Regulation of CRF, POMC and MC4R gene expression after electrical foot shock stress in the rat amygdala and hypothalamus

Fam163a knockdown and mitochondrial stress in the arcuate nucleus of hypothalamus reduce AgRP neuron activity and differentially regulate mitochondrial dynamics in mice

AIM

Mitochondria play key roles in neuronal activity, particularly in modulating agouti-related protein (AgRP) and proopiomelanocortin (POMC) neurons in the arcuate nucleus of the hypothalamus (ARC), which regulates food intake. FAM163A, a newly identified protein, is suggested to be part of the mitochondrial proteome, though its functions remain largely unknown. This study aimed to investigate the effects of Fam163a knockdown and mitochondrial dysfunction on food intake, AgRP neuron activity, and mitochondrial function in the hypothalamus.

METHODS

Male C57BL/6 and AgRP-Cre mice received intracranial injections of either Fam163a shRNA, rotenone, or appropriate controls. Behavioral assessments included food intake, locomotor activity, and anxiety-like behaviors. qRT-PCR was used to quantify the expression of the genes related to food intake, mitochondrial biogenesis, dynamics, and oxidative stress. Blood glucose, serum insulin, and leptin levels were measured. Electrophysiological patch-clamp recordings were used to assess the AgRP neuronal activity.

RESULTS

Fam163a knockdown in the ARC increased the cumulative food intake in short term (first 7 days) without altering the 25-day food intake and significantly increased the Pomc mRNA expression. Fam163a silencing significantly reduced leptin levels. Both Fam163a knockdown and rotenone significantly reduced the firing frequency of AgRP neurons. Neither Fam163a silencing nor rotenone altered locomotor or anxiety-like behaviors. Fam163a knockdown and rotenone differentially altered the expression of mitochondrial biogenesis-, mitophagy-, fusion-, and oxidative stress-related genes.

CONCLUSION

Hypothalamic FAM163A may play a role in modulating AgRP neuronal activity through regulating mitochondrial biogenesis, dynamics, and redox state. These findings provide insights into the role of FAM163A and mitochondrial stress in the central regulation of metabolism.

Peripubertal antagonism of corticotropin-releasing factor receptor 1 results in sustained changes in behavioral plasticity and the transcriptomic profile of the amygdala

Peripuberty is a significant period of neurodevelopment with long-lasting effects on the brain and behavior. Blocking type 1 corticotropin-releasing factor receptors (CRFR1) in neonatal and peripubertal rats attenuates detrimental effects of early-life stress on neural plasticity, behavior, and stress hormone action, long after exposure to the drug has ended. CRFR1 antagonism can also impact neural and behavioral development in the absence of stressful stimuli, suggesting sustained alterations under baseline conditions. To investigate this further, we administered the CRFR1 antagonist (CRFR1a) R121919 to young adolescent male and female rats across 4 days. Following each treatment, rats were tested for locomotion, social behavior, mechanical allodynia, or prepulse inhibition (PPI). Acute CRFR1 blockade immediately reduced PPI in peripubertal males, but not females. In adulthood, each assay was repeated without CRFR1a exposure to test for persistent effects of the adolescent treatment. Males continued to experience deficits in PPI while females displayed altered locomotion, PPI, and social behavior. The amygdala was collected to measure long-term effects on gene expression. In the adult amygdala, peripubertal CRFR1a induced alterations in pathways related to neural plasticity and stress in males. In females, pathways related to central nervous system myelination, cell junction organization, and glutamatergic regulation of synaptic transmission were affected. Understanding how acute exposure to neuropharmacological agents can have sustained impacts on brain and behavior, in the absence of further exposures, has important clinical implications for developing adolescents.

Multiple metabolic signals in the CeA regulate feeding: The role of AMPK

BACKGROUND

The central nucleus of the amygdala (CeA) is part of the dopaminergic reward system and controls energy balance. Recently, a cluster of neurons was identified as responsive to the orexigenic effect of ghrelin and fasting. However, the signaling pathway by which ghrelin and fasting induce feeding is unknown. AMP-activated protein kinase (AMPK) is a cellular energy sensor, and its Thr172 phosphorylation (AMPKThr172) in the mediobasal hypothalamus regulates food intake. However, whether the expression and activation of AMPK in CeA could be one of the intracellular signaling activated in response to ghrelin and fasting eliciting food intake is unknown.

AIM

To evaluate the activation of AMPK into CeA in response to ghrelin, fasting, and 2-deoxy-D-glucose (2DG) and whether feeding accompanied these changes. In addition, to investigate whether the inhibition of AMPK into CeA could decrease food intake.

METHODS

On a chow diet, eight-week-old Wistar male rats were stereotaxically implanted with a cannula in the CeA to inject several modulators of AMPKα1/2Thr172 phosphorylation, and we performed physiological and molecular assays.

KEY FINDINGS

Fasting increased, and refeeding reduced AMPKThr172 in the CeA. Intra-CeA glucose injection decreased feeding, whereas injection of 2DG, a glucoprivation inductor, in the CeA, increased food intake and blood glucose, despite faint increases in AMPKThr172. Intra-CeA ghrelin injection increased food intake and AMPKThr172. To further confirm the role of AMPK in the CeA, chronic injection of Melanotan II (MTII) in CeA reduced body mass and food intake over seven days together with a slight decrease in AMPKThr172.

SIGNIFICANCE

Our findings identified that AMPK might be part of the signaling machinery in the CeA, which responds to nutrients and hormones contributing to feeding control. The results can contribute to understanding the pathophysiological mechanisms of altered feeding behavior/consumption, such as binge eating of caloric-dense, palatable food.

Role of brain NUCB2/nesfatin-1 in stress and stress-related gastrointestinal disorders

Since the discovery of NUCB2/nesfatin-1 as a novel anorexigenic factor, the expanding function of this peptide has been elucidated in recent years. Increasing evidence suggests that NUCB2/nesfatin-1 is also involved in the regulation of stress and stress-related gastrointestinal disorders. Therefore, we investigated the relationship between NUCB2/nesfatin-1, stress and stress-related gastrointestinal disorders and summarized the results of these studies. Different stressors and duration of stress activate different NUCB2/nesfatin-1-associated brain regions and have different effects on serum corticosterone levels. Central and peripheral NUCB2/nesfatin-1 mediates stress-related gastrointestinal disorders but appears to be protective against inflammatory bowel disease. NUCB2/nesfatin-1 plays an important role in mediating the brain-gut crosstalk, but precise clarification is still needed to gain more insight into these complex relationships.

The Neurophysiology Behind Trauma-Focused Therapy Modalities Used to Treat Post-Traumatic Stress Disorder Across the Life Course: A Systematic Review

This review presents the current state of understanding of trauma-informed modalities in light of current research in neuroscience, analyzing which brain structures and processes are impacted by these modalities. Studies included in the present review met the inclusion criteria of 1) addressing post-traumatic stress disorder (PTSD) in a specific population, 2) treatment of PTSD using any of the evidence-based trauma-informed modalities considered in this review, and 3) presenting functional magnetic resonance imagery (fMRI) data, derived from BOLD signals and voxel-compression maps, of brain structures impacted by these trauma-informed modalities. Articles for this review were collated through PubMed and MEDLINE, using key terms in descending order, such as 'childhood trauma', 'adolescent trauma', and 'adulthood trauma', to 'PTSD', 'fMRI', and so on, depending on the modality in question. Based on these criteria and research methods, 37 studies remained for inclusion in the present review. Among a number of critical findings, this review demonstrates that eye movement desensitization and reprocessing (EMDR) and mindfulness therapy effectively deactivate hindbrain regions implicated in the downregulation of autonomic nervous system (ANS) hyperarousal. This review also shows that trauma-focused cognitive behavioral therapy (TF-CBT) and EMDR activate the hippocampus, anterior cingulate cortex (ACC), medial prefrontal cortex (mPFC), and orbitofrontal cortex (OFC)-areas that are implicated in crucial cognitive, affective, and behavioral processes that aid trauma survivors in navigating their challenges.

Increased intrinsic and synaptic excitability of hypothalamic POMC neurons underlies chronic stress-induced behavioral deficits

Chronic stress exposure induces maladaptive behavioral responses and increases susceptibility to neuropsychiatric conditions. However, specific neuronal populations and circuits that are highly sensitive to stress and trigger maladaptive behavioral responses remain to be identified. Here we investigate the patterns of spontaneous activity of proopiomelanocortin (POMC) neurons in the arcuate nucleus (ARC) of the hypothalamus following exposure to chronic unpredictable stress (CUS) for 10 days, a stress paradigm used to induce behavioral deficits such as anhedonia and behavioral despair [1, 2]. CUS exposure increased spontaneous firing of POMC neurons in both male and female mice, attributable to reduced GABA-mediated synaptic inhibition and increased intrinsic neuronal excitability. While acute activation of POMC neurons failed to induce behavioral changes in non-stressed mice of both sexes, subacute (3 days) and chronic (10 days) repeated activation of POMC neurons was sufficient to induce anhedonia and behavioral despair in males but not females under non-stress conditions. Acute activation of POMC neurons promoted susceptibility to subthreshold unpredictable stress in both male and female mice. Conversely, acute inhibition of POMC neurons was sufficient to reverse CUS-induced anhedonia and behavioral despair in both sexes. Collectively, these results indicate that chronic stress induces both synaptic and intrinsic plasticity of POMC neurons, leading to neuronal hyperactivity. Our findings suggest that POMC neuron dysfunction drives chronic stress-related behavioral deficits.

The Role of Melanocortin Plasticity in Pain-Related Outcomes After Alcohol Exposure

The global COVID-19 pandemic has shone a light on the rates and dangers of alcohol misuse in adults and adolescents in the US and globally. Alcohol exposure during adolescence causes persistent molecular, cellular, and behavioral changes that increase the risk of alcohol use disorder (AUD) into adulthood. It is established that alcohol abuse in adulthood increases the likelihood of pain hypersensitivity and the genesis of chronic pain, and humans report drinking alcohol to relieve pain symptoms. However, the longitudinal effects of alcohol exposure on pain and the underlying CNS signaling that mediates it are understudied. Specific brain regions mediate pain effects, alcohol effects, and pain-alcohol interactions, and neural signaling in those brain regions is modulated by neuropeptides. The CNS melanocortin system is sensitive to alcohol and modulates pain sensitivity, but this system is understudied in the context of pain-alcohol interactions. In this review, we focus on the role of melanocortin signaling in brain regions sensitive to alcohol and pain, in particular the amygdala. We also discuss interactions of melanocortins with other peptide systems, including the opioid system, as potential mediators of pain-alcohol interactions. Therapeutic strategies that target the melanocortin system may mitigate the negative consequences of alcohol misuse during adolescence and/or adulthood, including effects on pain-related outcomes.

Antistress Action of Melanocortin Derivatives Associated with Correction of Gene Expression Patterns in the Hippocampus of Male Rats Following Acute Stress

Natural melanocortins (MCs) have been used in the successful development of drugs with neuroprotective properties. Here, we studied the behavioral effects and molecular genetic mechanisms of two synthetic MC derivatives-ACTH(4-7)PGP (Semax) and ACTH(6-9)PGP under normal and acute restraint stress (ARS) conditions. Administration of Semax or ACTH(6-9)PGP (100 μg/kg) to rats 30 min before ARS attenuated ARS-induced behavioral alterations. Using high-throughput RNA sequencing (RNA-Seq), we identified 1359 differentially expressed genes (DEGs) in the hippocampus of vehicle-treated rats subjected to ARS, using a cutoff of >1.5 fold change and adjusted p-value (Padj) < 0.05, in samples collected 4.5 h after the ARS. Semax administration produced > 1500 DEGs, whereas ACTH(6-9)PGP administration led to <400 DEGs at 4.5 h after ARS. Nevertheless, ~250 overlapping DEGs were identified, and expression of these DEGs was changed unidirectionally by both peptides under ARS conditions. Modulation of the expression of genes associated with biogenesis, translation of RNA, DNA replication, and immune and nervous system function was produced by both peptides. Furthermore, both peptides upregulated the expression levels of many genes that displayed decreased expression after ARS, and vice versa, the MC peptides downregulated the expression levels of genes that were upregulated by ARS. Consequently, the antistress action of MC peptides may be associated with a correction of gene expression patterns that are disrupted during ARS.

The Melanocortin System behind the Dysfunctional Eating Behaviors

The dysfunction of melanocortin signaling has been associated with obesity, given the important role in the regulation of energy homeostasis, food intake, satiety and body weight. In the hypothalamus, the melanocortin-3 receptor (MC3R) and melanocortin-4 receptor (MC4R) contribute to the stability of these processes, but MC3R and MC4R are also localized in the mesolimbic dopamine system, the region that responds to the reinforcing properties of highly palatable food (HPF) and where these two receptors seem to affect food reward and motivation. Loss of function of the MC4R, resulting from genetic mutations, leads to overeating in humans, but to date, a clear understanding of the underlying mechanisms and behaviors that promote overconsumption of caloric foods remains unknown. Moreover, the MC4R demonstrated to be a crucial modulator of the stress response, factor that is known to be strictly related to binge eating behavior. In this review, we will explore the preclinical and clinical studies, and the controversies regarding the involvement of melanocortin system in altered eating patterns, especially binge eating behavior, food reward and motivation.

Transcriptional study of appetite regulating genes in the brain of zebrafish (Danio rerio) with impaired leptin signalling

The hormone leptin is a key regulator of body weight, food intake and metabolism. In mammals, leptin acts as an anorexigen and inhibits food intake centrally by affecting the appetite centres in the hypothalamus. In teleost fish, the regulatory connections between leptin and other appetite-regulating genes are largely unknown. In the present study, we used a zebrafish mutant with a loss of function leptin receptor to investigate brain expression patterns of 12 orexigenic and 24 anorexigenic genes under different feeding conditions (normal feeding, 7-day fasting, 2 and 6-hours refeeding). Expression patterns were compared to wild-type zebrafish, in order to identify leptin-dependent differentially expressed genes under different feeding conditions. We provide evidence that the transcription of certain orexigenic and anorexigenic genes is influenced by leptin signalling in the zebrafish brain. We found that the expression of orexigenic genes was not affected by impaired leptin signalling under normal feeding conditions; however, several orexigenic genes showed increased transcription during fasting and refeeding, including agrp, apln, galr1a and cnr1. This suggests an inhibitory effect of leptin signal on the transcription of these orexigenic genes during short-term fasting and refeeding in functional zebrafish. Most pronounced effects were observed in the group of anorexigenic genes, where the impairment of leptin signalling resulted in reduced gene expression in several genes, including cart family, crhb, gnrh2, mc4r, pomc and spx, in the control group. This suggests a stimulatory effect of leptin signal on the transcription of these anorexigenic genes under normal feeding condition. In addition, we found multiple gain and loss in expression correlations between the appetite-regulating genes, in zebrafish with impaired leptin signal, suggesting the presence of gene regulatory networks downstream of leptin signal in zebrafish brain. The results provide the first evidence for the effects of leptin signal on the transcription of various appetite-regulating genes in zebrafish brain, under different feeding conditions. Altogether, these transcriptional changes suggest an anorexigenic role for leptin signal, which is likely to be mediated through distinct set of appetite-regulating genes under different feeding conditions.

Methanol extract of semen Ziziphi Spinosae attenuates ethanol withdrawal anxiety by improving neuropeptide signaling in the central amygdala

BACKGROUND

Ethanol withdrawal (EtOHW) anxiety is a crucial risk factor for alcoholic relapse. The neuropeptide nociceptin/orphanin FQ (N/OFQ) acts upon its receptor (NOP) to antagonize corticotropin-releasing factor (CRF) and elicit anxiolytic actions. Semen Ziziphi Spinosae (SZS), a prototypical hypnotic-sedative herb in Oriental medicine, exhibits anxiolytic effects during nicotine withdrawal by improving amygdaloid CRF/CRF1 receptor (CRFR1) signaling. Therefore, we evaluated the effects of SZS on EtOHW anxiety and the involvement of amygdaloid CRF/CRFR1 and N/OFQ/NOP pathways.

METHODS

Male Sprague Dawley rats received intraperitoneal injections of 2 g/kg EtOH (20% v/v) once daily for 28 d followed by a 3-d withdrawal. During EtOHW, the rats were given once-daily intragastric treatments of a methanol extract of SZS (MESZS, 60 or 180 mg/kg/d). Anxiety-like behaviors were measured with the open field (OF) and elevated plus maze (EPM) tests, and plasma corticosterone (CORT) levels were examined by an enzyme-linked immunosorbent assay. mRNA and protein expression levels of the neuropeptides and their receptors were determined by quantitative polymerase chain reaction and Western blot assays.

RESULTS

MESZS increased the distance traveled in the center zone of the OF and dose-dependently elongated the duration of staying in the center zone in EtOHW rats. MESZS increased both the number of entries into and the time spent in the open arms of the EPM by EtOHW rats. And, MESZS inhibited the over secretion of plasma CORT during EtOHW. EtOHW enhanced CRF and CRFR1 gene and protein expression in the central nucleus of the amygdala (CeA), which were inhibited by 180 mg/kg/d MESZS. EtOHW increased amygdaloid NOP mRNA and protein expression but spared N/OFQ mRNA expression, and 180 mg/kg/d MESZS further promoted these increases. Additionally, a post-MESZS intra-CeA infusion of either CRF or the selective NOP antagonist UFP-101 abolished the expected anxiolytic effect of 180 mg/kg/d MESZS.

CONCLUSIONS

These results suggest that MESZS ameliorates EtOHW anxiety by improving both CRF/CRFR1 and N/OFQ/NOP transmissions in the CeA.

Tectal corticotropin-releasing factor (CRF) neurons respond to fasting and a reactive stressor in the African Clawed Frog, Xenopus laevis

It is well established that hypothalamic neurons producing the peptide corticotropin-releasing factor (CRF) play a key role in stress adaptation, including reduction of food intake when a threat or stressor is present. We have previously reported on the presence of an intrinsic CRF signaling system within the optic tectum (OT), a brain area that plays a key role in visually guided prey capture/predator avoidance decisions. To better understand the potential role of tectal CRF neurons in regulating adaptive behavior and energy balance during stress we examined evidence for modulation of tectal CRF neuronal activity after stressor exposure and food deprivation in the African clawed frog Xenopus laevis. We tested two predictions, 1) that exposure to categorically distinct stressors (ether vapors and shaking) will reduce food intake and modulate the activity of tectal CRF cells, and 2) that food deprivation will modulate the activity of tectal CRF cells. Exposure to ether increased tectal content of CRF and CRF transcript, but lowed CRFR1 transcript abundance. Two weeks of food deprivation reduced total fat stores in frogs and decreased tectal content of CRF content while having no effect on CRF and CRFR1 transcript abundance. Our data are consistent with a role for tectal CRF neurons in modulating food intake in response to certain stressors.

Stress-induced suppression of neuropeptide Y-induced hunger in anorexic chicks involves corticotrophin-releasing factor signalling and the paraventricular nucleus of the hypothalamus

The Virginia lines of chickens have been selected for low (LWS) or high (HWS) juvenile body weight and have different severities of anorexia and obesity, respectively. The LWS that are exposed to stressors at hatch are refractory to neuropeptide Y (NPY)-induced food intake and the objective of the present study was to determine the underlying mechanisms. Chicks were exposed to a stressor (-20°C for 6 minutes and 22°C and delayed access to food for 24 hours) after hatching and the hypothalamic nuclei, including the lateral hypothalamus (LH), paraventricular nucleus (PVN), ventromedial hypothalamus (VMH) and arcuate nucleus (ARC), were collected 5 days later. In LWS but not HWS, stress exposure up-regulated corticotrophin-releasing factor (CRF), CRF receptor subtypes 1 and 2 (CRFR1 and CRFR2, respectively), melanocortin receptor 4 and urocortin 3 in the PVN, as well as CRFR2 mRNA in the VMH and ARC. In LWS, stress exposure was also associated with greater NPY and NPY receptor subtype 5 mRNA in the ARC and PVN, respectively, as well as decreased agouti-related peptide mRNA in the ARC. In HWS, stress exposure was associated with increased CRFR1 and decreased cocaine- and amphetamine-regulated transcript in the ARC and PVN, respectively. Refractoriness of the food intake response to NPY in LWS may thus result from the over-riding anorexigenic tone in the PVN associated with CRF signalling. Indeed, the orexigenic effect of NPY was restored when LWS were injected with a CRF receptor antagonist, astressin, before stress exposure. The results of the present study provide insights into the molecular basis of eating disorders and suggest that CRF signalling in the PVN may exacerbate the anorexic phenotype in the presence of environmental stressors.

Adolescent Alcohol Exposure-Induced Changes in Alpha-Melanocyte Stimulating Hormone and Neuropeptide Y Pathways via Histone Acetylation in the Brain During Adulthood

Background

Adolescent intermittent ethanol exposure causes long-lasting alterations in brain epigenetic mechanisms. Melanocortin and neuropeptide Y signaling interact and are affected by ethanol exposure in the brain. Here, the persistent effects of adolescent intermittent ethanol on alpha-melanocyte stimulating hormone, melanocortin 4 receptor, and neuropeptide Y expression and their regulation by histone acetylation mechanisms were investigated in adulthood.

Methods

Male rats were exposed to adolescent intermittent ethanol (2 g/kg, i.p.) or volume-matched adolescent intermittent saline from postnatal days 28 to 41 and allowed to grow to postnatal day 92. Anxiety-like behaviors were measured by the elevated plus-maze test. Brain regions from adult rats were used to examine changes in alpha-melanocyte stimulating hormone, melanocortin 4 receptor, and neuropeptide Y expression and the histone acetylation status of their promoters.

Results

Adolescent intermittent ethanol-exposed adult rats displayed anxiety-like behaviors and showed increased pro-opiomelanocortin mRNA levels in the hypothalamus and increased melanocortin 4 receptor mRNA levels in both the amygdala and hypothalamus compared with adolescent intermittent saline-exposed adult rats. The alpha-Melanocyte stimulating hormone and melanocortin 4 receptor protein levels were increased in the central and medial nucleus of the amygdala, paraventricular nucleus, and arcuate nucleus of the hypothalamus in adolescent intermittent ethanol-exposed compared with adolescent intermittent saline-exposed adult rats. Neuropeptide Y protein levels were decreased in the central and medial nucleus of the amygdala of adolescent intermittent ethanol-exposed compared with adolescent intermittent saline-exposed adult rats. Histone H3K9/14 acetylation was decreased in the neuropeptide Y promoter in the amygdala but increased in the melanocortin 4 receptor gene promoter in the amygdala and the melanocortin 4 receptor and pro-opiomelanocortin promoters in the hypothalamus of adolescent intermittent ethanol-exposed adult rats compared with controls.

Conclusions

Increased melanocortin and decreased neuropeptide Y activity due to changes in histone acetylation in emotional brain circuitry may play a role in adolescent intermittent ethanol-induced anxiety phenotypes in adulthood.

Acute stress diminishes M-current contributing to elevated activity of hypothalamic-pituitary-adrenal axis

Acute stress stimulates corticotrophin-releasing hormone (CRH)-expressing neurons in the hypothalamic paraventricular nucleus (PVN), which is an essential component of hypothalamic-pituitary-adrenal (HPA) axis. However, the cellular and molecular mechanisms remain unclear. The M-channel is a voltage-dependent K⁺ channel involved in stabilizing the neuronal membrane potential and regulating neuronal excitability. In this study, we tested our hypothesis that acute stress suppresses expression of Kv7 channels to stimulate PVN-CRH neurons and the HPA axis. Rat PVN-CRH neurons were identified by expressing enhanced green fluorescent protein driven by Crh promoter. Acute restraint stress attenuated the excitatory effect of Kv7 blocker XE-991 on the firing activity of PVN-CRH neurons and blunted the increase in plasma corticosterone (CORT) levels induced by microinjection of XE-991 into the PVN. Furthermore, acute stress significantly decreased the M-currents in PVN-CRH neurons and reduced PVN expression of Kv7.3 subunit in the membrane. In addition, acute stress significantly increased phosphorylated AMP-activated protein kinase (AMPK) levels in the PVN tissue. Intracerebroventricular injection of the AMPK inhibitor dorsomorphin restored acute stress-induced elevation of CORT levels and reduction of membrane Kv7.3 protein level in the PVN. Dorsomorphin treatment increased the M-currents and reduced the firing activity of PVN-CRH neurons in acutely stressed rats. Collectively, these data suggest that acute stress diminishes Kv7 channels to stimulate PVN-CRH neurons and the HPA axis potentially via increased AMPK activity.

Involvement of CRFR1 in the Basolateral Amygdala in the Immediate Fear Extinction Deficit

Several animal and clinical studies have highlighted the ineffectiveness of fear extinction sessions delivered shortly after trauma exposure. This phenomenon, termed the immediate extinction deficit, refers to situations in which extinction programs applied shortly after fear conditioning may result in the reduction of fear behaviors (in rodents, frequently measured as freezing responses to the conditioned cue) during extinction training, but failure to consolidate this reduction in the long term. The molecular mechanisms driving this immediate extinction resistance remain unclear. Here we present evidence for the involvement of the corticotropin releasing factor (CRF) system in the basolateral amygdala (BLA) in male Wistar rats. Intra-BLA microinfusion of the CRFR₁ antagonist NBI30775 enhances extinction recall, whereas administration of the CRF agonist CRF_6–33 before delayed extinction disrupts recall of extinction. We link the immediate fear extinction deficit with dephosphorylation of GluA1 glutamate receptors at Ser⁸⁴⁵ and enhanced activity of the protein phosphatase calcineurin in the BLA. Their reversal after treatment with the CRFR₁ antagonist indicates their dependence on CRFR₁ actions. These findings can have important implications for the improvement of therapeutic approaches to trauma, as well as furthering our understanding of the neurobiological mechanisms underlying fear-related disorders.

Pituitary adenylate cyclase-activating polypeptide (PACAP) in the central nucleus of the amygdala induces anxiety via melanocortin receptors

RATIONALE

Anxiety disorders are the most common mental disorders in the USA. Characterized by feelings of uncontrollable apprehension, they are accompanied by physical, affective, and behavioral symptoms. The neuropeptide pituitary adenylate cyclase-activating polypeptide (PACAP) and its receptor PAC1 (PAC1R) are highly expressed in the central nucleus of the amygdala (CeA), and they have gained growing attention for their proposed role in mediating the body's response to stress.

OBJECTIVES

The aim of this study was to evaluate the anxiogenic effects of PACAP in the CeA and its effects on the hypothalamic-pituitary-adrenal (HPA) axis. Furthermore, the mechanism of action of PACAP in the CeA was investigated.

METHODS

PACAP was microinfused into the CeA of rats, and its effects in the elevated plus maze (EPM), the defensive withdrawal tests, and plasma corticosterone levels were evaluated. The ability of the melanocortin receptor antagonist SHU9119 to block PACAP effect in the EPM was assessed.

RESULTS

Intra-CeA PACAP exerted a dose-dependent anxiogenic effect and activated the HPA axis. In contrast, PACAP microinfused into the basolateral nucleus of the amygdala (BlA) had no effect. Finally, the anxiogenic effect of intra-CeA PACAP was prevented by SHU9119.

CONCLUSIONS

These data prove an anxiogenic role for the PACAP system of the CeA and reveal that the melanocortin receptor 4 (MC4R) system of CeA mediates these effects. Our data provide insights into this neuropeptide system as a mechanism for modulating the behavioral and endocrine response to stress and suggest that dysregulations of this system may contribute to the pathophysiology of anxiety-related disorders.

Cognitive disruptions in stress-related psychiatric disorders: A role for corticotropin releasing factor (CRF)

This article is part of a Special Issue "SBN 2014". Stress is a potential etiology contributor to both post-traumatic stress disorders (PTSD) and major depression. One stress-related neuropeptide that is hypersecreted in these disorders is corticotropin releasing factor (CRF). Dysregulation of CRF has long been linked to the emotion and mood symptoms that characterize PTSD and depression. However, the idea that CRF also mediates the cognitive disruptions observed in patients with these disorders has received less attention. Here we review literature indicating that CRF can alter cognitive functions. Detailed are anatomical studies revealing that CRF is poised to modulate regions required for learning and memory. We also describe preclinical behavioral studies that demonstrate CRF's ability to alter fear conditioning, impair memory consolidation, and alter a number of executive functions, including attention and cognitive flexibility. The implications of these findings for the etiology and treatment of the cognitive impairments observed in stress-related psychiatric disorders are described.

A critical role for the melanocortin 4 receptor in stress-induced relapse to nicotine seeking in rats

Tobacco addiction is characterized by a lack of control over smoking and relapse after periods of abstinence. Smoking cessation leads to a dysphoric state that contributes to relapse to smoking. After the acute withdrawal phase, exposure to stressors increases the risk for relapse. Blockade of melanocortin 4 (MC4 ) receptors has anxiolytic and antidepressant-like effects in animal models. The aim of these studies was to investigate the role of MC4 receptors in the dysphoria associated with nicotine withdrawal and stress-induced reinstatement of nicotine seeking. To study stress-induced reinstatement, rats self-administered nicotine for 16 days and then nicotine seeking was extinguished by substituting saline for nicotine. Nicotine seeking was reinstated by intermittent footshock stress. The intracranial self-stimulation (ICSS) procedure was used to assess the negative mood state associated with nicotine withdrawal. Elevations in the ICSS thresholds are indicative of a dysphoric state. The selective MC4 receptor antagonists HS014 and HS024 prevented stress-induced reinstatement of extinguished nicotine seeking. Drug doses that prevented stress-induced relapse did not affect responding for food pellets, which indicates that the drugs did not induce sedation or motor impairments. In the ICSS experiments, the nicotinic acetylcholine receptor antagonist mecamylamine elevated the ICSS thresholds of the nicotine-dependent rats. Pre-treatment with HS014 or HS024 did not prevent the elevations in ICSS thresholds. These studies indicate that MC4 receptors play a critical role in stress-induced reinstatement of nicotine seeking, but these receptors may not play a role in the dysphoria associated with acute nicotine withdrawal.

Leptin and its receptors

Leptin is mainly produced in the white adipose tissue before being secreted into the blood and transported across the blood-brain barrier. Leptin binds to a specific receptor (LepR) that has numerous subtypes (LepRa, LepRb, LepRc, LepRd, LepRe, and LepRf). LepRb, in particular, is expressed in several brain nuclei, including the arcuate nucleus, the paraventricular nucleus, and the dorsomedial, lateral and ventromedial regions of the hypothalamus. LepRb is also co-expressed with several neuropeptides, including proopiomelanocortin, neuropeptide Y, galanin, galanin-like peptide, gonadotropin-releasing hormone, tyrosine hydroxylase and neuropeptide W. Functionally, LepRb induces activation of the JAK2/ERK, /STAT3, /STAT5 and IRS/PI3 kinase signaling cascades, which are important for the regulation of energy homeostasis and appetite in mammals. In this review, we discuss the structure, genetics and distribution of the leptin receptors, and their role in cell signaling mechanisms.

Blockage of melanocortin-4 receptors by intranasal HS014 attenuates single prolonged stress-triggered changes in several brain regions

Melanocortin receptor four (MC4R) is implicated in regulation of stress-related functions. We previously demonstrated that intranasal infusion of MC4R antagonist HS014, shortly before single prolonged stress (SPS) animal model of post-traumatic stress disorder, lessened the development of anxiety- and depression-like behavior depending on the dose. Here, we evaluated effects of HS014 on SPS-elicited changes in hypothalamic-pituitary-adrenal axis and expression of several genes of interest in mediobasal hypothalamus, hippocampus, and locus coeruleus. Rats were given intranasal infusion of HS014 (3.5 ng or 100 μg) and 30 min later subjected to SPS stressors. Short-term responses of HS014 rats in comparison with vehicle-treated, evident 30 min following SPS stressors, included smaller rise in plasma corticosterone (100 μg HS014), absence of induction of corticotrophin-releasing hormone mRNA in mediobasal hypothalamus and of mRNA for tyrosine hydroxylase and dopamine-β hydroxylase in locus coeruleus. Long-term responses found 7 days after SPS stressors, included lower induction corticotrophin-releasing hormone mRNA levels in the mediobasal hypothalamus without effect on mRNAs for the glucocorticoid receptor (GR) and FK506-binding protein 51 (FKBP5), a component of GR co-chaperone complex; and no induction of GR protein in ventral hippocampus. Thus, antagonism of MC4R prior to SPS attenuates development of several abnormalities in gene expression in regions implicated in post-traumatic stress disorder. Blockade of brain melanocortine receptor 4 (MC4R) with intranasal infusion of the MC4R antagonist HS014 to rats prior to single prolonged stress (SPS) leads to faster termination of stress responses (30 min later) and prevents or attenuates SPS-triggered abnormal gene expression related to post-traumatic stress disorder (7 days later). Targeting of brain MC4R is a promising strategy to protect HPA axis, LC-NE (locus coeruleus-norepinephrine) systems and hippocampus from overstimulation.

Involvement of the central melanocortin system in the effects of caffeine on anxiety-like behavior in mice

AIMS

To investigate the role of the melanocortin (MC) system in the framework of the central nucleus of the amygdala (CeA) in the differential effects of the adenosine receptor blocker caffeine on anxiety-like behavior, using the social interaction (SI) test.

MAIN METHODS

Caffeine was injected intraperitoneally, alone or in combination with alpha-melanocyte stimulating hormone (α-MSH), the MC4 receptor agonist RO27-3225 or the antagonist HS014 via the intra-CeA route. The effects of chronic (21 days) caffeine, given alone or concurrently with α-MSH, or RO27-3225, were investigated. The effects of withdrawal of these treatments on SI time were also evaluated. Furthermore, the acute effects of HS014 were investigated in different sets of caffeine-withdrawn mice.

KEY FINDINGS

Acute injection of caffeine, RO27-3225, or α-MSH produced anxiety-like behavior. Prior treatment with α-MSH, or RO27-3225 potentiated the caffeine-induced anxiety-like behavior. Subchronic treatment with HS014 increased the SI time, which was attenuated by caffeine. Chronic administration of caffeine resulted in tolerance to caffeine's anxiogenic effect, while abrupt discontinuation of the treatment produced peak anxiety-like behavior at 72 h post-withdrawal. Concurrent administration of α-MSH, or RO27-3225 with chronic caffeine delayed the development of tolerance and prevented withdrawal-induced anxiety-like behavior. Moreover, acute treatment with HS014 at 72 h post-withdrawal attenuated the anxiety-like behavior.

SIGNIFICANCE

α-MSH, possibly via MC4 receptor in the neuroanatomical framework of the CeA, may contribute to the acute, chronic and withdrawal actions of caffeine associated with anxiety-like behavior in the neuroanatomical framework of the CeA.

Enhancement of Anxiety and Modulation of TH and pERK Expressions in Amygdala by Repeated Injections of Corticosterone

Repeated stress induces corticosterone release. However, it is not clear that stress results in further elevation of corticosterone levels, and the roles of released corticosterone to aggravate stress-related symptoms are also not clear. This study investigated whether neuronal modulation was induced in the amygdala after two kinds of stress, that is, such as electric shock and corticosterone injection. It was found that stress by electric shock decreased the expression of tyrosine hydoroxylase (TH) in the amygdala while the expression of pERK was increased. However, there is no difference in the expressions of TH and pERK in the frontal cortex compared with those of the control group. The level of corticosterone was significantly increased in the serum after stress. To determine the effect of corticosterone on the induction of anxiety and the expression of TH, the rats received corticosterone (20 mg or 40 mg/kg i.p.) for 1 day, 1 week, 2 weeks and 3 weeks, respectively. The spent time in open arms of the EPM (elevated plus maze) test was significantly decreased after 1 week, 2 weeks and 3 weeks. The time spent in open arms of the EPM test after repeated injections of corticosterone was significantly decreased in a dose-dependent manner. The expression of TH in the amygdala was reduced after following repeated corticosterone treatment for 2 weeks and 3 weeks. Collectively, this study suggests that corticosterone has a major role in the induction of anxiety and the modulation of TH expression, at least, in the amygdala.

Food-intake regulation during stress by the hypothalamo-pituitary-adrenal axis

The prevalence of obesity is increasing worldwide with serious consequences such as diabetes mellitus type 2 and cardiovascular diseases. Emotional stress is considered to be one of the main reasons of obesity development in humans. However, there are some contradictory results, which should be addressed. First of all stress induces anorexia, but not overeating in laboratory animals. Glucocorticoids, the effector molecules of the hypothalamo-pituitary-adrenocortical (HPA) axis stimulate and stress inhibits food intake. It is also not clear if stress is diabetogenic or an antidiabetogenic factor. The review will discusses these issues and the involvement of the whole HPA axis and its separate molecules (glucocorticoids, adrenocorticotropin, corticotropin-releasing hormone) in food intake regulation under stress.

Involvement of parasympathetic pelvic efferent pathway in psychological stress-induced defecation

AIM: To investigate the role of the pelvic nerve pathway in stress-induced acceleration of colorectal transit and defecation in rats.

METHODS: Surgical transection of rectal nerves (rectal branches of the pelvic nerve), vagotomy (Vag) or adrenalectomy (Adx) were performed bilaterally in rats. Number of fecal pellet output of these rats was measured during 1-h water avoidance stress (WAS). To evaluate the colonic transit, rats were given phenol red through the catheter indwelled in the proximal colon and subjected to WAS. After WAS session, entire colon and rectum were isolated and distribution of phenol red was measured. Distal colonic and rectal transit was evaluated using glass bead. Rats were inserted the glass bead into the distal colon and evacuation rate of the bead was measured. Neural activation was assessed by immunohistochemical staining of c-Fos and PGP9.5 in colonic whole-mount preparations of longitudinal muscle myenteric plexus (LMMP).

RESULTS: In the sham-operated rats (sham op), WAS significantly increased defecation and accelerated colorectal transit with marked elevation of plasma corticosterone level. Compared with sham-operated rats, increase in the excretion of fecal pellets during WAS was significantly reduced by rectal nerve transection (RNT) (sham op: 6.9 ± 0.8 vs RNT: 4.3 ± 0.6, P < 0.05) or Vag (sham op: 6.4 ± 0.8 vs Vag: 3.7 ± 1.1, P < 0.05), although corticosterone level remained elevated. Adx-rats significantly increased the defecation despite the lower corticosterone level. Distribution pattern of phenol red showed RNT inhibited distal colonic and rectal transit accelerated by WAS, while Vag inhibited proximal colonic transit. Suppression of distal colonic and rectal transit by RNT was further confirmed by the bead evacuation rate (sham op: 80.0% vs RNT: 53.8%). WAS significantly increased the number of c-Fos-immunoreactive neural cells in the LMMP of the proximal and distal colon, whereas c-Fos expression was decreased by RNT in the distal colon (sham op: 9.0 ± 2.0 vs RNT: 4.4 ± 1.0, P < 0.05) and decreased by Vag in the proximal colon.

CONCLUSION: Pelvic nerve conveys WAS stimuli from the brain to the distal colon, and directly activate the myenteric neurons, followed by the increase of its motility.

Melanocortin-4 receptor in the medial amygdala regulates emotional stress-induced anxiety-like behaviour, anorexia and corticosterone secretion

The central melanocortin system has been implicated in emotional stress-induced anxiety, anorexia and activation of the hypothalamo-pituitary-adrenal (HPA) axis. However, the underlying neural substrates have not been identified. The medial amygdala (MeA) is highly sensitive to emotional stress and expresses high levels of the melanocortin-4 receptor (MC4R). This study investigated the effects of activation and blockade of MC4R in the MeA on anxiety-like behaviour, food intake and corticosterone secretion. We demonstrate that MC4R-expressing neurons in the MeA were activated by acute restraint stress, as indicated by induction of c-fos mRNA expression. Infusion of a selective MC4R agonist into the MeA elicited anxiogenic-like effects in the elevated plus-maze test and decreased food intake. In contrast, local MeA infusion of SHU 9119, a MC4R antagonist, blocked restraint stress-induced anxiogenic and anorectic effects. Moreover, plasma corticosterone levels were increased by intra-MeA infusion of the MC4R agonist under non-stressed conditions and restraint stress-induced elevation of plasma corticosterone levels was attenuated by pretreatment with SHU 9119 in the MeA. Thus, stimulating MC4R in the MeA induces stress-like anxiogenic and anorectic effects as well as activation of the HPA axis, whereas antagonizing MC4R in this region blocks such effects induced by restraint stress. Together, our results implicate MC4R signalling in the MeA in behavioural and endocrine responses to stress.

Distribution and homing pattern of c-kit+ Sca-1+ CXCR4+ resident cardiac stem cells in neonatal, postnatal, and adult mouse heart

INTRODUCTION

The origin of heart-forming cells and their roles in organ development have fascinated biologists for over a century. C-X-C chemokine receptor type 4 plays a crucial role during embryonic development and in maintaining the stem cell niche and homing. The aim of the present was to study the expression pattern of resident cardiac stem cell markers and their homing factor in neonatal, postnatal, and adult mouse heart.

METHODS

Cardiac stem cell protein expression was analyzed using immunofluorescence, immunohistochemistry, and Western blotting. The messenger ribonucleic acid expression of cardiac stem cell markers c-kit, stem cell antigen-1, and homing factor C-X-C chemokine receptor type 4 was quantitatively analyzed using quantitative polymerase chain reaction. Data were analyzed using Student's t test and two-way analysis using SPSS software.

RESULTS

Stem cell antigen-1- and c-kit-positive cell populations were heterogeneously distributed in the adult and postnatal hearts but scattered in the neonatal heart. The expression of c-kit showed a significant difference between right and left atrium, though it was higher compared to ventricles. The homing factor C-X-C chemokine receptor type 4 expression was higher in the neonatal heart than in the postnatal heart but was not detectable in the adult heart.

CONCLUSIONS

The present study reveals the distribution of cardiac stem cells in the different compartments of the heart and significant reduction in their number in adult heart. Cardiac stem cells are higher in the atrium than in the ventricle, suggesting the atria as the source of cardiac stem cell.

Anti-neuropeptide Y plasma immunoglobulins in relation to mood and appetite in depressive disorder

Depression and eating disorders are frequently associated, but the molecular pathways responsible for co-occurrence of altered mood, appetite and body weight are not yet fully understood. Neuropeptide Y (NPY) has potent antidepressant and orexigenic properties and low central NPY levels have been reported in major depression. In the present study, we hypothesized that in patients with major depression alteration of mood, appetite and body weight may be related to NPY-reactive autoantibodies (autoAbs). To test this hypothesis, we compared plasma levels and affinities of NPY-reactive autoAbs between patients with major depression and healthy controls. Then, to evaluate if changes of NPY autoAb properties can be causally related to altered mood and appetite, we developed central and peripheral passive transfer models of human autoAbs in mice and studied depressive-like behavior in forced-swim test and food intake. We found that plasma levels of NPY IgG autoAbs were lower in patients with moderate but not with mild depression correlating negatively with the Montgomery-Åsberg Depression Rating Scale scores and with immobility time of the forced-swim test in mice after peripheral injection of autoAbs. No significant differences in NPY IgG autoAb affinities between patients with depression and controls were found, but higher affinity of IgG autoAbs for NPY was associated with lower body mass index and prevented NPY-induced orexigenic response in mice after their central injection. These data suggest that changes of plasma levels of anti-NPY autoAbs are relevant to altered mood, while changes of their affinity may participate in altered appetite and body weight in patients with depressive disorder.

Induction of ovarian maturation in Penaeus monodon by molecular signal interventional approach

Vitellogenin (VTG) synthesis in the hepatopancreas and ovary is negatively regulated by vitellogenesis-inhibiting hormone (VIH) produced in the neurosecretory cell of X-organ/sinus gland complex of the eyestalks of penaeid shrimp. Eyestalk ablation is used commercially to induce ovarian maturation in shrimps which leads to an eventual loss of the spawner. The aim of the present study was to understand the molecular mechanism of VIH regulation in ovarian development and its inhibition of VTG gene expression by using a MEK-specific inhibitor (U0126). The real-time quantitative PCR results showed VTG mRNA level was progressively increased in the ovary and hepatopancreas of unilateral eyestalk-ablated and inhibitor-treated shrimps. Western blot analysis also showed that phosphoMEK was detected only in the unilateral eyestalk-ablated and control shrimp, whereas phospho-MEK was not detected in inhibitor-treated shrimp. DAX-1, SF-1, and StAR expression correlated with changes in VIH mRNA and altered phospho-ERK levels. This is consistent with the hypothesis that suppression of DAX-1 results in SF-1-mediated StAR protein upregulation of estradiol that is implicated in vitellogenesis. This is the first report that demonstrates the molecular mechanism of VIH suppression via MEK pathway to induce ovarian maturation in female Penaeus monodon by molecular signal intervention, a less-invasive method than traditional eyestalk ablation.

The link between stress and feeding behaviour

Exposure to stress is inevitable, and it may occur, to varying degrees, at different phases throughout the lifespan. The impact of stress experienced in later life has been well documented as many populations in modern society experience increasing socio-economic demands. The effects of stress early in life are less well known, partly as the impact of an early exposure may be difficult to quantify, however emerging evidence shows it can impact later in life. One of the major impacts of stress besides changes in psychosocial behaviour is altered feeding responses. The system that regulates stress responses, the hypothalamo-pituitary-adrenal axis, also regulates feeding responses because the neural circuits that regulate food intake converge on the paraventricular nucleus, which contains corticotrophin releasing hormone (CRH), and urocortin containing neurons. In other words the systems that control food intake and stress responses share the same anatomy and thus each system can influence each other in eliciting a response. Stress is known to alter feeding responses in a bidirectional pattern, with both increases and decreases in intake observed. Stress-induced bidirectional feeding responses underline the complex mechanisms and multiple contributing factors, including the levels of glucocorticoids (dependent on the severity of a stressor), the interaction between glucocorticoids and feeding related neuropeptides such as neuropeptide Y (NPY), alpha-melanocyte stimulating hormone (α-MSH), agouti-related protein (AgRP), melanocortins and their receptors, CRH, urocortin and peripheral signals (leptin, insulin and ghrelin). This review discusses the neuropeptides that regulate feeding behaviour and how their function can be altered through cross-talk with hormones and neuropeptides that also regulate the hypothalamo-pituitary-adrenal axis. In addition, long-term stress induced alterations in feeding behaviour, and changes in gene expression of neuropeptides regulating stress and food intake through epigenetic modifications will be discussed. This article is part of a Special Issue entitled 'SI: Central Control of Food Intake'.

Effects of weaning and syndyphalin-33 on expression of melanocortinergic appetite-regulating genes in swine

Syndyphalin-33 (SD-33) increases feed intake in sheep and recently weaned pigs. To assess the effects of SD-33 on hypothalamic gene expression, hypothalami were collected from unweaned pigs (n=19; 21±3 d of age) on day 0. Remaining pigs received an intramuscular injection of 0.5 μmole/kg SD-33 (SD) or saline (VEH) and weaned into individual pens. On days 1, 4, and 7 after weaning, hypothalami were collected from subsets of pigs (n=8 or 9) within each treatment group. Expression of μ-opioid receptor (MOR) was less in SD pigs than in VEH pigs on day 1 and day 4, suggesting down-regulation of the receptor by SD-33. Expression of hypothalamic melanocortin 4 receptor (MC4R) at 1 d after weaning was increased in VEH pigs (but not SD pigs) relative to levels before weaning. Expression of AGRP was not significantly altered by weaning or treatment at 1 d after weaning. At 4 d after weaning, expression of AGRP was greater in SD pigs than in VEH pigs, but at day 7 expression was less in SD pigs than in VEH pigs. A strong positive correlation was noted between expression levels of MOR and MC4R across treatment and time. Treatment with SD-33 appeared to partially abrogate the effects of weaning on expression of two key appetite-regulating genes within 24 h. Effects of SD-33 appear to be mediated at least in part by the μ-opioid receptor and include actions on the melanocortinergic pathway.

Emotional memory in early steroid abnormalities: an FMRI study of adolescents with congenital adrenal hyperplasia

Hormonal imbalances during development may have long-lasting effects. Using functional magnetic resonance imaging (fMRI), we compared 14 youths with Congenital Adrenal Hyperplasia (CAH), a genetic disorder of hormonal dysfunction, with 22 healthy controls on memory encoding of emotional faces. Patients remembered fewer faces than controls, particularly fearful faces. FMRI data to successfully encoded fearful faces revealed that males with CAH showed significant activations in amygdala, hippocampus, and anterior cingulate relative to unaffected males, while females with CAH demonstrated deactivations relative to unaffected females in these regions. Findings indicate that steroid abnormalities during development can have important effects on neural correlates of emotional memory.

Distribution and function of melanocortin receptors within the brain

Biological responses to pro-opiomelanocortin (POMC)-derived peptides administered in the brain were documented in the 1950s but their molecular mechanisms of action only began to be resolved with the mapping of melanocortin receptor subtypes to specific brain regions in the 1990s. Out of the five melanocortin receptor subtypes, MC3R and MC4R are widely recognised as 'neural' melanocortin receptors. In situ hybridization anatomical mapping of these receptor subtypes to distinct hypothalamic nuclei first indicated their roles in energy homeostasis, roles that were later confirmed with the obese phenotypes exhibited by Mc3R and Mc4R knockout mice. It is perhaps less well known however, that all five melanocortin receptor subtypes have been detected in developing and/or adult brains of various species. This chapter provides a comprehensive summary of the detection and mapping of each melanocortin receptor subtype in mammalian, chicken and fish brains and relates the sites of expression to functions that are either known or proposed for each receptor subtype.

High-fat diets induce a rapid loss of the insulin anorectic response in the amygdala

Intracerebroventricular insulin decreases food intake (FI). The central bed nucleus of the amygdala (CeA), as other regions of the brain regulating feeding behavior, expresses insulin receptors. Our objectives were to show an insulin anorectic response in the amygdala, study the effect of high-fat diets on this response, and map the neural network activated by CeA insulin using c-Fos immunohistochemistry. Sprague-Dawley (SD) rats fitted with unilateral CeA cannulas were adapted to a low-fat (LFD) diet before they were fed a high-fat diet (HFD). Their feeding response to CeA saline or insulin (8 mU) was tested after 24 h, 72 h, or 7 days of being on a HFD. In a second experiment, SD rats were fed the HFD for 3, 7, or 49 days and were then refed with the LFD. They were tested for their insulin response before and after an HFD and every 3 days for the following weeks. Insulin tolerance tests were performed in a parallel group of rats. The CeA insulin stimulation c-Fos expression was studied to identify the distribution of activated neuronal populations. Feeding an HFD for 72 h or more induced a CeA, but not peripheral, insulin resistance, which was slowly reversed by LFD refeeding. The duration of HFD feeding determined the time frame for reversal of the insulin resistance. CeA insulin increased c-Fos in multiple brain regions, including the arcuate nucleus/paraventricular nucleus region of the hypothalamus. We conclude that the amygdala may be an important site for insulin regulation of food intake and may have a significant role in determining susceptibility to HFD-induced obesity.

Corticotropin-releasing factor (CRF) is involved in the acute anorexic effect of alpha-melanocyte-stimulating hormone: a study using CRF-deficient mice

Alpha-melanocyte-stimulating hormone (alpha-MSH) and its receptors are critical and indispensable for maintaining appropriate feeding behavior and energy homeostasis in both mice and humans. Corticotropin-releasing factor (CRF) is a candidate for mediating the anorexic effect of alpha-MSH. In the present study, we examined whether CRF and its receptors are involved in the anorexic effect of alpha-MSH, using CRF-deficient (CRFKO) mice and a CRF receptor antagonist. Intracerebroventricular administration of NDP-MSH, a synthetic alpha-MSH analogue, suppressed food intake in wild-type (WT) mice. This effect was abolished by pretreatment with a non-selective CRF receptor antagonist, astressin, suggesting that the effect of alpha-MSH-induced anorexia was mediated by a CRF receptor. In CRFKO mice, administration with NDP-MSH did not affect food intake at an early phase (0-4h). In addition, CRF mRNA levels in the hypothalamus were significantly increased in NDP-MSH-treated mice. Therefore, our findings, using CRFKO, strongly support evidence that CRF is involved in the acute anorexic effect of alpha-MSH. On the other hand, NDP-MSH administered to CRFKO mice led to suppressed food intake at the late phase (4-12h), similar to the effect in WT mice. Further, NDP-MSH similarly reduced food intake during the late phase in all types of mice, including WT, CRFKO, and CRFKO with corticosterone replacement. The results would suggest that alpha-MSH-induced suppression of food intake at late phase was independent of glucocorticoids and CRF.

Endocrine and gene expression changes following forced swim stress exposure during cocaine abstinence in mice

RATIONALE

Stress can reinstate previous cocaine-seeking long after drug is no longer present. However, little is known regarding the effect of chronic drug exposure and subsequent drug abstinence on responsivity to stress.

OBJECTIVE

To determine the effect of acute (24-h) and prolonged (14-day) drug-free periods in cocaine-experienced mice on behavioral, endocrine, and molecular outputs following stress exposure.

MATERIALS AND METHODS

Mice were administered a cocaine binge (15 mg/kg, every hour for 3h) for 2 weeks. Following a 24-h or 14-day drug-free period, stress responsivity, along with levels of anxiety, were measured using the forced swim test and elevated zero maze, respectively. In addition, alterations in the levels of plasma corticosterone, corticotrophin-releasing factor (CRF) mRNA, brain-derived neurotrophic factor (BDNF) mRNA, and histone acetylation at their respective promoters were examined following stress exposure.

RESULTS

At both acute and prolonged abstinence time points, behavioral measures were essentially unaltered; however, cocaine-experienced mice exhibited an augmented corticosterone response to the forced swim stress compared to saline-treated mice. Stress exposure increased BDNF mRNA levels in the ventral tegmental area (VTA) and nucleus accumbens (NAc) only in cocaine-experienced mice following a prolonged, but not acute, drug-free period. Increased BDNF mRNA in the NAc was associated with an increase in acetylated histone 3 (AcH3) at the BDNF I promoter. CRF mRNA levels were increased in the amygdala (AMYG); however, this was not associated with alterations in histone acetylation at the promoter.

CONCLUSION

These results demonstrate that drug history and prolonged abstinence can alter the endocrine and molecular responses to stress, which may facilitate the reinstatement of drug-seeking behaviors.

Acute stress differentially affects corticotropin-releasing hormone mRNA expression in the central amygdala of the "depressed" flinders sensitive line and the control flinders resistant line rats

Preclinical and clinical evidence suggests that neuropeptides play a role in the pathophysiology of mood disorders. In the present study, we investigated the involvement of the peptides corticotropin-releasing hormone (CRH), neuropeptide Y (NPY) and nociceptin/orphanin FQ (N/OFQ) and of their receptors in the regulation of emotional behaviours. In situ hybridization experiments were performed in order to evaluate the mRNA expression levels of these neuropeptidergic systems in limbic and limbic-related brain regions of the Flinders Sensitive Line (FSL) rats, a putative genetic animal model of depression. The FSL and their controls, the Flinders Resistant Line (FRL) rats, were subjected to one hour acute restraint and the effects of the stress exposure, including possible strain specific changes on these neuropeptidergic systems, were studied. In basal conditions, no significant differences between FSL and FRL rats in the CRH mRNA expression were found, however an upregulation of the CRH mRNA hybridization signal was detected in the central amygdala of the stressed FRL, compared to the non stressed FRL rats, but not in the FSL, suggesting a hypoactive mechanism of response to stressful stimuli in the "depressed" FSL rats. Baseline levels of NPY and N/OFQ mRNA were lower in the FSL rats compared to the FRL in the dentate gyrus of hippocampus and in the medial amygdala, respectively. However, the exposure to stress induced a significant upregulation of the N/OFQ mRNA levels in the paraventricular thalamic nucleus, while in the same nucleus the N/OFQ receptor mRNA expression was higher in the FSL rats. In conclusion, selective alterations of the NPY and N/OFQ mRNA in limbic and limbic-related regions of the FSL rats, a putative animal model of depression, provide further support for the involvement of these neuropeptides in depressive disorders. Moreover, the lack of CRH activation following stress in the "depressed" FSL rats suggests a form of allostatic load, that could alter their interpretation of environmental stimuli and influence their behavioural response to stressful situations.

Steroid abnormalities and the developing brain: declarative memory for emotionally arousing and neutral material in children with congenital adrenal hyperplasia

Steroid hormones modulate memory in animals and human adults. Little is known on the developmental effects of these hormones on the neural networks underlying memory. Using Congenital adrenal hyperplasia (CAH) as a naturalistic model of early steroid abnormalities, this study examines the consequences of CAH on memory and its neural correlates for emotionally arousing and neutral material in children. Seventeen patients with CAH and 17 age- and sex-matched healthy children (ages 12-14 years) completed the study. Subjects were presented positive, negative and neutral pictures. Memory recall occurred about 30min after viewing the pictures. Children with CAH showed memory deficits for negative pictures compared to healthy children (p<0.01). There were no group differences on memory performance for either positive or neutral pictures (p>0.1). In patients, 24h urinary-free cortisol levels (reflecting glucocorticoid replacement therapy) and testosterone levels were not associated with memory performance. These findings suggest that early steroid imbalances affect memory for negative material in children with CAH. Such memory impairments may result from abnormal brain organization and function following hormonal dysfunction during critical periods of development.

Stress induces the expression of heterotrimeric G protein β subunits and the phosphorylation of PKB/Akt and ERK1/2 in rat brain

Various heterotrimeric G protein betagamma subunits (Gbetagamma) are region-specifically expressed in brain where associated with "stress-axis", however, the role of Gbetagamma-mediated signaling in regulating stress is unknown. This study was designed to examine the changes of Gbetagamma expression and Gbetagamma-mediated signaling in rat brain by stress. Experimental stress was induced by immobilization (2h/day for 7 days) and the level of mRNAs and proteins for Gbeta(1-5), and the phosphorylation of PKB/Akt (phosphatidylinositol 3-kinase-linked protein kinase B) and ERK1/2 (extracellular signal-regulated kinase 1/2) were measured in five different regions of rat brain including frontal cortex, striatum, hypothalamus, hippocampus, and cerebellum. As compared in not-handled non-stressed animals, the expression of both mRNAs and proteins for Gbeta(1-5) in brain regions associated with stress was increased in stressed animals. Especially, a significant increase in Gbetas immunoreactivity in the caudate putamen, the paraventricular nucleus of the hypothalamus (PVN), and the dentate gyrus of the hippocampus (DG) of stressed rats was observed. Stress significantly induced the phosphorylation of PKB/Akt and ERK1/2 in striatum, hypothalamus and hippocampus. Therefore, these results suggest that stress may activate, at least in part, the Gbetagamma-mediated PKB/Akt and ERK1/2 signaling pathway by increasing the expression of Gbetas to regulate the physiological responses.