Differential expression of PACAP receptors in postnatal rat brain

Circulating PACAP levels are associated with altered imaging measures of entorhinal cortex neurite density in posttraumatic stress disorder

Introduction: Pituitary adenylate cyclase-activating polypeptide (PACAP) regulates plasticity in brain systems underlying arousal and memory and is associated with posttraumatic stress disorder (PTSD). Research in animal models suggests that PACAP modulates entorhinal cortex (EC) input to the hippocampus, contributing to impaired contextual fear conditioning. In PTSD, PACAP is associated with higher activity of the amygdala to threat stimuli and lower functional connectivity of the amygdala and hippocampus. However, PACAP-affiliated structural alterations of these regions have not been investigated in PTSD. Here, we examined whether peripheral PACAP levels were associated with neuronal morphology of the amygdala and hippocampus (primary analyses), and EC (secondary) using Neurite Orientation Dispersion and Density Imaging.Methods: Sixty-four (44 female) adults (19 to 54 years old) with DSM-5 Criterion A trauma exposure completed the Clinician-Administered PTSD Scale (CAPS-5), a blood draw, and magnetic resonance imaging. PACAP38 radioimmunoassay was performed and T1-weighted and multi-shell diffusion-weighted images were acquired. Neurite Density Index (NDI) and Orientation Dispersion Index (ODI) were quantified in the amygdala, hippocampus, and EC. CAPS-5 total score and anxious arousal score were used to test for clinical associations with brain structure.Results: Higher PACAP levels were associated with greater EC NDI (β = 0.0099, q = 0.032) and lower EC ODI (β = -0.0073, q = 0.047), and not hippocampal or amygdala measures. Neither EC NDI nor ODI was associated with clinical measures.Conclusions: Circulating PACAP levels were associated with altered neuronal density of the EC but not the hippocampus or amygdala. These findings strengthen evidence that PACAP may impact arousal-associated memory circuits in PTSD.

Alterations in pituitary adenylate cyclase-activating polypeptide in major depressive disorder, bipolar disorder, and comorbid depression in Alzheimer's disease in the human hypothalamus and prefrontal cortex

BACKGROUND

Pituitary Adenylate Cyclase-Activating Polypeptide (PACAP) is involved in the stress response and may play a key role in mood disorders, but no information is available on PACAP for the human brain in relation to mood disorders.

METHODS

PACAP-peptide levels were determined in a major stress-response site, the hypothalamic paraventricular nucleus (PVN), of people with major depressive disorder (MDD), bipolar disorder (BD) and of a unique cohort of Alzheimer's disease (AD) patients with and without depression, all with matched controls. The expression of PACAP-(Adcyap1mRNA) and PACAP-receptors was determined in the MDD and BD patients by qPCR in presumed target sites of PACAP in stress-related disorders, the dorsolateral prefrontal cortex (DLPFC) and anterior cingulate cortex (ACC).

RESULTS

PACAP cell bodies and/or fibres were localised throughout the hypothalamus with differences between immunocytochemistry and in situ hybridisation. In the controls, PACAP-immunoreactivity-(ir) in the PVN was higher in women than in men. PVN-PACAP-ir was higher in male BD compared to the matched male controls. In all AD patients, the PVN-PACAP-ir was lower compared to the controls, but higher in AD depressed patients compared to those without depression. There was a significant positive correlation between the Cornell depression score and PVN-PACAP-ir in all AD patients combined. In the ACC and DLPFC, alterations in mRNA expression of PACAP and its receptors were associated with mood disorders in a differential way depending on the type of mood disorder, suicide, and psychotic features.

CONCLUSION

The results support the possibility that PACAP plays a role in mood disorder pathophysiology.

Calcitonin/PAC1 receptor splice variants: a blind spot in migraine research

The neuropeptides calcitonin gene-related peptide (CGRP) and pituitary adenylate cyclase-activating polypeptide (PACAP) and their receptors are linked to migraine neurobiology. Recent antimigraine therapeutics targeting the signaling of these neuropeptides are effective; however, some patients respond suboptimally, indicating an incomplete understanding of migraine pathophysiology. The CGRP- and PACAP-responsive receptors can be differentially spliced. It is known that receptor splice variants can have different pathophysiological effects in other receptor-mediated pain pathways. Despite considerable knowledge on the structural and pharmacological differences of the CGRP- and PACAP-responsive receptor splice variants and their expression in migraine-relevant tissues, their role in migraine is rarely considered. Here we shine a spotlight on the calcitonin and PACAP (PAC1) receptor splice variants and examine what implications they may have for drug activity and design.

Circulating PACAP levels are associated with altered imaging measures of entorhinal cortex neurite density in posttraumatic stress disorder

Background

Pituitary adenylate cyclase-activating polypeptide (PACAP) regulates plasticity in brain systems underlying arousal and memory and is associated with posttraumatic stress disorder (PTSD). Research in animal models suggests that PACAP modulates entorhinal cortex (EC) input to the hippocampus, contributing to impaired contextual fear conditioning. In PTSD, PACAP is associated with higher activity of the amygdala to threat stimuli and lower functional connectivity of the amygdala and hippocampus. However, PACAP-affiliated structural alterations of these regions have not been reported. Here, we examined whether peripheral PACAP levels were associated with neuronal morphology of the amygdala and hippocampus (primary analysis), and EC (secondary analysis) using Neurite Orientation Dispersion and Density Imaging.

Methods

Sixty-four (44 female) adults (19 to 54 years old) with DSM-5 Criterion A trauma exposure completed the Clinician-Administered PTSD Scale (CAPS-5), a blood draw, and magnetic resonance imaging. PACAP38 radioimmunoassay was performed and T1-weighted and multi-shell diffusion- weighted images were acquired. Neurite Density Index (NDI) and Orientation Dispersion Index (ODI) were quantified in the amygdala, hippocampus, and EC. CAPS-5 total score and anxious arousal score were used to test for clinical associations with brain structure.

Results

Higher PACAP levels in blood were associated with greater EC NDI (β=0.31, q=0.034) and lower EC ODI (β=-0.30, q=0.042) and not hippocampal or amygdala measures. Neither EC NDI nor ODI was associated with clinical measures.

Conclusions

Circulating PACAP levels were associated with altered neuronal density of the EC but not hippocampus or amygdala. These findings strengthen evidence that PACAP may impact arousal- associated memory circuits.

Targeting VIP and PACAP Receptor Signaling: New Insights into Designing Drugs for the PACAP Subfamily of Receptors

Pituitary Adenylate Cyclase-Activating Peptide (PACAP) and Vasoactive Intestinal Peptide (VIP) are neuropeptides involved in a diverse array of physiological and pathological processes through activating the PACAP subfamily of class B1 G protein-coupled receptors (GPCRs): VIP receptor 1 (VPAC1R), VIP receptor 2 (VPAC2R), and PACAP type I receptor (PAC1R). VIP and PACAP share nearly 70% amino acid sequence identity, while their receptors PAC1R, VPAC1R, and VPAC2R share 60% homology in the transmembrane regions of the receptor. PACAP binds with high affinity to all three receptors, while VIP binds with high affinity to VPAC1R and VPAC2R, and has a thousand-fold lower affinity for PAC1R compared to PACAP. Due to the wide distribution of VIP and PACAP receptors in the body, potential therapeutic applications of drugs targeting these receptors, as well as expected undesired side effects, are numerous. Designing selective therapeutics targeting these receptors remains challenging due to their structural similarities. This review discusses recent discoveries on the molecular mechanisms involved in the selectivity and signaling of the PACAP subfamily of receptors, and future considerations for therapeutic targeting.

Dosage sensitivity intolerance of VIPR2 microduplication is disease causative to manifest schizophrenia-like phenotypes in a novel BAC transgenic mouse model

Recent genome-wide association studies (GWAS) have identified copy number variations (CNVs) at chromosomal locus 7q36.3 that significantly contribute to the risk of schizophrenia, with all of the microduplications occurring within a single gene: vasoactive intestinal peptide receptor 2 (VIPR2). To confirm disease causality and translate such a genetic vulnerability into mechanistic and pathophysiological insights, we have developed a series of conditional VIPR2 bacterial artificial chromosome (BAC) transgenic mouse models of VIPR2 CNV. VIPR2 CNV mouse model recapitulates gene expression and signaling deficits seen in human CNV carriers. VIPR2 microduplication in mice elicits prominent dorsal striatal dopamine dysfunction, cognitive, sensorimotor gating, and social behavioral deficits preceded by an increase of striatal cAMP/PKA signaling and the disrupted early postnatal striatal development. Genetic removal of VIPR2 transgene expression via crossing with Drd1a-Cre BAC transgenic mice rescued the dopamine D2 receptor abnormality and multiple behavioral deficits, implicating a pathogenic role of VIPR2 overexpression in dopaminoceptive neurons. Thus, our results provide further evidence to support the GWAS studies that the dosage sensitivity intolerance of VIPR2 is disease causative to manifest schizophrenia-like dopamine, cognitive, and social behavioral deficits in mice. The conditional BAC transgenesis offers a novel strategy to model CNVs with a gain-of -copies and facilitate the genetic dissection of when/where/how the genetic vulnerabilities affect development, structure, and function of neural circuits. Our findings have important implications for therapeutic development, and the etiology-relevant mouse model provides a useful preclinical platform for drug discovery.

Social defeat-induced Cingulate gyrus immediate-early gene expression and anxiolytic-like effect depend upon social rank

Social hierarchy is considered to impart an adaptive advantage to the species by reducing long-term conflict between conspecifics. While social stratification is frequently established via stress-inducing stimuli, the subsequent integration of individuals into the hierarchy may attenuate anxiety. Presently, we hypothesized that repeated reinforcement of murine social hierarchy in the dominant-submissive relationship (DSR) food-competition test would engender divergent neuroplastic changes mediating both social and anxiety-like behavior among selectively-bred Dominant (Dom) and Submissive (Sub) mice. Two weeks of repeated respective social victory or defeat reduced serum corticosterone levels of both Dom and Sub mice, whereas socially-defeated Sub mice demonstrated markedly greater exploration of the open arms of the elevated plus maze (EPM). At the same time, social victory led to markedly greater expression of the immediate-early genes (IEGs) c-Jun and EGR-1 in the lateral septal nucleus (LSN) among Dom mice, in contrast with defeated Sub counterparts which demonstrated four-fold greater IEG expression in the cingulate gyrus (Cg). These findings point towards involvement of the Cg in the anxiety-like effect among Sub mice after repeated social defeat, and suggest stabilization of the social hierarchy to attenuate the stress-inducing nature of social interaction, particularly for subordinates. Further study of the potentially anxiolytic-like effects of Cg activity should shed light upon the functional significance of the Cg in social interaction, social hierarchical sorting and anxiety.

Social dominance predicts hippocampal glucocorticoid receptor recruitment and resilience to prenatal adversity

The developing fetus is highly sensitive to prenatal stress, which may alter Hypothalamic-Pituitary-Adrenal (HPA) axis programming and increase the risk of behavioral disorders. There is high variability among the human population, wherein many offspring of stressed pregnancies display resilience to adversity, while the remainder displays vulnerability. In order to identify biological substrates mediating between resilience or vulnerability to prenatal adversity, we exposed stress-resistant Dominant (Dom) and stress-sensitive Submissive (Sub) mice to mild prenatal restraint stress (PRS, 45 min on gestational days (GD) 15, 16 and 17). We hypothesized that PRS would differentially alter prenatal programming of limbic regions regulating the HPA axis and affect among Dom and Sub offspring. Indeed, PRS increased Sub offspring’s serum corticosterone, and exaggerated their anxiety- and depressive-like behavior, while Dom offspring remained resilient to the hormonal and behavioral consequences of PRS. Moreover, PRS exposure markedly facilitated glucocorticoid receptor (GR) recruitment to the hippocampus among Dom mice in response to restraint stress, which may be responsible for their resilience to stressful challenge. These findings suggest proclivity to adaptive or maladaptive prenatal programming of hippocampal GR recruitment to be inheritable and predictable by social dominance or submissiveness.

The immunomodulatory tellurium compound ammonium trichloro (dioxoethylene-O,O') tellurate reduces anxiety-like behavior and corticosterone levels of submissive mice

Ammonium trichloro (dioxoethylene-O,O') tellurate (AS101) is a synthetic organotellurium compound with potent immunomodulatory and neuroprotective properties shown to inhibit the function of integrin αvβ3, a presynaptic cell-surface-adhesion receptor. As partial deletion of αvβ3 downregulated reuptake of serotonin by the serotonin transporter, we hypothesized that AS101 may influence pathways regulating anxiety. AS101 was tested in the modulation of anxiety-like behavior using the selectively bred Submissive (Sub) mouse strain that develop anxiety-like behavior in response to an i.p. injection. Mice were treated daily with AS101 (i.p., 125 or 200 μg/kg) or vehicle for 3 weeks, after which their anxiety-like behavior was measured in the elevated plus maze. Animals were then culled for the measurement of serum corticosterone levels by ELISA and hippocampal expression of brain-derived neurotrophic factor (BDNF) by RT-PCR. Chronic administration of AS101 significantly reduced anxiety-like behavior of Sub mice in the elevated plus maze, according to both time spent and entries to open arms, relative to vehicle-treated controls. AS101 also markedly reduced serum corticosterone levels of the treated mice and increased their hippocampal BDNF expression. Anxiolytic-like effects of AS101 may be attributed to the modulation of the regulatory influence integrin of αvβ3 upon the serotonin transporter, suggesting a multifaceted mechanism by which AS101 buffers the hypothalamic-pituitary-adrenal axis response to injection stress, enabling recovery of hippocampal BDNF expression and anxiety-like behavior in Sub mice. Further studies should advance the potential of AS101 in the context of anxiety-related disorders.

Seasonality and BDNF polymorphism influences depression outcome in patients with atopic dermatitis and psoriasis

OBJECTIVES

To examine the effect of seasonality and rs6265 genotype on depression outcome and brain-derived neurotrophic factor (BDNF) level with dermatitis patients from onset through remission.

METHODS

Atopic dermatitis (AD, 56) and psoriasis (PS, 33) patients and healthy controls (HC, 49) were recruited over the 2014 calendar year. Patients were subdivided by immunoglobulin E (IgE) sensitivity (AD only), season and rs6265 genotype. Assessments were performed at onset and week 10 (Hamilton Depression Rating Scale [HAM-D], SCORAD/PASI, IgE, BDNF). Patients received standard corticosteroid and antihistamine interventions.

RESULTS

All patients responded to corticosteroid treatment. Seasonally differential outcomes were observed in all groups. HAM-D was elevated at onset and improved over 10 weeks: AD cohort 1 (autumn/winter, AD-1) patients improved and AD cohort 2 (spring/summer, AD-2) patients remained elevated. BDNF levels were elevated in AD and seasonal differential: AD-2 declined at 10 weeks, whereas AD-1 remained high (intrinsic AD) or elevated further (extrinsic AD). PS cohort 2 declined to below control at 10 weeks. AD Val/Val had persistently elevated HAM-D and AD Val/Met were either normal (AD-1) or persistently elevated (AD-2).

CONCLUSIONS

Findings presented here suggest a strong influence of seasonality on depression outcome and BDNF expression in AD and PS and likely reflect separate patient populations which differentially respond to environment-based stressors.

Pituitary adenylate cyclase activating polypeptide (PACAP), stress, and sex hormones

Stressor exposure is associated with the onset and severity of many psychopathologies that are more common in women than men. Moreover, the maladaptive expression and function of stress-related hormones have been implicated in these disorders. Evidence suggests that PACAP has a critical role in the stress circuits mediating stress-responding, and PACAP may interact with sex hormones to contribute to sex differences in stress-related disease. In this review, we describe the role of the PACAP/PAC1 system in stress biology, focusing on the role of stress-induced alterations in PACAP expression and signaling in the development of stress-induced behavioral change. Additionally, we present more recent data suggesting potential interactions between stress, PACAP, and circulating estradiol in pathological states, including PTSD. These studies suggest that the level of stress and circulating gonadal hormones may differentially regulate the PACAPergic system in males and females to influence anxiety-like behavior and may be one mechanism underlying the discrepancies in human psychiatric disorders.

Pituitary adenylate cyclase activating polypeptide (PACAP) and its receptor 1 (PAC1) in the human infant brain and changes in the Sudden Infant Death Syndrome (SIDS)

Pituitary adenylate cyclase activating polypeptide (PACAP) and its complementary receptor, PAC1, are crucial in central respiratory control. PACAP Knockout (KO) mice exhibit a SIDS-like phenotype, with an inability to overcome noxious insults, compression of baseline ventilation, and death in the early post-neonatal period. PAC1 KO demonstrate similar attributes to PACAP-null mice, but with the addition of increased pulmonary artery pressure, consequently leading to heart failure and death. This study establishes a detailed interpretation of the neuroanatomical distribution and localization of both PACAP and PAC1 in the human infant brainstem and hippocampus, to determine whether any changes in expression are evident in infants who died of Sudden Infant Death Syndrome (SIDS) and any relationships to risk factors of SIDS including smoke exposure and sleep related parameters. Immunohistochemistry for PACAP and PAC1 was performed on formalin fixed and paraffin embedded human infant brain tissue of SIDS (n=32) and non-SIDS (n=12). The highest expression of PACAP was found in the hypoglossal (XII) of the brainstem medulla and lowest expression in the subiculum of the hippocampus. Highest expression of PAC1 was also found in XII of the medulla and lowest in the midbrain dorsal raphe (MBDR) and inferior colliculus. SIDS compared to non-SIDS had higher PACAP in the MBDR (p<0.05) and lower PAC1 in the medulla arcuate nucleus (p<0.001). Correlations were found between PACAP and PAC1 with the risk factors of smoke exposure, bed sharing, upper respiratory tract infection (URTI) and seasonal temperatures. The findings of this study show for the first time that some abnormalities of the PACAP system are evident in the SIDS brain and could contribute to the mechanisms of infants succumbing to SIDS.

Long-Term Estrogen Receptor Beta Agonist Treatment Modifies the Hippocampal Transcriptome in Middle-Aged Ovariectomized Rats

Estradiol (E2) robustly activates transcription of a broad array of genes in the hippocampal formation of middle-aged ovariectomized rats via estrogen receptors (ERα, ERβ, and G protein-coupled ER). Selective ERβ agonists also influence hippocampal functions, although their downstream molecular targets and mechanisms are not known. In this study, we explored the effects of long-term treatment with ERβ agonist diarylpropionitrile (DPN, 0.05 mg/kg/day, sc.) on the hippocampal transcriptome in ovariectomized, middle-aged (13 month) rats. Isolated hippocampal formations were analyzed by Affymetrix oligonucleotide microarray and quantitative real-time PCR. Four hundred ninety-seven genes fulfilled the absolute fold change higher than 2 (FC > 2) selection criterion. Among them 370 genes were activated. Pathway analysis identified terms including glutamatergic and cholinergic synapse, RNA transport, endocytosis, thyroid hormone signaling, RNA degradation, retrograde endocannabinoid signaling, and mRNA surveillance. PCR studies showed transcriptional regulation of 58 genes encoding growth factors (Igf2, Igfb2, Igf1r, Fgf1, Mdk, Ntf3, Bdnf), transcription factors (Otx2, Msx1), potassium channels (Kcne2), neuropeptides (Cck, Pdyn), peptide receptors (Crhr2, Oprm1, Gnrhr, Galr2, Sstr1, Sstr3), neurotransmitter receptors (Htr1a, Htr2c, Htr2a, Gria2, Gria3, Grm5, Gabra1, Chrm5, Adrb1), and vesicular neurotransmitter transporters (Slc32a1, Slc17a7). Protein-protein interaction analysis revealed networking of clusters associated with the regulation of growth/troph factor signaling, transcription, translation, neurotransmitter and neurohormone signaling mechanisms and potassium channels. Collectively, the results reveal the contribution of ERβ-mediated processes to the regulation of transcription, translation, neurogenesis, neuromodulation, and neuroprotection in the hippocampal formation of ovariectomized, middle-aged rats and elucidate regulatory channels responsible for DPN-altered functional patterns. These findings support the notion that selective activation of ERβ may be a viable approach for treating the neural symptoms of E2 deficiency in menopause.

The effects of sex and neonatal stress on pituitary adenylate cyclase-activating peptide expression

NEW FINDINGS

What is the central question of this study? Does sex or neonatal stress affect the expression of pituitary adenylate cyclase-activating peptide or its receptors? What is the main finding and its importance? Neonatal-maternal separation stress has little long-lasting effect on the expression of pituitary adenylate cyclase-activating peptide or its receptors, but sex differences exist in these genes between males and females at baseline. Sex differences in classic stress hormones have been studied in depth, but pituitary adenylate cyclase-activating peptide (PACAP), recently identified as playing a critical role in the stress axes, has not. Here we studied whether baseline levels of PACAP differ between sexes in various stress-related tissues and whether neonatal-maternal separation stress has a sex-dependent effect on PACAP gene expression in stress pathways. Using quantitative RT-PCR, we found sex differences in PACAP and PACAP receptor gene expression in several respiratory and/or stress-related tissues, while neonatal-maternal separation stress did little to affect PACAP signalling in adult animals. We propose that sex differences in PACAP expression are likely to contribute to differences between males and females in responses to stress.

Regulating the ubiquitin/proteasome pathway via cAMP-signaling: neuroprotective potential

The cAMP-signaling pathway has been under intensive investigation for decades. It is a wonder that such a small simple molecule like cAMP can modulate a vast number of diverse processes in different types of cells. The ubiquitous involvement of cAMP-signaling in a variety of cellular events requires tight spatial and temporal control of its generation, propagation, compartmentalization, and elimination. Among the various steps of the cAMP-signaling pathway, G-protein-coupled receptors, adenylate cyclases, phosphodiesterases, the two major cAMP targets, i.e., protein kinase A and exchange protein activated by cAMP, as well as the A-kinase anchoring proteins, are potential targets for drug development. Herein we review the recent progress on the regulation and manipulation of different steps of the cAMP-signaling pathway. We end by focusing on the emerging role of cAMP-signaling in modulating protein degradation via the ubiquitin/proteasome pathway. New discoveries on the regulation of the ubiquitin/proteasome pathway by cAMP-signaling support the development of new therapeutic approaches to prevent proteotoxicity in chronic neurodegenerative disorders and other human disease conditions associated with impaired protein turnover by the ubiquitin/proteasome pathway and the accumulation of ubiquitin-protein aggregates.

Endocannabinoid receptor deficiency affects maternal care and alters the dam's hippocampal oxytocin receptor and brain-derived neurotrophic factor expression

Maternal care is the newborn's first experience of social interaction, and this influences infant survival, development and social competences throughout life. We recently found that postpartum blocking of the endocannabinoid receptor-1 (CB1R) altered maternal behaviour. In the present study, maternal care was assessed by the time taken to retrieve pups, pups' ultrasonic vocalisations (USVs) and pup body weight, comparing CB1R deleted (CB1R KO) versus wild-type (WT) mice. After culling on postpartum day 8, hippocampal expression of oxytocin receptor (OXTR), brain-derived neurotrophic factor (BDNF) and stress-mediating factors were evaluated in CB1R KO and WT dams. Comparisons were also performed with nulliparous (NP) CB1R KO and WT mice. Compared to WT, CB1R KO dams were slower to retrieve their pups. Although the body weight of the KO pups did not differ from the weight of WT pups, they emitted fewer USVs. This impairment of the dam-pup relationship correlated with a significant reduction of OXTR mRNA and protein levels among CB1R KO dams compared to WT dams. Furthermore, WT dams exhibited elevated OXTR mRNA expression, as well as increased levels of mineralocorticoid and glucocorticoid receptors, compared to WT NP mice. By contrast, CB1R KO dams showed no such elevation of OXTR expression, alongside lower BDNF and mineralocorticoid receptors, as well as elevated corticotrophin-releasing hormone mRNA levels, when compared to CB1R KO NP. Thus, it appears that the disruption of endocannabinoid signalling by CB1R deletion alters expression of the OXTR, apparently leading to deleterious effects upon maternal behaviour.

The specific VPAC2 agonist Bay 55-9837 increases neuronal damage and hemorrhagic transformation after stroke in type 2 diabetic rats

VPAC2 receptor is a potential target for the treatment of type 2 diabetes and may also convey neuroprotective effects. The aim of this study was to determine the potential efficacy of the VPAC2 receptor agonist Bay 55-9837 against stroke in type-2 diabetic Goto-Kakizaki (GK) rats. GK rats were treated intravenously once daily for 7 days with 0.25 or 0.025 nmol/kg Bay 55-9837 or vehicle before inducing stroke by transient middle cerebral artery occlusion. Treatments were then continued for 7 further days. The glycemic effects of Bay 55-9837 were assessed by measuring fasting blood glucose and oral glucose tolerance. The severity of stroke was measured by assessing ischemic volume. The results show that Bay 55-9837 is not effective in lowering fasting glycemia and does not facilitate glucose disposal. The highest dose of Bay 55-9837 (0.25 nmol/kg) led to increased mortality and brain hemorrhage when compared to control. The lower dose of Bay 55-9837 (0.025 nmol/kg) did not increase mortality rate but caused a threefold increase of the ischemic lesion size with signs of brain hemorrhages as compared to control. In conclusion, Bay 55-9837 did not show antidiabetic or antistroke efficacy in the type 2 diabetic GK rat. Contrarily, Bay 55-9837 treatment led to increased mortality and worsening of the severity of stroke.

Alternative Splicing of the Pituitary Adenylate Cyclase-Activating Polypeptide Receptor PAC1: Mechanisms of Fine Tuning of Brain Activity

Alternative splicing of the precursor mRNA encoding for the neuropeptide receptor PAC1/ADCYAP1R1 generates multiple protein products that exhibit pleiotropic activities. Recent studies in mammals and zebrafish have implicated some of these splice isoforms in control of both cellular and body homeostasis. Here, we review the regulation of PAC1 splice variants and their underlying signal transduction and physiological processes in the nervous system.

The expression of PAC1 increases in the degenerative thymus and low dose PACAP protects female mice from cyclophosphamide induced thymus atrophy

Pituitary adenylate cyclase activating polypeptide (PACAP) is a neuropeptide with cytoprotective ability mediated by its specific receptor PAC1. In this research, firstly the thymus index and the expression of PAC1 in the normal and degenerative thymus with different gender were assayed; secondly PACAP in different dose was used to treat the female mice with cyclophosphamide (CPS) and the changes in thymus index, the expression of PAC1, histopathology, apoptosis, oxidative status and the caspase 3 activity in thymus were determined and compared. It was found that in the mice of age from 1 to 9 weeks in the stage of sex development, the thymus index was significantly higher in female mice than in male mice. And it was found for the first time that the PAC1 expression level in thymus of female mice was significantly higher than that of male mice and the expression of the PAC1 and PACAP increased significantly in the degenerative thymus induced by CPS. After PACAP was co-injected with CPS to the female mice, it was shown that only low dose (1 nmol/kg) of PACAP promoted the thymus index, inhibited the cell apoptosis, ameliorated the oxidative status and decreased the caspase activity significantly, while high dose (10 nmol/kg) of PACAP had no significant protective effects against CPS-induced thymus atrophy. It was concluded that the expression of PAC1 in the thymus changes in reverse ratio with thymus index and in direct ratio with cell apoptosis and only low dose of PACAP had positive effects against the CPS-induced thymus atrophy.

Incensole acetate reduces depressive-like behavior and modulates hippocampal BDNF and CRF expression of submissive animals

Incensole acetate (IA), a constituent of Boswellia resin ('frankincense'), was previously demonstrated to exhibit an antidepressive-like effect in the Forced Swim Test (FST) in mice following single dose administration (50 mg/kg). Here, we show that acute administration of considerably lower dose (10 mg/kg) IA to selectively bred mice, showing prominent submissive behavior, exerted significant antidepressant-like effects in the FST. Furthermore, chronic administration of 1 or 5 mg/kg per day of IA for three consecutive weeks dose- and time-dependently reduced the submissiveness of the mice in the Dominant-Submissive Relationship test, developed to screen the chronic effect of antidepressants. This behavioral effect was concomitant to reduced serum corticosterone levels, dose-dependent down-regulation of corticotropin releasing factor and up-regulation of brain derived neurotrophic factor transcripts IV and VI expression in the hippocampus. These data suggest that IA modulates the hypothalamic-pituitary-adrenal (HPA) axis and influences hippocampal gene expression, leading to beneficial behavioral effects supporting its potential as a novel treatment of depressive-like disorders.

Pituitary adenylate cyclase-activating polypeptide counteracts the impaired adult neural stem cell viability induced by palmitate

Diabetes and obesity are characterized by hyperlipidemia and represent risk factors for premature neurological disorders. Diabetic/obese animals have impaired adult neurogenesis. We hypothesize that lipotoxicity leading to neurogenesis impairment plays a role in the development of neurological complications. If so, normalizing neurogenesis in diabetes/obesity could be therapeutically useful in counteracting neurological dysfunction. The goal of this study was to determine the potential of pituitary adenylate cyclase-activating polypeptide (PACAP) to protect adult neural stem cells (NSCs) from lipotoxicity and to study the expression of PACAP receptors in NSCs under lipotoxic conditions in vitro and in the subventricular zone in vivo. The viability of NSCs isolated from the adult mouse brain subventricular zone was assessed in the presence of a high-fat milieu, as mimicked by palmitate, which characterizes diabetic lipotoxicity. Regulation studies of PACAP receptors were performed by quantitative PCR on NSCs in vitro or on subventricular tissues isolated from obese ob/ob mice and their lean littermates. We show that palmitate impairs NSC viability by promoting lipoapoptosis. We also show that PACAP counteracts lipotoxicity via PAC-1 receptor activation. Studies on PACAP receptor expression revealed that PAC-1 and VPAC-2 are expressed by NSC in vitro and are upregulated by palmitate treatment and that PAC-1, VPAC-1, and VPAC-2 are expressed in the subventricular zone/striatum in vivo and are upregulated in ob/ob mice. The present study reveals a previously uncharacterized role of PACAP to protect NSC from lipotoxicity and suggests a potential therapeutic role for PACAP receptor agonists in the treatment of neurological complications in obesity and diabetes.