Potentiation of the classic ovine corticotrophin releasing hormone stimulation test by the combined administration of small doses of lysine vasopressin

Sex differences in the hypothalamic-pituitary-adrenal axis: An obstacle to antidepressant drug development?

Hypothalamic-pituitary-adrenal (HPA) axis dysfunction has long been implicated in the pathophysiology of depression, and HPA axis-based compounds have served as potential new therapeutic targets, but with no success. This review details sex differences from animal and human studies in the function of HPA axis elements (glucocorticoids, corticotropin releasing factor, and vasopressin) and related compounds tested as candidate antidepressants. We propose that sex differences contribute to the failure of novel HPA axis-based drugs in clinical trials. Compounds studied preclinically in males were tested in clinical trials that recruited more, if not exclusively, women, and did not control, but rather adjusted, for potential sex differences. Indeed, clinical trials of antidepressants are usually not stratified by sex or other important factors, although preclinical and epidemiological data support such stratification. In conclusion, we suggest that clinical testing of HPA axis-related compounds creates an opportunity for targeted, personalized antidepressant treatments based on sex. LINKED ARTICLES: This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc.

Arginine vasotocin is the major adrenocorticotropic hormone-releasing factor in the bullfrog Rana catesbeiana

In a previous study, we showed that corticotropin-releasing factor (CRF) is the major thyroid-stimulating hormone (TSH)-releasing factor in the bullfrog (Rana catesbeiana) hypothalamus. Our findings prompted us to ascertain whether CRF or arginine vasotocin (AVT), a known adrenocorticotropic hormone (ACTH) secretagogue in several vertebrates, is the main stimulator of the release of ACTH from the bullfrog pituitary. Both the frog CRF and AVT stimulated the release of immunoassayable ACTH from dispersed anterior pituitary cells in vitro in a concentration-dependent manner. AVT, however, exhibited far more potent ACTH-releasing activity than CRF. Although CRF by itself weakly stimulated ACTH release, it acted synergistically with AVT to enhance the release of ACTH markedly. Mesotocin and AVT-related peptides such as hydrin 1 and hydrin 2 showed relatively weak ACTH-releasing activity. Subsequently, cDNAs encoding the bullfrog AVT V1a-type and V1b-type receptors were molecularly cloned. Reverse transcriptase-PCR using specific primers revealed that the anterior lobe of the pituitary predominantly expressed AVT V1b-type receptor mRNA but scarcely expressed AVT V1a-type receptor mRNA. Abundant signals for V1b-type receptor mRNA in the corticotropes were also detected by in situ hybridization. The results obtained by the experiments with the bullfrog pituitary indicate that AVT acts as the main ACTH-releasing factor through the AVT V1b-type receptor and that CRF acts synergistically with AVT to enhance the release of ACTH.

Stress responsiveness of the hypothalamic-pituitary-adrenal axis: age-related features of the vasopressinergic regulation

The hypothalamic-pituitary-adrenal (HPA) axis plays a key role in adaptation to environmental stresses. Parvicellular neurons of the hypothalamic paraventricular nucleus secrete corticotrophin releasing hormone (CRH) and arginine vasopressin (AVP) into pituitary portal system; CRH and AVP stimulate adrenocorticotropic hormone (ACTH) release through specific G-protein-coupled membrane receptors on pituitary corticotrophs, CRHR1 for CRH and V1b for AVP; the adrenal gland cortex secretes glucocorticoids in response to ACTH. The glucocorticoids activate specific receptors in brain and peripheral tissues thereby triggering the necessary metabolic, immune, neuromodulatory, and behavioral changes to resist stress. While importance of CRH, as a key hypothalamic factor of HPA axis regulation in basal and stress conditions in most species, is generally recognized, role of AVP remains to be clarified. This review focuses on the role of AVP in the regulation of stress responsiveness of the HPA axis with emphasis on the effects of aging on vasopressinergic regulation of HPA axis stress responsiveness. Under most of the known stressors, AVP is necessary for acute ACTH secretion but in a context-specific manner. The current data on the AVP role in regulation of HPA responsiveness to chronic stress in adulthood are rather contradictory. The importance of the vasopressinergic regulation of the HPA stress responsiveness is greatest during fetal development, in neonatal period, and in the lactating adult. Aging associated with increased variability in several parameters of HPA function including basal state, responsiveness to stressors, and special testing. Reports on the possible role of the AVP/V1b receptor system in the increase of HPA axis hyperactivity with aging are contradictory and requires further research. Many contradictory results may be due to age and species differences in the HPA function of rodents and primates.

Desmopressin as a pharmacological tool in vasopressinergic hypothalamus-pituitary-adrenal axis modulation: neuroendocrine, cardiovascular and coagulatory effects

Arginine-vasopressin (AVP) is a physiological co-activator of the hypothalamus-pituitary-adrenal (HPA) axis, together with corticotrophin releasing hormone (CRH). A synthetic analogue of AVP, desmopressin (dDAVP), is often used as a pharmacological tool to assess co-activation in health and disease. The relation between dDAVP's neuroendocrine, cardiovascular, pro-coagulatory, anti-diuretic and non-specific stress effects has not been studied. A randomized, double-blind, placebo-controlled, three-way crossover study was performed in 12 healthy male and female volunteers (6 : 6). dDAVP was administered intravenously as a 10 μg bolus (over 1 min) or a 30 μg incremental infusion (over 60 min). Neuroendocrine, cardiovascular, pro-coagulatory, anti-diuretic effects and adverse events (AEs) were recorded, and autonomic nervous system (ANS) activation evaluated. The incremental infusion reached 1.8-fold higher dDAVP concentrations than the bolus. Neuroendocrine effects were similar for the 10 μg dDAVP bolus and the 30 μg incremental infusion, while cardiovascular and coagulatory effects were greater with the 30 µg dose. Osmolality and ANS activity remained uninfluenced. AEs corresponded to dDAVP's side-effect profile. In conclusion, the neuroendocrine effects of a 10 μg dDAVP bolus administered over 1 min are similar to those of a 30 μg incremental infusion administered over one hour, despite higher dDAVP concentrations after the infusion. Cardiovascular and coagulatory effects showed clear dose-related responses. A 10 μg dDAVP bolus is considered a safe vasopressinergic function test at which no confounding effects of systemic or autonomic stress were seen.

A pharmacological tool to assess vasopressinergic co-activation of the hypothalamus-pituitary-adrenal axis more integrally in healthy volunteers

Pharmacological function tests consisting of 100 µg hCRH (corticorelin) and 10 µg dDAVP (desmopressin) mimic endogenous hypothalamus-pituitary-adrenal (HPA) axis activation. However, physiological CRH concentrations preclude informative vasopressinergic co-activation (using dDAVP) and independent quantification of both corticotrophinergic (using hCRH) and vasopressinergic (using dDAVP) activation is limited due to administration on separate occasions. This randomized, double-blind, placebo-controlled, partial five-way crossover study in healthy males and females (six : six) examined whether (1) concomitant administration of dDAVP and hCRH provides more informative vasopressinergic co-activation than dDAVP alone; and (2) whether the administration of dDAVP followed two hours later by hCRH can quantify both vasopressinergic and corticotrophinergic activation on a single test day. Combining 10 µg dDAVP with 10 µg and 30 µg hCRH caused dose-related ACTH and cortisol release which was larger than with 10 µg dDAVP alone and respectively comparable to and greater than that induced by 100 µg hCRH. Using 10 µg dDAVP alone demonstrated limited ACTH release while the effects of 100 µg hCRH two hours later were three times as large. ACTH and cortisol released by 10 µg dDAVP returned to baseline prior to 100 µg hCRH administration and dDAVP did not influence the response to subsequent hCRH administration. Dose-related vasopressinergic co-activation of the HPA axis was induced by combining 10 µg dDAVP with 10 µg and 30 µg hCRH. Combining 10 µg dDAVP with 10 µg hCRH induced the potentially most informative vasopressinergic co-activation since it is not restricted by ceiling or flooring effects. The hCRH response was not affected by prior dDAVP, allowing for a practical function test examining both HPA activation routes on the same day.

Metoclopramide as pharmacological tool to assess vasopressinergic co-activation of the hypothalamus-pituitary-adrenal (HPA) axis: a study in healthy volunteers

The synthetic vasopressin (AVP) analogue desmopressin (dDAVP) has been used as pharmacological function test to quantify vasopressinergic co-activation of the hypothalamus-pituitary-adrenal (HPA) axis in the past. Such exogenous vasopressinergic stimulation may induce confounding cardiovascular, pro-coagulatory and anti-diuretic effects and low endogenous corticotrophin-releasing-hormone (CRH) levels may limit its potential to reliably assess co-activation. Alternatively, the dopamine-2-(D2)-antagonist metoclopramide is believed to induce co-activation indirectly by releasing endogenous AVP. We investigated this indirect co-activation with metoclopramide under conditions of low and enhanced endogenous CRH release in healthy volunteers. A randomized, double-blind, placebo-controlled, four-way crossover study was performed in 12 healthy males. CRH release was induced by administering an oral 5-hydroxytryptophan (5-HTP) 200 mg function test. Co-activation was investigated by administering metoclopramide 10mg intravenously around the expected maximal effect of 5-HTP. The neuroendocrine effects were compared to those of metoclopramide alone, the 5-HTP test alone and matching placebo. Metoclopramide safely induced HPA-axis activation by itself, and potently synergized 5-HTP-induced corticotrophinergic activation of the HPA axis. These findings are indicative of vasopressinergic co-activation and suggest a role for metoclopramide as a practical function test for co-activation of the HPA axis. However, its application will be hampered pending clarification of the exact pharmacological mechanism by which metoclopramide induces co-activation of the HPA axis.

Desipramine prevents stress-induced changes in depressive-like behavior and hippocampal markers of neuroprotection

Extracellular signal-regulated kinases (ERKs) are widely implicated in multiple physiological processes. Although ERK1/2 has been proposed as a common mediator of antidepressant action in naive rodents, it remains to be determined whether the ERK1/2 pathway plays a role in depressive disorder. Here, we investigated whether chronic restraint stress (14 days) and antidepressant treatment [desipramine (DMI), 10 mg/kg intraperitoneally] induce changes in animal behavior and hippocampal levels of phospho-ERK1/2 and its substrate phospho-cAMP response element-binding protein (CREB). The results indicated that stress-induced depressive-like behaviors were correlated with an increase in P-ERK1/2 and P-CREB in the hippocampus evaluated by immunoblot analysis. As an indication of CREB activity, we evaluated changes in mRNA levels of its target genes. Brain-derived neurotrophic factor (BDNF) mRNA was reduced by stress, an effect prevented by DMI only in the CA3 area of hippocampus. Bcl-2 mRNA was reduced in all hippocampal regions by stress, an effect independent of DMI treatment. However, immunoblot from hippocampal extracts revealed that stress increased BCL-2 levels, an effect prevented by chronic DMI. These results suggest that ERKs and BDNF may be altered in depressive disorder, modifications that are sensitive to DMI action. In contrast, the stress-induced increase in BCL-2 may correspond to a neuroprotective response.

Anatomy of melancholia: focus on hypothalamic-pituitary-adrenal axis overactivity and the role of vasopressin

Overactivity of the hypothalamic-pituitary-adrenal (HPA) axis characterized by hypercortisolism, adrenal hyperplasia and abnormalities in negative feedback is the most consistently described biological abnormality in melancholic depression. Corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) are the main secretagogues of the HPA/stress system. Produced in the parvicellular division of the hypothalamic paraventricular nucleus the release of these peptides is influenced by inputs from monoaminergic neurones. In depression, anterior pituitary CRH1 receptors are down-regulated and response to CRH infusion is blunted. By contrast, vasopressin V3 receptors on the anterior pituitary show enhanced response to AVP stimulation and this enhancement plays a key role in maintaining HPA overactivity.

Vasopressin as a target for antidepressant development: an assessment of the available evidence

Hyperactivity of the hypothalamic-pituitary-adrenal (HPA) axis is one of the key biological abnormalities described in major depressive disorder, occurring in 30-50% of depressed subjects. Corticotropin-releasing hormone (CRH) and vasopressin (AVP) are the main regulators of this stress system, with the two neuropeptides acting synergistically in bringing about adrenocorticotropin (ACTH) release from the anterior pituitary and cortisol from the adrenal gland. Based on the demonstration of elevated cerebrospinal fluid levels of CRH in depressives, and other evidence, it has been postulated that excess CRH and the resultant increased HPA forward drive form the basis of neuroendocrine dysregulation in depression. However, there is an accumulating body of evidence to support a significant role for AVP in the regulation of pituitary-adrenal activity in health and also in depressive disorder. This review, based on a Medline search from 1980 to 2001, focuses on the functional neuroanatomy, receptor pharmacology, VP synergism with CRH, and the data from clinical and pre-clinical studies that support an important role for AVP in the pathophysiology of major depression. We suggest that future antidepressants may target the vasopressinergic system.

Desmopressin augments pituitary-adrenal responsivity to corticotropin-releasing hormone in subjects with chronic fatigue syndrome and in healthy volunteers

BACKGROUND

Corticotropin-releasing hormone (CRH) and vasopressin (VP) are the two principal neuropeptide regulators of the hypothalamic-pituitary-adrenal axis in man, with VP serving to augment CRH-induced adrenocorticotropic hormone (ACTH) release. Unlike VP, desmopressin (DDAVP), which is a synthetic analogue of VP, when administered alone, has not been shown in healthy subjects to have consistent ACTH-releasing properties. It has been suggested that chronic fatigue syndrome (CFS), characterized by profound fatigue and a constellation of other symptoms, may be caused by a central deficiency of CRH.

METHODS

We administered 100 micrograms ovine CRH (oCRH) and 10 micrograms DDAVP, both alone and in combination, to a group of subjects with CFS, and to a group of healthy volunteers. Our aim was to establish the effect of DDAVP on CRH-induced ACTH release in these two groups.

RESULTS

The delta-ACTH responses to oCRH were attenuated in the CFS (21.0 +/- 4.5 ng/L) compared to the control subjects (57.8 +/- 11.0 ng/L; t = 3.2, df = 21, p < .005). The delta-cortisol responses were also reduced in the CFS (157.6 +/- 40.7 nmol/L) compared to the healthy subjects (303.5 +/- 20.9 nmol/L; t = 3.1, df = 21, p < .01). The delta-ACTH and delta-cortisol responses to DDAVP alone did not differ between the two groups. On administration of both CRH and DDAVP no response differences between the two groups for either ACTH (p = .3) or cortisol output (p = .87) were established. Comparing the ACTH and cortisol responses to CRH and CRH/DDAVP in only those individuals from each group who had both tests, the cortisol output to the combination was significantly greater in the CFS compared to the healthy group. The ACTH output was also increased in the former group, though this was not significant.

CONCLUSIONS

DDAVP augments CRH-mediated pituitary-adrenal responsivity in healthy subjects and in patients with CFS. That DDAVP was capable of normalizing the pituitary-adrenal response to oCRH in the CFS group suggests there may be increased vasopressinergic responsivity of the anterior pituitary in CFS and/or that DDAVP may be exerting an effect at an adrenal level.

Physiological and emotional response to psychological stressors in psychiatric and psychosomatic disorders

Deviations from emotional and physiological homeostasis in humans occur under episodic, chronic, or traumatic stress experiences. These dysregulations can provoke emotional and physical disturbances that may result in stress-related psychiatric or psychosomatic disorders. This brief review discusses a variety of both naturally occurring and experimental stressors and the complexity of intervening variables on cardiovascular and hormonal dysregulations of the hypothalamic-pituitary-adrenal (HPA) axis. In addition to the type, intensity, and duration of the stressor, subject variables such as dispositional factors (e.g., age and sex), personality traits, and coping styles are considered. Finally, emotional and physiological stress responses to naturally occurring stressors and psychological challenge tests in depressed patients and anxiety disorder patients are presented and discussed. Stressors in humans induce emotional arousal, which leads to physiological activation of the central nervous system, an increase of hormones of the HPA axis, and coping reactions on the psychological and behavioral level. Depending on the type, intensity, and duration of the stressor, on personal and psychosocial resources of the individual, stressful situations may provoke emotional and physical disturbances. These dysfunctions may result in psychosomatic or psychiatric disorders. The following brief review intends to discuss a variety of stressors that have been examined in humans in order to gain insight into the complex relationship between physiological and behavioral stress reactions and the occurrence or maintenance of stress related psychosomatic and psychiatric disorders.

Corticotroph axis sensitivity after exercise in endurance-trained athletes

OBJECTIVE

The present study was conducted in order to describe human hypothalamo-pituitary adrenal (HPA) axis adaptation in a model of repeated physical stress (endurance training) that causes a moderate increase in cortisol levels.

SUBJECTS

We performed the same stimulation tests (adrenal stimulation with ACTH or pituitary stimulation with combined CRH/LVP) in a population of 8 endurance-trained athletes in two distinct situations: resting (baseline cortisol values) and 2 h after the end of strenuous exercise (increased cortisol values) to evaluate the HPA axis sensitivity to endogenous sustained increases in cortisol concentrations.

MEASUREMENTS

During these tests, saliva and plasma cortisol (Fs and Fp, respectively) were assessed and compared.

RESULT

Cortisol values in both plasma and saliva at the end of 2 h of exercise were significantly higher than in rested controls: Fs 11.5 +/- 1.3 vs 6.5 +/- 0.8 nmol.l-1 and Fp 428 +/- 36 vs 279 +/- 27 nmol.l-1 (post exercise vs post rest sessions, respectively, P < 0.001 for both). After either hormone test (CRH/LVP or ACTH), cortisol levels in plasma and saliva increased similarly when rest was compared to post exercise. Saliva variations (delta %) under exogenous hormone stimulation were dramatically greater than plasma variations. For example, under ACTH stimulation, the relative increments in cortisol were on control day: delta Fs 980 +/- 139 vs delta Fp 218 +/- 43% (saliva vs plasma, respectively, P < 0.05) and on exercise day: delta Fs 605 +/- 89 vs delta Fp 102 +/- 14% (saliva vs plasma, respectively, P < 0.05).

CONCLUSIONS

In endurance-trained athletes, displaying a moderate but sustained endogenous cortisol increase: (1) ACTH responses following pituitary stimulation are not blunted, (2) cortisol responses following maximal adrenal stimulation are not blunted. Our results favour the hypothesis of a decreased pituitary sensitivity to cortisol negative feedback whereas the hypothesis of a major decreased adrenal sensitivity to ACTH was discarded. The greater ability of saliva assays to detect a cortisol increase strongly supports its use in the study of HPA physiology, whether under basal or dynamic conditions.

[Cushing disease in children and in adolescents. Therapeutic results]

BACKGROUND

Trans-sphenoidal surgery is currently the treatment of choice for Cushing's disease in children.

PATIENTS AND METHODS

The results obtained in 20 consecutive patients referred to the Pediatric Endocrinology Department of hôpital Saint-Vincent-de-Paul are reported.

RESULTS

A remission of Cushing's disease was observed in 12/16 (75%) patients in whom surgery was the first treatment. Among these 12 patients, three relapsed (25%) 21 to 80 months after surgery. Four patients were initially treated with steroid synthesis inhibitors: three of those patients were subsequently operated on and their disease remitted. Among the seven patients in whom surgery failed (primary failure or relapse), two were reoperated and also remitted. Taken together, 21 operations were performed and resulted in four immediate failures (19%), three relapses (14%) and 14 long-term remissions (67%, follow-up 40 +/- 35 months). None of the biological, radiological or operative criteria were predictive of the therapeutic results.

CONCLUSION

Our results illustrate the efficacy and limits of trans-sphenoidal surgery for Cushing's disease of children and emphasize the need for a very long follow-up of these patients. Treatment of patients in whom surgery has failed (initially or secondarily) is particularly difficult and requires a multidisciplinary approach.