Loss of hypothalamic corticotropin-releasing hormone markedly reduces anxiety behaviors in mice.

A long-standing paradigm posits that hypothalamic corticotropin-releasing hormone (CRH) regulates neuroendocrine functions such as adrenal glucocorticoid release, whereas extra-hypothalamic CRH has a key role in stressor-triggered behaviors. Here we report that hypothalamus-specific Crh knockout mice (Sim1CrhKO mice, created by crossing Crhflox with Sim1Cre mice) have absent Crh mRNA and peptide mainly in the paraventricular nucleus of the hypothalamus (PVH) but preserved Crh expression in other brain regions including amygdala and cerebral cortex. As expected, Sim1CrhKO mice exhibit adrenal atrophy as well as decreased basal, diurnal and stressor-stimulated plasma corticosterone secretion and basal plasma adrenocorticotropic hormone, but surprisingly, have a profound anxiolytic phenotype when evaluated using multiple stressors including open-field, elevated plus maze, holeboard, light-dark box and novel object recognition task. Restoring plasma corticosterone did not reverse the anxiolytic phenotype of Sim1CrhKO mice. Crh-Cre driver mice revealed that PVHCrh fibers project abundantly to cingulate cortex and the nucleus accumbens shell, and moderately to medial amygdala, locus coeruleus and solitary tract, consistent with the existence of PVHCrh-dependent behavioral pathways. Although previous, nonselective attenuation of CRH production or action, genetically in mice and pharmacologically in humans, respectively, has not produced the anticipated anxiolytic effects, our data show that targeted interference specifically with hypothalamic Crh expression results in anxiolysis. Our data identify neurons that express both Sim1 and Crh as a cellular entry point into the study of CRH-mediated, anxiety-like behaviors and their therapeutic attenuation.

Maternal first trimester serum levels of free-beta human chorionic gonadotrophin and male genital anomalies.

STUDY QUESTION: Are maternal first trimester levels of serum free-beta hCG associated with the development of hypospadias or undescended testis (UDT) in boys? SUMMARY ANSWER: Overall, first trimester maternal levels of serum free-beta hCG are not associated with hypospadias or UDT. However, elevated levels were found in severe phenotypes (proximal hypospadias and bilateral UDT) suggesting an altered pathway of hormonal release in early pregnancy. WHAT IS KNOWN ALREADY: Human chorionic gonadotrophin peaks in first trimester of pregnancy stimulating fetal testosterone production, which is key to normal male genital development. Endocrine-disrupting insults early in pregnancy have been associated with increased risk of common genital anomalies in males such as hypospadias and UDT. One plausible etiological pathway is altered release of hCG. STUDY DESIGN, SIZE, DURATION: We conducted a record-linkage study of two separate populations of women attending first trimester aneuploidy screening in two Australian states, New South Wales (NSW) and Western Australia (WA), in 2006-2009 and 2001-2003, respectively. PARTICIPANTS/MATERIALS, SETTING, METHODS: Included were women who gave birth to a singleton live born male infant. There were 12 099 boys from NSW and 10 518 from WA included, of whom 90 and 77 had hypospadias; and 107 and 109 UDT, respectively. Serum levels of free-beta hCG were ascertained from laboratory databases and combined with relevant birth outcomes and congenital anomalies via record linkage of laboratory, birth, congenital anomalies and hospital data. Median and quartile levels of gestational age specific free-beta hCG multiple of the median (MoM) were compared between affected and unaffected boys. Logistic regression was used to evaluate the association between levels of free-beta hCG MoM and hypospadias or UDT, stratified by suspected placental dysfunction and co-existing anomalies. Where relevant, pooled analysis was conducted. MAIN RESULTS AND THE ROLE OF CHANCE: There was no difference in median hCG levels amongst women with an infant with hypospadias (NSW = 0.88 MoM, P = 0.83; WA = 0.84 MoM, P = 0.76) or UDT (NSW = 0.89 MoM, P = 0.54; WA = 0.95 MoM, P = 0.95), compared with women with an unaffected boy (NSW = 0.92 MoM; WA = 0.88 MoM). Low (<25th centile) or high (>75th centile) hCG levels were not associated with hypospadias or UDT, nor when stratifying by suspected placental dysfunction and co-existing anomalies. However, there was a tendency towards high levels for severe types, although confidence intervals were wide. When combining NSW and WA results, high hCG MoM levels (>75th centile) were associated with increased risk of proximal hypospadias (odds ratio (OR) 4.34; 95% CI: 1.08-17.4) and bilateral UDT (OR 2.86; 95% CI: 1.02-8.03). LIMITATIONS, REASONS FOR CAUTION: There were only small numbers of proximal hypospadias and bilateral UDT in both cohorts and although we conducted pooled analyses, results reported on these should be interpreted with caution. Gestational age by ultrasound may have been inaccurately estimated in small and large for gestational age fetuses affecting hCG MoM calculation in those pregnancies. Despite the reliability of our datasets in identifying adverse pregnancy outcomes, we did not have pathology information to confirm tissue lesions in the placenta and therefore our composite outcome should be considered as a proxy for placental dysfunction. WIDER IMPLICATIONS OF THE FINDINGS: This is one of the largest population-based studies examining the association between maternal first trimester serum levels of free-beta hCG and genital anomalies-hypospadias and UDT; and the first to compare specific phenotypes by severity. Overall, our findings does not support the hypothesis that alteration in maternal hCG levels is associated with the development of male genital anomalies; however, high hCG free-beta levels found in severe types suggest different underlying etiology involving higher production and secretion of hCG. These findings require further exploration and replication. STUDY FUNDING/COMPETING INTERESTS: This work was funded by the National Health and Medical Research Council (NHMRC) grant APP1047263. N.N. is supported by a NHMRC Career Development Fellowship APP1067066. C.B. was supported by a NHMRC Principal Research Fellowship #634341. The funding agencies had no role in the design, analysis, interpretation or reporting of the findings. There are no competing interests. TRIAL REGISTRATION NUMBER: Not applicable.

Urocortin III, a brain neuropeptide of the corticotropin-releasing hormone family: modulation by stress and attenuation of some anxiety-like behaviours.

Following its discovery 20 years ago, corticotropin-releasing hormone (CRH) has been postulated to mediate both hormonal and behavioural responses to stressors. Here, we characterize and describe a behavioural role for the murine gene, UcnIII, which encodes a recently discovered CRH-related neuropeptide, urocortin III. We found that mouse UcnIII is expressed predominantly in regions of the brain known to be involved in stress-related behaviours, and its expression in the hypothalamus increases following restraint. In addition, we found that intracerebroventricular administration of mUcnIII stimulates behaviours that are associated with reduced anxiety, including exploration of an open field and decreased latency to enter the lit compartment of a dark-light chamber, but has no effect on the elevated-plus maze. Finally, we found that mUcnIII does not exert any effects on the hormonal stress response. Based upon our findings, UcnIII may be an endogenous brain neuropeptide that is modulated by stress and stimulates behaviours associated with reduced anxiety. In this capacity, UcnIII may attenuate stress-related behaviours, which may be useful both to help cope with stressful situations as well as to avoid pathology associated with excessive reaction to stressors.

Neural substrates of anorexia nervosa: a behavioral challenge study with positron emission tomography.

OBJECTIVE: To delineate functional brain abnormalities associated with anorexia nervosa (AN). STUDY DESIGN: Positron emission tomographic measurements of regional cerebral blood flow (rCBF) were performed on 8 female patients with AN and 8 healthy female control subjects during exposure to 3 types of stimuli: high-calorie foods, low-calorie foods, and non-food items. Heart rate and internal state analog scale scores were also obtained. Stereotactic transformation and statistical parametric mapping techniques were used to analyze imaging data. RESULTS: During the high-calorie condition, control subjects reported a significant desire to eat, whereas subjects with AN reported elevated anxiety and exhibited increases in heart rate. Patients with AN had elevated bilateral medial temporal lobe rCBF compared with control subjects. Planned comparisons for group-by-condition interactions demonstrated greater activation within left occipital cortex and right temporo-occipital cortex for the high-calorie versus low-calorie contrast in patients with AN compared with control subjects. CONCLUSIONS: Our finding of elevated rCBF within bilateral medial temporal lobes is similar to published results in patients with psychotic disorders and may be related to the body image distortion common to AN. The high-calorie food phobia exhibited by patients with AN appears to be associated with exaggerated responses in visual association cortex, as has been previously observed in studies of specific phobias.

The physiology of corticotropin-releasing hormone deficiency in mice.

A review of the generation and characterization of corticotropin-releasing hormone (CRH)-deficient mice is presented. The studies summarized demonstrate the central role of CRH in the pituitary-adrenal axis response to stress, circadian stimulation, and glucocorticoid withdrawal. Additionally, pro-inflammatory actions of CRH at sites of local inflammation are given further support. In contrast, behavioral effects during stress that had been ascribed to CRH action are not altered in CRH-deficient mice. The normal behavioral response to stress in CRH-deficient mice strongly suggests the importance of other, possibly as yet undiscovered, CRH-like molecules.

Repressor element silencing transcription factor/neuron-restrictive silencing factor (REST/NRSF) can act as an enhancer as well as a repressor of corticotropin-releasing hormone gene transcription.

The repressor element-1/neuron-restrictive silencing element (RE-1/NRSE) mediates transcriptional repression by the repressor element silencing transcription factor/neuron-restrictive silencing factor (REST/NRSF) in many neuron-specific genes. REST/NRSF is expressed most highly in non-neural tissues, where it is thought to repress gene transcription, but is also found in developing neurons and at low levels in the brain. Its null mutation in vivo results in embryonic lethality in mice. While the RE-1/NRSE-mediated repressive influence of REST/NRSF is well established, results in transgenic studies have suggested that the action of the system is more complex. Here, we report that transcription of the corticotropin releasing hormone (CRH) gene is regulated by REST/NRSF, in part through the RE-1/NRSE. Expression of transfected Crh-luciferase constructs was down-regulated by REST/NRSF in a RE-1/NRSE-dependent fashion in both muscle-derived L6 and REST/NRSF co-transfected neuronal PC12 cells. Treatment of L6 cells with trichostatin A revealed that REST/NRSF repression depends, in part, on histone deacetylase activity in these cells. In another neuronal cell line, NG108, REST/NRSF also repressed expression from constructs containing an intact RE-1/NRSE. However, unexpectedly, REST/NRSF up-regulated expression levels of constructs lacking an intact RE-1/NRSE. These results suggest that REST/NRSF can act as both a repressor of Crh transcription, via the Crh RE-1/NRSE, and an enhancer of Crh transcription, via a mechanism independent of the Crh RE-1/NRSE.

Endocrinologic and psychological effects of short-term dexamethasone in anorexia nervosa.

Patients with anorexia nervosa (AN) have hyperactivity of their hypothalamic-pituitary-adrenal (HPA) axis, sometimes accompanied by elevations of cortisol. We examined whether the normal effects of short-term dexamethasone treatment upon HPA axis suppression and appetite stimulation are observed in these patients. Five young women with AN and ten healthy female controls received one week of high-dose oral dexamethasone (2 mg/m2/d) preceded and followed by hormonal evaluation of sensitivity to glucocorticoids and psychological assessments. No differences in hormone levels of the HPA axis were observed between the two groups and control groups at baseline, after dexamethasone suppression, or following ACTH stimulation testing. However, fasting insulin levels were significantly lower in the AN group, both before and after dexamethasone therapy and their serum leptin levels were also significantly lower. The AN group had significantly lower scores on the Anorexia Nervosa Subtest and the Beck Depression Inventory after dexamethasone compared to controls. On daily analog scales, AN patients had higher anxiety scores while on dexamethasone. Normal sensitivity to glucocorticoids was observed in all parameters examined except for mild abnormalities in pancreatic beta-cell function. These data suggest that AN may represent a state of partial glucocorticoid resistance, as in other states of restricted food intake. Furthermore, these pilot data, including the effects of dexamethasone upon psychological outlook in AN, suggest that glucocorticoids are not an effective therapy for these patients.

Effects of various mutations in the neurophysin/glycopeptide portion of the vasopressin gene on vasopressin expression in vitro.

The vasopressin gene encodes three polypeptides besides the signal peptide: vasopressin, neurophysin II (neurophysin), and the carboxy-terminal glycopeptide (glycopeptide). Although the function of vasopressin is well characterized, those of the latter two are not completely understood. In the present study, we investigated the effects of various mutations within the neurophysin/glycopeptide portion of the vasopressin gene on vasopressin secretion in vitro, to clarify the role of each peptide in vasopressin biosynthesis. Expression vectors containing the vasopressin gene, either wild-type or various mutants, were transiently transfected into AtT20 cells, which are known to have the enzymes necessary for the proper processing of the vasopressin precursor protein. The amount of vasopressin secreted into the culture medium was estimated by specific radioimmunoassay. Variable degrees of decreased vasopressin secretion were observed with mutant vasopressin genes harboring deletions or amino acid substitutions in neurophysin. The naturally-occurring frame-shift mutation in the hereditary diabetes insipidus (Brattleboro) rat completely eliminated vasopressin expression. In contrast, a missense mutation found in patients with familial neurogenic diabetes insipidus only partially decreased vasopressin secretion. Finally, the mutant vasopressin gene lacking the N-linked glycosylation site in glycopeptide had no effect on vasopressin expression. Our data suggest that 1) intact neurophysin is not indispensable for vasopressin expression, although an altered structure of neurophysin significantly affects the secretion of the hormone; 2) the pathogenesis of diabetes insipidus with the two naturally-occurring mutations found in the rat (Brattleboro rat) and human (familial central diabetes insipidus) seem to be different; and 3) glycosylation of the carboxy-terminal glycopeptide is not essential for the expression of vasopressin.

Circadian rise in maternal glucocorticoid prevents pulmonary dysplasia in fetal mice with adrenal insufficiency.

The hypothalamic-pituitary-adrenal (HPA) axis, including hypothalamic corticotropin-releasing hormone (CRH) and pituitary corticotropin, is one of the first endocrine systems to develop during fetal life, probably because glucocorticoid secretion is necessary for the maturation of many essential fetal organs. Consistent with this, pregnant mice with an inactivating mutation in the Crh gene deliver CRH-deficient offspring that die at birth with dysplastic lungs, which can be prevented by prenatal maternal glucocorticoid treatment. But children lacking the ability to synthesize cortisol (because of various genetic defects in adrenal gland development or steroidogenesis) are not born with respiratory insufficiency or abnormal lung development, suggesting that the transfer of maternal glucocorticoid across the placenta might promote fetal organ maturation in the absence of fetal glucocorticoid production. We used pregnant mice with a normal HPA axis carrying fetuses with CRH deficiency to characterize the relative contributions of the fetal and maternal adrenal to the activity of the fetal HPA axis, and related these findings to fetal lung development. We found that in the presence of fetal adrenal insufficiency, normal fetal lung development is maintained by the transfer of maternal glucocorticoid to the fetus, specifically during the circadian peak in maternal glucocorticoid secretion.

Corticotropin-releasing hormone links pituitary adrenocorticotropin gene expression and release during adrenal insufficiency.

Corticotropin-releasing hormone (CRH)-deficient (KO) mice provide a unique system to define the role of CRH in regulation of the hypothalamic-pituitary-adrenal (HPA) axis. Despite several manifestations of chronic glucocorticoid insufficiency, basal pituitary proopiomelanocortin (POMC) mRNA, adrenocorticotrophic hormone (ACTH) peptide content within the pituitary, and plasma ACTH concentrations are not elevated in CRH KO mice. The normal POMC mRNA content in KO mice is dependent upon residual glucocorticoid secretion, as it increases in both KO and WT mice after adrenalectomy; this increase is reversed by glucocorticoid, but not aldosterone, replacement. However, the normal plasma levels of ACTH in CRH KO mice are not dependent upon residual glucocorticoid secretion, because, after adrenalectomy, these levels do not undergo the normal increase seen in KO mice despite the increase in POMC mRNA content. Administration of CRH restores ACTH secretion to its expected high level in adrenalectomized CRH KO mice. Thus, in adrenal insufficiency, loss of glucocorticoid feedback by itself can increase POMC gene expression in the pituitary; but CRH action is essential for this to result in increased secretion of ACTH. This may explain why, after withdrawal of chronic glucocorticoid treatment, reactivation of CRH secretion is a necessary prerequisite for recovery from suppression of the HPA axis.

Impaired basal and restraint-induced epinephrine secretion in corticotropin-releasing hormone-deficient mice.

CRH is thought to play a role in responses of the adrenocortical and adrenomedullary systems during stress. To investigate the role of CRH in stress-induced secretions of corticosterone and epinephrine, we subjected wild-type (WT) and CRH-deficient (knockout, KO) mice to restraint, and analyzed plasma corticosterone, plasma catecholamines, and adrenal phenylethanolamine N-methyltransferase (PNMT) gene expression and activity before and during 3 h of restraint. Plasma corticosterone increased over 40-fold in WT mice, but minimally in CRH KO mice. Adrenal corticosterone content tended to increase in CRH KO mice, although to levels 5-fold lower than that in WT mice. CRH KO mice had significantly lower plasma epinephrine and higher norepinephrine than WT mice at baseline, and delayed epinephrine secretion during restraint. Adrenal PNMT messenger RNA content in CRH KO mice tended to be lower than that in WT mice, though the degree of induction was similar in both genotypes. PNMT enzyme activity was significantly lower in CRH KO mice. Pharmacological adrenalectomy abolished restraint-induced corticosterone secretion and PNMT gene expression in WT mice, consistent with an absolute requirement of glucocorticoids for PNMT gene expression. We conclude that glucocorticoid insufficiency in CRH KO mice leads to decreased basal and restraint-induced plasma epinephrine and adrenal PNMT gene expression and enzyme activity.

CRH deficiency impairs but does not block pituitary-adrenal responses to diverse stressors.

We have previously observed significant, albeit decreased, corticosterone responses to restraint stress in corticotropin releasing hormone (CRH)-deficient (knockout, CRH KO) mice. Because different stressors have been shown to engage different populations of hypophysiotropic neurons, we have used hypoglycemia and hypovolemia to test whether CRH-independent pituitary-adrenal activation is evoked by stimuli other than restraint. Insulin injection in fasted CRH KO mice elicited increases in corticosterone that were markedly lower than those in wild type but marginally significant relative to corresponding KO controls. Consistent with impaired adrenocortical function, hypoglycemia-induced epinephrine secretion was reduced in female CRH KO mice. Hypovolemia produced by retro-orbital bleeding also significantly elevated corticosterone in CRH KO mice. In contrast to significant stress-induced increases in corticotropin (ACTH) in wild-type mice, those in CRH KO mice were slight, transient and difficult to detect without frequent sampling. Restraint-induced interleukin-6 (IL-6) levels were similar between wild-type and CRH KO mice, arguing against compensatory changes in IL-6 responses to restraint due to CRH deficiency. CRH infusion enhanced adrenocortical responses to restraint independently of effects on basal corticosterone levels, suggesting that pituitary-adrenal activity is augmented by factors besides CRH during stress. We conclude that although stress-induced pituitary-adrenal activity does not require acute increases in CRH, CRH is required to support the normal amplitude of adrenocortical axis responsiveness to other endocrine or neural factors during stress.

Neuroanatomy of human appetitive function: A positron emission tomography investigation.

OBJECTIVE: The mediating neuroanatomy of human appetitive function is poorly understood. A state induction paradigm was employed, in conjunction with positron emission tomography, to test the hypothesis that limbic/paralimbic regions respond to the desirability of food stimuli. METHODS: Eight normal subjects were studied during each of three conditions, involving visual exposure to high-caloric food, low-caloric food, and nonfood stimuli. Subjective indices of hunger were measured via analog scales. RESULTS: Planned contrasts demonstrated significant increases in desire to eat and decreases in left temporoinsular cortical blood flow during the high-caloric versus control conditions. DISCUSSION: Results implicate the temporo-insular cortex in normal appetitive function, suggesting that activity within this region is associated with the desirability or valence of food stimuli, prior to ingestion. These data will provide a broad foundation for future studies of patients with eating disorders.

Pituitary-adrenal axis regulation in CRH-deficient mice.

Corticotropin-releasing hormone (CRH)-deficient (knockout (KO)) mice demonstrate severely impaired adrenal responses to restraint, ether, and fasting, and lack the normal diurnal glucocorticoid (GC) rhythm. Here, we summarize recent studies determining the role of CRH in augmenting plasma adrenocorticotrophic hormone (ACTH) concentration after glucocorticoid withdrawal and pituitary-adrenal axis stimulation in the context of inflammation. Even though GC insufficient, basal pituitary proopiomelanocortin (POMC) mRNA, ACTH peptide content within the pituitary, and plasma ACTH concentrations are not elevated in CRH KO mice. POMC mRNA content in CRH KO mice increases following adrenalectomy, and this increase is reversed by GC, but not aldosterone, replacement. In marked contrast to the increase in POMC mRNA, plasma ACTH does not increase in the CRH KO mice following adrenalectomy. Administration of CRH to adrenalectomized CRH KO mice results in acute, robust ACTH secretion. Thus, loss of GC feedback can increase POMC gene expression in the pituitary, but CRH action is essential for increased secretion of ACTH into the circulation. While GC secretion is impaired in CRH KO mice after most stimuli, we have found near-normal GC responses to inflammation and systemic immune challenge. Studies in mice with CRH and IL-6 deficiency reveal that IL-6 is essential for activation of the pituitary-adrenal axis during inflammatory and other stressors in the absence of CRH.

Urocortin expression in the Edinger-Westphal nucleus is up-regulated by stress and corticotropin-releasing hormone deficiency.

Urocortin is a 40-amino acid mammalian peptide related to CRH and urotensin. The physiological role of urocortin is unknown, but it has been postulated to serve some of the functions previously attributed to CRH. We had earlier found that urocortin messenger RNA (mRNA) expression within the mouse brain is confined to the region of the Edinger-Westphal (EW) nucleus of the midbrain. To further characterize the regulation of the urocortin gene, we first cloned and sequenced the mouse gene, confirming the presence of a single gene in the murine genome. A general survey of mouse tissues using Northern blot analysis revealed the presence of urocortin mRNA only within the midbrain. By in situ hybridization analysis, we found that urocortin mRNA expression in the EW nucleus is responsive to stress, as mRNA levels increased approximately 3-fold after 3 h of restraint. Chronic glucocorticoid treatment, although not affecting basal levels, blocked the stress-induced rise in urocortin mRNA. Using CRH-deficient [knockout (KO)] mice, we examined the effect of combined CRH and glucocorticoid deficiency upon urocortin mRNA expression. As in wild-type (WT) mice, we had previously found that urocortin expression in CRHKO mouse brain was not detected outside of the EW nucleus. However, we found that urocortin expression within the EW of CRHKO mice is up-regulated 2- to 3-fold compared with that in WT mice. This up-regulation is not due to a lack of inhibition by glucocorticoids, as urocortin mRNA levels in the EW nucleus of CRHKO mice did not change after glucocorticoid supplementation. As the EW does not project to any brain regions known to be involved in the behavioral responses to stress, urocortin expressed in this site is unlikely to mediate stress-induced behaviors. On the other hand, as the EW nucleus may play a role in the regulation of the autonomic nervous system and projects to various brain stem nuclei that express the CRH receptor, urocortin originating in the EW may play a role in the regulation of the autonomic nervous system during stress.

Virilising 21-hydroxylase deficiency: timing of newborn screening and confirmatory tests can be crucial.

Early diagnosis of congenital adrenal hyperplasia (CAH) can be lifesaving. With the advent of newborn screening programs employing blood 17-hydroxyprogesterone, fewer cases are missed. Because false positive results occur, especially in premature and low birth weight babies, infants with borderline elevations, although requiring follow-up, are often considered normal. We describe a newborn female that, despite severe virilization, only had a borderline elevation in 17-hydroxyprogesterone (17OHP) on newborn screening, as well as on initial confirmatory testing in our clinical laboratory. Our confirmatory method, which employs high performance liquid chromatography (HPLC) separation, because of its high specificity, yields steroid values from both normal children and those with CAH that are lower than found with older, less specific methods. Given the heterogeneity of phenotypes of CAH, less severe forms, especially in males, could result in marginally abnormal laboratory results early in life, with possible adverse effects later. Although in retrospect the diagnosis of the described patient was clear and not a novel entity, we consider it an important example for several reasons. It emphasizes the broad range of 17OHP levels in CAH, the lack of correlation of these levels with clinical phenotype and the importance of the timing of both screening and confirmatory tests. Due to the complexity of interpreting these tests, any screening program for CAH should be controlled by an experienced pediatric endocrinologist.

Corticotropin-releasing hormone stimulates angiogenesis and epithelial tumor growth in the skin.

The hypothalamic neuropeptide corticotropin-releasing hormone is the major hypothalamic regulator of the endocrine pituitary-adrenal axis. Corticotropin-releasing hormone is also expressed in many peripheral sites, where its functions are unclear. It is also secreted by diverse neoplasms, where it may be associated with malignant behavior. To provide information regarding the function of corticotropin-releasing hormone in peripheral sites and in tumors, we asked whether corticotropin-releasing hormone has angiogenic properties. In vitro, we found that human corticotropin-releasing hormone specifically stimulates endothelial chemotaxis via a corticotropin-releasing hormone receptor-dependent mechanism. In vivo, subcutaneous inoculation of nude mice with human epithelial tumor cells engineered to secrete corticotropin-releasing hormone was associated with significantly enhanced angiogenesis (2.3-fold over control) and tumor growth (5-fold over control). Peripheral corticotropin-releasing hormone may thus enhance local angiogenesis, which may provide clues to its function outside of the nervous system.

CRH-deficient mice have a normal anorectic response to chronic stress.

Many studies have implicated corticotropin-releasing hormone (CRH) as a mediator of stress-induced decreases in food intake. However, urocortin, sauvagine, and urotensin, other members of the family of CRH-like molecules, have also been shown to be potent inhibitors of food intake. This raises the possibility that a CRH-related molecule might also be responsible for stress-induced anorexia. We therefore examined the effects of three chronic stressors, repetitive daily restraint, turpentine abscess, and surgical stress, upon food intake in wildtype and CRH-deficient mice created by targeted inactivation of the CRH gene. We have found that both genotypes have similar basal food intake which initially decreases to the same degree following initiation of each stress paradigm. Food intake also recovers following the same time course and to the same degree in both genotypes. Therefore, CRH is not necessary for decreases in food-intake induced by the chronic stressors examined in this study.

Stress-induced behaviors require the corticotropin-releasing hormone (CRH) receptor, but not CRH.

Corticotropin-releasing hormone (CRH) is a central regulator of the hormonal stress response, causing stimulation of corticotropin and glucocorticoid secretion. CRH is also widely believed to mediate stress-induced behaviors, implying a broader, integrative role for the hormone in the psychological stress response. Mice lacking the CRH gene exhibit normal stress-induced behavior that is specifically blocked by a CRH type 1 receptor antagonist. The other known mammalian ligand for CRH receptors is urocortin. Normal and CRH-deficient mice have an identical distribution of urocortin mRNA, which is confined to the region of the Edinger-Westphal nucleus, and is absent from regions known to mediate stress-related behaviors. Since the Edinger-Westphal nucleus is not known to project to any brain regions believed to play a role in anxiety-like behavior, an entirely different pathway must be postulated for urocortin in the Edinger-Westphal nucleus to mediate these behaviors in CRH-deficient mice. Alternatively, an unidentified CRH-like molecule other than CRH or urocortin, acting through the CRH receptors in brain regions believed to mediate stress-induced behaviors, may mediate the behavioral response to stress, either alone or in concert with CRH.