Reward Network Immediate Early Gene Expression in Mood Disorders

Immediate-Early Genes as Influencers in Genetic Networks and their Role in Alzheimer's Disease

Immediate-early genes (IEGs) are a class of activity-regulated genes (ARGs) that are transiently and rapidly activated in the absence of de novo protein synthesis in response to neuronal activity. We explored the role of IEGs in genetic networks to pinpoint potential drug targets for Alzheimer's disease (AD). Using a combination of network analysis and genome-wide association study (GWAS) summary statistics we show that (1) IEGs exert greater topological influence across different human and mouse gene networks compared to other ARGs, (2) ARGs are sparsely involved in diseases and significantly more mutational constrained compared to non-ARGs, (3) Many AD-linked variants are in ARGs gene regions, mainly in MARK4 near FOSB, with an AD risk eQTL that increases MARK4 expression in cortical areas, (4) MARK4 holds an influential place in a dense AD multi-omic network and a high AD druggability score. Our work on IEGs' influential network role is a valuable contribution to guiding interventions for diseases marked by dysregulation of their downstream targets and highlights MARK4 as a promising underexplored AD-target.

Repeated pre-exposure to morphine inhibited the amnesic effect of ethanol on spatial memory: Involvement of CaMKII and BDNF

Evidence has suggested that addiction and memory systems are related, but the signaling cascades underlying this interaction have not been completelyealed yet. The importance of calcium-calmodulin-dependent protein kinase II (CaMKII) and brain-derived neurotrophic factor (BDNF) in the memory processes and also in drug addiction has been previously established. In this present investigation, we examined the effects of repeated morphine pretreatment on impairment of spatial learning and memory acquisition induced by systemic ethanol administration in adult male rats. Also, we assessed how these drug exposures influence the expression level of CaMKII and BDNF in the hippocampus and amygdala. Animals were trained by a single training session of 8 trials, and a probe test containing a 60-s free-swim without a platform was administered 24 h later. Before training trials, rats were treated with a once-daily subcutaneous morphine injection for 3 days followed by a 5-day washout period. The results showed that pre-training ethanol (1 g/kg) impaired spatial learning and memory acquisition and down-regulated the mRNA expression of CaMKII and BDNF. The amnesic effect of ethanol was suppressed in morphine- (15 mg/kg/day) pretreated animals. Furthermore, the mRNA expression level of CaMKII and BDNF increased significantly following ethanol administration in morphine-pretreated rats. Conversely, this improvement in spatial memory acquisition was prevented by daily subcutaneous administration of naloxone (2 mg/kg) 15 min prior to morphine administration. Our findings suggest that sub-chronic morphine treatment reverses ethanol-induced spatial memory impairment, which could be explained by modulating CaMKII and BDNF mRNA expressions in the hippocampus and amygdala.

SRF deletion results in earlier disease onset in a mouse model of amyotrophic lateral sclerosis

Changes in neuronal activity modulate the vulnerability of motoneurons (MNs) in neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS). So far, the molecular basis of neuronal activity's impact in ALS is poorly understood. Herein, we investigated the impact of deleting the neuronal activity-stimulated transcription factor (TF) serum response factor (SRF) in MNs of SOD1G93A mice. SRF was present in vulnerable MMP9+ MNs. Ablation of SRF in MNs induced an earlier disease onset starting around 7-8 weeks after birth, as revealed by enhanced weight loss and decreased motor ability. This earlier disease onset in SRF-depleted MNs was accompanied by a mild elevation of neuroinflammation and neuromuscular synapse degeneration, whereas overall MN numbers and mortality were unaffected. In SRF-deficient mice, MNs showed impaired induction of autophagy-encoding genes, suggesting a potentially new SRF function in transcriptional regulation of autophagy. Complementary, constitutively active SRF-VP16 enhanced autophagy-encoding gene transcription and autophagy progression in cells. Furthermore, SRF-VP16 decreased ALS-associated aggregate induction. Chemogenetic modulation of neuronal activity uncovered SRF as having important TF-mediating activity-dependent effects, which might be beneficial to reduce ALS disease burden. Thus, our data identify SRF as a gene regulator connecting neuronal activity with the cellular autophagy program initiated in degenerating MNs.

Chemically targeting the redox switch in AP1 transcription factor ΔFOSB

The AP1 transcription factor ΔFOSB, a splice variant of FOSB, accumulates in the brain in response to chronic insults such as exposure to drugs of abuse, depression, Alzheimer's disease and tardive dyskinesias, and mediates subsequent long-term neuroadaptations. ΔFOSB forms heterodimers with other AP1 transcription factors, e.g. JUND, that bind DNA under control of a putative cysteine-based redox switch. Here, we reveal the structural basis of the redox switch by determining a key missing crystal structure in a trio, the ΔFOSB/JUND bZIP domains in the reduced, DNA-free form. Screening a cysteine-focused library containing 3200 thiol-reactive compounds, we identify specific compounds that target the redox switch, validate their activity biochemically and in cell-based assays, and show that they are well tolerated in different cell lines despite their general potential to bind to cysteines covalently. A crystal structure of the ΔFOSB/JUND bZIP domains in complex with a redox-switch-targeting compound reveals a deep compound-binding pocket near the DNA-binding site. We demonstrate that ΔFOSB, and potentially other, related AP1 transcription factors, can be targeted specifically and discriminately by exploiting unique structural features such as the redox switch and the binding partner to modulate biological function despite these proteins previously being thought to be undruggable.

ΔFOSB: A Potentially Druggable Master Orchestrator of Activity-Dependent Gene Expression

ΔFOSB is a uniquely stable member of the FOS family of immediate early gene AP1 transcription factors. Its accumulation in specific cell types and tissues in response to a range of chronic stimuli is associated with biological phenomena as diverse as memory formation, drug addiction, stress resilience, and immune cell activity. Causal connections between ΔFOSB expression and the physiological and behavioral sequelae of chronic stimuli have been established in rodent and, in some cases, primate models for numerous healthy and pathological states with such preclinical observations often supported by human data demonstrating tissue-specific ΔFOSB expression associated with several specific syndromes. However, the viability of ΔFOSB as a target for therapeutic intervention might be questioned over presumptive concerns of side effects given its expression in such a wide range of cell types and circumstances. Here, we summarize numerous insights from the past three decades of research into ΔFOSB structure, function, mechanisms of induction, and regulation of target genes that support its potential as a druggable target. We pay particular attention to the potential for targeting distinct ΔFOSB isoforms or distinct ΔFOSB-containing multiprotein complexes to achieve cell type or tissue specificity to overcome off-target concerns. We also cover critical gaps in knowledge that currently limit the exploitation of ΔFOSB's therapeutic possibilities and how they may be addressed. Finally, we summarize both current and potential future strategies for generating small molecules or genetic tools for the manipulation of ΔFOSB in the clinic.

Single-chain Fragment variable antibody targeting cholecystokinin-B receptor for pain reduction

The cholecystokinin B receptor and its neuropeptide ligand are upregulated in chronic neuropathic pain models. Single-chain Fragment variable antibodies were generated as preferred non-opioid targeting therapy blocking the cholecystokinin B receptor to inhibit chronic neuropathic pain models in vivo and in vitro. Engineered antibodies of this type feature binding activity similar to monoclonal antibodies but with stronger affinity and increased tissue penetrability due to their smaller size. More importantly, single-chain Fragment variable antibodies have promising biotherapeutic applications for both nervous and immune systems, now recognized as interactive in chronic pain. A mouse single-chain Fragment variable antibody library recognizing a fifteen amino acid extracellular peptide fragment of the cholecystokinin B receptor was generated from immunized spleens. Ribosome display, a powerful cell-free technology, was applied for recombinant antibody selection. Antibodies with higher affinity, stability, solubility, and binding specificity for cholecystokinin B not A receptor were selected and optimized for in vivo and in vitro efficacy. A single dose of the lead candidate reduced mechanical and cold hypersensitivity in two rodent models of neuropathic pain for at least seven weeks. Continuing efficacy was evident with either intraperitoneal or intranasal dosing. Likewise, the lead single-chain Fragment variable antibody totally prevented development of anxiety- and depression-like behaviors and cognitive deficits typical in the models. Reduction of neuronal firing frequency was evident in trigeminal ganglia primary neuronal cultures treated in vitro with the cholecystokinin B receptor antibody. Immunofluorescent staining intensity in the trigeminal neuron primary cultures was significantly reduced incrementally after overnight binding with increasingly higher dilutions of the single-chain Fragment variable antibody. While it is reported that single-chain Fragment variable antibodies are removed systemically within 2-6 h, Western blot evidence indicates the His-tag marker remained after 7 weeks in the trigeminal ganglia and in the dorsolateral medulla, providing evidence of brain and ganglia penetrance known to be compromised in overactivated states. This project showcases the in vivo efficacy of our lead single-chain Fragment variable antibody indicating its potential for development as a non-opioid, non-addictive therapeutic intervention for chronic pain. Importantly, studies by others have indicated treatments with cholecystokinin B receptor antagonists suppress maintenance and reactivation of morphine dependence in place preference tests while lowering tolerance and dose requirements. Our future studies remain to address these potential benefits that may accompany the cholecystokinin B receptor biological therapy. Both chronic sciatic and orofacial pain can be unrelenting and excruciating, reducing quality of life as well as diminishing physical and mental function. An effective non-opiate, non-addictive therapy with potential to significantly reduce chronic neuropathic pain long term is greatly needed.

Neuronal activity-induced BRG1 phosphorylation regulates enhancer activation

Neuronal activity-induced enhancers drive gene activation. We demonstrate that BRG1, the core subunit of SWI/SNF-like BAF ATP-dependent chromatin remodeling complexes, regulates neuronal activity-induced enhancers. Upon stimulation, BRG1 is recruited to enhancers in an H3K27Ac-dependent manner. BRG1 regulates enhancer basal activities and inducibility by affecting cohesin binding, enhancer-promoter looping, RNA polymerase II recruitment, and enhancer RNA expression. We identify a serine phosphorylation site in BRG1 that is induced by neuronal stimulations and is sensitive to CaMKII inhibition. BRG1 phosphorylation affects its interaction with several transcription co-factors, including the NuRD repressor complex and cohesin, possibly modulating BRG1-mediated transcription outcomes. Using mice with knockin mutations, we show that non-phosphorylatable BRG1 fails to efficiently induce activity-dependent genes, whereas phosphomimic BRG1 increases enhancer activity and inducibility. These mutant mice display anxiety-like phenotypes and altered responses to stress. Therefore, we reveal a mechanism connecting neuronal signaling to enhancer activities through BRG1 phosphorylation.

DNA Methylation and Expression Profiles of Whole Blood in Parkinson's Disease

Parkinson’s disease (PD) is the second most common age-related neurodegenerative disease. It is presently only accurately diagnosed at an advanced stage by a series of motor deficits, which are predated by a litany of non-motor symptoms manifesting over years or decades. Aberrant epigenetic modifications exist across a range of diseases and are non-invasively detectable in blood as potential markers of disease. We performed comparative analyses of the methylome and transcriptome in blood from PD patients and matched controls. Our aim was to characterize DNA methylation and gene expression patterns in whole blood from PD patients as a foundational step toward the future goal of identifying molecular markers that could predict, accurately diagnose, or track the progression of PD. We found that differentially expressed genes (DEGs) were involved in the processes of transcription and mitochondrial function and that PD methylation profiles were readily distinguishable from healthy controls, even in whole-blood DNA samples. Differentially methylated regions (DMRs) were functionally varied, including near transcription factor nuclear transcription factor Y subunit alpha (NFYA), receptor tyrosine kinase DDR1, RING finger ubiquitin ligase (RNF5), acetyltransferase AGPAT1, and vault RNA VTRNA2-1. Expression quantitative trait methylation sites were found at long non-coding RNA PAX8-AS1 and transcription regulator ZFP57 among others. Functional epigenetic modules were highlighted by IL18R1, PTPRC, and ITGB2. We identified patterns of altered disease-specific DNA methylation and associated gene expression in whole blood. Our combined analyses extended what we learned from the DEG or DMR results alone. These studies provide a foundation to support the characterization of larger sample cohorts, with the goal of building a thorough, accurate, and non-invasive molecular PD biomarker.

Drug-activated cells: From immediate early genes to neuronal ensembles in addiction

Beyond their rapid rewarding effects, drugs of abuse can durably alter an individual's response to their environment as illustrated by the compulsive drug seeking and risk of relapse triggered by drug-associated stimuli. The persistence of these associations even long after cessation of drug use demonstrates the enduring mark left by drugs on brain reward circuits. However, within these circuits, neuronal populations are differently affected by drug exposure and growing evidence indicates that relatively small subsets of neurons might be involved in the encoding and expression of drug-mediated associations. The identification of sparse neuronal populations recruited in response to drug exposure has benefited greatly from the study of immediate early genes (IEGs) whose induction is critical in initiating plasticity programs in recently activated neurons. In particular, the development of technologies to manipulate IEG-expressing cells has been fundamental to implicate broadly distributed neuronal ensembles coincidently activated by either drugs or drug-associated stimuli and to then causally establish their involvement in drug responses. In this review, we summarize the literature regarding IEG regulation in different learning paradigms and addiction models to highlight their role as a marker of activity and plasticity. As the exploration of neuronal ensembles in addiction improves our understanding of drug-associated memory encoding, it also raises several questions regarding the cellular and molecular characteristics of these discrete neuronal populations as they become incorporated in drug-associated neuronal ensembles. We review recent efforts towards this goal and discuss how they will offer a more comprehensive understanding of addiction pathophysiology.

Acute mitragynine administration suppresses cortical oscillatory power and systems theta coherence in rats

BACKGROUND

Mitragynine is the major alkaloid of Mitragyna speciosa (kratom) with potential as a therapeutic in pain management and in depression. There has been debate over the potential side effects of the drug including addiction risk and cognitive decline.

AIMS

To evaluate the effects of mitragynine on neurophysiological systems function in the prefrontal cortex (PFC), cingulate cortex (Cg), orbitofrontal cortex, nucleus accumbens (NAc), hippocampus (HIP), thalamus (THAL), basolateral amygdala (BLA) and ventral tegmental area of rats.

METHODS

Local field potential recordings were taken from animals at baseline and for 45 min following mitragynine administration (10 mg/kg, intraperitoneally). Drug-induced changes in spectral power and coherence between regions at specific frequencies were evaluated. Mitragynine-induced changes in c-fos expression were also analyzed.

RESULTS

Mitragynine increased delta power and reduced theta power in all three cortical regions that were accompanied by increased c-fos expression. A transient suppression of gamma power in PFC and Cg was also evident. There were no effects of mitragynine on spectral power in any of the other regions. Mitragynine induced a widespread reduction in theta coherence (7-9 Hz) that involved disruptions in cortical and NAc connectivity with the BLA, HIP and THAL.

CONCLUSIONS

These findings show that mitragynine induces frequency-specific changes in cortical neural oscillatory activity that could potentially impact cognitive functioning. However, the absence of drug effects within regions of the mesolimbic pathway may suggest either a lack of addiction potential, or an underlying mechanism of addiction that is distinct from other opioid analgesic agents.

Atopic dermatitis induces anxiety- and depressive-like behaviors with concomitant neuronal adaptations in brain reward circuits in mice

Clinically, it has been reported that atopic dermatitis (AD) has been linked with negative emotional problems such as depression and anxiety, thereby reducing the quality of life, but little is known about the molecular mechanism that underlies AD-associated emotional impairments. We sought to determine whether AD could induce anxiety- and depressive-like symptoms in mice and to identify pertinent signaling changes in brain reward circuitry. AD-like lesions were induced by the repeated intradermal application of MC903 into the cheek of the mouse. We assessed dermatitis severity with scratching behavior, histopathological changes, anxiety- and depressive-like behaviors using the elevated plus maze, open field and tail suspension tests, and serum corticosterone levels. In the nucleus accumbens (NAc), dorsal striatum (DS) and ventral tegmental area (VTA), protein levels of dopamine- and plasticity-related signaling molecules were determined by Western immunoblotting assay. Intradermal administration of MC903 into mouse cheek provoked a strong hind limb scratching behavior as well as the robust skin inflammation with epidermal thickening. MC903-treated mice also displayed markedly increased anxiety- and depressive-like behaviors, along with elevated serum corticosterone levels. Under these conditions, enhanced cAMP response element binding protein (CREB) and dopamine and cAMP-regulated phosphoprotein, 32 kDa (DARPP32) phosphorylation, significantly higher brain-derived neurotrophic factor (BDNF) and ΔFosB, but reduced tyrosine hydroxylase (TH) and dopamine D1 receptor (D1R) protein expression were found in the NAc, DS and VTA. Striatal BDNF, phospho-DARPP32 and phospho-CREB levels were significantly associated with the levels of depressive-like behavior in these mice. Taken together, these findings demonstrate that AD-like skin lesion elicits anxiety- and depressive-like phenotypes that are associated with neuroplasticity-related changes in reward circuitry, providing a better understanding of AD-associated emotional impairments.

Adverse Effects of Circadian Disorganization on Mood and Molecular Rhythms in the Prefrontal Cortex of Mice

Disturbance of the daily cycles in sleep and wakefulness induced by conditions such as shift work and jet lag can increase the risk of affective disorders including anxiety and depression. The way such circadian disorganization disrupts the regulation of mood, however, is not well understood. More specifically, the impact of circadian disorganization on the daily rhythms of the neuronal function that controls mood remains unclear. We therefore investigated the effects of circadian disorganization on expression rhythms of clock genes as well as immediate early genes (IEGs) in several mood-controlling regions of the brain. To introduce circadian disorganization of behaviors, we exposed male C57BL/6J mice to chronic reversal of the light-dark cycle and we found a marked negative mood phenotype in these mice. Importantly, the most adverse effect of circadian disorganization on expression rhythms of clock and IEGs was observed in the prefrontal cortex (PFC) when compared to that in other mood-related areas of the brain. Dysregulation of molecular rhythms in the PFC is therefore suggested to be associated with the development of mood disorders in conditions including shift work and jet lag.

Sex differences in adult mood and in stress-induced transcriptional coherence across mesocorticolimbic circuitry

Women are approximately two times as likely to be diagnosed with major depressive disorder (MDD) compared to men. While sex differences in MDD might be driven by circulating gonadal hormones, we hypothesized that developmental hormone exposure and/or genetic sex might play a role. Mice were gonadectomized in adulthood to isolate the role of developmental hormones. We examined the effects of developmental gonadal and genetic sex on anhedonia-/depressive-like behaviors under non-stress and chronic stress conditions and performed RNA-sequencing in three mood-relevant brain regions. We used an integrative network approach to identify transcriptional modules and stress-specific hub genes regulating stress susceptibility, with a focus on whether these differed by sex. After identifying sex differences in anhedonia-/depressive-like behaviors (female > male), we show that both developmental hormone exposure (gonadal female > gonadal male) and genetic sex (XX > XY) contribute to the sex difference. The top biological pathways represented by differentially expressed genes were related to immune function; we identify which differentially expressed genes are driven by developmental gonadal or genetic sex. There was very little overlap in genes affected by chronic stress in males and females. We also identified highly co-expressed gene modules affected by stress, some of which were affected in opposite directions in males and females. Since all mice had equivalent hormone exposure in adulthood, these results suggest that sex differences in gonadal hormone exposure during sensitive developmental periods program adult sex differences in mood, and that these sex differences are independent of adult circulating gonadal hormones.

The molecular and cellular mechanisms of depression: a focus on reward circuitry

Depression is a complex disorder that takes an enormous toll on individual health. As affected individuals display a wide variation in their clinical symptoms, the precise neural mechanisms underlying the development of depression remain elusive. Although it is impossible to phenocopy every symptom of human depression in rodents, the preclinical field has had great success in modeling some of the core affective and neurovegetative depressive symptoms, including social withdrawal, anhedonia, and weight loss. Adaptations in select cell populations may underlie these individual depressive symptoms and new tools have expanded our ability to monitor and manipulate specific cell types. This review outlines some of the most recent preclinical discoveries on the molecular and neurophysiological mechanisms in reward circuitry that underlie the expression of behavioral constructs relevant to depressive symptoms.

Effects of cocaine base paste on anxiety-like behavior and immediate-early gene expression in nucleus accumbens and medial prefrontal cortex of female mice

RATIONALE

Cocaine base paste (CBP) is an illegal drug of abuse usually consumed by adolescents in a socio-economically vulnerable situation. Repeated drug use targets key brain circuits disrupting the processes that underlie emotions and cognition. At the basis of such neuroadaptations lie changes in the expression of immediate-early genes (IEGs). Nevertheless, changes in transcriptional regulation associated with CBP consumption remain unknown.

OBJECTIVES

We aimed to describe behavioral phenotype related to locomotion, anxiety-like behavior, and memory of CBP-injected mice and to study IEGs expression after an abstinence period.

METHODS

Five-week-old female CF-1 mice were i.p. injected daily with vehicle or CBP (40 mg/kg) for 10 days and subjected to a 10-day period of abstinence. Open field and novel object recognition tests were used to evaluate locomotion and anxiety-like behaviors and recognition memory, respectively, during chronic administration and after abstinence. After abstinence, prefrontal cortex (mPFC) and nucleus accumbens (NAc) were isolated and gene expression analysis performed through real-time PCR.

RESULTS

We found an increase in locomotion and anxiety-like behavior during CBP administration and after the abstinence period. Furthermore, the CBP group showed impaired recognition memory after abstinence. Egr1, FosB, ΔFosB, Arc, Bdnf, and TrkB expression was upregulated in CBP-injected mice in NAc and FosB, ΔFosB, Arc, and Npas4 expression was downregulated in mPFC. We generated an anxiety score and found positive and negative correlations with IEGs expression in NAc and mPFC, respectively.

CONCLUSION

Our results suggest that chronic CBP exposure induced alterations in anxiety-like behavior and recognition memory. These changes were accompanied by altered IEGs expression.

Role of the galanin N-terminal fragment (1-15) in anhedonia: Involvement of the dopaminergic mesolimbic system

BACKGROUND

Anhedonia is a core feature of depressive disorders. The galanin N-terminal fragment (1-15) plays a role in mood regulation since it induces depression and anxiogenic-like effects in rats. In this study, we analysed galanin N-terminal fragment (1-15) actions in anhedonic-like behaviours in rats using operant and non-operant tests and the areas involved with these effects.

METHODS

Galanin N-terminal fragment (1-15) effects were analysed in saccharin self-administration, sucrose preference, novelty-suppressed feeding and female urine sniffing tests. The areas involved in galanin N-terminal fragment (1-15)-mediated effects were studied with positron emission tomography for in vivo imaging, and we analysed the ventral tegmental area and nucleus accumbens. Galanin N-terminal fragment (1-15) had effects on the mRNA expression of the dopamine transporters Dat and Vmat2; the C-Fos gene; the dopamine receptors D1, D2, D3, D5; and the galanin receptors 1 and 2.

RESULTS

Galanin N-terminal fragment (1-15) at a concentration of 3 nmol induced a strong anhedonia-like phenotype in all tests. The involvement of galanin receptor 2 was demonstrated with the galanin receptor 2 antagonist M871 (3 nmol). The 18F-fluorodeoxyglucose positron emission tomography images indicated the action of galanin N-terminal fragment (1-15) over several nuclei of the limbic system. Galanin N-terminal fragment (1-15)-mediated effects also involved changes in the expression of Dat, Vmat2, D3 and galanin receptors in the ventral tegmental area as well as the expression of C-Fos, D1, D2 and D3 and TH immunoreactivity in the nucleus accumbens.

CONCLUSIONS

Our results indicated that galanin N-terminal fragment (1-15) exerts strong anhedonic-like effects and that this effect was accompanied by changes in the dopaminergic mesolimbic system. These results may provide a basis for the development of novel therapeutic strategies using galanin N-terminal fragment (1-15) analogues for the treatment of depression and reward-related diseases.

Amylin - Its role in the homeostatic and hedonic control of eating and recent developments of amylin analogs to treat obesity

BACKGROUND

Amylin is a pancreatic β-cell hormone that produces effects in several different organ systems. One of its best-characterized effects is the reduction in eating and body weight seen in preclinical and clinical studies. Amylin activates specific receptors, a portion of which it shares with calcitonin gene-related peptide (CGRP). Amylin's role in the control of energy metabolism relates to its satiating effect, but recent data indicate that amylin may also affect hedonic aspects in the control of eating, including a reduction of the rewarding value of food. Recently, several amylin-based peptides have been characterized. Pramlintide (Symlin^®) is currently the only one being used clinically to treat type 1 and type 2 diabetes. However other amylin analogs with improved pharmacokinetic properties are being considered as anti-obesity treatment strategies. Several other studies in obesity have shown that amylin agonists could also be useful for weight loss, especially in combination with other agents.

SCOPE OF REVIEW

This review will briefly summarize amylin physiology and pharmacology and then focus on amylin's role in food reward and the effects of amylin analogs in pre-clinical testing for anti-obesity drugs.

CONCLUSION

We propose here that the effects of amylin may be homeostatic and hedonic in nature.

The Traditional Japanese Herbal Medicine Hachimijiogan Elicits Neurite Outgrowth Effects in PC12 Cells and Improves Cognitive in AD Model Rats via Phosphorylation of CREB

Hachimijiogan (HJG) is a traditional herbal medicine that improves anxiety disorders in patients with dementia. In this study, we tested the hypothesis that HJG exerts neurotrophic factor-like effects to ameliorate memory impairment in Alzheimer disease (AD) model rats. First, we describe that HJG acts to induce neurite outgrowth in PC12 cells (a rat pheochromocytoma cell line) like nerve growth factor (NGF) in a concentration-dependent manner (3 μg/ml HJG, p < 0.05; 10–500 μg/ml HJG, p < 0.001). While six herbal constituents of HJG, Rehmannia root, Dioscorea rhizome, Rhizoma Alismatis, Poria sclerotium, Moutan bark, and Cinnamon bark, could induce neurite outgrowth effects, the effect was strongest with HJG (500 μg/ml). Second, we demonstrated that HJG-induced neurite outgrowth was blocked by an inhibitor of cAMP response element binding protein (CREB), KG-501 (10 μM, p < 0.001). Moreover, HJG was observed to induce CREB phosphorylation 20–90 min after treatment (20 min, 2.50 ± 0.58-fold) and CRE-mediated transcription in cultured PC12 cells (500 μg/ml, p < 0.01; 1000 μg/ml, p < 0.001). These results suggest a CREB-dependent mechanism underlies the neurotrophic effects of HJG. Finally, we examined improvements of memory impairment following HJG treatment using a Morris water maze in AD model animals (CI + Aβ rats). Repeated oral administration of HJG improved memory impairment (300 mg/kg, p < 0.05; 1000 mg/kg, p < 0.001) and induced CREB phosphorylation within the hippocampus (1000 mg/kg, p < 0.01). Together, our results suggest that HJG possesses neurotrophic effects similar to those of NGF, and can ameliorate cognitive dysfunction in a rat dementia model via CREB activation. Thus, HJG could potentially be a substitute for neurotrophic factors as a treatment for dementia.

Comparison of chronic physical and emotional social defeat stress effects on mesocorticolimbic circuit activation and voluntary consumption of morphine

Chronic social defeat stress (CSDS) is a well-established rodent model of depression that induces persistent social avoidance. CSDS triggers molecular adaptations throughout the mesocorticolimbic reward circuit, including changes in the activity of dopamine neurons in the ventral tegmental area (VTA), that may also influence drug reward. One limitation of traditional, physical CSDS (PS) is that injury complicates the study of opiate drugs like morphine. Thus, we sought to characterize a variation of CSDS, termed emotional CSDS (ES), that eliminates this confound. We assessed the effect of PS and ES on mesocorticolimbic circuit activation, VTA gene expression, and morphine intake. We found that PS and ES similarly induced ΔFosB in the hippocampus, but only PS significantly increased ΔFosB expression in the prefrontal cortex and striatum. In contrast, cFos expression was similarly reduced by both PS and ES. Interestingly, we found that PS and ES similarly increased voluntary morphine consumption immediately following stress, despite differences in the magnitude of the depressive phenotype and striatal ΔFosB expression at this time point. Combined, these data suggest that both stress paradigms may be useful for investigation of stress-induced changes in drug behavior.