Increase in substance P and CGRP, but not somatostatin content of innervating dorsal root ganglia in adjuvant monoarthritis in the rat

Neuropeptides, synthesized in dorsal root ganglia (DRG), are implicated in nociception and neurogenic inflammation. Alterations in DRG neuropeptide levels have been described in polyarthritic rats, but these models are associated with widespread systemic disease. Using mild adjuvant-mediated monoarthritis of the left carpal joint we found significant increases in substance P (+69%) and calcitonin gene-related peptide (CGRP; +204+), but not somatostatin in ipsilateral C6/7 DRG. Peptide levels in contralateral DRG and other ipsilateral DRG were unaltered. Substance P and CGRP in DRG may be of importance in the pathogenesis and maintenance of adjuvant arthritis.

Atriopeptin: an endogenous corticotropin-release inhibiting hormone

Activation of the hypothalamic-pituitary-adrenocortical axis is a major component of the body's response to stress. Current theories on the pathophysiology of disorders associated with hyperfunction of the axis, such as depression and Cushing's stress, are based on the concept that anterior pituitary adrenocorticotropin (ACTH) secretion is stimulated by hypothalamic corticotropin-releasing hormones and inhibited by adrenal corticosteroids. Hypothalamic inhibitory control of pituitary ACTH secretion has been also postulated, but has not gained general acceptance because of the lack of definitive evidence for a corticotropin-release inhibiting hormone. It is shown here that in conscious rats stress-induced secretion of ACTH and corticosterone is markedly enhanced by the immunoneutralisation of atriopeptin. Therefore, we propose that atriopeptin is a physiologically relevant corticotropin-release inhibiting hormone.

Ontogeny of 11 beta-hydroxysteroid dehydrogenase in rat brain and kidney

Close regulation of circulating corticosteroid levels during the early postnatal period is crucial for normal development and maturation of the central nervous system. In the first weeks of life cerebral glucocorticoid receptor concentrations are low and the hypothalamic-pituitary-adrenal axis is relatively unresponsive to stress, which might, in part, protect the developing brain from elevated corticosteroid levels. However, central mineralocorticoid receptors are at near adult levels and free glucocorticoid concentrations may approximate adult values as corticosteroid binding globulin is absent. Thus other mechanisms controlling cerebral exposure to corticosteroids may be of importance. 11 beta-Hydroxysteroid dehydrogenase (11 beta-OHSD) determines the access of corticosterone to peripheral mineralocorticoid and glucocorticoid receptors in adults in vivo by metabolizing corticosterone to inactive 11-dehydrocorticosterone. The enzyme has recently been demonstrated in brain subregions and may modulate local corticosteroid-receptor interactions. We therefore examined 11 beta-OHSD bioactivity and messenger RNA (mRNA) expression in the brain, compared with kidney, during the neonatal period. 11 beta-OHSD bioactivity (expressed as the percentage conversion of corticosterone to 11-dehydrocorticosterone) was moderately high in hippocampus and parietal cortex at birth (46 +/- 4% and 48 +/- 5%, respectively), fell significantly to a nadir (32 +/- 1% and 30 +/- 1%, respectively) at postnatal day 10 and then gradually rose to adult values (52 +/- 3% and 58 +/- 3%). By contrast, 11 beta-OHSD activity in cerebellum was high at birth (60 +/- 3%), rose significantly to a peak at postnatal day 10 (74 +/- 3%), and then fell to adult values by postnatal day 15 (64 +/- 3%). Renal 11 beta-OHSD activity was moderately high (69 +/- 3%) at birth and reached adult values (80 +/- 2%) by postnatal day 5. Northern blots showed high and similar expression of a single species of 11 beta-OHSD mRNA from birth to adulthood in the hippocampus. Only low expression of 11 beta-OHSD (two or three separate species) was found in the kidney during the first 2 weeks of life, whereas, in adults high expression of 11 beta-OHSD mRNA was detected in kidney (four species). Using in situ hybridization high 11 beta-OHSD mRNA expression was localized to the neuronal layers of the postnatal hippocampus, neocortex, and cerebellum, and low but detectable expression was found in the neonatal renal cortex. Thus, 11 beta-OHSD is highly expressed in rat brain subregions in the early postnatal period with specific developmental patterns of activity.(ABSTRACT TRUNCATED AT 400 WORDS)

11 beta-hydroxysteroid dehydrogenase in vascular smooth muscle and heart: implications for cardiovascular responses to glucocorticoids

The enzyme 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) converts the active glucocorticoid corticosterone to inactive 11-dehydrocorticosterone in the rat (or cortisol to cortisone in man), thereby protecting renal mineralocorticoid receptors from corticosterone or cortisol and allowing preferential access for aldosterone. We have previously demonstrated that cortisol-induced cutaneous vasoconstriction in man is potentiated by the 11 beta-OHSD inhibitor glycyrrhetinic acid, suggesting that 11 beta-OHSD may protect vascular corticosteroid receptors. In this study we report quantitation of 11 beta-OHSD bioactivity in homogenates of rat aorta, mesenteric artery, caudal artery, and heart, expressed as the percent in vitro conversion of 3H-corticosterone to 3H-11-dehydrocorticosterone. Nicotinamide adenine dinucleotide phosphate (NADP+)-dependent 11 beta-OHSD activity was found in all of these tissues and was significantly higher in resistance vessels than aorta (P less than 0.05) [without NADP+: caudal artery (4.2 +/- 0.2%) greater than mesenteric artery (2.5 +/- 0.7%) = heart (1.67 +/- 0.2%) greater than aorta (0.79 +/- 0.2%); with 200 microM NADP+: caudal artery (43.9 +/- 2.1%) greater than heart (20.6 +/- 1.0%) = mesenteric artery (17.7 +/- 3.1%) = aorta (11.4 +/- 0.4%); heart greater than aorta]. All of these were lower than renal cortex (29.4 +/- 1.8% without NADP+; 82.4 +/- 0.4% with NADP+; P less than 0.001). 3H-11-dehydrocorticosterone was the major metabolite of 3H-corticosterone (greater than 97% of 3H-corticosterone metabolized). Reduction of 3H-11-dehydrocorticosterone to 3H-corticosterone was not detected in these experiments. We also report localization of 11 beta-OHSD-like immunoreactivity by immunohistochemistry using antisera raised against rat liver 11 beta-OHSD, and of 11 beta-OHSD messenger RNA expression by in situ hybridization using complementary RNA probes transcribed from complementary DNA encoding rat liver 11 beta-OHSD. We found 11 beta-OHSD immunoreactivity and messenger RNA expression in vascular and cardiac smooth muscle cytoplasm but not in endothelium. Thus, 11 beta-OHSD is appropriately sited to modulate access of corticosterone to vascular receptors and could influence vascular resistance, cardiac output and thereby blood pressure.

Effect of adrenalectomy and dexamethasone on neuropeptide content of dorsal root ganglia in the rat

Neuropeptides, including substance P (SP), calcitonin gene-related peptide (CGRP) and somatostatin (SS) in dorsal root ganglia (DRG) may play a role in neurogenic inflammation and pain transmission. Adrenal corticosteroids regulate neuropeptide synthesis in some areas of the CNS and may modulate neurogenic inflammation and sensory perception. We have investigated the effects of adrenalectomy and dexamethasone (0.2 mg/kg/day) treatment on neuropeptide content of rat cervical DRG using specific and sensitive radioimmunoassays. In control animals, a differential distribution of neuropeptide was found; SP and CGRP content increased from C4 to C7 in contrast to SS content, which decreased from C4 to C7. Ten days following adrenalectomy, the mean SS content of cervical DRG decreased significantly to 79.6 +/- 4.5% of sham-operated controls. In contrast, SP and CGRP content increased significantly 10 days after adrenalectomy to 134.6 +/- 6.9% and 132.0 +/- 11.6% of sham-operated controls, respectively. The effects of adrenalectomy on CGRP and SS were reversed by administration of dexamethasone. These results suggest that glucocorticoids affect the neuropeptide content of DRG in the adult rat.

Glycyrrhetinic acid, an inhibitor of 11 beta-hydroxysteroid dehydrogenase, alters local cerebral glucose utilization in vivo

11 beta-Hydroxysteroid dehydrogenase (11 beta-OHSD) metabolizes corticosterone (B) to inactive 11-dehydrocorticosterone and thus protects the non-specific renal mineralocorticoid receptor from exposure to B in vivo. There is regional 11 beta-OHSD mRNA expression and bioactivity in brain in vitro, but any in vivo function is unknown. We used the [14C]2-deoxyglucose technique in conscious rats to investigate whether 11 beta-OHSD inhibition with glycyrrhetinic acid alters local cerebral metabolic activity. We found increased glucose use in subregions of the hypothalamus, hippocampus, neocortex and subthalamus. Thus, 11 beta-OHSD may play a role in regulating the effects of B in the brain, in vivo.

Distribution of glucocorticoid and mineralocorticoid receptor messenger RNA expression in human postmortem hippocampus

Corticosteroids bind to hippocampal glucocorticoid (GR) and mineralocorticoid (MR) receptors, thereby affecting behaviour and neurochemical transmission. Rat hippocampus has high levels of both receptors and their messenger RNAs (mRNA), but there is little information on receptors in human brain. We used in situ hybridization to determine the distribution of GR and MR mRNA expression in human hippocampus. Frozen sections of human postmortem hippocampus (5 patients, 58-88 years old, without cerebral pathology) were postfixed in paraformaldehyde and hybridized with 35S-UTP-labelled cRNA probes (transcribed in vitro from human cDNA subclones) under stringent conditions. Control included hybridization with sense probes and heterologous cRNA competition studies. GR mRNA was highly expressed in dentate gyrus, CA3 and CA4, but levels were significantly lower in CA1 and CA2. MR mRNA was also very highly expressed in hippocampus, with significantly higher levels in dentate gyrus and CA2, CA3 and CA4 than CA1. Controls confirmed the specificity of hybridization and there was little hybridization of sense probes. High GR and MR mRNA expression is found in both rat and human hippocampus but the subregional distributions clearly differ between the species.

Reversible pituitary stalk enlargement in cranial diabetes insipidus

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11 beta-Hydroxysteroid dehydrogenase mRNA expression in rat kidney

11 beta-Hydroxysteroid dehydrogenase (11 beta-OHSD) protects nonspecific renal mineralocorticoid receptors from exposure to circulating glucocorticoid in vivo by catalyzing the conversion of corticosterone to inactive 11-dehydrocorticosterone. Although 11 beta-OHSD bioactivity and aldosterone binding sites are found in distal tubular cells, mineralocorticoid receptor and 11 beta-OHSD immunoreactivities are not colocalized. However, there are several kidney isoforms of 11 beta-OHSD, not all of which may be immunoreactive, whereas only a single mRNA species has been described. Using in situ hybridization we found 11 beta-OHSD mRNA is highly expressed in all renal tubular epithelia in the rat. It is therefore likely that 11 beta-OHSD is colocalized with mineralocorticoid receptors in distal tubular cells.

Intracerebroventricular vasopressin reduces CSF absorption rate in the conscious goat

Cerebrospinal fluid (CSF) levels of vasopressin (AVP) are elevated in some disorders associated with raised intracranial pressure. We have previously demonstrated that intracerebroventricular infusion of AVP in the conscious goat leads to elevation of intracranial pressure by a mechanism independent of changes in arterial blood pressure or circulating neurohypophysial peptide concentrations. We have now examined the effect of increasing CSF AVP levels on CSF dynamics using the technique of ventriculo-cisternal perfusion in the conscious goat. Intracerebroventricular perfusion with 5 pmol/min AVP in artificial CSF did not alter CSF formation rate but significantly reduced CSF absorption rate (24% decrease; p less than 0.01), when compared with perfusion using artificial CSF alone. This AVP-mediated reduction in CSF absorption rate may represent increased resistance to resorption of CSF or may reflect the effect of raised intracranial pressure.

Use of in situ hybridization to investigate the regulation of hippocampal corticosteroid receptors by monoamines

The hippocampus receives major noradrenergic and serotoninergic (5-HT) innervations which interact with corticosteroid-sensitive cells. However, the subregional localization of these actions and the corticosteroid receptor types involved have not been defined and current ligand binding techniques for estimating corticosteroid receptors are hampered by several methodological limitations. We have developed in situ hybridization histochemical techniques to allow specific and sensitive estimation of glucocorticoid (GR) and mineralocorticoid receptor (MR) mRNA expression in rat hippocampus. Investigation of the effects of 5,7-dihydroxytryptamine lesions of 5-HT neurons showed significantly reduced GR and MR mRNA expression in some hippocampal subregions. Both abnormal 5-HT neurotransmission and excessive corticosteroid secretion are associated with major affective disorder, particularly depression. The crucial interaction between these two systems may occur, at least in part, at the level of regulation of hippocampal corticosteroid receptor expression.

11Beta-Hydroxysteroid Dehydrogenase Messenger Ribonucleic Acid Expression, Bioactivity and Immunoreactivity in Rat Cerebellum

Abstract 11beta-Hydroxysteroid dehydrogenase (11beta-OHSD) metabolizes corticosterone to inactive 11-dehydrocorticosterone and thus protects non-specific mineralocorticoid receptors from exposure to corticosterone in the kidney in vivo. Clearly, 11beta-OHSD might also regulate corticosterone access to glucocorticoid receptors. We have investigated cerebellum, a tissue with high glucocorticoid receptor, but very low mineralocorticoid receptor levels and have shown marked 11beta-OHSD bioactivity with similar co-substrate requirements and inhibition kinetics to the renal enzyme. 11beta-OHSD messenger ribonucleic acid was expressed in cerebellum and was localized in Purkinje and granule cells. This distribution was confirmed immunohistochemically. Thus, we provide evidence for 11beta-OHSD in cerebellum and suggest that it may regulate the access of corticosterone to glucocorticoid receptors in addition to mineralocorticoid receptors.

Central 5,7-dihydroxytryptamine lesions decrease hippocampal glucocorticoid and mineralocorticoid receptor messenger ribonucleic Acid expression

Abstract Corticosteroids exert effects on the hippocampus by binding to intracellular glucocorticoid and/or mineralocorticoid receptors, but the relative importance of each receptor type in mediating corticosteroid effects is poorly understood. There is an extensive serotoninergic (5-HT) innervation of the hippocampus which interacts with corticosteroid-sensitive cells. We have investigated the effect of intracerebroventricular 5,7-dihydroxytryptamine lesions of 5-HT neurons on glucocorticoid and mineralocorticoid receptor messenger ribonucleic acid (mRNA) expression in the rat hippocampus using in situ hybridization histochemistry. In controls, glucocorticoid receptor mRNA was highly expressed in dentate gyrus granule cell neurons, and in pyramidal cells of CA1 and CA2, but levels in CAS and CA4 were significantly lower. 5,7-dihydroxytryptamine-lesioned animals showed significantly less glucocorticoid receptor mRNA in the dentate gyrus (76% decrease), CA1 (42% decrease) and CA2 (52% decrease; all P<0.05 compared with controls). Mineralocorticoid receptor mRNA was expressed at a similar level in all hippocampal subregions in control rats. 5,7-dihydroxytryptamine lesioning led to a significant decrease in mineralocorticoid receptor mRNA expression in CA3 (56% fall) and CA4 (45% fall; both P<0.05), but not in the other subregions. Thus the 5-HT innervation regulates hippocampal corticosteroid receptor mRNA expression.

Naloxone inhibits oxytocin release at orgasm in man

We examined the effect of naloxone on plasma oxytocin levels during sexual activity in men. Eight normal men took part in a double-blind, two-period, cross-over design. Mean plasma oxytocin rose to 362% of baseline values at orgasm with placebo (saline) but showed no increase with naloxone (P less than 0.01). While naloxone had no effect on heart rate or blood pressure at orgasm, a decrease in the level of subjective arousal and pleasure at orgasm was noted. We conclude that opioid receptor blockade with naloxone has an inhibitory effect on the neural pathways mediating the oxytocin response at orgasm.

11 beta-hydroxysteroid dehydrogenase bioactivity and messenger RNA expression in rat forebrain: localization in hypothalamus, hippocampus, and cortex

In peripheral aldosterone target sites (e.g., kidney), 11 beta-hydroxysteroid dehydrogenase (11 beta-OHSD) metabolizes corticosterone to inactive 11-dehydrocorticosterone and thus protects mineralocorticoid receptors from exposure to corticosterone in vivo. We have investigated whether 11 beta-OHSD could account for the site-specific differences in corticosteroid receptor sensitivity to corticosterone in rat brain. Enzyme activity, estimated as the percentage conversion of [3H]corticosterone to [3H]11-dehydrocorticosterone in the presence of NADP+ (200 microM), was: hippocampus, 55.8 +/- 2.7%; cortex, 52 +/- 3.1%; pituitary; 40 +/- 2%, hypothalamus, 26.1 +/- 1.2%; brain stem, 21.4 +/- 1.7%; and spinal cord, 12.3 +/- 1.8%. Northern blots, using [32P]dCTP-labeled probes from an 11 beta-OHSD cDNA clone derived from rat liver, showed expression of a single mRNA species in all brain areas, of identical size to 11 beta-OHSD mRNA in liver and kidney. Highest expression was found in hippocampus and cortex. In situ hybridization, using [35S]UTP-labeled cRNA probes, localized high mRNA expression to cerebral cortex (particularly parietal cortex, layer IV), hippocampus (highest in CA3), hypothalamic medial preoptic area and arcuate nuclei and anterior pituitary. In conclusion, there is localized 11 beta-OHSD mRNA expression and enzyme bioactivity in rat brain. The distribution of 11 beta-OHSD corresponds to areas of reduced glucocorticoid or mineralocorticoid receptor affinity for corticosterone. Therefore, 11 beta-OHSD may regulate the access of corticosterone to cerebral mineralocorticoid and/or glucocorticoid receptors and thus modulate corticosteroid effects on brain function.

Effect of naloxone on neurohypophyseal peptide responses to breast feeding and breast stimulation in man

We have investigated the role of endogenous opioid peptides in the release of oxytocin (OT) in response to breast feeding and breast stimulation in humans. Five breast feeding women were studied on two separate occasions within 4 weeks of delivery. Saline or naloxone, 4 mg bolus and 6 mg/h, was administered intravenously, in random order. Blood samples were taken at regular intervals. In the saline-infused group OT rose from a baseline of 1.1 +/- 0.1 pmol/l (mean +/- SEM) to a peak of 7.0 +/- 0.9 after 6 min, and in the naloxone-infused group from 1.0 +/- 0.1 pmol/l to 5.8 +/- 1.3 (P less than 0.05). There were no significant differences between the two groups at any time point. Plasma vasopressin (AVP) did not change. In the second study six women in the luteal phase of the menstrual cycle were investigated on two occasions at least 48 h apart. They were similarly infused with either naloxone or saline in random sequence. A mechanical breast pump provided breast stimulation. In saline-infused women OT levels rose from a baseline of 1.0 +/- 0.1 pmol/l (mean +/- SEM) to a peak of 3.0 +/- 1.1 (P less than 0.05) after 6 min, and in naloxone infused women from 1.1 +/- 0.1 pmol/l to 3.0 +/- 1.4 (NS). There were no differences in OT between the groups. AVP did not change. We conclude that endogenous opioid peptides do not modulate OT release during breast feeding or breast stimulation in women.

Vasopressin antagonist in early postoperative diabetes insipidus

23 patients without diabetes insipidus before transfrontal (hypothalamic) or trans-sphenoidal (pituitary) surgery were studied prospectively to investigate the pathogenesis of early postoperative diabetes insipidus. 12 patients who underwent trans-sphenoidal surgery and who did not develop diabetes insipidus were used as controls. All received prophylactic corticosteroid replacement. Blood samples were obtained immediately after operation, at the onset of diabetes insipidus, and 24 h later. Immediately after trans-sphenoidal pituitary surgery, plasma vasopressin (AVP) was raised but had fallen to subnormal concentrations by the onset of diabetes insipidus. After transfrontal hypothalamic surgery diabetes insipidus occurred sooner and was associated with high plasma AVP immunoreactivity--but the plasma showed no antidiuretic bioactivity and greatly attenuated the antidiuretic response to standard AVP. Early diabetes insipidus after hypothalamic surgery is associated with release of a substance, presumably an analogue, from the damaged hypothalamo-neurohypophyseal system, which acts as an antagonist to normal AVP activity; after trans-sphenoidal operations diabetes insipidus seems to be caused by failure of AVP release.

Neurohypophysial secretion to insulin-induced hypoglycemia and its regulation by endogenous opioids in women

In animals, there is sexual dimorphism of both neurohypophysial peptide secretion in response to stressful stimuli and to the inhibitory effects of opioids. In men, endogenous opioids inhibit the release of oxytocin when AVP secretion is stimulated by insulin-induced hypoglycemia. We have now investigated the role of endogenous opioids in the AVP and oxytocin response to insulin-induced hypoglycemia in women. Twelve subjects, 6 in the follicular and 6 in the luteal phase of the menstrual cycle, were infused on 2 occasions with naloxone (4 mg bolus and 6 mg/h) or saline. Soluble insulin (Human Actrapid, 0.15 mu/kg, iv) was given and serial blood samples taken. Blood sugar fell significantly (p less than 0.05) and similarly in all groups. In the follicular phase hypoglycemia led to a rise in plasma AVP from 1.3 +/- 0.2 to 1.8 +/- 0.2 pmol/l in the saline-infused subjects (NS), and from 1.0 +/- 0.1 to 2.0 +/- 0.2 pmol/l in the naloxone-infused (p less than 0.05). AVP rose similarly from 0.6 +/- 0.1 to 1.6 +/- 0.5 pmol/l (p less than 0.05) in the luteal phase controls and from 0.8 +/- 0.1 to 1.5 +/- 0.3 pmol/l (p less than 0.05) in naloxone-infused subjects in the luteal phase. There were no significant differences between any of these groups. There were no significant changes in plasma oxytocin in any group. We therefore conclude that in women, unlike men, endogenous opioids do not modulate oxytocin or vasopressin release during insulin-induced hypoglycemia.

Diurnal variation of plasma corticosterone in depression

Hypersecretion of cortisol is associated with depression. Because corticosterone may show greater responsiveness than cortisol to exogenous ACTH in depression and it has behavioural effects in rodents, we determined whether depression is also associated with hypersecretion of corticosterone. Both cortisol and corticosterone were significantly elevated in depression, with greatest differences from control subjects during the afternoon and evening. The ratio of corticosterone/cortisol was constant and similar throughout the day in both depressed patients and controls. We conclude that there is no disproportionate endogenous hypersecretion of corticosterone in depression.

The frequency and natural history of diabetes insipidus in children with Langerhans-cell histiocytosis

Diabetes insipidus is a well-recognized complication of Langerhans-cell histiocytosis (histiocytosis X), but its frequency and natural history are not well defined. Of 52 children with histiocytosis whom we studied, 12 (23 percent) had diabetes insipidus. Only two children had diabetes insipidus at presentation with histiocytosis, but the cumulative risk that it would develop during the first four years after the presentation and diagnosis of histiocytosis was found to be 42 percent. Diabetes insipidus occurred most often among children with multisystem disease and those with proptosis. To determine the natural history of diabetes insipidus in children with histiocytosis, we measured the response of urinary arginine vasopressin to water deprivation every six months in 21 children who did not have diabetes insipidus and who had had histiocytosis for less than four years. Five of the 21 children (24 percent) had subnormal responses during the initial test. One subsequently had spontaneous improvement in the functioning of the posterior pituitary, and diabetes insipidus subsequently developed in two, as it did in one of the children who initially had normal function of the posterior pituitary. Two of the children received irradiation to the pituitary within two to four weeks after diabetes insipidus developed, but they had no improvement in pituitary function. However, diabetes insipidus improved transiently during prednisolone therapy in one of these children and improved permanently after etoposide therapy in another child. We conclude that prospective study with the use of a simple water-deprivation test will allow partial defects of posterior-pituitary function to be detected in patients with histiocytosis and will permit a more appropriate evaluation of the effects of therapeutic intervention.

Dependent effect of drinking volume on vasopressin but not atrial peptide in humans

The act of drinking causes a fall in plasma arginine vasopressin (AVP) concentration that precedes changes in plasma osmolality. To investigate the specificity of this drinking stimulus on hormone secretion, six volunteers (5 male, 1 female, aged 22-39 yr) were water deprived for 36 h and then drank 15 ml/kg water at 10-12 degrees C using 15-20 swallowing actions/min over 3.5 +/- 0.5 min (mean +/- SE). This caused a fall in plasma AVP from 4.5 +/- 0.7 to 3.2 +/- 0.5 pmol/l (P less than 0.05) and in thirst (by 5.7 +/- 0.6 on a 10-cm linear analog scale) (P less than 0.05) 5 min after drinking. No significant changes occurred in mean arterial pressure, heart rate, or plasma atrial natriuretic peptide (ANP) concentration. A second study was undertaken to determine whether the reflex inhibition of AVP secretion is activated simply by the act of swallowing regardless of the volume of liquid consumed. The six volunteers were water deprived for 36 h and then sipped and swallowed 1 ml/kg water at 10-12 degrees C using 15-20 swallowing actions/min over 3.0 +/- 0.1 min. There was no change in plasma AVP concentration, although thirst was reduced by 2.3 +/- 0.6 (P less than 0.05) at 5 min. Plasma AVP 10 min after sipping and swallowing (4.2 +/- 0.8 pmol/l) was significantly greater than at 10 min after drinking 15 ml/kg (2.8 +/- 0.5 pmol/l) (P less than 0.05) despite the fact that plasma osmolality at this stage was similar in both studies. We conclude that the drinking-mediated reflex inhibition of AVP secretion in humans is dependent on swallowing an adequate volume and is not accompanied by changes in hemodynamics or in plasma ANP concentration.

Vasopressin and oxytocin responses to hypertonic saline infusion: effect of the opioid antagonist naloxone

Endogenous opioids inhibit the release of oxytocin (OT) when vasopressin (AVP) is secreted in response to acute pharmacological stimuli in man and to a variety of physiological and pharmacological stimuli to animals. We have investigated the effect of naloxone on the AVP and OT responses to hypertonic saline in man. In two separate studies, six male subjects were infused with hypertonic saline (675 mmol/l, 0.05 ml/kg/min for 2 h) and either naloxone (4 mg bolus and 6 mg/h) or normal saline in random order. Hypertonic saline resulted in similar significant rises of plasma osmolality and AVP in both groups and a small but significant decrease in OT. Thirst sensation was not altered by naloxone. Endogenous opioids do not play an important role in the suppression of OT release when AVP is secreted in response to an osmotic stimulus in man.

A rational approach for assessing the hypothalamo-pituitary-adrenal axis

In 70 paired insulin tolerance tests (ITTs) and short 'Synacthen' tests (SSTs), both of which have been advocated for assessment of the hypothalamo-pituitary-adrenal (HPA) axis, there were 51 passes on both tests, 9 failures on both, and 10 discrepant results (9 failures on the SST, 1 failure on the ITT). There was a close correlation between the maximum cortisol value achieved in the two tests. A survey of British endocrinologists showed that only 24% used the SST to assess the HPA axis. It is suggested that the SST should be used for the initial assessment of the HPA axis and the ITT reserved for patients who fail the SST, those on corticosteroid therapy, and those who have had an acute pituitary insult within 14 days.

Opioid-mediated inhibition of oxytocin during insulin-induced hypoglycemic stimulation of vasopressin in man

We have investigated the importance of endogenous opioids in the differential control of neurohypophysial peptide secretion. The effect of the opioid antagonist naloxone on the vasopressin and oxytocin responses to insulin-induced hypoglycemia was studied in 14 male subjects. Either saline (N = 8) or naloxone (4 mg bolus + 6 mg/h, N = 6) was infused iv during the study. After 60 min infusion soluble insulin 0.15 U/kg was injected. Naloxone infusion for 60 min did not alter basal plasma AVP or OT levels. Insulin-induced hypoglycemia led to a significant rise in plasma AVP in both saline and naloxone-infused subjects (P less than 0.05), which was maximal 45 min after insulin. There was no significant difference in the plasma AVP response to hypoglycemia between the 2 groups. Saline-infused subjects did not show any change in plasma OT in response to hypoglycemia whilst during concurrent naloxone infusion there was a significant rise in OT from 1.9 +/- 0.4 pmol/l before insulin to 3.2 +/- 1.3 pmol/l at 45 min (P less than 0.05). We conclude that there is opioid-mediated inhibition of OT which prevents its release when AVP is secreted in response to insulin-induced hypoglycemia.

Endogenous opioids inhibit oxytocin release during nicotine-stimulated secretion of vasopressin in man

The effects of the opioid antagonist naloxone on the vasopressin (AVP) and oxytocin (OT) responses to nicotine were studied in male non-smokers (21-30 years old). Either saline (n = 6) or naloxone (4 mg bolus + 6 mg/h, n = 6) was infused i.v. during the study. After 60 min infusion the subjects smoked one high-nicotine content cigarette. Naloxone infusion for 60 min did not alter basal plasma AVP or OT levels. Smoking led to a significant rise in plasma vasopressin in both saline and naloxone-infused subjects (P less than 0.05). There was no significant difference in the plasma AVP response to smoking between the two groups. Saline-infused subjects did not show any change in plasma OT in response to smoking. Naloxone infusion was associated with a significant rise in OT from 1.3 +/- 0.1 pmol/l to 4.3 +/- 2.4 pmol/l 5 min after smoking (P less than 0.05). We conclude that there is endogenous opioid-mediated inhibition of OT which prevents its release when AVP is secreted in response to nicotine in man.

Potentiation of lactation-induced oxytocin secretion by intracerebroventricular oxytocin in the conscious goat

The release of oxytocin into the cerebrospinal fluid (CSF) and plasma of lactating goats was studied following implantation of cisternal and lateral ventricular cannulae. Hand milking was associated with a significant increase in plasma concentrations of oxytocin, but no change in plasma concentrations of vasopressin or CSF concentrations of oxytocin. Intracerebroventricular (i.c.v.) infusion of oxytocin itself (1 pmol/min for 60 min) had no effect on basal plasma levels of oxytocin. It did, however, markedly potentiate the milking-induced increase in plasma oxytocin above the levels achieved during i.c.v. infusion of artificial CSF alone. In the goat, therefore, milking results in a selective release of oxytocin into the plasma, and this release can be potentiated by the presence of increased concentrations of oxytocin in the CSF.

A short water deprivation test incorporating urinary arginine vasopressin estimations for the investigation of posterior pituitary function in children

The value of a 7-h water deprivation test incorporating urinary osmolality and urinary arginine vasopressin (AVP) measurements was investigated in 20 children with suspected anterior or posterior pituitary dysfunction (group A) and 11 presenting with polyuria and polydipsia (group B). A control group of 16 healthy children was also studied. Urinary osmolalities in the control subjects after 7 h of water deprivation were 827-1136 mosmol/kg and urinary AVP 114-320 pmol/l. Of the group A patients, 5 had symptomatic diabetes insipidus with urinary osmolalities less than 300 mosmol/kg, and urinary AVP concentrations of less than 10 pmol/l, and 5 had normal urinary concentrating ability. The other 10 patients had varying degrees of partial diabetes insipidus (urinary AVP 6-53 pmol/l) although in 3 urinary concentrating ability was well maintained (osmolality 650-747 mosmol/kg). In group B, a diagnosis of compulsive water drinking was made in 9 patients, 1 had nephrogenic diabetes insipidus (urinary osmolality 68 mosmol/kg, AVP 782 pmol/l), and the final patient had transient diabetes insipidus. The test described was easy to perform and well tolerated even in young children. Using this test alone, it was possible to identify patients with partial defects of posterior pituitary function even when urinary concentrating ability was maintained, as well as those with complete cranial diabetes insipidus, nephrogenic diabetes insipidus, and compulsive water drinking.

Effect of naloxone on oxytocin and vasopressin release during vaginocervical stimulation in the goat

We have investigated the secretion of oxytocin and arginine vasopressin (AVP) during vaginocervical stimulation in the conscious goat and examined the effect of the opioid antagonist naloxone on peptide release to this stimulus. Goats were implanted with guide tubes overlying the cisterna magna under anaesthesia and allowed to recover. Vaginocervical stimulation for 60 s resulted in a marked (P less than 0.01) release of oxytocin into the plasma but neither plasma AVP nor cerebrospinal fluid (CSF) concentrations of oxytocin changed significantly. In a second series of experiments, unoperated goats were infused with saline or naloxone (4 mg bolus + 12 mg/h) in random order on two separate occasions. Infusion of naloxone had no effect on basal plasma concentrations of oxytocin or AVP. There was a marked and significant (P less than 0.01) potentiation of oxytocin secretion following vaginocervical stimulation in animals infused with naloxone. Naloxone-infused animals showed a significant (P less than 0.01) rise in plasma AVP after stimulation but plasma AVP did not change in the saline-infused controls. We conclude that vaginocervical stimulation leads to the selective release of oxytocin from the neurohypophysis without affecting concentrations of oxytocin in the CSF. Endogenous opioids inhibit the stimulated secretion of oxytocin and AVP in vivo in response to vaginocervical stimulation in the goat.

Acute mastitis; a novel presentation of relapsing polychondritis

A 30 year old female with previous Crohn's disease presented with recurrent cutaneous vasculitis and polyarthritis. She subsequently developed recurrent transient bilateral mastitis with auricular and laryngotracheal chondritis typical of relapsing polychondritis. Acute mastitis is a previously unrecognized association of this disorder.

Intracerebroventricular arginine vasopressin causes intracranial pressure to rise in conscious goats

The effects of intracerebroventricular (i.c.v.) infusion of arginine vasopressin (AVP) on intracranial pressure (ICP), blood pressure (BP) and plasma AVP were investigated in conscious goats. The animals were implanted with ventricular (V) and cisternal (C) cannulae under halothane anaesthesia and allowed to recover prior to experimentation. After 30 min infusion of 20 microliter/min artificial cerebrospinal fluid (CSF) alone, to allow the animals to settle, ICP (estimated at both C and V cannulae), BP and plasma AVP were measured. Then the animals were infused with either artificial CSF alone or 1 or 10 pmol/min AVP for a further 150 min. One pmol/min AVP i.c.v. resulted in significant ICP increases of +2.2 cm CSF (C) and +3.1 cm CSF (V) when compared with artificial CSF alone. Ten pmol/min AVP also led to significant ICP rises of +3.2 cm CSF (C) and +4.2 cm CSF (V). There were no significant changes of BP or plasma AVP during the infusions. We conclude that central infusion of AVP leads to elevated ICP in conscious goats by a mechanism that does not involve BP alteration or changes in plasma AVP.

Changes in oxytocin and vasopressin secretion during sexual activity in men

We measured plasma oxytocin (OT) and arginine vasopressin (AVP) concentrations in 13 normal men during sexual arousal and ejaculation. Mean plasma AVP increased from 1.4 +/- 0.2 (+/- SE) to 5.3 +/- 1.7 pmol/L (P less than 0.05) during arousal, but there was no significant change in OT. In contrast, at ejaculation mean plasma OT rose from a basal value of 1.4 +/- 0.3 to 7.3 +/- 0.6 pmol/L (P less than 0.01) and then fell to basal concentrations in 30 min. AVP, however, had returned to basal levels at the time of ejaculation and remained stable thereafter. We conclude that in man AVP is secreted during sexual arousal, and there is, subsequently, a selective release of OT at the time of ejaculation.

Diurnal rhythm of vasopressin but not of oxytocin in the cerebrospinal fluid of the goat: lack of association with plasma cortisol rhythm

Diurnal rhythms in the concentrations of vasopressin (AVP) and oxytocin in cerebrospinal fluid (CSF) differ between species and are unrelated to changes in the levels of these hormones in the peripheral circulation. We have investigated neurohypophysial hormone rhythms in the CSF of the conscious goat by determining whether they are entrained by daily cycles of light and darkness and by assessing the effect of the suppression of plasma cortisol. Goats were implanted with cisternal cannulae under halothane anaesthesia and allowed to recover. They were accustomed to a 12 h light:12 h darkness lighting cycle (lights on from 07.30 to 19.30 h). After initial serial CSF and plasma sampling the daily cycle of light and darkness was reversed. Three goats were kept in constant light for 8 days before the study and five were given dexamethasone (5 mg/12 h) for 4 days. There was a significant (P less than 0.01) diurnal variation in CSF concentrations of AVP, with a maximum of 3.6 +/- 0.8 (S.E.M.) pmol/l at 12.00 h and a minimum of 1.4 +/- 0.3 pmol/l at 24.00 h. There were no significant changes in CSF concentrations of oxytocin or plasma AVP. After the light:darkness cycle was reversed the AVP rhythm in the CSF was disrupted after 24 h and reversed after 8 days. The diurnal rhythm of AVP in CSF persisted in animals exposed to constant light. After treatment with dexamethasone plasma cortisol was suppressed and showed no diurnal rhythm but the AVP rhythm in CSF remained unchanged.

Neurohypophyseal peptide function during early postoperative diabetes insipidus

Neurohypophyseal function has been investigated in 11 children undergoing pituitary or suprasellar surgery. All had corticosteroid and thyroxine replacement; 9 developed diabetes insipidus (DI) within 1-12 h of operation. At the onset of DI, the plasma vasopressin (AVP) concentration was 3.9 +/- 1.2 pmol/l, considerably higher values usually associated with cranial DI (less than 0.9 pmol/l). AVP fell significantly to 1.1 +/- 0.2 pmol/l by the second day of DI. There was a similar change of levels of the AVP prohormone/carrier peptide, neurophysin I, but plasma oxytocin did not change significantly. High performance liquid chromatography of plasma at the onset of DI revealed a major peak that coeluted with synthetic AVP and two smaller peaks of AVP immunoreactivity. Seven patients required very large doses of desamino-8-D-arginine vasopressin (DDAVP) during the first day; 4 needed smaller doses on day 2. Water deprivation tests were performed on days 6 and 14 after operation in 5 patients with prolonged DI (2 with a triple response). There were no differences in plasma AVP on the two occasions but urinary AVP excretion rate was significantly higher on day 6 (2.4 +/- 0.8 pmol/h) than day 14 (0.7 +/- 0.3 pmol/h). It is concluded that early postoperative DI is not due to decreased levels of circulating AVP but may be related to the release of biologically inactive precursors from the damaged neurohypophysis. These may lead to renal refractoriness to AVP. There is a higher urinary AVP excretion rate on day 6 than day 14 after operation in both patients with a triple response and those with uninterrupted DI. Other factors may determine whether or not a transient resolution phase of DI occurs.

Elevated cerebrospinal fluid vasopressin in motor neuron disease

CSF vasopressin levels were significantly elevated in eight patients with motor neuron disease (2.5 +/- 0.4 pmol/l) compared with controls (0.7 +/- 0.1 pmol/l). CSF oxytocin and plasma vasopressin concentrations were similar in the two groups. This finding may be a primary part of the disease process or an epiphenomenon related to increased autonomic and descending pathway activity secondary to abnormal function and/or loss of anterior horn cells.

The plasma arginine vasopressin response to insulin-induced hypoglycaemia in children with short stature is related to age and the onset of puberty

The plasma arginine vasopressin (AVP) response to insulin-induced hypoglycaemia was investigated in 27 children with short stature. None had diabetes insipidus. Six patients were excluded from further analysis because of hypothalamo-pituitary dysfunction. Of the remainder, 14 were prepubertal (Tanner 1) and seven were pubertal (Tanner 2-4). Both groups had similar height velocity retardation. There was a significant rise of AVP of 3.4 +/- 1.3 pmol/l at 30 min in the pubertal group (P less than 0.05) but no significant change in prepubertal patients. There was a significant relationship between chronological age and AVP response 30 min after insulin (r = 0.45, P less than 0.05) and a closer correlation between bone age and AVP response (r = 0.62, P less than 0.01). The data suggest that insulin-induced hypoglycaemia does not reliably stimulate AVP secretion in children and that this response is related to age and pubertal stage.

Increased renal sensitivity to vasopressin in two patients with essential hypernatremia

Patients with essential hypernatremia maintain urinary concentrating ability despite plasma hyperosmolality and low plasma vasopressin concentrations. We investigated renal sensitivity to ultralow dose vasopressin infusions in two patients with a syndrome of hypodipsia, hypernatremia with selective osmoreceptor dysfunction, early puberty, and aggressive behavior. The patients were water loaded until a hypotonic diuresis was established. Vasopressin was infused in stepwise increments from 0.4-12 fmol/kg X min. Both patients had increased renal sensitivity to vasopressin, achieving negative free water clearance at infusion rates of 0.4 and 4 fmol/kg X min (normal greater than or equal to 6). Treatment for 3 months with 1-desamino-8-D-arginine vasopressin (DDAVP) led to an improvement in behavior and the reporting, for the first time, of a sensation of thirst. After DDAVP therapy both patients had a reduction of their renal sensitivity to infused vasopressin. We conclude that untreated patients with essential hypernatremia have increased renal sensitivity to vasopressin which is reduced by DDAVP administration.

Oral hypertonic saline causes transient fall of vasopressin in humans

After dehydration, oral rehydration causes a fall in plasma arginine vasopressin (AVP) that precedes changes in plasma osmolality. To investigate further the stimulus for this effect, its specificity, and association with thirst, six volunteers were deprived of water for 24 h and given a salt load on two separate occasions. On each study day they then drank rapidly 10 ml/kg of either tap water or hypertonic saline (360 mosmol/kg). There was a significant fall in plasma AVP from 2.0 +/- 0.3 to 1.2 +/- 0.4 pmol/l (P less than 0.05) 5 min after drinking water and from 1.8 +/- 0.3 to 0.9 +/- 0.2 pmol/l (P less than 0.05) after hypertonic saline. Plasma osmolality fell 30-60 min after water and was unchanged after saline. Plasma renin activity, oxytocin, and total protein all remained unchanged. All subjects reported diminished thirst after hypertonic saline. Gargling with water reduced thirst but did not affect plasma AVP. There appears to be a drinking-mediated neuroendocrine reflex that decreases plasma AVP irrespective of the osmolality of the liquid consumed. The sensation of thirst did not correlate with plasma osmolality and was not always related to plasma AVP concentration.