Therapeutic potential of CRF receptor antagonists: a gut-brain perspective

Activation of the corticotropin-releasing factor (CRF) family of neuropeptide receptors in the brain and periphery appears to mediate stress-related changes in a variety of physiological and functional domains. Comparative pharmacology of CRF receptor agonists suggests that CRF, urocortin, sauvagine and urotensin consistently mimic, and conversely peptide CRF receptor antagonists lessen, the functional consequences of stressor exposure. Together with the development of novel non-peptide CRF receptor antagonists, a growing number of CRF receptor selective ligands are available to elucidate the neurobiology and physiological role of CRF systems. The present review considers available preclinical evidence as well as results from one Phase II clinical trial which address the hypothesis that CRF receptor antagonists may represent a new option for pharmacotherapy of stress-related disorders.     

Therapeutic potential of CRF receptor antagonists: a gut-brain perspective

Activation of the corticotropin-releasing factor (CRF) family of neuropeptide receptors in the brain and periphery appears to mediate stress-related changes in a variety of physiological and functional domains. Comparative pharmacology of CRF receptor agonists suggests that CRF, urocortin, sauvagine and urotensin consistently mimic, and conversely peptide CRF receptor antagonists lessen, the functional consequences of stressor exposure. Together with the development of novel non-peptide CRF receptor antagonists, a growing number of CRF receptor selective ligands are available to elucidate the neurobiology and physiological role of CRF systems. The present review considers available preclinical evidence as well as results from one Phase II clinical trial which address the hypothesis that CRF receptor antagonists may represent a new option for pharmacotherapy of stress-related disorders.     

CRF1 receptor signaling pathways are involved in stress-related alterations of colonic function and viscerosensitivity: implications for irritable bowel syndrome

1. The characterization of corticotropin releasing factor (CRF) and, more recently, the discovery of additional CRF-related ligands, urocortin 1, urocortin 2 and urocortin 3, the cloning of two distinct CRF receptor subtypes, 1 (CRF(1)) and 2 (CRF(2)), and the development of selective CRF receptor antagonists provided new insight to unravel the mechanisms of stress. Activation of brain CRF(1) receptor signaling pathways is implicated in stress-related endocrine response and the development of anxiety-like behaviors. 2. Compelling evidence in rodents showed also that both central and peripheral injection of CRF and urocortin 1 mimic acute stress-induced colonic response (stimulation of motility, transit, defecation, mucus and watery secretion, increased ionic permeability and occurrence of diarrhea) in rodents. Central CRF enhances colorectal distention-induced visceral pain in rats. Peripheral CRF reduced pain threshold to colonic distention and increased colonic motility in humans. 3. Nonselective CRF(1)/CRF(2) antagonists and selective CRF(1) antagonists inhibit exogenous (central or peripheral) CRF- and acute stress-induced activation of colonic myenteric neurons, stimulation of colonic motor function and visceral hyperalgesia while selective CRF(2) antagonists have no effect. None of the CRF antagonists influence basal or postprandial colonic function in nonstressed animals. 4. These findings implicate CRF(1) receptors in stress-related stimulation of colonic function and hypersensitivity to colorectal distention. Targeting CRF(1)-dependent pathways may have potential benefit against stress or anxiety-/depression-related functional bowel disorders.     

Urocortin and cardiovascular protection

UROCORTIN AND CRFRECEPTORS Urocortin, a 40 amino acid peptide belongs to thehypothalamic CRF family, which also include CRF,urotensin and sauvagine. CRF polypeptides play bio-logically diverse roles in the stress responses by actingon central neurons expressing CRF receptors. CRFreceptor agonists acting on the peripheral CRF recep-tors contribute to the regulation of cardiovascular andinflammatory responses. Abnormal CRF receptor-me-diated cellular signaling might be closely a…     

Corticotropin-releasing factor receptors 1 and 2 in anxiety and depression.

Corticotropin-releasing factor (CRF) and its related family members are implicated in stress-related disorders such as anxiety and depression. Recently, two new members of this neuropeptide family have been discovered in the brain: urocortin II (also known as stresscopin-related peptide) and urocortin III (also known as stresscopin). These urocortins are selective agonists for the CRF(2) receptor, show a distinct neuroanatomical localization and are involved in stress-coping responses such as anxiolysis. Thus, CRF, the urocortins and their receptors form an intricate network in the brain involved in the acute phase as well as the recovery phase of the stress response.     

Role of corticotropin releasing factor (CRF) receptors 1 and 2 in CRF-potentiated acoustic startle in mice

Rationale Hypersecretion of corticotropin releasing factor (CRF) has been implicated in both severe anxiety disorders and major depression. Although the role of the CRF₁ receptor in the anxiogenic effects of CRF is well supported, the role of CRF₂ receptors in anxiety-like behaviors is less clear. In rats, CRF increases the acoustic startle reflex (ASR) via its action in the extended amygdala, providing a putative measure of CRF-mediated anxiogenic activity.Objective To characterize the effect of CRF on ASR in mice and determine the respective roles of CRF₁ and CRF₂ receptors in CRF-potentiated ASR.Methods The present study examined: (1) the time course and dose response functions for the effects of human/rat (h/r)-CRF (0.02–0.6 nmol, ICV (intracerebroventricular)) on ASR in two inbred strains of mice; (2) the effects of the CRF₁ receptor antagonist NBI-30775 (20 mg/kg, intraperitoneal) and the CRF₂ receptor antagonist Antisauvagine-30 (1–10 nmol, ICV) on CRF-potentiated ASR and (3) the effects of the CRF₂ receptor agonist urocortin 2 (0.2–6 nmol, ICV) on ASR in mice.Results h/r-CRF significantly increased ASR in mice in a time-dependent manner with maximal efficacy at the 0.2 and 0.6 nmol doses. 129S6/SvEvTac mice exhibited a slightly increased duration of action and lower minimal effective dose threshold for CRF effects on ASR compared to C57BL/6J mice. Both selective CRF₁ and CRF₂ antagonists attenuated h/r-CRF-potentiated ASR without affecting acoustic startle when given alone. The selective CRF₂ receptor agonist urocortin 2 increased ASR (1 and 2 nmol), albeit with less efficacy than the non-selective CRF receptor agonist h/r-CRF.Conclusions Both CRF₁ and CRF₂ receptors appear to contribute to the h/r-CRF-induced increases in ASR in mice. These data support the hypothesis that both receptors contribute to the anxiogenic effects of CRF.     

Cloning and functional pharmacology of two corticotropin-releasing factor receptors from a teleost fish

Although it is well established that fish possess corticotropin-releasing factor (CRF) and a CRF-like peptide, urotensin I, comparatively little is known about the pharmacology of their cognate receptors. Here we report the isolation and functional expression of two complementary DNAs (cDNAs), from the chum salmon Oncorhynchus keta, which encode orthologues of the mammalian and amphibian CRF type 1 (CRF(1)) and type 2 (CRF(2)) receptors. Radioligand competition binding experiments have revealed that the salmon CRF(1) and CRF(2) receptors bind urotensin I with approximately 8-fold higher affinity than rat/human CRF. These two peptides together with two related CRF-like peptides, namely, sauvagine and urocortin, were also tested in cAMP assays; for cells expressing the salmon CRF(1) receptor, EC(50) values for the stimulation of cAMP production were between 4.5+/-1.8 and 15.3+/-3.1 nM. For the salmon CRF(2) receptor, the corresponding values were: rat/human CRF, 9.4+/-0.4 nM; urotensin I, 21.2+/-2.1 nM; sauvagine, 0.7+/-0.1 nM; and urocortin, 2.2+/-0.7 nM. We have also functionally coupled the O. keta CRF(1) receptor, in Xenopus laevis oocytes, to the endogenous Ca(2+)-activated chloride conductance by co-expression with the G-protein alpha subunit, G(alpha16). The EC(50) value for channel activation by rat/human CRF (11.2+/-2.6 nM) agrees well with that obtained in cAMP assays (15.3+/-3.1 nM). We conclude that although sauvagine is 13- and 30-fold more potent than rat/human CRF and urotensin I, respectively, in activating the salmon CRF(2) receptor, neither receptor appears able to discriminate between the native ligands CRF and urotensin I.     

Functional CRF receptors in BON cells stimulate serotonin release

BON cells are human, pancreatic carcinoid-derived, endocrine-like cells that share functional similarities with intestinal enterochromaffin (EC) cells. We investigated the presence of corticotropin-releasing factor (CRF) receptors, their signalling pathways and the functional effects of their stimulation in BON cells (clone #7). Expression analysis showed that BON cells contain mRNA for the CRF receptor types 1 and 2 (CRF1/2), although CRF2 mRNA levels were 23-fold higher than those of CRF1 mRNA. The CRF1/2 ligand, rat/human (r/h)CRF (EC50 = 233 nM), and the selective CRF2 ligand, human urocortin 3 (Ucn 3) (EC50 = 48 nM), induced a dose-dependent increase in cAMP formation. Effects of r/hCRF were blocked by 44% with the selective CRF1 antagonist DMP-696, while the selective CRF2 antagonist antisauvagine-30 had only marginal effects. Both ligands (100 nM) stimulated the release of serotonin with similar efficacy (3-fold increase over basal). Effects of r/hCRF, but not Ucn 3, were blocked by pre-incubation with antisauvagine-30. These observations demonstrate that the EC cell-related BON cells express functional CRF2 receptors linked to the release of serotonin. This suggests that EC cells may be a target for CRF and/or Ucn 3 in the intestine during stress-related responses. Actions of CRF/Ucn 3 and EC cell-derived mediators, such as serotonin, might underlie several motor, secretory and/or sensory disorders of the gastrointestinal (GI) tract which may play a role in the pathophysiology of functional GI disorders, such as irritable bowel syndrome.     

Human CRF2 alpha and beta splice variants: pharmacological characterization using radioligand binding and a luciferase gene expression assay

Corticotropin releasing factor (CRF) receptors belong to the super-family of G protein-coupled receptors. These receptors are classified into two subtypes (CRF1 and CRF2). Both receptors are positively coupled to adenylyl cyclase but they have a distinct pharmacology and distribution in brain. Two isoforms belonging to the CRF2 subtype receptors, CRF2alpha and CRF2beta, have been identified in rat and man. The neuropeptides CRF and urocortin mediate their actions through this CRF G protein-coupled receptor family. In this report, we describe the pharmacological characterization of the recently identified hCRF2, receptor. We have used radioligand binding with [125I]-tyr0-sauvagine and a gene expression assay in which the firefly luciferase gene expression is under the control of cAMP responsive elements. Association kinetics of [125I]-tyr0-sauvagine binding to the hCRF2beta receptor were monophasic while dissociation kinetics were biphasic, in agreement with the kinetics results obtained with the hCRF2alpha receptor. Saturation binding analysis revealed two affinity states in HEK 293 cells with binding parameters in accord with those determined kinetically and with parameters obtained with the hCRF2alpha receptor. A non-hydrolysable GTP analog, Gpp(NH)p, reduced the high affinity binding of [125I]-tyr0-sauvagine to both hCRF2 receptor isoforms in a similar manner. The rank order of potency of CRF agonist peptides in competition experiments was identical for both hCRF2 isoforms (urocortin > sauvagine > urotensin 1 > r/hCRF > alpha-helical CRF(9-41) > oCRF). Similarly, agonist potency was similar for the two isoforms when studied using the luciferase gene reporter system. The peptide antagonist alpha-helical CRF(9-41) exhibited a non-competitive antagonism of urocortin-stimulated luciferase expression with both hCRF2 receptor isoforms. Taken together, these results indicate that the pharmacological profiles of the CRF2 splice variants are identical. This indicates that the region of the N-terminus that varies between the receptors is probably not important in the binding of peptide CRF receptor ligands or functional activation of the receptor.     

CRF2 receptors are highly expressed in the human cardiovascular system and their cognate ligands urocortins 2 and 3 are potent vasodilators

1. Systemic infusions of urocortin 1 produce a decrease in mean arterial pressure. This effect may be mediated by a direct action on novel corticotropin-releasing factor type 2 (CRF(2)) receptors predicted to be expressed in blood vessels and the heart. Our objectives were to determine the presence of CRF(2) receptors in the human cardiovascular system using the selective radioligand [(125)I]antisauvagine 30. We also investigated the potential functional roles of novel CRF(2) ligands in the regulation of vascular tone in human arteries in vitro. 2. Radioligand binding techniques were used to characterise the CRF(2) receptor. [(125)I]antisauvagine 30 bound specifically, saturably, reversibly and with high affinity to CRF(2) receptors in human left ventricle (K(D) 0.21+/-0.03 nm, B(MAX) 0.80+/-0.18 fmol mg(-1) protein), and no change in receptor density or affinity was observed in the dilated cardiomyopathy group. 3. Autoradiographical studies revealed highly localised binding of [(125)I]antisauvagine 30 to intramyocardial blood vessels. Binding sites were also detected in the myocardium and in the medial layer of internal mammary arteries. 4. In endothelium-denuded human internal mammary artery in vitro, all peptides tested produced a potent and sustained vasodilator response reversing endothelin-1-induced constrictions (10 nm) (urocortin 1: pD(2) 8.39+/-0.32, E(MAX) 46+/-7.7%; urocortin 2: pD(2) 8.27+/-0.17, E(MAX) 60+/-8.5%; urocortin 3: pD(2) 8.61+/-0.25, E(MAX) 61+/-7.2%; CRF: pD(2) 8.28+/-0.27, E(MAX): 40+/-10%). 5. We have demonstrated the presence of CRF(2) receptors in the human cardiovascular system and a direct, endothelium-independent vasodilator action of urocortins 2 and 3, which may counter-balance the centrally mediated pressor effects of CRF and urocortin 1.     

Characterisation using microphysiometry of CRF receptor pharmacology.

We have assessed the utility of the Cytosensor microphysiometer for studying the pharmacology of recombinant CRF receptors. Chinese hamster ovary cells stably expressing the human CRF1 or CRF2 receptor were perfused in the Cytosensor with bicarbonate-free Hams F12 (pH 7.4) containing 0.2% bovine serum albumin. The rank order of potencies of agonist peptides were CRF = sauvagine = urocortin = urotensin at CRF1 (pEC50 values 11.16 +/- 0.17, 11.37 +/- 0.14, 11.43 +/- 0.09 and 11.46 +/- 0.13; n = 4), and urocortin = sauvagine > urotensin > CRF at CRF2 (pEC50 values 10.88 +/- 0.12, 10.44 +/- 0.05, 9.36 +/- 0.12 and 8.53 +/- 0.07; n = 7-9). alpha-Helical CRF (9-41) was a competitive antagonist at the CRF2 receptor (pK(B) = 6.99 +/- 0.08, n = 4), but was a partial agonist at the CRF1 receptor (pEC50 = 6.85 +/- 0.08, Emax = 33%, n = 3). CP 154,526 was a competitive antagonist at the CRF1 receptor (pK(B) = 8.17 +/- 0.05, n = 6), but was inactive at the CRF2 receptor. These data are consistent with established CRF receptor pharmacology and show that the Cytosensor is a viable method for assessing the functional activity of CRF-receptor agonists and antagonists.     

Nibbling at CRF receptor control of feeding and gastrocolonic motility

Inadequate pharmacological tools, until recently, hindered the understanding of the roles of corticotropin-releasing factor (CRF) receptor subtypes in appetite regulation and gastrocolonic motor function. Now, novel ligands that are selective for CRF(1) or CRF(2) receptors are helping to uncover the specific functions of CRF receptor subtypes. Central or peripheral CRF(2) receptor activation suppresses feeding independently of CRF(1) receptors. In the rat, central administration of CRF(2) receptor agonists promotes satiation without eliciting the malaise, behavioral arousal or anxiogenesis associated with CRF(1) receptor agonists. Conversely, central administration of CRF(1) receptor agonists elicits short-onset anorexia independently of CRF(2) receptor activation. With respect to gastrointestinal motor function, stress inhibits gastric motility through CRF(2) receptor-dependent central autonomic and peripheral myenteric systems. By contrast, stress stimulates colonic motility via CRF(1) receptor-dependent sacral parasympathetic and colonic myenteric mechanisms. These findings have important physiological implications and suggest targeted approaches for the pharmacotherapy of obesity and stress-related functional gastrointestinal and eating disorders.     

Vasodilative effects of urocortin II via protein kinase A and a mitogen-activated protein kinase in rat thoracic aorta

Four corticotropin-releasing factor (CRF)-related peptides have been found in mammals and are known as CRF, urocortin, urocortin II, and urocortin III (also known as stresscopin). The three urocortins have considerably higher affinities for CRF receptor type 2 (CRF R2) than CRF, and urocortin II and urocortin III are highly selective for CRF R2. In the present study, the authors examined the hypothesis that urocortin II or urocortin III, in addition to urocortin, produces vasodilation as a candidate for natural ligands of CRF R2beta in rat thoracic aorta. Involvement of protein kinases on urocortin-induced vasodilation was also explored. The vasodilative effects of urocortin II and urocortin III were more potent than that of CRF, but less potent than that of urocortin. Urocortin II-induced vasodilation was significantly attenuated by a CRF R2-selective antagonist, antisauvagine-30. Both SQ22536, an adenylate cyclase inhibitor, and Rp-8-Br-cAMPS, a protein kinase A (PKA) inhibitor, were found to attenuate the urocortin II-induced vasodilation. SB203580, a p38 mitogen-activated protein (MAP) kinase inhibitor, also inhibited the effects of urocortin and urocortin II on vasodilation. Thus, urocortins contribute to vasodilation via p38 MAP kinase as well as PKA pathways.     

Achieving signalling selectivity of ligands for the corticotropin-releasing factor type 1 receptor by modifying the agonist's signalling domain

BACKGROUND AND PURPOSE: Most of the pharmaceuticals target G-protein-coupled receptors (GPCRs) which can generally activate different signalling events. The aim of this study was to achieve functional selectivity of corticotropin-releasing factor receptor type 1 (CRF(1)) ligands. EXPERIMENTAL APPROACH: We systematically substituted urocortin, a natural peptide agonist of CRF(1), with bulky amino acids (benzoyl-phenylalanine, naphthylalanine) and determined the effect of the analogues on coupling of CRF(1) to Gs- and Gi-protein in human embryonic kidney cells, using receptor binding, [(35)S]-GTPgammaS binding stimulation, and cAMP accumulation assays. KEY RESULTS: Native ligands stimulated Gs and Gi activation through CRF(1), resulting in stimulation and then inhibition of cAMP accumulation. Single replacements in urocortin at positions 6-15 led, dependent on the position and nature of the substituent, to ligands that conserved Gs activity, but were devoid of Gi activity, only stimulating cAMP accumulation, and competitively antagonized the Gi activation by sauvagine. In contrast, analogues with substitutions outside this sequence non-selectively activated Gs and Gi, as urocortin did. CONCLUSIONS AND IMPLICATIONS: Modifications in a specific region, which we have called the signalling domain, in the polypeptide agonist urocortin resulted in analogues that behaved as agonists and, at the same time, antagonists for the activation of different G-proteins by CRF(1). This finding implies significant differences between active conformations of the receptor when coupled to different G-proteins. A similar structural encoding of signalling information in other polypeptide hormone receptor ligands would result in a general concept for the development of signalling-selective drug candidates.     

CRF receptor antagonists: utility in research and clinical practice

CRF, CRF-related peptides and CRF receptors constitute a complex physiological system which has a key role in facilitating the adaptation of the organism to the stressful stimuli of the environment. The behavioral, endocrine, autonomic and immune branches of stress response are considered to be under the coordinating effects of CRF and its related peptides. The effects of these peptides are mediated through two distinct receptors, types 1 and 2 CRF receptors (CRF(1) and CRF(2)). The two receptors are encoded by separate genes and belong to the G-coupled receptor superfamily. The wide influence of the CRF system on physiological processes in both brain and periphery, suggests the implication of the respective peptides in the pathophysiology of numerous disorders which involve dysregulated stress responses. The potential use of CRF antagonists in such disorders is currently under intense investigation. Furthermore, such compounds have been invaluable in elucidating the physiology of the CRF system. This review will focus on existing data on the structural and pharmacological characteristics as well as the experimental and potential clinical uses of non-peptide, small molecule CRF antagonists.     

Effects of a selective agonist and antagonist of CRF2 receptors on cardiovascular function in the rat

The aim of the present study was to investigate the effects of activation or blockade of the CRF(2) receptor subtype on cardiovascular function in conscious rats following systemic i.v. administration of the CRF(2) receptor peptide agonist urocortin 2 given alone and the selective CRF(2) receptor peptide antagonist antisauvagine-30 given alone. Urocortin 2 caused a dose-dependent reduction in mean arterial blood pressure and a dose-dependent increase in heart rate. Pretreatment with antisauvagine-30 blocked the hypotensive effect of urocortin 2. Antisauvagine-30 failed to produce any statistically significant effects on mean arterial blood pressure and heart rate at doses that completely blocked the effects of urocortin 2. These data verify the cardiovascular effects of selective CRF(2) receptor activation, but find no evidence for an endogenous CRF(2)-mediated tone.     

Suppression of food intake induced by corticotropin-releasing factor family in neonatal chicks.

Corticotropin-releasing factor (CRF), urocortin and urotensin I share amino acid sequences, and they inhibit food intake in mammals. CRF plays a potent role in decreasing food intake in avian species, but the effects of urocortin and urotensin I have not been investigated. Therefore, the effect of these three peptides on food intake in the neonatal chick was compared. In Experiment 1, birds were injected intracerebroventricularly (i.c.v.) with either 0, 0.01, 0.1 or 1 microg of urocortin following a 3-h fast, and food intake was measured for 2 h post-injection. Food intake was suppressed in a dose-dependent manner. Using a similar design in Experiment 2, the effect of urotensin I was investigated. Urotensin I appeared to suppress food intake in neonatal chicks more than urocortin did. In Experiment 3, the efficacy of CRF, urocortin and urotensin I was directly compared using one dose, 0.1 microg. The results indicated that the suppressive effect on food intake was strongest for CRF followed by urotensin I, then urocortin. These results suggest that the structure of receptors for the CRF family in chicks may be somewhat different than in mammals.     

Recent advances with the CRF1 receptor: design of small molecule inhibitors, receptor subtypes and clinical indications

Corticotropin-releasing factor (CRF) has been widely implicated as playing a major role in modulating the endocrine, autonomic, behavioral and immune responses to stress. The recent cloning of multiple receptors for CRF as well as the discovery of non-peptide receptor antagonists for CRF receptors have begun a new era of CRF study. Presently, there are five distinct targets for CRF with unique cDNA sequences, pharmacology and localization. These fall into three distinct classes, encoded by three different genes and have been termed the CRF1 and CRF2 receptors (belonging to the superfamily of G-protein coupled receptors) and the CRF-binding protein. The CRF2 receptor exists as three splice variants of the same gene and have been designated CRF2a CRF2b and CRF2g. The pharmacology and localization of all of these proteins in brain has been well established. The CRF1 receptor subtype is localized primarily to cortical and cerebellar regions while the CRF2a receptor is localized to subcortical regions including the lateral septum, and paraventricular and ventromedial nuclei of the hypothalamus. The CRF2b receptor is primarily localized to heart, skeletal muscle and in the brain, to cerebral arterioles and choroid plexus. The CRF2g receptor has most recently been identified in human amygdala. Expression of these receptors in mammalian cell lines has made possible the identification of non-peptide, high affinity, selective receptor antagonists. While the natural mammalian ligands oCRF and r/hCRF have high affinity for the CRF1 receptor subtype, they have lower affinity for the CRF2 receptor family making them ineffective labels for CRF2 receptors. [125I]Sauvagine has been characterized as a high affinity ligand for both the CRF1 and the CRF2 receptor subtypes and has been used in both radioligand binding and receptor autoradiographic studies as a tool to aid in the discovery of selective small molecule receptor antagonists. A number of non-peptide CRF1 receptor antagonists that can specifically and selectively block the CRF1 receptor subtype have recently been identified. Compounds such as CP 154,526 (12), NBI 27914 (129) and Antalarmin (154) inhibit CRF-stimulation of cAMP or CRF-stimulated ACTH release from cultured rat anterior pituitary cells. Furthermore, when administered peripherally, these compounds compete for ex vivo [125I]sauvagine binding to CRF1 receptors in brain sections demonstrating their ability to cross the blood-brain-barrier. In in vivo studies, peripheral administration of these compounds attenuate stress-induced elevations in plasma ACTH levels in rats demonstrating that CRF1 receptors can be blocked in the periphery. Furthermore, peripherally administered CRF1 receptor antagonists have also been demonstrated to inhibit CRF-induced seizure activity. These data clearly demonstrate that non-peptide CRF1 receptor antagonists, when administered systemically, can specifically block central CRF1 receptors and provide tools that can be used to determine the role of CRF1 receptors in various neuropsychiatric and neurodegenerative disorders. In addition, these molecules will prove useful in the discovery and development of potential orally active therapeutics for these disorders.     

Neuropeptide Y and corticotropin-releasing factor bi-directionally modulate inhibitory synaptic transmission in the bed nucleus of the stria terminalis

Neuropeptide Y (NPY) and corticotropin-releasing factor (CRF) have opposing effects on stress and anxiety. Both can modify synaptic activity through their binding to NPY receptors (YRs) and CRF receptors (CRFRs) respectively. The bed nucleus of the stria terminalis (BNST) is a brain region with enriched expression of both NPY and YRs and CRF and CRFRs. A component of the "extended amygdala", the BNST is anatomically well-situated to integrate stress and reward-related processing in the CNS, regulating activation of the hypothalamic-pituitary-adrenal (HPA) axis and reward circuits. Using whole-cell recordings in a BNST slice preparation, we found that NPY and CRF inhibit and enhance GABAergic transmission, respectively. Pharmacological experiments suggest that NPY depresses GABAergic transmission through activation of the Y2 receptor (Y2R), while both pharmacological and genetic experiments suggest that CRF and urocortin enhance GABAergic transmission through activation of the CRF receptor 1 (CRFR1). Further, the data suggest that NPY acts to regulate GABA release, while CRF enhances postsynaptic responses to GABA. These results suggest potential anatomical and cellular substrates for the robust behavioral interactions between NPY and CRF.