Basolateral amygdala corticotropin-releasing factor receptor type 1 regulates context-cocaine memory strength during reconsolidation in a sex-dependent manner.

The basolateral amygdala (BLA) is a critical brain region for cocaine-memory reconsolidation. Corticotropin-releasing factor receptor type 1 (CRFR1) is densely expressed in the BLA, and CRFR1 stimulation can activate intra-cellular signaling cascades that mediate memory reconsolidation. Hence, we tested the hypothesis that BLA CRFR1 stimulation is necessary and sufficient for cocaine-memory reconsolidation. Using an instrumental model of drug relapse, male and female Sprague-Dawley rats received cocaine self-administration training in a distinct environmental context over 10 days followed by extinction training in a different context over 7 days. Next, rats were re-exposed to the cocaine-paired context for 15 min to initiate cocaine-memory retrieval and destabilization. Immediately or 6 h after this session, the rats received bilateral vehicle, antalarmin (CRFR1 antagonist; 500 ng/hemisphere), or corticotropin-releasing factor (CRF; 0.2, 30 or 500 ng/hemisphere) infusions into the BLA. Resulting changes in drug context-induced cocaine seeking (index of context-cocaine memory strength) were assessed three days later. Female rats self-administered more cocaine infusions and exhibited more extinction responding than males. Intra-BLA antalarmin treatment immediately after memory retrieval (i.e., when cocaine memories were labile), but not 6 h later (i.e., after memory reconsolidation), attenuated drug context-induced cocaine seeking at test independent of sex, relative to vehicle. Conversely, intra-BLA CRF treatment increased this behavior selectively in females, in a U-shaped dose-dependent fashion. In control experiments, a high (behaviorally ineffective) dose of CRF treatment did not reduce BLA CRFR1 cell-surface expression in females. Thus, BLA CRFR1 signaling is necessary and sufficient, in a sex-dependent manner, for regulating cocaine-memory strength.

A role of noradrenergic receptors in anxiolytic-like effect of high CRF in the rat frontal cortex.

Corticotropin releasing factor (CRF) is a neuropeptide widely distributed in the brain as a hormonal modulator and neurotransmitter. The best known behavioral function of CRF is activation of stress and anxiety via the hypothalamus and limbic structures but the role of CRF in the cortex is still poorly understood. Our previous studies have shown anxiolytic-like effects of high doses of CRF injected into the Fr2 frontal cortex and involvement of CRF1 receptors (R) in that effect. These results seemed to be controversial as most other studies suggested anxiogenic and not anxiolytic effects of CRF1R stimulation. Since stress is associated with adrenergic system, in the present study, we focused on participation of alpha1 and alpha2 or beta adrenergic receptors in the anxiolytic-like effect of CRF. Moreover, we verified whether these effects of CRF in the Fr2 were really connected with CRF1R. Male Wistar rats were bilaterally microinjected with CRF in a dose of 0.2 µg/1 µl/site or with the specific agonist of CRF1R, stressin 1 (0.2-0.0125 µg/1 µl/site) into the Fr2 area. The elevated plus maze (EPM) test was performed 30 min later to assess the anxiolysis. An involvement of noradrenergic receptors in the CRF induced anxiolytic-like effect in the Fr2 was studied by pretreatment with the alpha1 antagonist prazosin, alpha2 agonist clonidine, alpha2 antagonist RS 79948 or beta antagonist propranolol, 20-30 min before CRF. The influence on anxiety was assessed in the EPM test. The results show that anxiolytic behavior after CRF microinjection into the Fr2 area seems to be mainly connected with the CRF1R activation because a similar effect was observed after stressin 1 administration and it was blocked by CRF1R antagonist. The results observed after administration of noradrenergic ligands indicated that anxiolytic effects of CRF in the Fr2 engaged the alpha1 and alpha2 adrenergic receptors but not beta receptors.

The effects of CRF and the urocortins on the hippocampal acetylcholine release in rats.

Corticotropin-releasing factor (CRF) and the urocortins (Ucn1, Ucn2 and Ucn3) are structurally related neuropeptides which act via two distinct CRF receptors, CRF1 and CRF2, with putatively antagonistic effects in the brain. CRF and Ucn1 activate both CRF1 and CRF2, while Ucn2 and Ucn3 activate selectively CRF2. The aim of the present study was to investigate the effects of CRF, Ucn1, Ucn2 and Ucn3 on the hippocampal acetylcholine release through which they may modulate cognitive functions, including attention, learning and memory. In this purpose male Wistar rats were used, their hippocampus was isolated, dissected, incubated, superfused and stimulated electrically. The hippocampal slices were first pretreated with selective CRF1 antagonist antalarmin or selective CRF2 antagonist astressin2B, and then treated with non-selective CRF1 agonists, CRF or Ucn1, and selective CRF2 agonists, Ucn2 or Ucn3. The hippocampal acetylcholine release was increased significantly by CRF and Ucn1 and decreased significantly by Ucn2 and Ucn3. The increasing effect of CRF and Ucn1 was reduced significantly by antalarmin, but not astressin2B. In contrast, the decreasing effect of Ucn2 and Ucn3 was reversed significantly by the selective CRF2, but not the selective CRF1 antagonist. Our results demonstrate that CRF and Ucn1 stimulate the hippocampal acetylcholine release through CRF1, whereas Ucn2 and Ucn3 inhibit the hippocampal acetylcholine release through CRF2. Therefore, the present study suggests the existence of two apparently opposing CRF systems in the hippocampus, through which CRF and the urocortins might modulate cholinergic activity and thereby cognitive functions.

Non-selective orexin-receptor antagonist attenuates stress-re-stress-induced core PTSD-like symptoms in rats: Behavioural and neurochemical analyses.

Post-traumatic stress disorder (PTSD) is a psychological disorder affecting many around the world. Growing evidence suggests that orexin-A is involved in the pathophysiology of depression and panic anxiety disorder. However, the role of orexin-A in PTSD remains unclear. Therefore, pharmacological manipulation of orexin-A can be a potential approach for the treatment of PTSD. Male Wistar rats were subjected to stress re-stress (SRS) by restraining them for 2 h followed by foot shock (FS) and halothane exposure on day-2 (D-2). Then the rats were weekly exposed to FS as re-stress cue . Suvorexant, an orexin antagonist (10, 20 and 30 mg/kg p.o.) and paroxetine (10 mg/kg p.o.) were administered from D-8 to D-32. Plasma and cerebrospinal fluid (CSF) were collected for corticosterone and orexin-A measurement. The analysis of serotonin and corticotropin-releasing factor receptor-1 (CRF-R1) were performed in the amygdalar tissue. SRS-induced PTSD-like symptoms like fear response, anxiety-like behaviour and hypocorticosteronism were attenuated by suvorexant and paroxetine. Interestingly, SRS exposed rats showed activation of orexin-A and serotonergic systems, which were also attenuated by suvorexant. Additionally, suvorexant ameliorated the extrahypothalamic induced upregulation of CRH-R1 in SRS-exposed rats. Therefore, orexin-A may be considered as a neurochemical-marker for PTSD and suvorexant alleviated PTSD-like symptoms through modulating orexinergic, serotonergic and neuroendocrine systems.

Corticotropin-releasing factor protects against ammonia neurotoxicity in isolated larval zebrafish brains.

The physiological roles of corticotropin-releasing factor (CRF) have recently been extended to cytoprotection. Here, to determine whether CRF is neuroprotective in fish, the effects of CRF against high environmental ammonia (HEA)-mediated neurogenic impairment and cell death were investigated in zebrafish. In vivo, exposure of 1 day post-fertilization (dpf) embryos to HEA only reduced the expression of the determined neuron marker neurod1 In contrast, in 5 dpf larvae, HEA increased the expression of nes and sox2, neural progenitor cell markers, and reduced the expression of neurog1, gfap and mbpa, proneuronal cell, radial glia and oligodendrocyte markers, respectively, and neurod1 The N-methyl-d-aspartate (NMDA) receptor inhibitor MK801 rescued the HEA-induced reduction in neurod1 in 5 dpf larvae but did not affect the HEA-induced transcriptional changes in other neural cell types, suggesting that hyperactivation of NMDA receptors specifically contributes to the deleterious effects of HEA in determined neurons. As observed in vivo, HEA exposure elicited marked changes in the expression of cell type-specific markers in isolated 5 dpf larval brains. The addition of CRF reversed the in vitro effects of HEA on neurod1 expression and prevented an HEA-induced increase in cell death. Finally, the protective effects of CRF against HEA-mediated neurogenic impairment and cell death were prevented by the CRF type 1 receptor selective antagonist antalarmin. Together, these results provide novel evidence that HEA has developmental time- and cell type-specific neurotoxic effects, that NMDA receptor hyperactivation contributes to HEA-mediated impairment of determined neurons, and that CRF has neuroprotective properties in the larval zebrafish brain.

Stress and nicotine during adolescence disrupts adult hippocampal-dependent learning and alters stress reactivity.

Adolescence represents increased susceptibility to stress that increases risk for nicotine dependence. The present study examined the interactive effects of brief exposure to stress (shipping/transportation or experimentally induced) and chronic nicotine during adolescence on cognitive function and stress reactivity in adulthood. Adolescent (P31), but not young adult (P47), C57BL/6J mice had higher levels of corticosterone after shipping vs mice bred onsite. Shipped preadolescent (P23) and adolescent (P38) mice, but not those bred onsite, exposed to nicotine showed deficits in contextual fear learning when tested in adulthood. Adult learning deficits were replicated in adolescent mice bred onsite, exposed to experimentally induced stress, and administered chronic nicotine. Stress and nicotine during adolescence resulted in higher expression of hippocampal glucocorticoid receptors and corticotropin-releasing factor receptors and blunted restraint induced CORT release in adulthood. Importantly, studies examining adolescent behavior in mice should consider stress influences outcomes.

Activation of CRF2 receptor increases gastric vagal afferent mechanosensitivity.

Gastric vagal afferent (GVA) sensing of food-related mechanical stimuli is a crucial mechanism in the control of feeding behavior and gastric function. Stress is an important factor contributing to eating disorders and gastric diseases. Chronic stress has been shown to increase the mechanosensitivity of GVAs in mice and to reduce food intake and body weight. Whether the mechanosensitivity of GVAs is modulated by stress hormones is not known. This study aimed to determine the effect of stress hormones on GVA mechanosensitivity. The expression of stress hormone receptors in GVA cell bodies was determined in 8-wk-old male C57BL/6 mice using quantitative RT-PCR combined with laser capture microdissection. The mechanosensitivity of GVAs was determined in the absence and presence of stress hormones using an in vitro single-fiber recording preparation. NR3C1 and CRHR2 (mRNA isoforms of glucocorticoid receptor and CRF2 receptor, respectively) were expressed in GVA neurons. The glucocorticoid receptor agonist corticosterone had no effect on the mechanosensitivity of either tension or mucosal GVAs. Activation of CRF2 receptor by its specific analog, urocortin 3, significantly increased the mechanosensitivity of both tension and mucosal GVAs, an effect prevented by the CRF2 receptor antagonist astressin 2B. In conclusion, activation of CRF2 receptor increases the mechanosensitivity of GVAs. This may contribute to the stress- and CRF2 receptor-associated changes in feeding behavior and gastric function, possibly contributing to the hypersensitivity of GVAs in chronic stress conditions.NEW & NOTEWORTHY Gastric vagal afferents (GVAs) relay food-related signals to the central nervous system, where they are processed, eventually leading to modulation of food intake and gastric function. GVA signaling can be modulated by an array of hormones. Stress has been shown to induce GVA hypersensitivity. This study demonstrates that GVA neurons express subtypes of stress hormone receptors, specifically CRF2. Furthermore, activation of CRF2 receptor increases GVA mechanosensitivity, which could have implications for food intake and gastric function.

Sex differences in morphine-induced trafficking of mu-opioid and corticotropin-releasing factor receptors in locus coeruleus neurons.

The locus coeruleus (LC)-norepinephrine (NE) system is a key nucleus in which endogenous opioid and stress systems intersect to regulate the stress response. LC neurons of male rats become sensitized to stress following chronic morphine administration. Whether sex dictates this pattern of opioid-induced plasticity has not been demonstrated. Delineating the neurobiological adaptations produced by chronic opioids will enhance our understanding of stress vulnerability in opioid-dependent individuals, and may reveal how stress negatively impacts addiction recovery. In the present study, the effect of chronic morphine on the subcellular distribution of mu-opioid (MOR) and CRF receptors (CRFR) was investigated in the LC of male and female rats using immunoelectron microscopy. Results showed that placebo-treated females exhibited higher MOR and CRFR cytoplasmic distribution ratio when compared to placebo-treated males. Chronic morphine exposure induced a shift in the distribution of MOR immunogold-silver particles from the plasma membrane to the cytoplasm selectively in male LC neurons. Interestingly, chronic morphine exposure induced CRFR recruitment to the plasma membrane of both male and female LC neurons. These findings provide a potential mechanism by which chronic opioid administration increases stress vulnerability in males and females via an increase in surface availability of CRFR in LC neurons. However, our results also support the notion that cellular adaptations to chronic opioids differ across the sexes as redistribution of MOR following morphine exposure was only observed in male LC neurons.

Chronic corticosterone increases ΔFOSB and CRFR1 immunoreactivity in brain regions that modulate aversive conditioning.

Previous studies showed that chronic treatment with corticosterone facilitates elevated T-maze (ETM) inhibitory avoidance and a step-down avoidance task, responses that have been used to investigate aversive conditioning and memory processes. On the other hand, chronic corticosterone does not alter ETM escape from the open arms. The purpose of the present study was to further investigate the effects of chronic corticosterone treatment (200 mg pellets, 21-day release) in an animal model of anxiety that does not involve aversive conditioning: the light/dark transition model. We also investigated the pattern of ΔFosB immunoreactivity (ΔFosB-ir) in different brain regions. To examine how treatment with chronic corticosterone interferes with CRFR1 expression we measured CRFR1 in the same brain structures that exhibited increased ΔFosB-ir. Results showed that chronic treatment with corticosterone did not alter behavioral measurements performed in the light/dark transition model. On the other hand, ΔFosB-ir was increased in several structures that modulate aversive conditioning: the cingulate cortex, the ventro and dorsolateral septum, the amygdala, the paraventricular, dorsomedial and ventromedial hypothalamus, the periaqueductal grey matter, the dorsal raphe, and the median raphe nucleus. Chronic treatment with corticosterone also increased CRFR1-immunoreactivity in the ventrolateral septum, central amygdala, dorsomedial hypothalamus, ventral region of the dorsal raphe and median raphe. These results contribute to a better understanding of the behavioral and neurobiological alterations induced by chronic exposure to glucocorticoids.

Interactive effects of prenatal alcohol exposure and chronic stress in adulthood on anxiety-like behavior and central stress-related receptor mRNA expression: Sex- and time-dependent effects.

Children and adults prenatally exposed to alcohol show higher rates of mental health problems than unexposed individuals, with depression and anxiety being among the more commonly encountered disorders. Previous studies in rats showed that prenatal alcohol exposure (PAE) can indeed increase depressive- and anxiety-like behavior in adulthood; however, depression and anxiety are often observed in the context of stress and/or a dysregulated stress response system (the hypothalamic-pituitary-adrenal [HPA] axis). PAE can dysregulate the HPA axis, resulting in hyperresponsivity to stress. In turn, this may predispose individuals prenatally exposed to alcohol to the adverse effects of stress compared to unexposed individuals. We have shown previously that PAE animals may be more sensitive to the effects of chronic stress on behavior, showing increased anxiety- and depressive-like behavior following chronic unpredictable stress (CUS) exposure. Here, we investigated the independent and interactive effects of PAE and adult CUS on anxiety-like behavior and receptor systems (corticotropin-releasing hormone receptor type 1 [CRHR1], mineralocorticoid receptor [MR], and glucocorticoid receptor [GR]), and underlying stress and emotional regulation, and whether exposure to CUS differentially results in immediate or delayed effects. Adult male and female offspring from PAE, pair-fed (PF), and ad libitum-fed control (C) dams were exposed to either 10 days of CUS or left undisturbed. Behavioral testing began 1 or 14 days post-CUS, and brains were collected following testing. Anxiety-like behaviors were evaluated using the open field, elevated plus maze and dark-light emergence tests. CRHR1, MR, and GR mRNA expression were assessed in the medial prefrontal cortex (mPFC), amygdala, and hippocampal formation, brain areas key to both stress and emotional regulation. We found that PAE differentially increased anxiety-like behavior and altered GR mRNA in males and females compared to their control counterparts. Furthermore, depending on the timing of testing, CUS unmasked alterations in GR and CRHR1 mRNA expression in the mPFC and amygdala in PAE males, and MR mRNA in the hippocampal formation in PAE females compared to their C counterparts. Overall, the changes observed in these receptor systems may underlie the increase in anxiety-like behavior following PAE and CUS exposure in adulthood. That CUS differentially affected brain and behavioral outcome of PAE and C animals, and did so in a sexually-dimorphic manner, has important implications for understanding the etiology of psychopathology in individuals prenatally exposed to alcohol.

Opposing actions of CRF-R1 and CB1 receptors on VTA-GABAergic plasticity following chronic exposure to ethanol.

Dopamine neurons in the ventral tegmental area (VTA) influence learned behaviors and neuropsychiatric diseases including addiction. The stress peptide corticotrophin-releasing factor (CRF) contributes to relapse to drug and alcohol seeking following withdrawal, although the cellular actions are poorly understood. In this study, we show that presynaptic CRF type 1 receptors (CRF-R1) potentiate GABA release onto mouse VTA dopamine neurons via a PKC-Ca2+ signaling mechanism. In naive animals, activation of CRF-R1 by bath application of CRF or ethanol enhanced GABAA inhibitory postsynaptic currents (IPSCs). Following 3 days of withdrawal from four weekly cycles of chronic intermittent ethanol (CIE) vapor exposure, spontaneous IPSC frequency was enhanced while CRF and ethanol potentiation of IPSCs was intact. However, withdrawal for 3 weeks or more was associated with reduced spontaneous IPSC frequency and diminished CRF and ethanol responses. Long-term withdrawal was also accompanied by decreased sensitivity to the CB1 receptor agonist WIN55212 as well as greatly enhanced sensitivity to the CB1 antagonist AM251. Inclusion of BAPTA in the internal recording solution restored the responsiveness to CRF or ethanol and reduced the potentiating actions of AM251. Together, these data suggest that GABAA inhibition of VTA dopamine neurons is regulated by presynaptic actions of CRF and endocannabinoids and that long-term withdrawal from CIE treatment enhances endocannabinoid-mediated inhibition, thereby suppressing CRF facilitation of GABA release. Such findings have implications for understanding the impact of chronic alcohol on stress-related, dopamine-mediated alcohol-seeking behaviors.

Perfluorooctane sulfonate (PFOS) can alter the hypothalamic-pituitary-adrenal (HPA) axis activity by modifying CRF1 and glucocorticoid receptors.

Perfluorooctane sulfonate (PFOS) is an endocrine disruptor highly persistent, bioaccumulative and neurotoxic, whose presence has been detected in different compartments of the environment. The aim of this study was to investigate whether PFOS could alter the HPA axis activity by modifying the gene and protein expression of corticotropin-releasing factor 1 receptor (CRF1r) and glucocorticoid receptor (Gr). For that purpose, Sprague-Dawley adult male rats were orally treated by gavage with 0.5; 1.0; 3.0 and 6.0 mg of PFOS/kg/day for 28 consecutive days. After PFOS administration, gene and protein expression of CRF1r were analysed in the hypothalamus, hippocampus, pituitary and adrenal glands. Moreover, Gr gene and protein expression were measured in hypothalamus, pituitary gland, prefrontal cortex, amygdala and hippocampus. The reported results indicate that (1) PFOS could inhibit HPA axis activity by diminishing gene and protein expression of CRF1r in the pituitary gland; (2) PFOS inhibits Gr protein expression in both prefrontal cortex and amygdala, which could be related to the toxic effects of this contaminant in this neuroendocrine axis and finally, (3) PFOS-treated rats would try to maintain the physiological levels of corticosterone by reducing the protein expression of Gr in the pituitary gland.

CRHR1 Mediates the Up-Regulation of Synapsin I Induced by Nesfatin-1 Through ERK 1/2 Signaling in SH-SY5Y Cells.

The anorexigenic molecule nesfatin-1 has recently been taken as a potential mood regulator, but the potential mechanisms remain unknown. Results of our previous study have demonstrated that nesfatin-1 could induce anxiety- and depression-like behaviors in rats, accompanied by the hyperactivity of the hypothalamic-pituitary-adrenal axis and the imbalanced mRNA expression of synaptic vesicle proteins. To explore the potential neurobiological mechanism underlying the effect of nesfatin-1 on the synaptic plasticity, the human neuroblastoma SH-SY5Y cells were cultured and treated with different concentrations of nesfatin-1 in the present study. The mRNA and protein expressions of corticotropin-releasing hormone (CRH) were measured via real-time fluorescent quantitative PCR and western blot, respectively. The protein expressions of extracellular signal-regulated kinase 1/2 (ERK1/2), phosphorylated-ERK1/2 (p-ERK1/2), and synapsin I were detected via western blot. The results confirmed that nesfatin-1 (10-9~10-7 mol/L) could up-regulate the expression of CRH. Moreover, nesfatin-1 (10-9~10-7 mol/L) could also increase the protein expressions of p-ERK1/2 and synapsin I, and these effects could be blocked by CP376395, a selective antagonist of CRH type 1 receptor (CRHR1). Furthermore, the increased expression of synapsin I induced by nesfatin-1 could also be reversed by PD98059, a specific inhibitor of the p-ERK. These results indicated that CRHR1 might mediate the effect of nesfatin-1 on the expressions of synapsin I via ERK1/2 signaling pathway.

Repeated corticosterone injections in adult mice alter stress hormonal receptor expression in the cerebellum and motor coordination without affecting spatial learning.

Receptors for glucocorticoid (GR) and corticotropin-releasing hormone (CRH) are largely found in brain sensorimotor structures, particularly in cerebellum, underlining a potential role of stress hormones in the regulation of motor function. Since CRH is involved in neuroplasticity, known for its trophic effect on synapses, we investigated how manipulations in corticosterone serum levels can modulate the CRH system in the cerebellum and affect motor coordination. Corticosterone at doses of either 15 or 30mg/kg was injected in mice and the status of hormonal expression evaluated in cerebellum, hippocampus, and hypothalamus in undisturbed housing conditions or after different behavioral tests. Under both conditions, metabolic activity in numerous brain regions involved in motor functions and emotion was measured by means of cytochrome oxidase (COX) activity labeling. After six consecutive days of corticosterone administration, CRH-R1 transcription was downregulated in hypothalamic and cerebellar regions and hypometabolic changes were observed in mice treated with the higher dose for several limbic and sensorimotor circuitries, notably basal ganglia, deep cerebellar nuclei, and red nucleus. Corticosterone did not modify motor activity, anxiety, and spatial orientation, but decreased latencies before falling from the rotorod and prevented mice from reaching targets in the coat-hanger test. In addition, COX activities were similar to control mice except in ventromedial thalamus and dorsal neostriatum, possibly indicating that physical activity protected brain energy metabolism against the stress hormone. The present findings showed that the CRH/CRH-R1 system might play a role in mediating the effects of stress on cerebellar function, affecting especially motor learning tasks.

A Functional Switch in Tonic GABA Currents Alters the Output of Central Amygdala Corticotropin Releasing Factor Receptor-1 Neurons Following Chronic Ethanol Exposure.

The corticotropin releasing factor (CRF) system in the central amygdala (CeA) has been implicated in the effects of acute ethanol and the development of alcohol dependence. We previously demonstrated that CRF receptor 1 (CRF1) neurons comprise a specific component of the CeA microcircuitry that is selectively engaged by acute ethanol. To investigate the impact of chronic ethanol exposure on inhibitory signaling in CRF1+ CeA neurons, we used CRF1:GFP mice subjected to chronic intermittent ethanol (CIE) inhalation and examined changes in local inhibitory control, the effects of acute ethanol, and the output of these neurons from the CeA. Following CIE, CRF1+ neurons displayed decreased phasic inhibition and a complete loss of tonic inhibition that persisted into withdrawal. CRF1- neurons showed a cell type-specific upregulation of both phasic and tonic signaling with CIE, the latter of which persists into withdrawal and is likely mediated by δ subunit-containing GABAA receptors. The loss of tonic inhibition with CIE was seen in CRF1+ and CRF1- neurons that project out of the CeA and into the bed nucleus of the stria terminalis. CRF1+ projection neurons displayed an increased baseline firing rate and loss of sensitivity to acute ethanol following CIE. These data demonstrate that chronic ethanol exposure produces profound and long-lasting changes in local inhibitory control of the CeA, resulting in an increase in the output of the CeA and the CRF1 receptor system, in particular. These cellular changes could underlie the behavioral manifestations of alcohol dependence and potentially contribute to the pathology of addiction. SIGNIFICANCE STATEMENT: The corticotropin releasing factor (CRF) system in the central amygdala (CeA) has been implicated in the effects of acute and chronic ethanol. We showed previously that CRF receptor 1-expressing (CRF1+) neurons in the CeA are under tonic inhibitory control and are differentially regulated by acute ethanol (Herman et al., 2013). Here we show that the inhibitory control of CRF1+ CeA neurons is lost with chronic ethanol exposure, likely by a functional switch in local tonic signaling. The loss of tonic inhibition is seen in CRF1+ projection neurons, suggesting that a critical consequence of chronic ethanol exposure is an increase in the output of the CeA CRF1 system, a neuroadaptation that may contribute to the behavioral consequences of alcohol dependence.

The Modulation of Cardiac Contractile Function by the Pharmacological and Toxicological Effects of Urocortin2.

Urocortin2 (Ucn2) has been revealed to enhance cardiac function in heart failure. However, the pharmacological and toxicological effects of Ucn2 on cardiomyocytes are incompletely understood. In this study, we investigated the possible mechanisms of Ucn2 on mediating the contractility of cardiomyocytes. Mechanical properties and intracellular Ca(2+) properties were measured in isolated cardiomyocytes from different treatment groups. The stress signaling was evaluated using Western blot. The results demonstrated that Ucn2 induced maximal velocity of shortening (+dL/dt), peak height, peak shortening (PS) amplitude, maximal velocity of relengthening (-dL/dt), accompanied by a significant rise in intracellular Ca(2+) level and a fall of the mean time constant of Ca(2+) transient decay (Tau) in WT cardiomyocytes. However, these effects were abolished by preincubation of type 2 CRF receptors (CRFR2) antagonist anti-sauvagine 30 (a-SVG-30). We also found that Ucn2 treatment activated the AMPK pathway in isolated cardiomyocytes via CRFR2. Furthermore, Ucn2 induced protein kinase A (PKA) and phospholamban (PLN) phosphorylation. Pretreatment of PKA inhibitor H89 reduced the inotropic and lusitropic effects of Ucn2 as well as decreased the intracellular Ca(2+) load and slowed down the Ca(2+) transient decay. We also showed that preincubation of Compound C, an inhibitor of AMPK, inhibited the phosphorylation of PKA and the intracellular Ca(2+) level in cardiomyocytes without affecting the contractile function and the Tau of cardiomyocytes. Taken together, it suggests that Ucn2 facilitate the contractility of cardiomyocytes via activating both AMPK and PKA.

Ethanol and corticotropin releasing factor receptor modulation of central amygdala neurocircuitry: An update and future directions.

The central amygdala is a critical brain region for many aspects of alcohol dependence. Much of the work examining the mechanisms by which the central amygdala mediates the development of alcohol dependence has focused on the interaction of acute and chronic ethanol with central amygdala corticotropin releasing factor signaling. This work has led to a great deal of success in furthering the general understanding of central amygdala neurocircuitry and its role in alcohol dependence. Much of this work has primarily focused on the hypothesis that ethanol utilizes endogenous corticotropin releasing factor signaling to upregulate inhibitory GABAergic transmission in the central amygdala. Work that is more recent suggests that corticotropin releasing factor also plays an important role in mediating anxiety-like behaviors via the enhancement of central amygdala glutamatergic transmission, implying that ethanol/corticotropin releasing factor interactions may modulate excitatory neurotransmission in this brain region. In addition, a number of studies utilizing optogenetic strategies or transgenic mouse lines have begun to examine specific central amygdala neurocircuit dynamics and neuronal subpopulations to better understand overall central amygdala neurocircuitry and the role of neuronal subtypes in mediating anxiety-like behaviors. This review will provide a brief update on this literature and describe some potential future directions that may be important for the development of better treatments for alcohol addiction.

Activation of corticotropin-releasing factor receptors in the rostral ventrolateral medulla is required for glucose-induced sympathoexcitation.

Energy expenditure is determined by metabolic rate and diet-induced thermogenesis. Normally, energy expenditure increases due to neural mechanisms that sense plasma levels of ingested nutrients/hormones and reflexively increase sympathetic nerve activity (SNA). Here, we investigated neural mechanisms of glucose-driven sympathetic activation by determining contributions of neuronal activity in the hypothalamic paraventricular nucleus (PVN) and activation of corticotropin-releasing factor (CRF) receptors in the rostral ventrolateral medulla (RVLM). Glucose was infused intravenously (150 mg/kg, 10 min) in male rats to raise plasma glucose concentration to a physiological postprandial level. In conscious rats, glucose infusion activated CRF-containing PVN neurons and TH-containing RVLM neurons, as indexed by c-Fos immunofluorescence. In α-chloralose/urethane-anesthetized rats, glucose infusion increased lumbar and splanchnic SNA, which was nearly prevented by prior RVLM injection of the CRF receptor antagonist astressin (10 pmol/50 nl). This cannot be attributed to a nonspecific effect, as sciatic afferent stimulation increased SNA and ABP equivalently in astressin- and aCSF-injected rats. Glucose-stimulated sympathoexcitation was largely reversed during inhibition of PVN neuronal activity with the GABA-A receptor agonist muscimol (100 pmol/50 nl). The effects of astressin to prevent glucose-stimulated sympathetic activation appear to be specific to interruption of PVN drive to RVLM because RVLM injection of astressin prior to glucose infusion effectively prevented SNA from rising and prevented any fall of SNA in response to acute PVN inhibition with muscimol. These findings suggest that activation of SNA, and thus energy expenditure, by glucose is initiated by activation of CRF receptors in RVLM by descending inputs from PVN.

Social stress and CRF-dopamine interactions in the VTA: role in long-term escalation of cocaine self-administration.

The nature of neuroadaptations in the genesis of escalated cocaine taking remains a topic of considerable interest. Intermittent social defeat stress induces both locomotor and dopaminergic cross-sensitization to cocaine, as well as escalated cocaine self-administration. The current study examines the role of corticotropin releasing factor receptor subtypes 1 and 2 (CRFR1, CRFR2) within the ventral tegmental area (VTA) during social defeat stress. This study investigated whether injecting either a CRFR1 or CRFR2 antagonist directly into the VTA before each social defeat would prevent the development of later (1) locomotor sensitization, (2) dopaminergic sensitization, and (3) escalated cocaine self-administration in rats. CRFR1 antagonist CP376395 (50 or 500 ng/side), CRFR2 antagonist Astressin2-B (100 or 1000 ng/side), or vehicle (aCSF) was microinjected into the VTA 20 min before social defeat stress (or handling) on days 1, 4, 7, and 10. Ten days later, rats were injected with cocaine (10 mg/kg, i.p.) and assessed for either locomotor sensitization, measured by walking activity, or dopaminergic sensitization, measured by extracellular dopamine (DA) in the nucleus accumbens shell (NAcSh) through in vivo microdialysis. Locomotor sensitization testing was followed by intravenous cocaine self-administration. Intra-VTA antagonism of CRFR1, but not CRFR2, inhibited the induction of locomotor cross-sensitization to cocaine, whereas both prevented dopaminergic cross-sensitization and escalated cocaine self-administration during a 24 h "binge." This may suggest dissociation between locomotor sensitization and cocaine taking. These data also suggest that interactions between CRF and VTA DA neurons projecting to the NAcSh are essential for the development of dopaminergic cross-sensitization to cocaine.

Neural circuitry underlying the central hypertensive action of nesfatin-1: melanocortins, corticotropin-releasing hormone, and oxytocin.

Nesfatin-1 is produced in the periphery and in the brain where it has been demonstrated to regulate appetite, stress hormone secretion, and cardiovascular function. The anorexigenic action of central nesfatin-1 requires recruitment of neurons producing the melanocortins and centrally projecting oxytocin (OT) and corticotropin-releasing hormone (CRH) neurons. We previously have shown that two components of this pathway, the central melanocortin and oxytocin systems, contribute to the hypertensive action of nesfatin-1 as well. We hypothesized that the cardiovascular effect of nesfatin-1 also was dependent on activation of neurons expressing CRH receptors, and that the order of activation of the melanocortin-CRH-oxytocin circuit was preserved for both the anorexigenic and hypertensive actions of the peptide. Pretreatment of male rats with the CRH-2 receptor antagonist astressin2B abrogated nesfatin-1-induced increases in mean arterial pressure (MAP). Furthermore, the hypertensive action of CRH was blocked by pretreatment with an oxytocin receptor antagonist ornithine vasotocin (OVT), indicating that the hypertensive effect of nesfatin-1 may require activation of oxytocinergic (OTergic) neurons in addition to recruitment of CRH neurons. Interestingly, we found that the hypertensive effect of α-melanocyte stimulating hormone (α-MSH) itself was not blocked by either astressin2B or OVT. These data suggest that while α-MSH-producing neurons are part of a core melanocortin-CRH-oxytocin circuit regulating food intake, and a subpopulation of melanocortin neurons activated by nesfatin-1 do mediate the hypertensive action of the peptide, α-MSH can signal independently from this circuit to increase MAP.