Is it really a matter of simple dualism? Corticotropin-releasing factor receptors in body and mental health

The effects of corticotropin-releasing factor (CRF) and urocortins on the serotonin (hydroxytryptamine, 5HT) released from the raphe nuclei (RN)

Corticotropin-releasing factor (CRF) and urocortins (UCN1, UCN2 and UCN3) belong to the same CRF family of neuropeptides. They regulate the neuroendocrine, autonomic and behavioral responses to stress via two CRF receptors (CRF1 and CRF2). Stress, anxiety and depression affects the activity of the hypothalamic-pituitary-adrenal (HPA) axis and the serotoninergic neurotransmission, both being regulated by CRF and CRF-related peptides. However, the exact action of CRF and urocortins on the serotonin (5-hydroxytryptamine, 5HT) release was not fully elucidated yet. Therefore, the aim of the present study was to investigate the actions of CRF and urocortins on the 5HT released from the rat raphe nuclei (RN), the most important brain regions producing 5HT, and the participation of CRF receptors in these actions. In order to do so, male Wistar rats were used, their RN were isolated and dissected, and the RN slices were incubated with tritium-labelled 5HT, superfused and stimulated electrically. During superfusion, the RN slices were treated with CRF, UCN1, UCN2 or UCN3, and, when significant effect was observed, pretreated with selective CRF1 antagonist antalarmin or selective CRF2 antagonist astressin2B. The release of tritium-labelled 5HT from the RN was determined by liquid scintillation counting. CRF and UCN1 decreased significantly the tritium-labelled 5HT release from the RN, and these effects were reversed by antalarmin, but not by astressin2B. In addition, UCN3, but not UCN2, increased significantly the tritium-labelled 5HT release from the RN, and this effect was reduced by astressin2B, but not antalarmin. Our results indicate the existence of two apparently opposing CRF systems in the RN: activation of CRF1 by CRF and UCN1 may inhibit, whereas activation of CRF2 by UCN3 may stimulate the 5HT release. The dysbalance between CRF1 and CRF2 activation and, consequently, alteration of serotoninergic signalling may result in anxiety and depression, associated with hyperactivity of the HPA axis.

The effects of corticotropin-releasing factor (CRF) and urocortins on the noradrenaline (NA) released from the locus coeruleus (LC)

Corticotropin-releasing factor (CRF) activates the hypothalamic-pituitary-adrenal (HPA) axis and stimulates the noradrenergic neurotransmission, both processes being implicated in the pathogenesis of anxiety and depression, but the intimate site and mechanism of interaction of CRF and CRF-related peptides, named urocortins (UCN1, UCN2, UCN3), with noradrenaline (NA) was not fully elucidated yet. Therefore, the aim of the present study was to investigate the actions of CRF and urocortins on the NA released from the rat locus coeruleus (LC), the primary source of NA in the brain, and the participation of CRF receptors (CRF1 and CRF2) in these actions. In order to do so, male Wistar rats were used, their LC were isolated and dissected, and the LC slices were incubated with tritium-labelled NA, superfused and stimulated electrically. During superfusion, the LC slices were treated with CRF, UCN1, UCN2 or UCN3, and, when significant effect was observed, pretreated with selective CRF1 antagonist antalarmin or selective CRF2 antagonist astressin2B. The release of tritium-labelled NA from the LC was determined by liquid scintillation counting. CRF and UCN1 increased significantly the tritium-labelled NA release from the LC, and these effects were reduced by antalarmin, but not by astressin2B. In addition, UCN2, but not UCN3, decreased significantly the tritium-labelled NA release from the LC, and this effect was reversed by astressin2B, but not antalarmin. Our results indicate the existence of two apparently opposing CRF systems in the LC, since activation of CRF1 by CRF and UCN1 stimulated, whereas activation of CRF2 by UCN2 inhibited the NA release.

Single Intranasal Administration of Ucn3 Affects the Development of PTSD Symptoms in an Animal Model

Post-traumatic stress disorder (PTSD) is a multifactorial psychological disorder that affects different neurotransmitter systems, including the central CRH system. CRH acts via the CRHR1 and CRHR2 receptors, which exert opposite effects, i.e., anxiogenic or anxiolytic. The aim of this work was to investigate how intranasal administration of the CRHR2-specific agonist urocortin 2 (Ucn2) or urocortin 3 (Ucn3) affects manifestations of PTSD in a single prolonged stress (SPS) animal model of PTSD. Elevated plus maze (EPM) and open field (OF) tests were used to assess anxiety-like behavior. Changes in the gene expressions of CRH, CRHR1, CRHR2, glucocorticoid receptor (GR), and FKBP5 were measured in brain regions (BNST, amygdala, and PVN) responsible for modulating the stress response. The SPS animals spent less time in the OF central zone and were less mobile than the controls; however, the Ucn3 treatment reversed this effect. SPS decreased the GR and FKPB5 mRNA levels in the PVN. Ucn3 suppressed the effect of SPS on FKBP5 mRNA expression in the PVN and increased FKBP5 mRNA in the BNST and PVN compared to the stressed animals. We demonstrate that Ucn3 has the potential to ameliorate anxiety-like behavior in SPS animals and also to affect the neuroendocrine system in the BNST and PVN. In addition, we confirm the important role of CRHR2 signaling in mediating the stress response.

The effects of alcohol on anxiety-like, depression-like, and social behavior immediately and a day after binge drinking

The aim of the present study was to determine the effects of binge drinking on anxiety-like, depression-like, and social behavior. The participation of the corticotropin-releasing factor (CRF) receptors (CRF1 and CRF2) in these effects was also investigated. Therefore, male C57BL/6 mice were exposed to drinking in the dark, a classical animal model for binge drinking, and treated intracerebroventricularly (icv) with selective CRF1 antagonist antalarmin or selective CRF2 antagonist astressin2B, immediately or 24 h after binge drinking. After 30 min, the animals were investigated in an elevated plus-maze test and a forced swim test for anxiety-like and depression-like signs, respectively. In addition, mice were tested in a three-chamber social interaction arena for sociability and preference for social novelty. Immediately after binge drinking, mice exposed to alcohol expressed anxiolytic and antidepressant effects, which were reduced by astressin2B, but not antalarmin. Moreover, mice exposed to alcohol showed increased sociability and preference for social novelty immediately after binge drinking. In contrast, 24 h after binge drinking mice exposed to alcohol presented anxiety-like and depression-like signs, which were reversed by antalarmin, but not astressin2B. However, mice exposed to alcohol did not show any significant change in social interaction after 24 h. The present study demonstrates that alcohol exerts different effects on anxiety-like, depression-like, and social behavior immediately and a day after binge drinking, and that the anxiolytic and antidepressant effects produced by binge drinking are mediated by CRF2, whereas the anxiety-like and depression-like signs observed the next day are promoted by CRF1.

The Role of Corticotropin-Releasing Factor (CRF) and CRF-Related Peptides in the Social Behavior of Rodents

Since the corticotropin-releasing factor (CRF) was isolated from an ovine brain, a growing family of CRF-related peptides has been discovered. Today, the mammalian CRF system consists of four ligands (CRF, urocortin 1 (Ucn1), urocortin 2 (Ucn2), and urocortin 3 (Ucn3)); two receptors (CRF receptor type 1 (CRF1) and CRF receptor type 2 (CRF2)); and a CRF-binding protein (CRF-BP). Besides the regulation of the neuroendocrine, autonomic, and behavioral responses to stress, CRF and CRF-related peptides are also involved in different aspects of social behavior. In the present study, we review the experiments that investigated the role of CRF and the urocortins involved in the social behavior of rats, mice, and voles, with a special focus on sociability and preference for social novelty, as well as the ability for social recognition, discrimination, and memory. In general, these experiments demonstrate that CRF, Ucn1, Ucn2, and Ucn3 play important, but distinct roles in the social behavior of rodents, and that they are mediated by CRF1 and/or CRF2. In addition, we suggest the possible brain regions and pathways that express CRF and CRF-related peptides and that might be involved in social interactions. Furthermore, we also emphasize the differences between the species, strains, and sexes that make translation of these roles from rodents to humans difficult.

Functionally active TRPA1 ion channel is downregulated in peptidergic neurons of the Edinger-Westphal nucleus upon acute alcohol exposure

Introduction: The centrally projecting Edinger-Westphal nucleus (EWcp) contributes to the control of alcohol consumption by its urocortin 1 (UCN1) and cocaine- and amphetamine-regulated transcript (CART) co-expressing peptidergic neurons. Our group recently showed that the urocortinergic centrally projecting EWcp is the primary seat of central nervous system transient receptor potential ankyrin 1 (TRPA1) cation channel mRNA expression. Here, we hypothesized that alcohol and its metabolites, that pass through the blood-brain barrier, may influence the function of urocortinergic cells in centrally projecting EWcp by activating TRPA1 ion channels. We aimed to examine the functional activity of TRPA1 in centrally projecting EWcp and its possible role in a mouse model of acute alcohol exposure. Methods: Electrophysiological measurements were performed on acute brain slices of C57BL/6J male mice containing the centrally projecting EWcp to prove the functional activity of TRPA1 using a selective, potent, covalent agonist JT010. Male TRPA1 knockout (KO) and wildtype (WT) mice were compared with each other in the morphological studies upon acute alcohol treatment. In both genotypes, half of the animals was treated intraperitoneally with 1 g/kg 6% ethanol vs. physiological saline-injected controls. Transcardial perfusion was performed 2 h after the treatment. In the centrally projecting EWcp area, FOS immunohistochemistry was performed to assess neuronal activation. TRPA1, CART, and urocortin 1 mRNA expression as well as urocortin 1 and CART peptide content was semi-quantified by RNAscope in situ hybridization combined with immunofluorescence. Results: JT010 activated TRPA1 channels of the urocortinergic cells in acute brain slices. Alcohol treatment resulted in a significant FOS activation in both genotypes. Alcohol decreased the Trpa1 mRNA expression in WT mice. The assessment of urocortin 1 peptide immunoreactivity revealed lower basal urocortin 1 in KO mice compared to WTs. The urocortin 1 peptide content was affected genotype-dependently by alcohol: the peptide content decreased in WTs while it increased in KO mice. Alcohol exposure influenced neither CART and urocortin 1 mRNA expression nor the centrally projecting EWcp/CART peptide content. Conclusion: We proved the presence of functional TRPA1 receptors on urocortin 1 neurons of the centrally projecting EWcp. Decreased Trpa1 mRNA expression upon acute alcohol treatment, associated with reduced neuronal urocortin 1 peptide content suggesting that this cation channel may contribute to the regulation of the urocortin 1 release.

The role of the corticotropin-releasing hormone and its receptors in the regulation of stress response

Stress is an essential part of everyday life. The neuropeptide corticotropin-releasing hormone (CRH, also called CRF and corticoliberin) plays a key role in the integration of neuroendocrine, autonomic and behavioral responses to stress. The activation of the hypothalamic-pituitary-adrenal axis (HPA axis) by neurons of the paraventricular hypothalamic nucleus (PVN), the primary site of synthesis CRH, triggers stress reactions. In addition to the hypothalamus, CRH is widespread in extrahypothalamic brain structures, where it functions as a neuromodulator for coordination and interaction between the humoral and behavioral aspects of a stress response. The axons of neurons expressing CRH are directed to various structures of the brain, where the neuropeptide interacts with specific receptors (CRHR1, CRHR2) and can affect various mediator systems that work together to transmit signals to different brain regions to cause many reactions to stress. Moreover, the effect of stress on brain functions varies from behavioral adaptation to increased survival and increased risk of developing mental disorders. Disturbances of the CRH system regulation are directly related to such disorders: mental pathologies (depression, anxiety, addictions), deviations of neuroendocrinological functions, inflammation, as well as the onset and development of neurodegenerative diseases such as Alzheimer’s disease. In addition, the role of CRH as a regulator of the neurons structure in the areas of the developing and mature brain has been established. To date, studies have been conducted in which CRHR1 is a target for antidepressants, which are, in fact, antagonists of this receptor. In this regard, the study of the participation of the CRH system and its receptors in negative effects on hormone-dependent systems, as well as the possibility of preventing them, is a promising task of modern physiological genetics. In this review, attention will be paid to the role of CRH in the regulation of response to stress, as well as to the involvement of extrahypothalamic CRH in pathophysiology and the correction of mental disorders.

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.

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.

Vagotomy Affects Lipopolysaccharide-Induced Changes of Urocortin 2 Gene Expression in the Brain and on the Periphery

The corticotropin-releasing hormone family of peptides is involved in regulating the neuroendocrine stress response. Also, the vagus nerve plays an important role in the transmission of immune system-related signals to brain structures, thereby orchestrating the neuroendocrine stress response. Therefore, we investigated gene expression of urocortin 2 (Ucn2) and c-fos, a markers of neuronal activity, within the hypothalamic paraventricular nucleus (PVN), a brain structure involved in neuroendocrine and neuroimmune responses, as well as in the adrenal medulla and spleen in vagotomized rats exposed to immune challenge. In addition, markers of neuroendocrine stress response activity were investigated in the adrenal medulla, spleen, and plasma. Intraperitoneal administration of lipopolysaccharide (LPS) induced a significant increase of c-fos and Ucn2 gene expression in the PVN, and adrenal medulla as well as increases of plasma corticosterone levels. In addition, LPS administration induced a significant increase in the gene expression of tyrosine hydroxylase (TH) and phenylethanolamine N-methyltransferase (PNMT) in the adrenal medulla. In the spleen, LPS administration increased gene expression of c-fos, while gene expression of TH and PNMT was significantly reduced, and gene expression of Ucn2 was not affected. Subdiaphragmatic vagotomy significantly attenuated the LPS-induced increases of gene expression of c-fos and Ucn2 in the PVN and Ucn2 in the adrenal medulla. Our data has shown that Ucn2 may be involved in regulation of the HPA axis in response to immune challenge. In addition, our findings indicate that the effect of immune challenge on gene expression of Ucn2 is mediated by vagal pathways.

Hypothalamic-pituitary-adrenal axis-related genes and cognition in major mood disorders and schizophrenia: a systematic review

Hypothalamic-pituitary-adrenal (HPA) axis dysregulation and cognitive deficits are two well-characterized endophenotypes present in different serious mental illnesses (SMIs), including major depressive disorder, bipolar disorder and schizophrenia. Our aim was to study the influence of genetic and epigenetic variations in HPA axis-related genes on cognitive performance in clinical samples, including patients with major mood disorders and schizophrenia. A systematic search was performed using PubMed (Medline), PsycINFO and Scopus databases. The systematic review identified 12 studies dealing with HPA-related genes and cognition in samples including patients with SMIs, focusing on single nucleotide polymorphism (SNP) variants, while no studies analysing epigenetic variations were found. The results suggest different and specific effects on the cognitive performance of SNP variants in the HPA axis-related genes studied, as well as interactions with traumatic experiences. There was high heterogeneity in the studied samples, genes analysed, and cognitive tasks evaluated. The relationship between HPA-related genes and cognition in SMIs is still largely unknown, and further studies including larger samples and epigenetic variations are needed.

Stressors affect urocortin 1 and urocortin 2 gene expression in rat spleen: The role of glucocorticoids

The mechanisms underlying stress-related modulation of immune function via urocortin 1 and urocortin 2 have been only vaguely described. Therefore, we investigated the effect of LPS injection or immobilization stress on gene expression of urocortin 1 and urocortin 2 in the rat spleen, along with the potential involvement of glucocorticoids. Our data showed: a) different regulation of urocortin 1 and urocortin 2 gene expression in the rat spleen under different stressful conditions (LPS vs. immobilization stress) and b) diverse effects of stress-induced adrenal glucocorticoids on this process. Our findings indicate a specific, rather than general regulation of splenic immune function by urocortins during stressful conditions.

Deletion of CRH From GABAergic Forebrain Neurons Promotes Stress Resilience and Dampens Stress-Induced Changes in Neuronal Activity

Dysregulation of the corticotropin-releasing hormone (CRH) system has been implicated in stress-related psychopathologies such as depression and anxiety. Although most studies have linked CRH/CRH receptor 1 signaling to aversive, stress-like behavior, recent work has revealed a crucial role for distinct CRH circuits in maintaining positive emotional valence and appetitive responses under baseline conditions. Here we addressed whether deletion of CRH, specifically from GABAergic forebrain neurons (Crh ^CKO-GABA mice) differentially affects general behavior under baseline and chronic stress conditions. Expression mapping in Crh ^{CK O-GABA} mice revealed absence of Crh in GABAergic neurons of the cortex and limbic regions including the hippocampus, central nucleus of the amygdala and the bed nucleus of the stria terminals, but not in the paraventricular nucleus of hypothalamus. Consequently, conditional CRH knockout animals exhibited no alterations in circadian and stress-induced corticosterone release compared to controls. Under baseline conditions, absence of Crh from forebrain GABAergic neurons resulted in social interaction deficits but had no effect on other behavioral measures including locomotion, anxiety, immobility in the forced swim test, acoustic startle response and fear conditioning. Interestingly, following exposure to chronic social defeat stress, Crh ^CKO-GABA mice displayed a resilient phenotype, which was accompanied by a dampened, stress-induced expression of immediate early genes c-fos and zif268 in several brain regions. Collectively our data reveals the requirement of GABAergic CRH circuits in maintaining appropriate social behavior in naïve animals and further supports the ability of CRH to promote divergent behavioral states under baseline and severe stress conditions.

Association of Corticotropin-Releasing Hormone Receptor-1 Gene Polymorphisms and Personality Traits with Violent Aggression in Male Adolescents

There is evidence that corticotropin-releasing hormone receptor 1 (CRHR1) gene polymorphisms and indifferent impulsive personality traits play an important role in violent aggression in male adolescents. Genotyping for two tag single-nucleotide polymorphisms (SNP) (rs242924, rs17689966) was conducted using TaqMan SNP for 138 violent young male criminals, 98 nonviolent young male criminals, and 153 noncriminal adults. The general situation and personality traits (SSP) questionnaire was given to the young violent and nonviolent male criminal groups. The results showed that the frequency of the G allele in rs242924 of the CRHR1 gene in the violent aggression group was higher than that in the normal adult controls (P < 0.025, OR = 2.29, 95% CI = 1.13-4.62). The difference in genotype distribution was significant among the three groups (P < 0.05), and when the violent group was compared with the two control groups, no significant difference was found (P > 0.025). The impulsiveness, trait irritability, verbal trait aggression, and physical trait aggression scores in the violent group were significantly higher than those in the nonviolent group of adolescents. These findings suggest that the variance in CRHR1 gene polymorphisms and personality traits may play a role in violent aggression in male adolescents, and that the interaction of the CRHR1 gene and the impulsive personality trait may cause an increased susceptibility to violence towards others.

The effects of the urocortins on the hypothalamic-pituitary-adrenal axis - similarities and discordancies between rats and mice

The urocortins (Ucn I, Ucn II and Ucn III) are structural analogues of corticotropin-releasing factor (CRF). The aim of our present experiments was to compare the effects of the urocortins on the hypothalamic-pituitary-adrenal (HPA) axis in rats and mice, including the hypothalamic adrenocorticotropic hormone (ACTH) secretagogues, such as CRF and arginine vasopressin (AVP). Therefore, male CFLP mice and male Wistar rats were injected intracerebroventricularly (icv) with 0.5, 1, 2 and 5 μg/2 μl of Ucn I, Ucn II or Ucn III. After 30 min the animals were decapitated, and then, hypothalamic CRF and AVP concentrations and plasma ACTH and corticosterone (CORT) levels were measured. All measurements were performed by enzyme-linked immunosorbent assays (ELISA), except that of the plasma CORT level, which was determined by chemofluorescent assay. Ucn I increased significantly the hypothalamic CRF and AVP concentrations in both rats and mice. Ucn II and Ucn III influenced significantly only the hypothalamic CRF concentration in rats, without affecting the hypothalamic AVP concentration. In contrast, Ucn II and Ucn III increased significantly only the hypothalamic AVP concentration in mice, without affecting the hypothalamic CRF concentration. The hypothalamic changes were reflected more or less accurately by changes of the plasma ACTH and CORT levels. The present experiments demonstrate that the urocortins regulate the HPA axis centrally via modulation of the hypothalamic ACTH secretagogues and that there are some similarities and discordancies between rats and mice regarding this regulation.

The corticotropin releasing factor binding protein: A strange case of Dr. Jekyll and Mr. Hyde in the stress system?

The corticotropin releasing factor (CRF) exerts its effects by acting on its receptors and on the binding protein (CRFBP). Extensive literature suggests a role of CRF in alcohol use disorder (AUD). Less is known about the specific role, if any, of CRFBP in AUD. In this review, we summarize recent interdisciplinary efforts toward identifying the contribution of CRFBP in mediating CRF activation. The role of CRFBP in alcohol-related behaviors has been evaluated with the ultimate goal of designing effective novel therapeutic strategies for AUD. A series of in vitro, in vivo, ex vivo, and genetic studies presented here provides initial evidence that CRFBP may possess both inhibitory and excitatory roles, and supports the original hypothesis that it represents a novel pharmacological target for the treatment of AUD. This report summarizes the proceedings of one of the talks at the Young Investigator Award symposium at the Alcoholism and Stress: A Framework for Future Treatment Strategies Conference, Volterra, Italy.

Changes in striatal dopamine release and locomotor activity following acute withdrawal from chronic nicotine are mediated by CRF1, but not CRF2, receptors

The aim of the present study was to investigate the participation of corticotropin-releasing factor (CRF) receptors (CRF1 and CRF2) in the alterations of the dorsal and ventral striatal dopamine release and the vertical and horizontal locomotor activity observed in rats following chronic nicotine treatment and consequent acute withdrawal. In this purpose, male Wistar rats were exposed to repeated intraperitoneal (ip) injection with nicotine or saline solution for 7 days. On the 8th day or the 9th day the rats were injected intracerebroventricularly (icv) with selective CRF1 antagonist antalarmin or selective CRF2 antagonist astressin_2B or saline solution. Thirty minutes after the icv injection the changes of the horizontal and vertical locomotor activity were recorded in an in vivo conducta system. Immediately after the behavioral recordings the changes of the dorsal and ventral striatal dopamine release were determined in an in vitro superfusion system. On the 8th day, the horizontal and vertical locomotor activities and the dorsal and ventral striatal dopamine releases increased significantly in nicotine-treated rats, compared to the saline-treated ones. On the 9th day, the horizontal locomotor activity and the dorsal striatal dopamine release increased significantly, whereas the vertical locomotor activity and the ventral striatal dopamine release decreased significantly in nicotine-treated rats, compared to the saline-treated ones. All the changes observed were attenuated significantly by antalarmin, but not astressin_2B. The present study demonstrates that the changes of striatal dopamine release and locomotor activity observed following chronic nicotine treatment and consequent acute withdrawal are mediated by CRF1, but not CRF2, receptor.

The Corticotropin-Releasing Factor Family: Physiology of the Stress Response

The physiological stress response is responsible for the maintenance of homeostasis in the presence of real or perceived challenges. In this function, the brain activates adaptive responses that involve numerous neural circuits and effector molecules to adapt to the current and future demands. A maladaptive stress response has been linked to the etiology of a variety of disorders, such as anxiety and mood disorders, eating disorders, and the metabolic syndrome. The neuropeptide corticotropin-releasing factor (CRF) and its relatives, the urocortins 1–3, in concert with their receptors (CRFR1, CRFR2), have emerged as central components of the physiological stress response. This central peptidergic system impinges on a broad spectrum of physiological processes that are the basis for successful adaptation and concomitantly integrate autonomic, neuroendocrine, and behavioral stress responses. This review focuses on the physiology of CRF-related peptides and their cognate receptors with the aim of providing a comprehensive up-to-date overview of the field. We describe the major molecular features covering aspects of gene expression and regulation, structural properties, and molecular interactions, as well as mechanisms of signal transduction and their surveillance. In addition, we discuss the large body of published experimental studies focusing on state-of-the-art genetic approaches with high temporal and spatial precision, which collectively aimed to dissect the contribution of CRF-related ligands and receptors to different levels of the stress response. We discuss the controversies in the field and unravel knowledge gaps that might pave the way for future research directions and open up novel opportunities for therapeutic intervention.

Targeted overexpression of CRH receptor subtype 1 in central amygdala neurons: effect on alcohol-seeking behavior

RATIONALE

The corticotropin-releasing hormone (CRH) system is a key mediator of stress-induced responses in alcohol-seeking behavior. Recent research has identified the central nucleus of the amygdala (CeA), a brain region involved in the regulation of fear and stress-induced responses that is especially rich in CRH-positive neurons, as a key player in mediating excessive alcohol seeking. However, detailed characterization of the specific influences that local neuronal populations exert in mediating alcohol responses is hampered by current limitations in pharmacological and immunohistochemical tools for targeting CRH receptor subtype 1 (CRHR1).

OBJECTIVE

In this study, we investigated the effect of cell- and region-specific overexpression of CRHR1 in the CeA using a novel transgenic tool.

METHODS

Co-expression of CRHR1 in calcium-calmodulin-dependent kinase II (αCaMKII) neurons of the amygdala was demonstrated by double immunohistochemistry using a Crhr1-GFP reporter mouse line. A Cre-inducible Crhr1-expressing adeno-associated virus (AAV) was site-specifically injected into the CeA of αCaMKII-Cre^ERT2 transgenic rats to analyze the role of CRHR1 in αCaMKII neurons on alcohol self-administration and reinstatement behavior.

RESULTS

Forty-eight percent of CRHR1-containing cells showed co-expression of αCaMKII in the CeA. AAV-mediated gene transfer in αCaMKII neurons induced a 24-fold increase of Crhr1 mRNA in the CeA which had no effect on locomotor activity, alcohol self-administration, or cue-induced reinstatement. However, rats overexpressing Crhr1 in the CeA increased responding in the stress-induced reinstatement task with yohimbine serving as a pharmacological stressor.

CONCLUSION

We demonstrate that CRHR1 overexpression in CeA-αCaMKII neurons is sufficient to mediate increased vulnerability to stress-triggered relapse into alcohol seeking.

Glucocorticoid withdrawal affects stress-induced changes of urocortin 2 gene expression in rat adrenal medulla and brain

Corticotropin-releasing factor is well known activator of the hypothalamic-pituitary-adrenocortical axis, that represents crucial system participating on stress response of the organism. Urocortins are members of the corticotropin-releasing factor family of peptides with proposed effects on neuroendocrine and behavioral stress response mechanisms. Urocortin 2, one of three known urocortins, is present in central and peripheral stress response system and its expression can be augmented by glucocorticoids. In the present study we have examined how glucocorticoid withdrawal affects urocortin 2 gene expression after acute immobilization in the adrenal medulla and selected brain areas in rats. We used pharmacological adrenalectomy to block synthesis of corticosterone. Our results show that the immobilization-induced rise in urocortin 2 mRNA levels in rat adrenal medulla was not inhibited by glucocorticoid withdrawal. On the other hand, observed changes in the brain indicate that the effect of stress and pharmacological adrenalectomy on urocortin 2 gene expression is site-specific. While in the paraventricular nucleus and locus coeruleus the immobilization induced rise of urocortin 2 was not inhibited by pharmacological adrenalectomy in the arcuate nucleus and central amygdala it was. Moreover, we have seen a significant depletion of urocortin 2 plasma levels after immobilization. The immobilization induced rise of urocortin 2 gene expression in rat adrenal medulla and brain areas regulating stress response pathways and preservation of its induction after adrenalectomy suggests a role of urocortin 2 in the neuroendocrine stress response of an organism. This article is protected by copyright. All rights reserved.

Corticotropin-Releasing Factor Receptors Modulate Oxytocin Release in the Dorsolateral Bed Nucleus of the Stria Terminalis (BNST) in Male Rats

The neuropeptide oxytocin (OT) plays an important role in the regulation of social and anxiety-like behavior. Our previous studies have shown that OT neurons send projections from the hypothalamus to the dorsolateral bed nucleus of the stria terminalis (BNST_dl), a forebrain region critically involved in the modulation of anxiety-like behavior. Importantly, these OT terminals in the BNST_dl express presynaptic corticotropin releasing factor (CRF) receptor type 2 (CRFR2). This suggests that CRFR2 might be involved in the modulation of OT release. To test this hypothesis, we measured OT content in microdialysates collected from the BNST_dl of freely-moving male Sprague-Dawley rats following the administration of a selective CRFR2 agonist (Urocortin 3) or antagonist (Astressin 2B, As2B). To determine if type 1 CRF receptors (CRFR1) are also involved, we used selective CRFR1 antagonist (NBI35965) as well as CRF, a putative ligand of both CRFR1 and CRFR2. All compounds were delivered directly into the BNST_dl via reverse dialysis. OT content in the microdialysates was measured with highly sensitive and selective radioimmunoassay. Blocking CRFR2 with As2B caused an increase in OT content in BNST_dl microdialysates, whereas CRFR2 activation by Urocortin 3 did not have an effect. The As2B-induced increase in OT release was blocked by application of the CRFR1 antagonist demonstrating that the effect was dependent on CRFR1 transmission. Interestingly, CRF alone caused a delayed increase in OT content in BNST_dl microdialysates, which was dependent on CRF2 but not CRF1 receptors. Our results suggest that members of the CRF peptide family modulate OT release in the BNST_dl via a fine-tuned mechanism that involves both CRFR1 and CRFR2. Further exploration of mechanisms by which endogenous OT system is modulated by CRF peptide family is needed to better understand the role of these neuropeptides in the regulation of anxiety and the stress response.

Anxiolytic- and antidepressant-like actions of Urocortin 2 and its fragments in mice

The aim of the present study was to investigate the potential anxiolytic- and antidepressant-like actions of Urocortin 2 (Ucn2) and its two fragments, Ucn2 (1-21) and Ucn2 (22-38), in mice, in an attempt to identify the biologically active sequence of this 38 amino acid neuropeptide. In this purpose, male C57BL/6 mice were treated intracerebroventricularly (icv) with 0.125, 0.25, 0.5 and 1 µg/2 µl of Ucn2, Ucn2 (1-21) or Ucn2 (22-38). After 30 min, the mice were evaluated in an elevated plus-maze test and a forced swim test for anxiety- and depression-like behavior, respectively. Each test lasted 5 min. Ucn2 at dose of 0.25 µg/2 µl and Ucn2 (1-21) at dose of 0.125 µg/2 µl, but not Ucn2 (22-38), increased significantly the number of entries into and the time spent in the open-arms, without influencing the total number of entries. In parallel, the same doses of Ucn2 and Ucn2 (1-21), but not Ucn2 (22-38), increased significantly the climbing and the swimming activity, while decreasing significantly the time of immobility. In addition, Ucn2 at doses of 0.125 µg/2 µl and 0.5 µg/2 µl decreased significantly the time of immobility, but they did not change the other parameters. The present study demonstrates that Ucn2 exerts anxiolytic- and antidepressant-like effects in C57BL/6 mice, which are mediated by the N-terminal, but not the C-terminal fragment of the peptide. The establishment of the smallest active sequence by further fragmentation of Ucn2 (1-21) may allow the synthesis of new anxiolytic and antidepressant drugs.

Construct and face validity of a new model for the three-hit theory of depression using PACAP mutant mice on CD1 background

Major depression is a common cause of chronic disability. Despite decades of efforts, no equivocally accepted animal model is available for studying depression. We tested the validity of a new model based on the three-hit concept of vulnerability and resilience. Genetic predisposition (hit 1, mutation of pituitary adenylate cyclase-activating polypeptide, PACAP gene), early-life adversity (hit 2, 180-min maternal deprivation, MD180) and chronic variable mild stress (hit 3, CVMS) were combined. Physical, endocrinological, behavioral and functional morphological tools were used to validate the model. Body- and adrenal weight changes as well as corticosterone titers proved that CVMS was effective. Forced swim test indicated increased depression in CVMS PACAP heterozygous (Hz) mice with MD180 history, accompanied by elevated anxiety level in marble burying test. Corticotropin-releasing factor neurons in the oval division of the bed nucleus of the stria terminalis showed increased FosB expression, which was refractive to CVMS exposure in wild-type and Hz mice. Urocortin1 neurons became over-active in CMVS-exposed PACAP knock out (KO) mice with MD180 history, suggesting the contribution of centrally projecting Edinger-Westphal nucleus to the reduced depression and anxiety level of stressed KO mice. Serotoninergic neurons of the dorsal raphe nucleus lost their adaptation ability to CVMS in MD180 mice. In conclusion, the construct and face validity criteria suggest that MD180 PACAP HZ mice on CD1 background upon CVMS may be used as a reliable model for the three-hit theory.

The effects of CRF and urocortins on the sociability of mice

The aim of our study was to determine the role of corticotropin-releasing factor (CRF), the urocortins (Ucn1, Ucn2 and Ucn3) and their receptors (CRF₁ and CRF₂) in the sociability of mice. Male CFLP mice were administered intracerebroventricularly (icv) with CRF and urocortins alone or in combination with antalarmin (specific CRF₁ antagonist) and astressin_2B (specific CRF₂ antagonist) and then investigated in a Crawley social interaction test arena, that consists of three chambers. An unknown male in a cage was put in the first chamber and an empty cage was put in the opposite chamber. The tested male was habituated with the middle chamber for 5min and then allowed to explore the remaining chambers for 5min, during which the number of entries and the time of interaction were measured. Intracerebroventricular administration of CRF decreased significantly the number of entries and the time of interaction with the unknown male and these effects were blocked by antalarmin, but not astressin_2B. In contrast, central administration of Ucn1 increased significantly the number of entries into the chamber of the unknown male, without changing the time of interaction and this effect was blocked by astressin_2B, but not antalarmin. Central administration of Ucn2 and Ucn3 didn't influence remarkably the number of entries, but it reduced the time of interaction between the male mice. Our study suggests that CRF and Ucn1 may play important, but different roles in sociability, and that Ucn2 and Ucn3, playing similar roles, must be also involved in social interactions.

Serotonin and urocortin 1 in the dorsal raphe and Edinger-Westphal nuclei after early life stress in serotonin transporter knockout rats

The interaction of early life stress (ELS) and the serotonin transporter (5-HTT) gene-linked polymorphic region (5-HTTLPR) has been associated with increased risk to develop depression in later life. We have used the maternal separation paradigm as a model for ELS exposure in homozygous and heterozygous 5-HTT knockout rats and measured urocortin 1 (Ucn1) mRNA and/or protein levels, Ucn1 DNA methylation, as well as 5-HT innervation in the centrally projecting Edinger-Westphal (EWcp) and dorsal raphe (DR) nuclei, both implicated in the regulation of stress response. We found that ELS and 5-HTT genotype increased the number of 5-HT neurons in specific DR subdivisions, and that 5-HTT knockout rats showed decreased 5-HT innervation of EWcp-Ucn1 neurons. Furthermore, ELS was associated with increased DNA methylation of the promoter region of the Ucn1 gene and increased expression of 5-HT receptor 1A in the EWcp. In contrast, 5-HTT deficiency was associated with site-specific alterations in DNA methylation of the Ucn1 promoter, and heterozygous 5-HTT knockout rats showed decreased expression of CRF receptor 1 in the EWcp. Together, our findings extend the existing literature on the relationship between EWcp-Ucn1 and DR-5-HT neurons. These observations will further our understanding on their potential contribution to mediate affect as a function of ELS interacting with 5-HTTLPR.

Defining the role of corticotropin releasing factor binding protein in alcohol consumption

The corticotropin releasing factor (CRF) exerts its effects by acting on its receptors and on the binding protein (CRFBP), and has been implicated in alcohol use disorder (AUD). Therefore, identification of the exact contribution of each protein that mediates CRF effects is necessary to design effective therapeutic strategies for AUD. A series of in vitro/in vivo experiments across different species were performed to define the biological discrete role of CRFBP in AUD. First, to establish the CRFBP role in receptor signaling, we developed a novel chimeric cell-based assay and showed that CFRBP full length can stably be expressed on the plasma membrane. We discovered that only CRFBP(10 kD) fragment is able to potentiate CRF-intracellular Ca²⁺ release. We provide evidence that CRHBP gene loss increased ethanol consumption in mice. Then, we demonstrate that selective reduction of CRHBP expression in the center nucleus of the amygdala (CeA) decreases ethanol consumption in ethanol-dependent rats. CRFBP amygdalar downregulation, however, does not attenuate yohimbine-induced ethanol self-administration. This effect was associated with decreased hemodynamic brain activity in the CRFBP-downregulated CeA and increased hemodynamic activity in the caudate putamen during yohimbine administration. Finally, in alcohol-dependent patients, genetic variants related to the CRFBP(10 kD) fragment were associated with greater risk for alcoholism and anxiety, while other genetic variants were associated with reduced risk for anxiety. Taken together, our data provide evidence that CRFBP may possess both inhibitory and excitatory roles and may represent a novel pharmacological target for the treatment of AUD.

Region-specific roles of the corticotropin-releasing factor-urocortin system in stress

Dysregulation of the corticotropin-releasing factor (CRF)-urocortin (UCN) system has been implicated in stress-related psychopathologies such as depression and anxiety. It has been proposed that CRF-CRF receptor type 1 (CRFR1) signalling promotes the stress response and anxiety-like behaviour, whereas UCNs and CRFR2 activation mediate stress recovery and the restoration of homeostasis. Recent findings, however, provide clear evidence that this view is overly simplistic. Instead, a more complex picture has emerged that suggests that there are brain region- and cell type-specific effects of CRFR signalling that are influenced by the individual's prior experience and that shape molecular, cellular and ultimately behavioural responses to stressful challenges.

CRF-like receptor SEB-3 in sex-common interneurons potentiates stress handling and reproductive drive in C. elegans

Environmental conditions can modulate innate behaviours. Although male Caenorhabditis elegans copulation can be perturbed in the presence of stress, the mechanisms underlying its decision to sustain copulation are unclear. Here we describe a mating interference assay, which quantifies the persistence of male C. elegans copulation in noxious blue light. We show that between copulations, the male escapes from blue light illumination at intensities over 370 μW mm⁻². This response is attenuated in mutants with constitutive activation of the corticotropin-releasing factor receptor family homologue SEB-3. We show that activation of this receptor causes sex-common glutamatergic lumbar ganglion interneurons (LUA) to potentiate downstream male-specific reproduction circuits, allowing copulatory behaviours to partially override the light-induced escape responses in the male. SEB-3 activation in LUA also potentiates copulation during mild starvation. We suggest that SEB-3 activation allows C. elegans to acclimate to the environment and thus continue to execute innate behaviours even under non-optimal conditions.

Innate animal behaviours can be negatively regulated by environmental stressors. Jee et al. show that suppression of male C. elegans copulation behaviour by noxious light can be overcome by activation of SEB-3, a homologue of the stress-associated mammalian corticotropin-releasing factor receptor family.

Dextran sulfate sodium-induced colitis alters stress-associated behaviour and neuropeptide gene expression in the amygdala-hippocampus network of mice

Psychological stress causes disease exacerbation and relapses in inflammatory bowel disease (IBD) patients. Since studies on stress processing during visceral inflammation are lacking, we investigated the effects of experimental colitis as well as psychological stress on neurochemical and neuroendocrine changes as well as behaviour in mice. Dextran sulfate sodium (DSS)-induced colitis and water avoidance stress (WAS) were used as mouse models of colitis and mild psychological stress, respectively. We measured WAS-associated behaviour, gene expression and proinflammatory cytokine levels within the amygdala, hippocampus and hypothalamus as well as plasma levels of cytokines and corticosterone in male C57BL/6N mice. Animals with DSS-induced colitis presented with prolonged immobility during the WAS session, which was associated with brain region-dependent alterations of neuropeptide Y (NPY), NPY receptor Y1, corticotropin-releasing hormone (CRH), CRH receptor 1, brain-derived neurotrophic factor and glucocorticoid receptor gene expression. Furthermore, the combination of DSS and WAS increased interleukin-6 and growth regulated oncogene-α levels in the brain. Altered gut-brain signalling in the course of DSS-induced colitis is thought to cause the observed distinct gene expression changes in the limbic system and the aberrant molecular and behavioural stress responses. These findings provide new insights into the effects of stress during IBD.

Residues remote from the binding pocket control the antagonist selectivity towards the corticotropin-releasing factor receptor-1

The corticotropin releasing factors receptor-1 and receptor-2 (CRF1R and CRF2R) are therapeutic targets for treating neurological diseases. Antagonists targeting CRF1R have been developed for the potential treatment of anxiety disorders and alcohol addiction. It has been found that antagonists targeting CRF1R always show high selectivity, although CRF1R and CRF2R share a very high rate of sequence identity. This has inspired us to study the origin of the selectivity of the antagonists. We have therefore built a homology model for CRF2R and carried out unbiased molecular dynamics and well-tempered metadynamics simulations for systems with the antagonist CP-376395 in CRF1R or CRF2R to address this issue. We found that the side chain of Tyr(6.63) forms a hydrogen bond with the residue remote from the binding pocket, which allows Tyr(6.63) to adopt different conformations in the two receptors and results in the presence or absence of a bottleneck controlling the antagonist binding to or dissociation from the receptors. The rotameric switch of the side chain of Tyr356(6.63) allows the breaking down of the bottleneck and is a perquisite for the dissociation of CP-376395 from CRF1R.

Preclinical evidence implicating corticotropin-releasing factor signaling in ethanol consumption and neuroadaptation

The results of many studies support the influence of the corticotropin-releasing factor (CRF) system on ethanol (EtOH) consumption and EtOH-induced neuroadaptations that are critical in the addiction process. This review summarizes the preclinical data in this area after first providing an overview of the components of the CRF system. This complex system involves hypothalamic and extra-hypothalamic mechanisms that play a role in the central and peripheral consequences of stressors, including EtOH and other drugs of abuse. In addition, several endogenous ligands and targets make up this system and show differences in their involvement in EtOH drinking and in the effects of chronic or repeated EtOH treatment. In general, genetic and pharmacological approaches paint a consistent picture of the importance of CRF signaling via type 1 CRF receptors (CRF(1)) in EtOH-induced neuroadaptations that result in higher levels of intake, encourage alcohol seeking during abstinence and alter EtOH sensitivity. Furthermore, genetic findings in rodents, non-human primates and humans have provided some evidence of associations of genetic polymorphisms in CRF-related genes with EtOH drinking, although additional data are needed. These results suggest that CRF(1) antagonists have potential as pharmacotherapeutics for alcohol use disorders. However, given the broad and important role of these receptors in adaptation to environmental and other challenges, full antagonist effects may be too profound and consideration should be given to treatments with modulatory effects.

Increased alcohol consumption in urocortin 3 knockout mice is unaffected by chronic inflammatory pain

AIMS

Stress neurocircuitry may modulate the relationship between alcohol drinking and chronic pain. The corticotropin-releasing factor (CRF) system is crucial for regulation of stress responses. The current study aimed to elucidate the role of the endogenous CRF ligand Urocortin 3 (Ucn3) in the relationship between alcohol drinking behavior and chronic pain using a genetic approach.

METHODS

Ucn3 (KO) and wildtype (WT) littermates were subjected to a 24-h access drinking procedure prior to and following induction of chronic inflammatory pain.

RESULTS

Ucn3 KO mice displayed significantly increased ethanol intake and preference compared with WT across the time course. There were no long-term effects of chronic pain on alcohol drinking behavior, regardless of genotype, nor any evidence for alcohol-induced analgesia.

CONCLUSION

The increased drinking in Ucn3 KO supports a role for this peptide in alcohol-related behavior. These data suggest the necessity for more research exploring the relationship between alcohol drinking, chronic pain and the CRF system in rodent models.

Sex- and region-specific pubertal maturation of the corticotropin-releasing factor receptor system in the rat

One of the most reliable findings in psychiatry is in the incidence of anxiety and depression. Beginning at puberty, women develop mood disorders twice as often as men. Because corticotropin-releasing factor (CRF) receptors are implicated, we compared CRF receptor binding in pre- and postpubertal rats. In each brain area, CRF receptor binding was sexually dimorphic, but no two areas were alike in the way the sexes differed. In the nucleus accumbens and olfactory tubercle, CRF1 binding was initially the same in juveniles, but became greater in adult females. In piriform cortex, CRF1 binding increased in females and decreased in males, again becoming sexually dimorphic. CRF1 binding in the anterior cingulate was greater in females than in males at both ages. In CA3, CRF1 binding was greater in males before puberty but decreased during puberty, abolishing the sex difference. CRF2 binding in the posterior bed nucleus of the stria terminalis was greater in males irrespective of age. In contrast, in each of three subdivisions of the lateral septum, females had greater CRF2 binding than males as juveniles, or, as juveniles and as adults. CRF2 binding in the ventromedial hypothalamus was the same in juveniles, but binding levels increased in males, leading to an adult sex difference. Thus, eight CRF receptor-expressing areas displayed eight distinct sex differences. These results show that sex differences pervade the CRF receptor system in juvenile and adult rats, and the mechanisms that control them are likely to be sex-, region-, and subtype-specific.

Effects of dorsal periaqueductal gray CRF1- and CRF2-receptor stimulation in animal models of panic

An increasing amount of evidence suggests that dysregulation of corticotrophin-releasing factor (CRF) signaling may contribute to the etiology of anxiety disorders such as post-traumatic stress disorder and panic. The dorsal periaqueductal gray matter (dPAG) in the midbrain has been considered a key region involved in the physiopathology of anxiety and panic. Administration of CRF in this structure enhances the expression of anxiety-related defensive behaviors in different animal models. Controversial results have been obtained regarding the involvement of CRF1 and CRF2 receptors in the regulation of panic-related responses. We report here that CRF (0.0625-1 μg) in the dPAG facilitates escape expression in two animal models that associate this behavior with panic, the elevated T-maze and the electrical stimulation of the dPAG. This effect, equally observed after CRF injection in the dorsomedial and dorsolateral columns of the PAG, is due to the activation of CRF1 receptors as revealed by its blockade by the CRF1 receptor antagonist antalarmin. In the elevated T-maze, CRF also facilitates inhibitory avoidance acquisition, suggesting an anxiogenic effect. Local administration of urocortin 2 (0.01-0.1 μg), a preferential CRF2 receptor agonist, failed to change escape expression, but impaired avoidance learning, indicating an anxiolytic effect. The results indicate that CRF1 receptors in the dPAG play a pervasive role in the regulation of defensive responses associated with both generalized anxiety and panic. Recruitment of CRF2 receptors only impacts upon the former type of behaviors, leading to an effect opposed to that caused by CRF1 receptor activation.

Nematode and arthropod genomes provide new insights into the evolution of class 2 B1 GPCRs

Nematodes and arthropods are the most speciose animal groups and possess Class 2 B1 G-protein coupled receptors (GPCRs). Existing models of invertebrate Class 2 B1 GPCR evolution are mainly centered on Caenorhabditis elegans and Drosophila melanogaster and a few other nematode and arthropod representatives. The present study reevaluates the evolution of metazoan Class 2 B1 GPCRs and orthologues by exploring the receptors in several nematode and arthropod genomes and comparing them to the human receptors. Three novel receptor phylogenetic clusters were identified and designated cluster A, cluster B and PDF-R-related cluster. Clusters A and B were identified in several nematode and arthropod genomes but were absent from D. melanogaster and Culicidae genomes, whereas the majority of the members of the PDF-R-related cluster were from nematodes. Cluster A receptors were nematode and arthropod-specific but shared a conserved gene environment with human receptor loci. Cluster B members were orthologous to human GCGR, PTHR and Secretin members with which they probably shared a common origin. PDF-R and PDF-R related clusters were present in representatives of both nematodes and arthropods. The results of comparative analysis of GPCR evolution and diversity in protostomes confirm previous notions that C. elegans and D. melanogaster genomes are not good representatives of nematode and arthropod phyla. We hypothesize that at least four ancestral Class 2 B1 genes emerged early in the metazoan radiation, which after the protostome-deuterostome split underwent distinct selective pressures that resulted in duplication and deletion events that originated the current Class 2 B1 GPCRs in nematode and arthropod genomes.

The effect of urocortin I on the hypothalamic ACTH secretagogues and its impact on the hypothalamic-pituitary-adrenal axis

Urocortin I (UCN I) is a structural analogue of corticotropin-releasing factor (CRF), which, together with arginine-vasopressin (AVP), are the principle adrenocorticotropic hormone (ACTH) secretagogues in mammals. The aim of the present study was to investigate the effects of UCN I on the hypothalamic CRF and AVP concentration and its impact on the hypothalamic-pituitary-adrenal (HPA) axis. First, male Wistar rats were injected intracerebroventricularly (ICV) with 0.5, 1, 2 and 5 μg of UCN I. After 30 min hypothalamic CRF and AVP concentrations were determined by immunoassays. In parallel, the trunk blood was collected and plasma ACTH and corticosterone concentration was determined by ELISA and chemofluorescent assay, respectively. Second, rats were pretreated ICV with selective antagonists of receptors being implicated in the regulation of the HPA axis (0.1 μg antalarmin for CRFR1, 1 μg astressin 2B for CRFR2 or 0.1 μg deamino-Pen1,Tyr2,Arg8-vasopressin for AVPR3) and treated ICV with the most effective dose of UCN I (5 μg). After 30 min plasma corticosterone concentration was determined by chemofluorescent assay. UCN I induced dose-dependent augmentation of the hypothalamic CRF and AVP concentration, associated with dose-dependent elevation of the plasma ACTH and corticosterone concentration. The most significant effect of UCN I on the plasma corticosterone concentration was inhibited by antalarmin, but was not influenced by astressin 2B or deamino-Pen1,Tyr2,Arg8-vasopressin. The present study demonstrates that UCN I modulates the concentration of the hypothalamic ACTH secretagogues in parallel with the concentration of the plasma ACTH and corticosterone. Our results suggest that UCN I may activate the HPA axis by stimulation of the hypothalamic CRF production, and this process is mediated by CRFR1, and not by CRFR2. UCN I may stimulate the AVP production, as well, but, based on the results with AVPR3 antagonist, this effect is not involved in the regulation of the HPA axis.

Role of neuropeptides in anxiety, stress, and depression: from animals to humans

Major depression, with its strikingly high prevalence, is the most common cause of disability in communities of Western type, according to data of the World Health Organization. Stress-related mood disorders, besides their deleterious effects on the patient itself, also challenge the healthcare systems with their great social and economic impact. Our knowledge on the neurobiology of these conditions is less than sufficient as exemplified by the high proportion of patients who do not respond to currently available medications targeting monoaminergic systems. The search for new therapeutical strategies became therefore a "hot topic" in neuroscience, and there is a large body of evidence suggesting that brain neuropeptides not only participate is stress physiology, but they may also have clinical relevance. Based on data obtained in animal studies, neuropeptides and their receptors might be targeted by new candidate neuropharmacons with the hope that they will become important and effective tools in the management of stress related mood disorders. In this review, we attempt to summarize the latest evidence obtained using animal models for mood disorders, genetically modified rodent models for anxiety and depression, and we will pay some attention to previously published clinical data on corticotropin releasing factor, urocortin 1, urocortin 2, urocortin 3, arginine-vasopressin, neuropeptide Y, pituitary adenylate-cyclase activating polypeptide, neuropeptide S, oxytocin, substance P and galanin fields of stress research.

The interaction of Urocortin II and Urocortin III with amygdalar and hypothalamic cotricotropin-releasing factor (CRF)--reflections on the regulation of the hypothalamic-pituitary-adrenal (HPA) axis

Urocortin II (Ucn II) and Urocortin III (Ucn III) are selective agonists of the CRF receptor type 2 (CRFR2). The aim of the present experiments was to investigate the effects of Ucn II and Ucn III on the central CRF and peripheral glucocorticoids in rats. Increasing doses (0.5-1-2-5 μg/2 μl) of Ucn II or Ucn III were administered intracerebroventricularly, then CRF concentration was determined by immunoassays in two different brain regions, the amygdala and the hypothalamus, and in two different time paradigms, 5 and 30 min after the administration of peptides. In parallel with the second determination, plasma corticosterone concentration was measured by chemofluorescent assay. The amygdalar CRF amount was increased significantly by 0.5 and 5 μg of UCN II and 2 and 5 μg of UCN III in the 5 min experiments and by 5 μg of UCN II and 0.5 and 5 μg of UCN III in the 30 min experiments. The hypothalamic CRF content was not affected considerably in the 5 min paradigm, but it was influenced significantly in the 30 min paradigm, with 0.5 and 1 μg of UCN II and 0.5-2 μg of UCN III decreasing, and 2 and 5 μg of UCN II and 5 μg of UCN III increasing the hormone concentration, respectively. The plasma corticosterone concentration was decreased by 1 and 2 μg of UCN II and UCN III and increased by 0.5 and 5 μg of UCN III. The present results demonstrate that central administration of Ucn II and Ucn III modulate time-dependently and dose-dependently the amygdalar and the hypothalamic CRF concentration, and, directly or indirectly, the plasma corticosterone concentration. The present experiments suggest that the role of CRFR2 in the regulation of the HPA axis can be inhibitory or stimulatory, depending on the actual concentration of their agonists.

Hypothalamic neurohormones and immune responses

The aim of this review is to provide a comprehensive examination of the current literature describing the neural-immune interactions, with emphasis on the most recent findings of the effects of neurohormones on immune system. Particularly, the role of hypothalamic hormones such as Thyrotropin-releasing hormone (TRH), Corticotropin-releasing hormone (CRH) and Gonadotropin-releasing hormone (GnRH). In the past few years, interest has been raised in extrapituitary actions of these neurohormones due to their receptors have been found in many non-pituitary tissues. Also, the receptors are present in immune cells, suggesting an autocrine or paracrine role within the immune system. In general, these neurohormones have been reported to exert immunomodulatory effects on cell proliferation, immune mediators release and cell function. The implications of these findings in understanding the network of hypothalamic neuropeptides and immune system are discussed.