIP may influence the secretion of pituitary hormones.

The origin and function of the pituitary adenylate cyclase-activating polypeptide (PACAP)/glucagon superfamily

The pituitary adenylate cyclase-activating polypeptide (PACAP)/ glucagon superfamily includes nine hormones in humans that are related by structure, distribution (especially the brain and gut), function (often by activation of cAMP), and receptors (a subset of seven-transmembrane receptors). The nine hormones include glucagon, glucagon-like peptide-1 (GLP-1), GLP-2, glucose-dependent insulinotropic polypeptide (GIP), GH-releasing hormone (GRF), peptide histidine-methionine (PHM), PACAP, secretin, and vasoactive intestinal polypeptide (VIP). The origin of the ancestral superfamily members is at least as old as the invertebrates; the most ancient and tightly conserved members are PACAP and glucagon. Evidence to date suggests the superfamily began with a gene or exon duplication and then continued to diverge with some gene duplications in vertebrates. The function of PACAP is considered in detail because it is newly (1989) discovered; it is tightly conserved (96% over 700 million years); and it is probably the ancestral molecule. The diverse functions of PACAP include regulation of proliferation, differentiation, and apoptosis in some cell populations. In addition, PACAP regulates metabolism and the cardiovascular, endocrine, and immune systems, although the physiological event(s) that coordinates PACAP responses remains to be identified.

VIP and PACAP 38 modulate ibotenate-induced neuronal heterotopias in the newborn hamster neocortex

Intracerebral administration of ibotenate produces, through activation of N-methyl-D-aspartate (NMDA) receptors, neuronal heterotopias in the newborn hamster neocortex: high doses of ibotenate induce periventricular and subcortical neuronal heterotopias, while low doses of ibotenate produce intracortical heterotopias and molecular layer ectopias. Vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are closely related peptides with neurotrophic properties. They share common VPAC1 and VPAC2 receptors, which use cAMP as a second messenger. Previous studies have shown that VIP prevents excitotoxic neuronal death and exacerbates glutamate-induced c-fos neuronal expression. In order to gain new insight into the molecular control of neuronal migration, the present study examined the effects of VIP and PACAP on ibotenate-induced heterotopias in the newborn hamster. Co-treatment with VIP and a high dose of ibotenate produced a pattern of neuronal heterotopias similar to the one observed in animals treated with low doses of ibotenate alone. Pups co-injected with a low dose of ibotenate and a VIP antagonist displayed cortical dysgeneses similar to those observed in animals treated with high doses of ibotenate alone. The modulating effects of VIP on excitotoxin-induced heterotopias were mimicked by forskolin, PACAP, and by a specific VPAC2 receptor agonist but not by a VPAC1 agonist, and were blocked by a protein kinase A (PKA) inhibitor. Taken together, these data suggest that VIP and PACAP can attenuate ibotenate-induced heterotopias in newborn hamster and that this effect is mediated by the VPAC2 receptor utilizing the cAMP-PKA pathway.

Splice variants of PAC(1) receptor during early neural development of rats

The specific pituitary adenylate cyclase-activating polypeptide (PACAP) receptor, PAC(1)-R, consists of at least seven isoforms, and they are differentially coupled to signal transduction pathways by alternative splicing. We have found that the major splice variants of the PAC(1) receptor seen during development are the short splice isoform, PAC(1)-R-s (which does not contain either the "hip" or "hop" cassette), and another form, PAC(1)-R-hop (which contains the "hop" cassette). We also have applied an innovative molecular histochemical technique, in situ reverse transcription-polymerase chain reaction (RT-PCR), and determined that these two splice isoforms are colocalized in the neuroepithelia from the primitive streak stage.

Prenatal blockade of vasoactive intestinal peptide alters cell death and synaptic equipment in the murine neocortex

Vasoactive intestinal peptide (VIP) is a potent growth factor that stimulates murine neocortical astrocyte genesis during the period of ontogenesis corresponding to premature delivery in humans. In rodents, part of the VIP supplied to the fetal brain is maternal VIP that crosses the placenta. If these data also apply to human brain development, premature newborns may be partly VIP-deficient because of loss of the maternal supply, and this may adversely affect their brain development. The goal of the present study was to determine the effects of VIP blockade during mouse neocortical astrocyte genesis on neuritic survival and maturation. VIP blockade by a specific VIP antagonist on embryonic d 17 and 18 induced transient, postnatal depletion of astrocytes in the upper neocortical layers. Combined use of in situ DNA fragmentation analysis (terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling method, a marker of cell death); immunohistochemical detection of synaptophysin, microtubule-associated proteins, and neurofilaments; and quantification of mRNA for synaptophysin and N-methyl-D-aspartate R1 receptor subunit revealed that early VIP blockade significantly altered programmed neuritic death and impaired neuritic differentiation. VIP inhibition induced 1) exaggerated postnatal terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling of cortical neurons, 2) long-term overexpression of synaptophysin and N-methyl-D-aspartate R1 receptor subunit, and 3) long-term overexpression of microtubule-associated protein-5 and neurofilament 160 kD. Although the functional consequences of this deviant pattern of murine neocortical development remain to be determined, these data open up new avenues for investigating some of the cognitive deficits observed in human premature infants.

Distribution of vasoactive intestinal peptide-like immunoreactivity in the brain and pituitary of the frog (Rana esculenta) during development

The localization of vasoactive intestinal peptide (VIP)-like immunoreactive (ir) elements was investigated in the brain of the anuran amphibian, Rana esculenta, during development. Using an antiserum raised against the porcine VIP, ir cell bodies and fibers were observed in the forebrain of tadpoles a few days after hatching. During early premetamorphosis, ir perikarya were distributed in the ventral infundibular nucleus of the hypothalamus and in the posterocentral nucleus of the thalamus. Labeled fibers were detected in the olfactory bulbs and in the hypothalamus. In these larvae, furthermore, several VIP-ir cells were found in the pars distalis of the pituitary and there were ir fibers in the pars nervosa. In tadpoles at stages VIII-IX, a new group of VIP-labeled neurons was observed in the dorsal part of the infundibular nucleus. In other brain regions, the distribution of the immunoreactivity was similar to that described in the earliest stages, i.e., IV-VII. During mid-premetamorphosis, stages X-XII of development, an additional set of ir perikarya appeared in the ventrolateral area of the thalamus. During late premetamorphosis, stages XIII-XVIII, the organization of VIP-like immunoreactivity was more complex and its distribution more widespread. Two new groups of ir cell bodies appeared, one in the preoptic nucleus and another in the anteroventral area of the thalamus, and for the first time, VIP immunoreactivity was observed in the median eminence. This distribution pattern persisted through to the prometamorphic, four-limb stage. Strikingly, no VIP-ir elements were observed anywhere in the mid- and hindbrain. The present results indicate that a VIP-like ir peptide may be involved in the processing of olfactory information or may act as a neurohormone, hypophysiotropic factor, and neuromodulator in the brain of R. esculenta during development.

Targeting of embryonic and postnatal autonomic and enteric neurons with a vasoactive intestinal peptide transgene

The neuropeptide vasoactive intestinal peptide (VIP) is expressed in several distinct sites in the CNS, in cholinergic and enteric ganglia, and in a small subpopulation of neurons within sympathetic ganglia. Previous studies on the human VIP gene indicate that transcription in neural crest-derived neuroblastoma and pheochromocytoma cell lines is controlled in part by multiple regulatory elements located along 4.5 kb of upstream 5' flanking sequence. In the current studies, transgenic mice were created with a chimeric gene consisting of 16.5 kb of the mouse VIP gene fused to the beta-galactosidase reporter. In situ hybridization analysis in adult mice indicated that reporter gene expression was correctly targeted to neurons in the esophagus, stomach, small intestine, and colon. No expression was observed in the brain, including regions that contain abundant VIP-expressing cells, such as the thalamus, amygdala, cerebral cortex, hippocampus, and suprachiasmatic nucleus. Analysis of transgene expression in neonatal and embryonic day 13.5 mice revealed a near perfect correlation between VIP and beta-galactosidase gene expression in cranial cholinergic ganglia and the superior cervical ganglia, and lack of transgene expression in sensory ganglia and in nonneuronal tissue. Potential ectopic transgene expression was observed in neonates, in the cerebellar external granule layer and in a small subpopulation of neurons in the olfactory epithelium. We conclude that the 16.5 kb of VIP gene used in these studies contains sequences sufficient for directing expression specifically to VIP neurons in the PNS, and that sequences located elsewhere on the gene are required for proper CNS expression. The VIP gene sequences used here should be capable of targeting other gene products to specific populations of embryonic and adult peripheral neurons without causing significant expression in the CNS.

Pituitary adenylate cyclase-activating polypeptide receptors during development: expression in the rat embryo at primitive streak stage

The distribution and localization of the pituitary adenylate cyclase-activating polypeptide (PACAP) receptor the PAC1 receptor (previously called the type 1 PACAP receptor or PVR1), which binds PACAP, but not vasoactive intestinal peptide, with high affinity] were first investigated in rats with in situ hybridization for its messenger RNA, and with immunohistochemical methods during prenatal and postnatal development. The expression of PACAP receptor messenger RNA was first detected in the rat embryo at the primitive streak stage as early as embryonic day 9, and it was intensely expressed in the neural plate. PACAP receptor messenger RNA was also intensely expressed in the neuroepithelia of the mesencephalon and rhombencephalon at embryonic day 11, and expressed in the basal telencephalon, hippocampal formation neuroepithelium, cortical neuroepithelium and cerebellar neuroepithelium after embryonic day 13. It was also expressed in the olfactory bulb neuroepithelium after embryonic day 16, and in mature regions of the older embryos. In postnatal developing brains, PACAP receptor messenger RNA was intensely expressed in the olfactory bulb, hippocampal formation, cerebellum and other scattered regions. The localization of PACAP receptor-like immunoreactivity coincided well with that of the gene transcripts. We also used reverse transcription-polymerase chain reaction methods to determine the expression of the splice variants of the PACAP receptor gene. At each ontogenetic stage of the rat from embryonic day 9 to postnatal day 60, two major products were detected with reverse transcription-polymerase chain reaction, a thick band (303 base pairs) corresponding to the short splice variant of the receptor that lacks both the "hip" and "hop" cassettes, and a thin band (387 base pairs) corresponding to the splice variant that contains one cassette of "hop" or "hip". There was no evidence for the other larger splice variants. Some of the amplified products were sequenced and found to have the exact sequences of "PACAP receptor" and "PACAP receptor-hopl", which are coupled to different signal transduction pathways. These results indicate that the PACAP receptor is actively expressed in different neuroepithelia from early developmental stages and expressed in various brain regions during prenatal and postnatal development, and that the major splice variants are "PACAP receptor" and "PACAP receptor-hopl". The initial mapping of ontogenetic localization of the PACAP receptor provides the basis for a better understanding of the functions of PACAP and its receptors during the development of the brain.

Maternal regulation of embryonic growth: the role of vasoactive intestinal peptide

Vasoactive intestinal peptide (VIP) is an important growth regulator of the embryonic day (E)9-E11 mouse. In comparably aged rat embryos, VIP messenger RNA (mRNA) is not detectable; however, peak concentrations of VIP in maternal rat serum indicate a nonembryonic source. In the current study, mouse maternal and embryonic tissues were examined from E6-E12. Although RT-PCR revealed VIP mRNA in E6-E7 conceptuses, by E8 (when extraembryonic tissues could be separated from the embryo), VIP mRNA was detected only in the decidua/trophoblast. Decidual/trophoblastic VIP mRNA decreased until E10, after which it was not detectable. VIP mRNA was not apparent in the embryo until E11-E12. At E9, VIP immunoreactivity was localized to abundant, diffuse cells in the decidua basalis, which were also immunoreactive for T cell markers. VIP binding sites were dense in the decidua/trophoblast at E6, but gradually decreased until E10, after which they were not apparent. VIP binding sites were detected in embryonic neuroepithelium by E9. The transient presence of VIP binding sites and mRNA in the decidua/trophoblast correlate with the critical period of VIP growth regulation, when VIP mRNA is absent in the embryo. These findings suggest that maternal lymphocytes are the source of VIP's regulating early postimplantation embryonic growth.

Neural tube expression of pituitary adenylate cyclase-activating peptide (PACAP) and receptor: potential role in patterning and neurogenesis

Neural tube patterning in vertebrates is controlled in part by locally secreted factors that act in a paracrine manner on nearby cells to regulate proliferation and gene expression. We show here by in situ hybridization that genes for the neuropeptide pituitary adenylate cyclase-activating peptide (PACAP) and one of its high-affinity receptors (PAC1) are widely expressed in the mouse neural tube on embryonic day (E) 10.5. Transcripts for the ligand are present in differentiating neurons in much of the neural tube, whereas the receptor gene is expressed in the underlying ventricular zone, most prominently in the alar region and floor plate. PACAP potently increased cAMP levels more than 20-fold in cultured E10.5 hindbrain neuroepithelial cells, suggesting that PACAP activates protein kinase A (PKA) in the neural tube and might act in the process of patterning. Consistent with this possibility, PACAP down-regulated expression of the sonic hedgehog- and PKA-dependent target gene gli-1 in cultured neuroepithelial cells, concomitant with a decrease in DNA synthesis. PACAP is thus an early inducer of cAMP levels in the embryo and may act in the neural tube during patterning to control cell proliferation and gene expression.

[Vasoactive intestinal peptide: a novel neurotrophic factor]

Vasoactive intestinal peptide (VIP) is a 28-amino acid neuropeptide with potent growth-related actions on dissociated neural cells. In recent years its role in brain development has been elucidated: VIP has been shown to be a regulator of early neurodevelopment and embryonic growth, a stimulator of neocortical astrocytogenesis and a neuroprotective molecule against excitotoxic and other neurotoxic substances. Thus VIP appears as a fundamental regulator of brain growth and development, and a potent neuroprotective agent, possibly involved in pathological processes such as microcephalies and some neurological impairments observed in very premature babies. Similarly, VIP and VIP derivatives could represent a new avenue in the search of therapeutics for excitotoxic lesions of the developing brain.

Vasoactive intestinal peptide stimulates testosterone production by cultured fetal rat testicular cells

As a part of a series of studies on the regulation of testicular steroidogenesis in the fetal rat, we found that VIP stimulated fetal testicular cAMP production at a dose of 10(-9) mol/l, while a dose as low as 10(-12) mol/l stimulated testosterone production. RT-PCR analysis could not reveal either VIP mRNA in fetal tissues or VIP1 receptor mRNA in the fetal or newborn testes, while VIP2 receptor mRNA was detected testes as early as E15.5. The testicular VIP content was unmeasurable by our radioimmunoassay method ( < 1 fmol/testis), while the circulating levels of VIP were 82.9+/-1.1 pmol/l at E17.5 and decreased with advanced fetal ages. In conclusion, our results suggest that VIP, from and extratesticular source, may regulate fetal testicular steroidogenesis through type 2 receptors as early as E15.5.

Embryonic expression of pituitary adenylate cyclase-activating polypeptide in sensory and autonomic ganglia and in spinal cord of the rat

Pituitary adenylate cyclase-activating polypeptide (PACAP), a neuropeptide that is related structurally to vasoactive intestinal polypeptide (VIP), has been shown to stimulate neuronal growth and differentiation, indicating a possible function in the development of the nervous system. Studies have indicated that the PACAP receptor is expressed during development, but data on PACAP expression are limited mainly to postnatal development. In the present study, we used immunohistochemistry and in situ hybridization histochemistry to examine the expression of PACAP in autonomic and sensory ganglia and spinal cord of rat fetuses at embryonic days 12-21 (E12-E21). PACAP immunoreactivity was visualized by using a specific monoclonal anti-PACAP antibody to detect both PACAP-38 and PACAP-27, and PACAP mRNA was visualized by using a [33P]-labeled cRNA-probe. PACAP- nerve fibers were observed in the spinal cord as early as E13. At E14, PACAP-immunoreactive nerve fibers projected to the sympathetic trunk, where few PACAP- nerve cell bodies were seen from E15. On the same embryonic day, PACAP-immunoreactive nerve cell bodies appeared in the intermediolateral column of the spinal cord. From E15 to E16, PACAP-immunoreactive nerve cell bodies were visible within sensory and autonomic ganglia, such as the dorsal root, the trigeminal, the sphenopalatine, the otic, the submandibular, and the nodose ganglia. At E16, PACAP+ nerve fibers were innervating the adrenal medulla, and immunoreactive fibers could also be observed in the superior cervical ganglion, in which PACAP-immunoreactive cell bodies were detected occasionally from E18. The synthesis of PACAP in neuronal cell bodies was confirmed by the demonstration of PACAP mRNA with in situ hybridization histochemistry. Thus, in all of the structures examined, PACAP appeared at roughly the same embryonic stage and, thereafter, increased to the adult level before birth. Because PACAP occurred with the same distribution pattern as that described in the adult rat, there is no evidence for transient expression. The early expression of PACAP suggests a possible role for the peptide in the developing nervous system.

Vasoactive intestinal peptide shortens both G1 and S phases of neural cell cycle in whole postimplantation cultured mouse embryos

Vasoactive intestinal peptide, a trophic and mitogenic factor, stimulates growth in whole cultured mouse embryos. Inhibition of this growth function between embryonic days 9 and 11 induces growth retardation accompanied by severe microcephaly. In the present study, to determine the effects of this peptide on the different phases of the cell cycle of neural cells, embryonic day 9.5 cultured mouse embryos were cumulatively labelled with bromodeoxyuridine. Vasoactive intestinal peptide (10(-7)M) shortened S phase and G1 phase of neuroepithelial cells by 50% (4.8-2.4 h) and 58% (1.9-0.8 h), respectively, compared with controls. G2 and M phases were not modified by vasoactive intestinal peptide treatment. Total cell cycle length was consequently reduced by 43% (8.2-4.7 h) in vasoactive intestinal peptide treated embryos, compared with controls. In contrast, vasoactive intestinal peptide did not modify the rate of neuroepithelial cell death as assessed by the proportion of nuclei containing fragmented DNA. These data suggest that vasoactive intestinal peptide stimulates growth in premigratory stages of nervous system development by shortening S and G1 phases of the cell cycle and that S phase duration can be regulated by a physiological peptide.

Vasoactive intestinal peptide is an important endocrine regulatory factor of fetal rat testicular steroidogenesis

This study elaborates our recent preliminary finding that vasoactive intestinal peptide (VIP) has a specific stimulatory effect on fetal rat Leydig cells. We examined the dose-response relationship for the effect of VIP on cAMP and testosterone production by dispersed fetal Leydig cells isolated from rat testes on embryonic day (E) 18.5. Further, we used RT-PCR to examine the expression of the VIP gene in fetal brain and testes and that of the VIP receptor genes in fetal testes and used RIA to measure VIP in testes and plasma during the fetal period. VIP stimulated fetal testicular cAMP production at a dose of 10(-9) mol/liter, whereas a dose as low as 10(-12) mol/liter stimulated testosterone production. This suggests that VIP at low doses may stimulate testosterone production using second messenger pathways other than cAMP. RT-PCR analysis could not reveal either VIP messenger RNA (mRNA) in fetal tissues or VIP1 receptor mRNA in the fetal or newborn testes, whereas VIP2 receptor mRNA was detected in fetal testes as early as E15.5. Northern hybridization analysis showed that the level of expression of VIP2 receptor mRNA is very low in fetal and neonatal testes and increases with age. The testicular VIP content was unmeasurable by our RIA method (i.e. <1 fmol/testis), whereas the circulating level of VIP was 82.9 +/- 1.1 pmol/liter on E17.5 and decreased with advancing fetal age. In conclusion, our results suggest that VIP from an extratesticular source, possibly from the maternal compartment, may regulate fetal testicular steroidogenesis through type 2 receptors as early as E15.5. These findings may be of physiological significance, because the onset of fetal testicular steroidogenesis occurs at an age (E15.5-19.5) before the onset of pituitary LH secretion.

The effects of axotomy and preganglionic denervation on the expression of pituitary adenylate cyclase activating peptide (PACAP), galanin and PACAP type 1 receptors in the rat superior cervical ganglion

The effects of axotomy, chemical sympathectomy and preganglionic denervation on the expression of the neuropeptides, pituitary adenylate cyclase-activating peptide (PACAP), galanin (GAL), and the PACAP type 1 receptor in the rat superior cervical ganglion (SCG) were investigated by immunocytochemistry, in situ hybridization and receptor autoradiography. An antibody recognizing the rat vesicular acetylcholine transporter (VAChT) was used for the detection of preganglionic cholinergic fibers. In the normal SCG, PACAP-immunoreactivity (-IR) was present in numerous, basket-forming, preganglionic nerve fibers, while very few SCG neurons expressed PACAP. GAL-IR was restricted to occasional neurons, and a few nerve fibers, most of which were, in addition, PACAP-IR. PACAP type 1 receptors were expressed in all nerve cell bodies. Axotomy resulted in a rapid and prominent upregulation of PACAP in a large number of nerve cell bodies. There was a large increase also in GAL expression in many nerve cell bodies. In contrast, there was a marked decline in PACAP type 1 receptor expression. Chemical sympathectomy by administration of the catcholaminergic neurotoxin, 6-hydroxydopamine (6-OHDA), gave rise to similar changes. Preganglionic denervation led to the disappearance of PACAP- and VAChT-IR baskets and to the upregulation of PACAP and GAL expression in neurons located close to the entrance of the sympathetic chain, whereas PACAP type 1 receptor expression was not affected. PACAP and GAL were coexpressed in most neurons after axotomy and chemical sympathectomy. Taken together, these results indicate that disruption of target contact and/or the infliction of an injury to the axons of the sympathetic neurons, rather than the preganglionic output, regulates the expression of PACAP, GAL and the PACAP type 1 receptor.

Genomic structure and embryonic expression of the rat type 1 vasoactive intestinal polypeptide receptor gene

The genomic structure of the rat vasoactive intestinal polypeptide type 1 receptor (VIPR I) gene was characterized using polymerase chain reactions (PCR) and DNA sequencing. These studies show that the rat VIPR I gene spans more than 20 kb of DNA sequence and includes thirteen exons separated by twelve introns, ranging from 0.2 to 4.5 kb. VIP is known to play an important role early in embryonic development. To elucidate the receptor-mediated biological functions of VIP in development, the temporal and spatial expression of VIPR I during rat embryonic development was examined in this study. Using in situ hybridization histochemistry with 35S-labeled riboprobe, VIPR I mRNA was detected as early as embryonic day 11 (E11), in the neuroepithelium, foregut, heart and in cells lining the blood vessels. From E14 through E18, VIPR I mRNA was detected in multiple tissues derived from all three germ layers. These include neuronal cells in brain and spinal cord (ectoderm); smooth muscle cells of intestines, cells lining the wall of the heart and blood vessels, kidney, adrenal gland (mesoderm); epithelial cells of airway and of liver (endoderm). The early onset and wide tissue expression of VIPR I suggests that binding of VIP to this receptor may play an important role in rat embryonic development.

Vasoactive intestinal peptide prevents excitotoxic cell death in the murine developing brain

Excitotoxic damage may be a critical factor in the formation of brain lesions associated with cerebral palsy. When injected at birth, the glutamatergic analog ibotenate induces mouse brain lesions that strikingly mimic human microgyria. When ibotenate is injected at postnatal day 5, it produces transcortical necrosis and white matter cysts that mimic human perinatal hypoxic-like lesions. Vasoactive intestinal peptide (VIP) has potent growth-related actions and neuroprotective properties that influence mitosis and neuronal survival in culture. The goal of this study was to assess the protective role of VIP against excitotoxic lesions induced by ibotenate in developing mouse brain. VIP cotreatment reduced ibotenate-induced microgyric-like cortical lesions and white matter cysts by up to 77 and 85%, respectively. VIP protective effects were reproduced by a peptide derived from activity-dependent neurotrophic factor (ADNF), a trophic factor released by VIP-stimulated astrocytes, and by stearyl norleucine VIP, a specific VIP agonist that does not activate adenylate cyclase. Neither forskolin, an adenylate cyclase activator, nor pituitary adenylate cyclase-activating peptide, provided VIP-like protection. VIP and neurotrophic analogs, acting through a cAMP-independent mechanism and inducing ADNF release, could represent new avenues in the understanding and prevention of human cerebral palsy.

Pituitary adenylate cyclase-activating polypeptide is an autocrine inhibitor of mitosis in cultured cortical precursor cells

During brain development, an intricate array of signals is likely to control the transition from proliferation to differentiation, particularly in the complex cerebral cortex. Although factors regulating proliferation and differentiation have been identified, little is known about mechanisms governing the exit of precursors from the cell cycle. We now report that pituitary adenylate cyclase-activating polypeptide (PACAP), a new member of the vasoactive intestinal peptide family expressed in embryonic brain, promotes this transition. In virtually pure cultures of embryonic day 13.5 (E13.5) rat cortical precursors, PACAP inhibited [3H]thymidine incorporation by 43%, decreasing the proportion of mitotic cells. Moreover, the peptide promoted morphological and biochemical differentiation; PACAP elicited a 2-fold increase in cells bearing neurites and a 30% increase in neurotrophin trkB receptor expression, indicating that PACAP induced cell cycle withdrawal and promoted neuronal differentiation. The expression of PACAP ligand and receptor in precursors raised the possibility of autocrine function. Indeed, 85% of cells exhibited PACAP immunoreactivity while 64% expressed type I receptor, which, in turn, mediated cAMP activation and phosphorylated cAMP response element binding protein nuclear signaling. Furthermore, treatment with the PACAP antagonist or neutralizing antibody increased DNA synthesis and proliferation, which is consistent with interruption of ongoing mitotic inhibition mediated by endogenous PACAP. Our observations suggest that cortical precursors produce PACAP as an autocrine signal to elicit cell cycle withdrawal, inducing the transition from proliferation to neuronal differentiation.