The Experts below are selected from a list of 288 Experts worldwide ranked by ideXlab platform
Joachim Spiess - One of the best experts on this subject based on the ideXlab platform.
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Corticotropin-releasing factor receptor 1 and central heart rate regulation in mice during expression of conditioned fear.
Journal of Pharmacology and Experimental Therapeutics, 2004Co-Authors: Oliver Stiedl, Olaf Jahn, Michael Meyer, Sven Ove Ögren, Joachim SpiessAbstract:The present study was performed to 1) determine heart rate (HR) effects mediated through central corticotropin-releasing factor receptor subtypes 1 (CRF1) investigate and 2 (CRF2) and 2) to the contribution of endogenous CRF to baseline HR and its fear-induced adjustment in freely moving mice. CRF ligands were injected into both lateral ventricles (i.c.v.) 15 min before the presentation of a conditioned auditory fear stimulus (CS). Initial behavioral results suggest an ovine CRF (oCRF)-mediated enhanced baseline fear and mildly enhanced conditioned auditory fear. In contrast, i.c.v. injection of oCRF (35–210 ng/mouse) dose-dependently decreased baseline HR, increased HR variability, and attenuated the CS-induced tachycardia. This effect is suggested to depend on a combined activation of sympathetic and parasympathetic activity referred to as enhanced sympathovagal antagonism. An extreme bradycardia was elicited by oCRF injection into the lower brainstem. All HR effects were probably mediated by CRF1 because injection of the CRF2-selective agonist mouse urocortin II was ineffective, and the baseline bradycardia by i.c.v. CRF was preserved in CRF2-deficient mice. Injection of various CRF receptor antagonists including the CRF2-selective Antisauvagine-30 did not affect the conditioned HR response. This finding suggests that endogenous CRF does not contribute to the fear-mediated tachycardia. Thus, the hypothesis of an involvement of CRF in HR responses of mice to acute aversive stimulation is rejected. Pharmacological evidence points at the involvement of CRF1 in enhanced sympathovagal antagonism, a pathological state contributing to elevated cardiac risk, whereas the physiological role of the brain CRF system in cardiovascular regulation remains to be determined.
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Mitogen-activated protein kinase signaling in the hippocampus and its modulation by corticotropin-releasing factor receptor 2: a possible link between stress and fear memory.
The Journal of Neuroscience, 2003Co-Authors: Farahnaz Sananbenesi, Joachim Spiess, Andre Fischer, Christina Schrick, Jelena RadulovicAbstract:A coordinated activation of multiple interlinked signaling pathways involving cAMP-dependent protein kinase (PKA) and mitogen-activated extracellular signal-regulated kinases (Mek-1/2) regulates gene expression and neuronal changes underlying memory consolidation. In the present study we investigated whether these molecular cascades might mediate the effects of stress on memory formation. We also investigated the role of hippocampal corticotropin-releasing factor receptor 2 (CRF 2 ) in stress-enhanced learning and molecular signaling mediated by PKA, Mek-1/2, and their downstream targets extracellularly regulated kinases 1 and 2 (Erk-1/2) and p90-ribosomal-s-kinase-1 (p90Rsk-1). Acute 1 hr immobilization was used as a stressful stimulus, and one-trial context-dependent fear conditioning was used as a model for associative learning. Training of BALB/c mice 3 hr after the end of immobilization resulted in an enhancement of conditioned fear, as indicated by significantly increased freezing behavior of stressed when compared with nonstressed mice. Interestingly, Erk-1/2 phosphorylation after conditioning of nonstressed and stressed mice depended on PKA and Mek-1/2, respectively. Intrahippocampal injection of the selective Mek-1/2 inhibitor U0126 or CRF 2 antagonist Antisauvagine-30 (aSvg-30) prevented stress-enhanced fear conditioning and Mek-1/2-dependent activation of Erk-1/2 and p90Rsk-1. aSvg-30 did not affect the phosphorylation of the PKA regulatory subunit II of stressed mice. The molecular and behavioral effects of CRF 2 coincided with stress-induced upregulation of CRF 2 mRNA. These results suggest that modulation of Mek-1/2-dependent signaling by hippocampal CRF 2 can be selectively involved in the delayed effects of stress on memory consolidation.
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Stress-mediated heart rate dynamics after deletion of the gene encoding corticotropin-releasing factor receptor 2.
European Journal of Neuroscience, 2003Co-Authors: Oliver Stiedl, Michael G Rosenfeld, Michael Meyer, Toshimitsu Kishimoto, Joachim SpiessAbstract:The objective of the present study was to investigate the potential role of corticotropin-releasing factor receptor subtype 2 (CRFR2) in autonomic regulation of heart rate and heart rate variability under physiological conditions in conscious mice. Heart rate dynamics during novelty exposure and auditory fear conditioning were assessed by radiotelemetry. Heart rate responses and heart rate variability values were not different in CRFR2 + / + and CRFR2 - / - mice during novelty exposure, which was associated with similar locomotor activity exhibited by both genotypes. The heart rate responses during retention of conditioned auditory fear were similar and the exponential relationship between heart rate and heart rate variability was independent of genotype. Pharmacological stimulation of the peripheral CRFR2β by intraperitoneal injection of 200 ng human/rat corticotropin-releasing factor yielded a sustained tachycardia in wildtype control (CRFR2 + / + ) mice which was absent in CRFR2-deficient (CRFR2 - / - ) mice. Similarly, the tachycardia was effectively blocked by preinjection of the CRFR2 antagonist Antisauvagine-30. In conclusion, the results indicate the involvement of CRFR2 in heart rate dynamics upon pharmacological stimulation but demonstrate that CRFR2 is not involved in baseline heart rate regulation and stress-mediated modulation of heart rate responses.
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Differential responsiveness of CRF receptor subtypes to N-terminal truncation of peptidic ligands.
Peptides, 2002Co-Authors: Olaf Brauns, Simone Brauns, Bodo Zimmermann, Olaf Jahn, Joachim SpiessAbstract:Abstract The role of the N-terminal domains of corticotropin-releasing factor (CRF) and CRF-like peptides in receptor subtype selectivity, ligand affinity and biological potency was investigated. Therefore, human CRF 12–41 , human URP 12–38 and Antisauvagine-30 (aSvg) were N-terminally prolonged by consecutive addition of one or two amino acids. The peptides obtained were tested for their binding affinities to rat CRF 1 and murine CRF 2β receptor, and their capability to stimulate cAMP-release by HEK cells producing either receptor. It was observed that human CRF N-terminally truncated by eight residues was bound with high affinity to CRF 2 receptor ( K i =5.4 nM), whereas affinity for CRF 1 receptor was decreased ( K i =250 nM). A similar shift of affinity was found with sauvagine (Svg) analogs. Truncation of human URP analogs did not affect their preference for CRF 2β receptor, but reduced their affinity. Changes in affinity were positively correlated with changes in potency. These results indicated that CRF 1 receptor was more stringent in its structural requirements for ligands to exhibit high affinity binding than CRF 2β receptor.
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pharmacological and chemical properties of astressin Antisauvagine 30 and α helcrf significance for behavioral experiments
Neuropharmacology, 2001Co-Authors: Olaf Brauns, Thomas Liepold, Jelena Radulovic, Joachim SpiessAbstract:Abstract Corticotropin releasing factor (CRF) represents an early chemical signal in the stress response and modulates various brain functions through G protein-coupled receptors. Two CRF receptor subtypes, CRF1 and CRF2, have been identified. Since the physicochemical properties of CRF receptor antagonists might influence their biological potency, the peptidic antagonists astressin, α-helical CRF9–41 (α-helCRF) and Antisauvagine-30 (aSvg-30) have been analyzed. The rank order of solubility of these compounds in artificial cerebrospinal fluid (aCSF, pH 7.4) was aSvg-30>α-helCRF>>astressin, whereas the rank order of relative lipophilicity as determined with RP–HPLC was α-helCRF>astressin>aSvg-30. The calculated isoelectric points were 4.1 (α-helCRF), 7.4 (astressin) and 10.0 (aSvg-30). According to Schild analysis of the CRF receptor-dependent cAMP production of transfected HEK cells, aSvg-30 exhibited a competitive antagonism and displayed a 340 fold selectivity for mCRF2β receptor. For astressin, however, the pharmacodynamic profile could not be explained by a simple competitive mechanism as indicated by Schild slopes >1 for rCRF1 or mCRF2β receptor. Behavioral experiments demonstrated that after i.c.v. injection, α-helCRF reduced oCRF-induced anxiety-like behavior in the elevated plus-maze, whereas astressin, despite its higher in vitro potency, did not. These findings could be explained by different physicochemical properties of the antagonists employed.
Tamotsu Shibasaki - One of the best experts on this subject based on the ideXlab platform.
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Corticotropin-releasing factor (CRF) receptor subtypes in mediating neuronal activation of brain areas involved in responses to intracerebroventricular CRF and stress in rats.
Peptides, 2011Co-Authors: Chiaki Takahashi, Hisayuki Ohata, Tamotsu ShibasakiAbstract:Abstract Corticotropin-releasing factor (CRF) plays an important role in stress responses through activation of its receptor subtypes, CRF1 receptor (CRF 1 ) and CRF2 receptor (CRF 2 ). The parvocellular paraventricular nucleus of the hypothalamus (PVNp), the central nucleus of the amygdala (CeA), and the oval nucleus of the bed nucleus of the stria terminalis (BNSTov), which are rich in CRF neurons with equivocal expression of CRF 1 and CRF 2 , are involved in stress-related responses. In these areas, Fos expression is induced by various stimuli, although the functions of CRF receptor subtypes in stimuli-induced Fos expression are unknown. To elucidate this issue and to examine whether Fos is expressed in CRF or non-CRF neurons in these areas, the effects of antalarmin and Antisauvagine-30 (AS-30), CRF 1 - and CRF 2 -specific antagonists, respectively, on intracerebroventricular (ICV) CRF- or 60 min-restraint-induced Fos expression were examined in rats. ICV CRF increased the number of Fos-positive CRF and non-CRF neurons in the PVNp, with the increases being inhibited by antalarmin in CRF and non-CRF neurons and by AS-30 in CRF neurons. Restraint also increased Fos-positive CRF and non-CRF neurons in the PVNp, with the increases being inhibited by antalarmin in the CRF neurons. ICV CRF also increased Fos-positive non-CRF neurons in the CeA and the BNSTov, which was inhibited by AS-30 in both areas, and inhibited by antalarmin in the BNSTov only. Restraint increased Fos-positive non-CRF neurons in the CeA and BNSTov, with the increases being almost completely inhibited by either antagonist. These results indicate that both ICV CRF and restraint activate both CRF and non-CRF neurons in the PVNp and non-CRF neurons in the CeA and BNSTov, and that the activation is mediated by CRF 1 and/or CRF 2 . However, the manner of involvement for CRF 1 and CRF 2 in ICV CRF- and restraint-induced activation of neurons differs with respect to the stimuli and brain areas; being roughly equivalent in the CeA and BNSTov, but different in the PVNp. Furthermore, the non-CRF 1&2 -mediated signals seem to primarily play a role in restraint-induced activation of non-CRF neurons in the PVNp since the activation was not inhibited by CRF receptor antagonists.
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Involvement of CRF2 receptor in the brain regions in restraint-induced anorexia.
Neuroreport, 2011Co-Authors: Hisayuki Ohata, Tamotsu ShibasakiAbstract:We have reported that corticotropin-releasing factor (CRF) receptor subtypes, CRF 1 and CRF 2 , are involved in stress-induced anorexia. To clarify in which brain regions the CRF receptor is involved in mediating stress-induced anorexia, we examined the effect of microinjecting CRF 1 -selective or CRF 2 -selective antagonist into the lateral septum or the bed nucleus of the stria terminalis (BNST), which are implicated in regulating stress response. The results demonstrated that injecting Antisauvagine-30 into the lateral septum or the BNST significantly attenuated restraint-induced anorexia, whereas injecting antalarmin into these regions did not affect anorexia. These results suggest that the CRF 2 receptor in the lateral septum and the BNST is involved in the stress-induced inhibitory mechanism of feeding behavior.
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Nicotine suppresses energy storage through activation of sympathetic outflow to brown adipose tissue via corticotropin-releasing factor type 1 receptor.
Neuroscience Letters, 2009Co-Authors: Asuka Mano-otagiri, Hisayuki Ohata, Azusa Iwasaki-sekino, Keiko Arai, Tamotsu ShibasakiAbstract:Abstract Nicotine is known to stimulate energy expenditure, although the precise mechanism is unclear. To clarify the involvement of corticotropin-releasing factor (CRF) in the mechanism by which nicotine increases energy expenditure, the effect of intraperitoneal injection of nicotine (0.1 or 0.5 mg/kg) on the release of noradrenaline (NA), a stimulator of thermogenesis, in brown adipose tissue (BAT) important for energy expenditure was examined in rats. We also examined the effects of CRF receptor subtype antagonists on the nicotine-induced change in BAT NA release. Nicotine significantly increased BAT NA release at a dose of 0.5 mg/kg, and the increase was completely blocked by antalarmin, a CRF type 1 receptor antagonist, but not by Antisauvagine-30, a CRF type 2 receptor antagonist. These results suggest that nicotine increases energy expenditure by activating BAT function, and that CRF type 1 receptors are involved in the mechanism by which nicotine affects energy balance.
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Both corticotropin-releasing factor receptor type 1 and type 2 are involved in stress-induced inhibition of food intake in rats
Psychopharmacology, 2004Co-Authors: Azusa Sekino, Hisayuki Ohata, Asuka Mano-otagiri, Keiko Arai, Tamotsu ShibasakiAbstract:Rationale Stress-induced inhibition of food intake is reportedly blocked by a selective corticotropin-releasing factor (CRF) type 1 receptor (CRF_1) antagonist, suggesting the involvement of CRF_1 in the inhibitory mechanism. CRF_1 and CRF_2 are considered to function in the inhibition of food intake by CRF-related peptides with different time courses. Objectives This study was designed to clarify whether CRF_2 is also involved in stress-induced inhibition of food intake and to examine the relation of CRF_1 to CRF_2 in the inhibitory mechanism. Methods Antisauvagine-30 (AS-30), a selective CRF_2 antagonist, and/or CRA1000, a selective CRF_1 antagonist, were pre-administered intracerebroventricularly and intraperitoneally, respectively, to male Wistar rats deprived of food for 24 h before the animals were exposed to a 1-h period of stressors and food intake in 1 h after stress exposure was examined. The effect of both antagonists on locomotor activity was also examined. Results Pre-administration of 5–30 μg of AS-30 attenuated inhibition of food intake induced by restraint, electric footshock or emotional stress using a communication box. CRA1000 also attenuated the restraint-induced inhibition of food intake at doses of 5 and 10 mg/kg body weight. The reversal of restraint-induced inhibition of food intake by co-administration of AS-30 and CRA1000 was not larger than that by AS-30 or CRA1000 alone. Both antagonists did not affect locomotor activity. Conclusions These results suggest that not only CRF_1, but also CRF_2, are involved in stress-induced inhibition of food intake, and that both subtypes of CRF receptor function probably in series in 1 h after stress exposure.
Frank M Dautzenberg - One of the best experts on this subject based on the ideXlab platform.
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Different binding modes of amphibian and human corticotropin-releasing factor type 1 and type 2 receptors: evidence for evolutionary differences.
Journal of Pharmacology and Experimental Therapeutics, 2020Co-Authors: Frank M Dautzenberg, Jacqueline Higelin, Gabrielle Py-lang, Christophe Fischer, Matthew B. Wright, Gerda HuberAbstract:The binding characteristics of corticotropin-releasing factor (CRF) type 1 (CRF 1 ) and type 2 (CRF 2 ) receptors from human (hCRF 1 and hCRF 2α ) and Xenopus (xCRF 1 and xCRF 2 ) were compared using four different 125 I-labeled CRF analogs, the agonists 125 I-CRF and 125 I-sauvagine, and the antagonists 125 I-astressin ( 125 I-AST) and 125 I-Antisauvagine-30 ( 125 I-aSVG). The hCRF 2α and xCRF 2 receptors bound all four radioligands with different affinities, whereas hCRF 1 did not bind 125 I-aSVG, and xCRF 1 bound neither 125 I-sauvagine nor 125 I-aSVG. Competitive binding studies using unlabeled agonists and antagonists with hCRF 1 and hCRF 2α receptors revealed that most agonists exhibited higher affinity in displacing agonist radioligands compared with displacement of antagonist radioligands. Exceptions were the agonists human and rat urocortin, which displayed high-affinity binding in the presence of either 125 I-labeled agonist or antagonist ligands. In contrast, the affinities of antagonists were independent of the nature of the radioligand. We also found that, in contrast to the mammalian CRF receptors, the affinity of ligand binding to xCRF 1 and xCRF 2 receptors strongly depended on the nature of the radioligand used for competition. For xCRF 1 , competitors showed different rank order binding profiles with 125 I-CRF compared with 125 I-AST as the displaceable ligand. Similarly, binding of competitors to the xCRF 2 receptor showed markedly different profiles with 125 I-CRF as the competed ligand compared with the other radioligands. These data demonstrate that amphibian CRF receptors have distinctly different binding modes compared with their mammalian counterparts.
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Secondary structure of Antisauvagine analogues is important for CRF receptor antagonism: development of antagonists with increased potency and receptor selectivity
Peptides, 2002Co-Authors: Olaf Brauns, Simone Brauns, Marc Jenke, Bodo Zimmermann, Frank M DautzenbergAbstract:Abstract Antisauvagine-30 (aSVG) is the only high-affinity antagonist for the corticotropin-releasing factor (CRF) type 2 (CRF 2 ) receptor. A structure–activity relationship study was performed to pinpoint residues conferring aSVG’s selectivity. The aSVG-analogues being N-terminally extended by one or two residues or containing the Ala 22 Arg 23 Ala 24 (ARA-motif) of CRF, were synthesized. Additionally, a lactam bridge between positions 29 and 32 was introduced. The modified peptides were analyzed for α-helicity properties, binding affinities and antagonistic potencies at the rat CRF 1 and mouse CRF 2B receptors. While N-terminal prolongation and replacement of d -Phe 11 by Tyr 11 increased the affinity for the CRF 2 receptor, the introduction of the ARA motif resulted in a loss of CRF 2 receptor selectivity. These data show that aSVG 10–40 analogues are more potent CRF 2 receptor antagonists than aSVG 11–40 peptides, while introduction of the ARA-motif or a cyclic constraint between residues 29 and 32 favors binding to the CRF 1 receptor.
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The highly selective CRF2 receptor antagonist K41498 binds to presynaptic CRF2 receptors in rat brain
British Journal of Pharmacology, 2002Co-Authors: Andrew J. Lawrence, Frank M Dautzenberg, Elena Krstew, Andreas RuhmannAbstract:Novel analogues of Antisauvagine-30 (aSvg-30), a selective antagonist for CRF2 receptors, have been synthesized and characterized in vitro and in vivo. The analogues were tested for their ability to compete for [125I-Tyr0]Svg binding and to inhibit Svg-stimulated adenylate cyclase activity in human embryonic kidney (HEK) 293 cells, permanently transfected with cDNA coding for the human CRF1 (hCRF1), hCRF2α and hCRF2β receptor. One analogue [D-Phe11, His12, Nle17]Svg(11-40), named K41498, showed high affinity binding to hCRF2α (Ki=0.66±0.03 nM) and hCRF2β (Ki=0.62±0.01 nM) but not the hCRF1 receptor (ki=425+50 nM) and decreased Svg-stimulated cAMP accumulation in hCRF2 expressing cells. In conscious Wistar-Kyoto rats, K41498 (1.84 μg, i.v.) antagonized the hypotensive response to systemic urocortin (1.4 μg, i.v.), but did not block the pressor response to centrally administered urocortin (2.35 μg, i.c.v.). K41498 was subsequently radio-iodinated, and in autoradiographic studies, specific (sensitive to rat urocortin, astressin and aSvg30, but insensitive to antalarmin) binding of 125I-K41498 (100 pM) was detected in the heart and in selected brain regions including the nucleus tractus solitarius (NTS), spinal trigeminal nucleus, lateral septum and around the anterior and middle cerebral arteries. Following unilateral nodose ganglionectomy, binding of 125I-K41498 was reduced by 65% in the ipsilateral NTS, indicative of presynaptic CRF2 receptors on vagal afferent terminals. These data demonstrate that K41498 is a useful tool to study native CRF2 receptors in the brain and periphery. British Journal of Pharmacology (2002) 136, 896–904. doi:10.1038/sj.bjp.0704783
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Design, synthesis and pharmacological characterization of new highly selective CRF2 antagonists: development of 123I-K31440 as a potential SPECT ligand
Peptides, 2002Co-Authors: A. Rühmann, J. Chapman, J. Higelin, B. Butscha, Frank M DautzenbergAbstract:Abstract Novel analogs of Antisauvagine-30 (aSvg-30), a specific antagonist for corticotropin-releasing factor (CRF) receptor, type 2 (CRF 2 ), have been synthesized and characterized in vitro and in vivo. The N-terminal amino acid D-phenylalanine in aSvg-30 was replaced by a D-tyrosine residue for specific radioactive labeling with 123 I. Additionally, Met 17 of aSvg-30 was substituted by norleucine and the N-terminus of the peptide was acetylated to increase in vivo metabolic stability. The aSvg-30 analogs were tested for their ability to displace [ 125 I-Tyr 0 ]Svg in binding experiments and to inhibit Svg-stimulated adenylate cyclase activity in human embryonic kidney (HEK) 293 cells, permanently transfected with cDNA coding for the human CRF 1 (hCRF 1 ), hCRF 2α and hCRF 2β receptor. Ac-[D-Tyr 11 , His 12 , Nle 17 Svg(11–40), named K31440, showed high specific binding to hCRF 2α ( K i = 1.48 ± 0.34 nM) and hCRF 2β ( K i = 2.05 ± 0.61 nM) but not the hCRF 1 receptor ( K i = 288 ± 13 nM) and decreased Svg-stimulated cAMP activity in hCRF 2 -expressing cells in a similar fashion as aSvg-30. In biodistribution studies specific uptake of 123 I-K31440 was detected after 1 h in small intestine of BALB/c nude mice. These data demonstrate that 123 I-K31440 may serve as a useful tool to detect native CRF 2 receptors and elucidate their role in gastrointestinal disorders and diseases such as irritable bowel syndrome or cancer.
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125i Antisauvagine 30 a novel and specific high affinity radioligand for the characterization of corticotropin releasing factor type 2 receptors
Neuropharmacology, 2001Co-Authors: Jacqueline Higelin, Gabrielle Pylang, Cristina Paternoster, Gareth J Ellis, Arvind Patel, Frank M DautzenbergAbstract:Corticotropin-releasing factor (CRF) receptors type 1 (CRF1) and type 2 (CRF2) differ from each other in their pharmacological properties. The human and ovine CRF versions bind to CRF1 receptors with significantly higher affinity than to CRF2 receptors. Recently Antisauvagine-30, an N-terminally truncated version of the CRF analog sauvagine, was characterized as a specific antagonist to mouse CRF2B. We have synthesized the radiolabeled version 125I-Antisauvagine-30 and tested it for its affinity at human CRF1 (hCRF1), hCRF2A, Xenopus CRF1 (xCRF1) and xCRF2 receptors. In control binding studies 125I-labeled hCRF, sauvagine and astressin were also bound to these receptors. 125I-Antisauvagine-30 exclusively bound to hCRF2A and xCRF2 but not to hCRF1 and xCRF1 receptors. 125I-Antisauvagine-30 binding to hCRF2A and xCRF2 receptors was saturable and of high affinity (hCRF2A: Kd=125 pM; xCRF2: Kd=1.1 nM). In displacement binding experiments using 125I-Antisauvagine-30 as radioligand several CRF analogs bound to hCRF2A and xCRF2 receptors with similar rank orders as reported with other CRF radioligands. Finally, preliminary studies using 125I-Antisauvagine-30 binding to membrane homogenates prepared from different rat brain structures showed that the peptide bound specifically to brain areas expressing CRF2 receptors. These data demonstrate that 125I-Antisauvagine-30 is the first high-affinity ligand to specifically label CRF2 receptors.
Christopher A Lowry - One of the best experts on this subject based on the ideXlab platform.
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corticotropin releasing factor in the dorsal raphe nucleus increases medial prefrontal cortical serotonin via type 2 receptors and median raphe nucleus activity
European Journal of Neuroscience, 2008Co-Authors: Gina L. Forster, R B Pringle, Nicholas J Mouw, Shawn M Vuong, Michael J Watt, Andrew R Burke, Christopher A Lowry, Cliff H Summers, Kenneth J RennerAbstract:: Interactions between central corticotropin-releasing factor (CRF) and serotonergic systems are believed to be important for mediating fear and anxiety behaviors. Recently we demonstrated that infusions of CRF into the rat dorsal raphe nucleus result in a delayed increase in serotonin release within the medial prefrontal cortex that coincided with a reduction in fear behavior. The current studies were designed to study the CRF receptor mechanisms and pathways involved in this serotonergic response. Infusions of CRF (0.5 microg/0.5 microL) were made into the dorsal raphe nucleus of urethane-anesthetized rats following either inactivation of the median raphe nucleus by muscimol (25 ng/0.25 microL) or antagonism of CRF receptor type 1 or CRF receptor type 2 in the dorsal raphe nucleus with antalarmin (25-50 ng/0.5 microL) or Antisauvagine-30 (2 microg/0.5 microL), respectively. Medial prefrontal cortex serotonin levels were measured using in-vivo microdialysis and high-performance liquid chromatography with electrochemical detection. Increased medial prefrontal cortex serotonin release elicited by CRF infusion into the dorsal raphe nucleus was abolished by inactivation of the median raphe nucleus. Furthermore, antagonism of CRF receptor type 2 but not CRF receptor type 1 in the dorsal raphe nucleus abolished CRF-induced increases in medial prefrontal cortex serotonin. Follow-up studies involved electrical stimulation of the central nucleus of the amygdala, a source of CRF afferents to the dorsal raphe nucleus. Activation of the central nucleus increased medial prefrontal cortex serotonin release. This response was blocked by CRF receptor type 2 antagonism in the dorsal raphe. Overall, these results highlight complex CRF modulation of medial prefrontal cortex serotonergic activity at the level of the raphe nuclei.
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Evidence supporting a role for corticotropin-releasing factor type 2 (CRF2) receptors in the regulation of subpopulations of serotonergic neurons.
Brain Research, 2006Co-Authors: Daniel R. Staub, Andrew K. Evans, Christopher A LowryAbstract:Abstract Corticotropin-releasing factor (CRF)-related peptides can modulate stress-related physiology and behavior. Some of these effects may be mediated via the CRF type 2 (CRF2) receptor on serotonergic neurons in the dorsal raphe nucleus (DR). To determine if the CRF2 receptor agonist urocortin 2 (Ucn 2) increases c-Fos expression in rat DR serotonergic neurons via actions on CRF2 receptors, we gave intracerebroventricular (icv) injections of mouse Ucn 2 after icv injections of either saline or the CRF2 receptor antagonist Antisauvagine-30 (ASV-30). Double immunostaining methods for c-Fos and tryptophan hydroxylase revealed that, consistent with previous studies, mouse Ucn 2 increased c-Fos expression in tryptophan hydroxylase immunostained neurons in the middle and caudal parts (−8.18, −8.54, and −9.16 mm bregma) of the dorsal subdivision of the dorsal raphe nucleus 2 h after drug treatment. Pre-treatment with ASV-30 blocked these effects. Mouse Ucn 2 had no effect on c-Fos expression within the median raphe nucleus, consistent with the hypothesis that Ucn 2 has specific actions on an anatomically and functionally distinct subset of serotonergic neurons via activation of CRF2 receptors. These findings are also consistent with the hypothesis that Ucn 2, or another CRF-related neuropeptide acting at CRF2 receptors, modulates physiological and behavioral responses to stress-related stimuli via actions on a specific subset of serotonergic neurons within the dorsal raphe nucleus.
Gina L. Forster - One of the best experts on this subject based on the ideXlab platform.
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Iron Oxide Nanoparticle Delivery of Peptides to the Brain: Reversal of Anxiety during Drug Withdrawal.
Frontiers in Neuroscience, 2017Co-Authors: Nathan Vinzant, Jamie L. Scholl, Chia-ming Wu, Trevor Kindle, Ranjit T. Koodali, Gina L. ForsterAbstract:Targeting neuropeptide systems is important for future advancements in treatment of neurological and psychiatric illnesses. However, many of the peptides and their analogues do not cross the blood-brain barrier (BBB) efficiently. Nanoparticles such as iron oxide can cross the BBB, and here we describe a novel method for the conjugation of a peptide Antisauvagine-30 (ASV-30) to iron oxide nanoparticles. Previous research has shown that direct infusion of ASV-30 into the brain reduces anxiety-like behavior in animal models via actions on corticotropin releasing factor type 2 (CRF2) receptors. Therefore, we tested whether iron oxide+ASV-30 complexes cross the BBB of rats and then determined whether iron oxide+ASV-30 nanoparticles are localized with CRF2-expressing neurons. Finally we tested the hypothesis that systemic infusion of iron oxide+ASV-30 can reduce anxiety-like behavior. First we describe the synthesis and demonstrate the stability of iron oxide-peptide nanoparticle complexes. Next, nanoparticles (87.7 μg/kg Fe2O3) with or without ASV-30 (200 μg/kg, ip) were injected into male rats 30 minutes prior to transcardial perfusion and brain fixation for immunohistochemical analysis, or before testing on the elevated plus maze in an amphetamine withdrawal model of anxiety. Systemically administered iron oxide+ASV-30 particles were present in the brain and associated with neurons, including those that express CRF2 receptors, but did not localize with the iron storage protein ferritin. Furthermore, systemic administration of ironoxide+ASV-30 reduced amphetamine withdrawal-induced anxiety without affecting locomotion, suggesting that the anxiolytic effects of ASV-30 were preserved and the bioavailability of ASV-30 was sufficient. The findings demonstrate a novel approach to peptide delivery across the BBB and provide insight as to the neural distribution and efficacy of this nanotechnology.
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Central CRF2 receptor antagonism reduces anxiety states during amphetamine withdrawal
Neuroscience Research, 2014Co-Authors: Emily D. Reinbold, Michael J Watt, Jamie L. Scholl, Kathryn M. Oliver, Gina L. ForsterAbstract:Abstract Increased depressive and anxiety-like behaviors are exhibited by rats and humans during withdrawal from psychostimulants. Anxiety-like behaviors observed during amphetamine withdrawal are mediated by increased expression and activity of corticotropin releasing factor type 2 (CRF 2 ) receptors in the dorsal raphe nucleus (dRN). Anxiety-like behavior of rats during withdrawal can be reversed by CRF 2 receptor antagonism in the dRN, but the efficacy of global central CRF 2 receptor antagonism is unknown. Rats were treated with amphetamine (2.5 mg/kg, ip.) or saline daily for 2 weeks, and were tested for anxiety-like behaviors during withdrawal. Rats undergoing withdrawal showed increased anxiety-like behavior, which was reduced by ventricular infusion of the CRF 2 antagonist Antisauvagine-30 (ASV 2 μg/2 μl). Surprisingly, ventricular ASV increased anxiety-like behavior in rats pre-treated with saline, but had an anxiolytic effect in un-treated rats. Western blots were performed to determine whether differences in CRF receptor densities could explain ASV-induced behavioral results. Saline pre-treated rats showed reduced CRF 1 receptor expression in the lateral septum compared to amphetamine pre-treated and un-treated rats. Overall, these results suggest that central CRF 2 antagonism reduces anxiety states during amphetamine withdrawal, and that behavioral effects may be dependent upon the balance of CRF 1 and CRF 2 receptor activity in anxiety-related regions.
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Anxiety states induced by post-weaning social isolation are mediated by CRF receptors in the dorsal raphe nucleus.
Brain Research Bulletin, 2011Co-Authors: Adam C. Bledsoe, Kathryn M. Oliver, Jamie L. Scholl, Gina L. ForsterAbstract:Abstract Post-weaning social isolation of rats is utilized as a model of early life stress. We have previously demonstrated that rats exposed to post-weaning social isolation exhibit greater anxiety-like behaviors as adults. Furthermore, these rats exhibit greater density of corticotropin-releasing factor (CRF) type 2 receptors in the dorsal raphe nucleus. Therefore, we examined whether antagonism of CRF 2 receptors in the dorsal raphe nucleus reverses the effects of post-weaning social isolation on anxiety states. Male rats were reared in isolation or in groups from day of weaning (postnatal day [PND] 21) to mid-adolescence (PND42) and then allowed to develop to early adulthood housed in groups. At PND62, rats were either infused with vehicle, the CRF 1 receptor antagonist antalarmin (0.25–0.5 μg) or the CRF 2 receptor antagonist Antisauvagine-30 (2 μg) into the dorsal raphe nucleus, 20 min prior to being introduced to the elevated plus maze. Isolation-reared rats showed reduced open arm behavior compared to group-reared rats, confirming the anxiogenic effects of post-weaning social isolation. Infusion of the CRF 2 receptor antagonist, but not the CRF 1 receptor antagonist, into the dorsal raphe nucleus of isolation-reared rats increased open arm behavior when compared to that of group-reared rats. Overall, the findings suggest that CRF 2 receptors within the dorsal raphe nucleus mediate anxiety-like states following post-weaning social isolation, and CRF 2 receptors may represent an important target for the treatment of anxiety disorders following early life stressors.
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Chronic amphetamine treatment enhances corticotropin-releasing factor-induced serotonin release in the amygdala.
European Journal of Pharmacology, 2010Co-Authors: Jamie L. Scholl, Shawn M Vuong, Gina L. ForsterAbstract:Abstract Amphetamine use is associated with dysphoric states, including heightened anxiety, that emerge within 24 h of withdrawal from the drug. Corticotropin-releasing factor increases serotonin release in the central nucleus of the amygdala, and this neurochemical circuitry may play a role in mediating fear and anxiety states. We have previously shown that chronic amphetamine treatment increases corticotropin-releasing factor receptor type-2 levels in the serotonergic dorsal raphe nucleus of the rat. Therefore, we hypothesized that chronic amphetamine treatment would enhance the amygdalar serotonergic response to corticotropin-releasing factor infused into the dorsal raphe nucleus. Male rats were injected once-daily with d-amphetamine (2.5 mg/kg i.p., or saline) for two weeks. Serotonin release within the central nucleus of the amygdala in response to intra-raphe infusion of corticotropin-releasing factor (100 ng) was measured 24 h after the last treatment in urethane-anesthetized (1.8 mg/kg, i.p.) rats using in vivo microdialysis. Rats pretreated with amphetamine showed significantly enhanced serotonin release in the central nucleus of the amygdala in response to corticotropin-releasing factor infusion when compared to saline pretreated rats. Furthermore, this enhanced response was blocked by the corticotropin-releasing factor type-2 receptor antagonist Antisauvagine-30 (2 μg) infused into the dorsal raphe nucleus. These results suggest increased sensitivity to corticotropin-releasing factor as mediated by type-2 receptors following chronic amphetamine treatment, which may underlie dysphoric states observed during amphetamine withdrawal.
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corticotropin releasing factor in the dorsal raphe nucleus increases medial prefrontal cortical serotonin via type 2 receptors and median raphe nucleus activity
European Journal of Neuroscience, 2008Co-Authors: Gina L. Forster, R B Pringle, Nicholas J Mouw, Shawn M Vuong, Michael J Watt, Andrew R Burke, Christopher A Lowry, Cliff H Summers, Kenneth J RennerAbstract:: Interactions between central corticotropin-releasing factor (CRF) and serotonergic systems are believed to be important for mediating fear and anxiety behaviors. Recently we demonstrated that infusions of CRF into the rat dorsal raphe nucleus result in a delayed increase in serotonin release within the medial prefrontal cortex that coincided with a reduction in fear behavior. The current studies were designed to study the CRF receptor mechanisms and pathways involved in this serotonergic response. Infusions of CRF (0.5 microg/0.5 microL) were made into the dorsal raphe nucleus of urethane-anesthetized rats following either inactivation of the median raphe nucleus by muscimol (25 ng/0.25 microL) or antagonism of CRF receptor type 1 or CRF receptor type 2 in the dorsal raphe nucleus with antalarmin (25-50 ng/0.5 microL) or Antisauvagine-30 (2 microg/0.5 microL), respectively. Medial prefrontal cortex serotonin levels were measured using in-vivo microdialysis and high-performance liquid chromatography with electrochemical detection. Increased medial prefrontal cortex serotonin release elicited by CRF infusion into the dorsal raphe nucleus was abolished by inactivation of the median raphe nucleus. Furthermore, antagonism of CRF receptor type 2 but not CRF receptor type 1 in the dorsal raphe nucleus abolished CRF-induced increases in medial prefrontal cortex serotonin. Follow-up studies involved electrical stimulation of the central nucleus of the amygdala, a source of CRF afferents to the dorsal raphe nucleus. Activation of the central nucleus increased medial prefrontal cortex serotonin release. This response was blocked by CRF receptor type 2 antagonism in the dorsal raphe. Overall, these results highlight complex CRF modulation of medial prefrontal cortex serotonergic activity at the level of the raphe nuclei.
