Vasopressin Concentrations Research Articles

Effect of tolvaptan on renal handling of water and sodium, GFR and central hemodynamics in autosomal dominant polycystic kidney disease during inhibition of the nitric oxide system: a randomized, placebo-controlled, double blind, crossover study

BackgroundTolvaptan slows progression of autosomal dominant polycystic kidney disease (ADPKD) by antagonizing the vasopressin-cAMP axis. Nitric oxide (NO) stimulates natriuresis and diuresis, but its role is unknown during tolvaptan treatment in ADPKD.MethodsEighteen patients with ADPKD received tolvaptan 60 mg or placebo in a randomized, placebo-controlled, double blind, crossover study. L-NMMA (L-NG-monomethyl-arginine) was given as a bolus followed by continuous infusion during 60 min. We measured: GFR, urine output (UO), free water clearance (CH2O), fractional excretion of sodium (FENa), urinary excretion of aquaporin-2 channels (u-AQP2) and epithelial sodium channels (u-ENaCγ), plasma concentrations of vasopressin (p-AVP), renin (PRC), angiotensinII (p-AngII), aldosterone (p-Aldo), and central blood pressure (cBP).ResultsDuring tolvaptan with NO-inhibition, a more pronounced decrease was measured in UO, CH2O (61% vs 43%) and FENa (46% vs 41%) after placebo than after tolvaptan; GFR and u-AQP2 decreased to the same extent; p-AVP increased three fold, whereas u-ENaCγ, PRC, p-AngII, and p-Aldo remained unchanged. After NO-inhibition, GFR increased after placebo and remained unchanged after tolvaptan (5% vs −6%). Central diastolic BP (CDBP) increased to a higher level after placebo than tolvaptan. Body weight fell during tolvaptan treatment.ConclusionsDuring NO inhibition, tolvaptan antagonized both the antidiuretic and the antinatriuretic effect of L-NMMA, partly via an AVP-dependent mechanism. U-AQP2 was not changed by tolvaptan, presumeably due to a counteracting effect of elevated p-AVP. The reduced GFR during tolvaptan most likely is caused by the reduction in extracellular fluid volume and blood pressure.Trial registrationClinical Trial no: NCT02527863. Registered 18 February 2015.

Validation of Surrogates of Urine Osmolality in Population Studies

Background: The importance of vasopressin and/or urine concentration in various kidney, cardiovascular, and metabolic diseases has been emphasized recently. Due to technical constraints, urine osmolality (U_osm), a direct reflect of urinary concentrating activity, is rarely measured in epidemiologic studies. Methods: We analyzed 2 possible surrogates of U_osm in 4 large population-based cohorts (total n = 4,247) and in patients with chronic kidney disease (CKD, n = 146). An estimated U_osm (eU_osm) based on the concentrations of sodium, potassium, and urea, and a urine concentrating index (UCI) based on the ratio of creatinine concentrations in urine and plasma were compared to the measured U_osm (mU_osm). Results: eU_osm is an excellent surrogate of mU_osm, with a highly significant linear relationship and values within 5% of mU_osm (r = 0.99 or 0.98 in each population cohort). Bland-Altman plots show a good agreement between eU_osm and mU_osm with mean differences between the 2 variables within ±24 mmol/L. This was verified in men and women, in day and night urine samples, and in CKD patients. The relationship of UCI with mU_osm is also significant but is not linear and exhibits more dispersed values. Moreover, the latter index is no longer representative of mU_osm in patients with CKD as it declines much more quickly with declining glomerular filtration rate than mU_osm. Conclusion: The eU_osm is a valid marker of urine concentration in population-based and CKD cohorts. The UCI can provide an estimate of urine concentration when no other measurement is available, but should be used only in subjects with normal renal function.

Perinatal exposure to organohalogen pollutants decreases vasopressin content and its mRNA expression in magnocellular neuroendocrine cells activated by osmotic stress in adult rats

Polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) are environmental pollutants that produce neurotoxicity and neuroendocrine disruption. They affect the vasopressinergic system but their disruptive mechanisms are not well understood. Our group reported that rats perinatally exposed to Aroclor-1254 (A1254) and DE-71 (commercial mixtures of PCBs and PBDEs) decrease somatodendritic vasopressin (AVP) release while increasing plasma AVP responses to osmotic activation, potentially emptying AVP reserves required for body-water balance. The aim of this research was to evaluate the effects of perinatal exposure to A1254 or DE-71 (30mgkg/day) on AVP transcription and protein content in the paraventricular and supraoptic hypothalamic nuclei, of male and female rats, by in situ hybridization and immunohistochemistry. cFOS mRNA expression was evaluated in order to determine neuroendocrine cells activation due to osmotic stimulation. Animal groups were: vehicle (control); exposed to either A1254 or DE-71; both, control and exposed, subjected to osmotic challenge. The results confirmed a physiological increase in AVP-immunoreactivity (AVP-IR) and gene expression in response to osmotic challenge as reported elsewhere. In contrast, the exposed groups did not show this response to osmotic activation, they showed significant reduction in AVP-IR neurons, and AVP mRNA expression as compared to the hyperosmotic controls. cFOS mRNA expression increased in A1254 dehydrated groups, suggesting that the AVP-IR decrease was not due to a lack of the response to the osmotic activation. Therefore, A1254 may interfere with the activation of AVP mRNA transcript levels and protein, causing a central dysfunction of vasopressinergic system.

Effect of sodium nitrite on renal function and sodium and water excretion and brachial and central blood pressure in healthy subjects: a dose-response study

Sodium nitrite (NaNO2) is converted to nitric oxide (NO) in vivo and has vasodilatory and natriuretic effects. Our aim was to examine the effects of NaNO2 on hemodynamics, sodium excretion, and glomerular filtration rate (GFR). In a single-blinded, placebo-controlled, crossover study, we infused placebo (0.9% NaCl) or 0.58, 1.74, or 3.48 μmol NaNO2·kg-1·h-1 for 2 h in 12 healthy subjects, after 4 days of a standard diet. Subjects were supine and water loaded. We measured brachial and central blood pressure (BP), plasma concentrations of renin, angiotensin II, aldosterone, arginine vasopressin (P-AVP), and plasma nitrite (P-[Formula: see text]), GFR by Cr-EDTA clearance, fractional excretion of sodium (FENa) free water clearance (CH2O), and urinary excretion rate of guanosine 3',5'-cyclic monophosphate (U-cGMP). The highest dose reduced brachial systolic BP (5.6 mmHg, P = 0.003), central systolic BP (5.6 mmHg, P = 0.035), and CH2O (maximum change from 3.79 to 1.27 ml/min, P = 0.031) and increased P-[Formula: see text] (from 0.065 to 0.766 μmol/l, P < 0.001), while reducing U-cGMP (from 444 to 247 pmol/min, P = 0.004). GFR, FENa, P-AVP, and the components in the renin-angiotensin-aldosterone system did not change significantly. In conclusion, intravenous NaNO2 induced a dose-dependent reduction of brachial and central BP. The hemodynamic effect was not mediated by the renin-angiotensin-aldosterone system. NaNO2 infusion resulted in a vasopressin-independent decrease in CH2O and urine output but no change in urinary sodium excretion or GFR. The lack of increase in cGMP accompanying the increase in [Formula: see text] suggests a direct effect of nitrite or nitrate on the renal tubules and vascular bed with little or no systemic conversion to NO.

Studies of Vasopressin Secretion in Krushinskii–Molodkina Rats in Normal Conditions and during Convulsive Seizures

The aim of the present work was to study the secretory activity of vasopressinergic neurons in the hypothalamus in Krushinskii–Molodkina rats, which have a predisposition to audiogenic epilepsy, in normal conditions and during audiogenic convulsive seizures. Serum vasopressin and neurohypophyseal neurophysin II levels were compared in Wistar and Krushinskii–Molodkina rats. These studies demonstrated a decreased blood vasopressin level and an increased neurohypophyseal neurophysin II level in rats predisposed to audiogenic epilepsy, which is evidence for inhibition of the release of vasopressin into the blood. Analysis of vasopressin levels at different stages of convulsive seizures revealed a significant increase in the plasma vasopressin concentration at the clinic-tonic stage of convulsive seizures. Thus, this is the first study demonstrating that Krushinskii–Molodkina rats predisposed to audiogenic epilepsy have lower levels of vasopressinergic neuron secretory activity than sound-insensitive Wistar rats. A significant increase in plasma vasopressin at the clonic-tonic stage of convulsive seizures is evidence that the vasopressinergic neurosecretory system has a role in mediating audiogenic convulsive seizures.

A translational approach for NMDA receptor profiling as a vulnerability biomarker for depression and schizophrenia.

What is the central question of this study? Can the change in plasma arginine vasopressin concentration (P[AVP] ) in response to osmotic stimulation (POsm ) serve as a biomarker for NMDA receptor signalling in schizophrenia and depression and thereby distinguish between these mental illnesses? What is the main finding and its importance? In response to hyperosmotic challenge, depressed subjects showed increased P[AVP] response compared with healthy control and schizophrenic subjects. However, schizophrenic subjects were not different from healthy control subjects in this small sample. The 'P[AVP] response to POsm ' is a suitable biomarker to distinguish depressed versus schizophrenic patients when used with psychiatric screening. This is the first objective physiological measure for schizophrenia or depression. Altered NMDA receptor activity and glutamate signalling might underlie the pathogenesis of both schizophrenia and depression in subgroups of patients. In schizophrenia, pharmacological modelling, post-mortem and imaging data suggest reduced NMDA signalling. In contrast, recent clinical trials demonstrating the efficacy of the NMDA antagonist ketamine in severely depressed patients suggest increased NMDA receptor signalling. We conducted a proof-of-concept study to assess whether there is any in vivo evidence for an inverse association in depression and schizophrenia with respect to the NMDA receptor function. For this purpose, we used a translational approach, based on findings from animal studies that NMDA receptor is a key mediator of arginine vasopressin (AVP) release into the bloodstream. Using hypertonic saline to increase plasma osmolality (POsm ) and thereby induce AVP release, as done in animal studies, we found that in depressed patients the NMDA receptor-mediated AVP release induced by hypertonic saline infusion was significantly increased [0.24 (0.15) pgml-1 mosmol-1 , P<0.05] compared with schizophrenia patients [0.07 (0.07) pgml-1 mosmol-1 ]. Slopes for healthy control subjects were 0.11 (0.09) pgml-1 mosmol-1 which was less than the depressed group. These findings are consistent with implicated NMDA receptor-related abnormalities in depression and schizophrenia in subgroups of patients and provide the first in vivo evidence of this dichotomy.

Condition of neuro-hormonal systems in traumatic brain injury and influence of Carbacetam

Use of GABA-ergic modulators in the traumatic brain injury (TBI) is actively investigated; their positive influence on brain circulation, inhibition of glutamate excitotoxicity, decrease of free radical damage, improvement of metabolism and power supply of neurons is determined. However, influence on functioning of neuro-hormonal systems in TBI isn't studied. The goal of given study was to investigate the Carbacetam effects on the condition of neuro-hormonal system in dynamics of experimental TBI. Methods. Research was carried out on white rat-males, age of six months, weighing 180–220 g. TBI was modeled by V. N. Elskyy and S. V. Ziablitsev model (2008) with the observance of Declaration of Helsinki adopted by the World Medical Association General Assembly, and general norms and principles of European Convention for the Protection of Vertebrate Animals. In comparison group 1 ml of normal saline solution was injected intraperitoneally. In animals of experimental groups 1 and 2 Carbacetam and Actovegin were injected intraperitoneally in doses of 5 mg/kg and 16 mg/kg of body weight, respectively, within 10 days after trauma. In blood the content of adrenocorticotropic hormone (ACTH), somatotropic hormone (STH), corticosterone and vasopressin were determined. Results and discussion . Administration of Carbacetam within 10 days after TBI prevented primary hyperactivation and contributed to the preservation of functioning of hypothalamic-neurohypophysis system and hypothalamic-pituitary-adrenal axis. In comparison with Actovegin, renewal of secretion of ACTH, corticosterone and vasopressin against the background of Carbacetam administration happened faster (from the 3 rd to the 7 th days). Administration of Carbacetam promoted prevention of the hyposecretion of STH significantly more than Actovegin. Identified modulating effects of Carbacetam could create conditions for more effective metabolism renewal and reparation processes in TBI. Conclusions . Administration of Carbacetam in the posttraumatic period renews functioning of neuro-hormonal systems more effectively than Actovegin, by prevention of their hyperactivation and exhaustion or excessive inhibition. Such an effect can be considered modulating with a positive restoring effect.

The Resuscitative and Pharmacokinetic Effects of Humeral Intraosseous Vasopressin in a Swine Model of Ventricular Fibrillation.

Twenty-seven Yorkshire-cross swine (60 to 80 kg) were assigned randomly to three groups: HIO (n=9), IV (n=9), and a control group (n=9). Ventricular fibrillation was induced and untreated for two minutes. Chest compressions began at two minutes post-arrest and vasopressin (40 U) administered at four minutes post-arrest. Serial blood specimens were collected for four minutes, then the swine were resuscitated until ROSC or 29 post-arrest minutes elapsed. Fisher's Exact test determined ROSC was significantly higher in the HIO 5/7 (71.5%) and IV 8/11 (72.7%) groups compared to the control 0/9 (0.0%; P=.001). Odds ratios of ROSC indicated no significant difference between the treatment groups (P=.68) but significant differences between the HIO and control, and the IV and control groups (P=.03 and .01, respectively). Analysis of Variance (ANOVA) indicated the mean time to ROSC for HIO and IV was 621.20 seconds (SD=204.21 seconds) and 554.50 seconds (SD=213.96 seconds), respectively, with no significant difference between the groups (U=11; P=.22). Multivariate Analysis of Variance (MANOVA) revealed the maximum plasma concentration (Cmax) and time to maximum concentration (Tmax) of vasopressin in the HIO and IV groups was 71753.9 pg/mL (SD=26744.58 pg/mL) and 61853.7 pg/mL (SD=22745.04 pg/mL); 111.42 seconds (SD=51.3 seconds) and 114.55 seconds (SD=55.02 seconds), respectively. Repeated measures ANOVA indicated no significant difference in plasma vasopressin concentrations between the treatment groups over four minutes (P=.48). The HIO route delivered vasopressin effectively in a swine model of VF. Occurrence, time, and odds of ROSC, as well as pharmacokinetic measurements of HIO vasopressin, were comparable to IV. Burgert JM , Johnson AD , Garcia-Blanco J , Fulton LV , Loughren MJ . The resuscitative and pharmacokinetic effects of humeral intraosseous vasopressin in a swine model of ventricular fibrillation. Prehosp Disaster Med. 2017;32(3):305-310.

Endothelin ETA Receptor Blockade, by Activating ETB Receptors, Increases Vascular Permeability and Induces Exaggerated Fluid Retention.

Endothelin (ET) receptor antagonists have been associated with fluid retention. It has been suggested that, of the two endothelin receptor subtypes, ETB receptors should not be blocked, because of their involvement in natriuresis and diuresis. Surprisingly, clinical data suggest that ETA-selective antagonists pose a greater risk of fluid overload than dual antagonists. The purpose of this study was to evaluate the contribution of each endothelin receptor to fluid retention and vascular permeability in rats. Sitaxentan and ambrisentan as ETA-selective antagonists and bosentan and macitentan as dual antagonists were used as representatives of each class, respectively. ETA-selective antagonism caused a dose-dependent hematocrit/hemoglobin decrease that was prevented by ETB-selective receptor antagonism. ETA-selective antagonism led to a significant blood pressure reduction, plasma volume expansion, and a greater increase in vascular permeability than dual antagonism. Isolated vessel experiments showed that ETA-selective antagonism increased vascular permeability via ETB receptor overstimulation. Acutely, ETA-selective but not dual antagonism activated sympathetic activity and increased plasma arginine vasopressin and aldosterone concentrations. The hematocrit/hemoglobin decrease induced by ETA-selective antagonism was reduced in Brattleboro rats and in Wistar rats treated with an arginine vasopressin receptor antagonist. Finally, the decrease in hematocrit/hemoglobin was larger in the venous than in the arterial side, suggesting fluid redistribution. In conclusion, by activating ETB receptors, endothelin receptor antagonists (particularly ETA-selective antagonists) favor edema formation by causing: 1) fluid retention resulting from arginine vasopressin and aldosterone activation secondary to vasodilation, and 2) increased vascular permeability. Plasma volume redistribution may explain the clinical observation of a hematocrit/hemoglobin decrease even in the absence of signs of fluid retention.

Altered functionality of the corticotrophin-releasing hormone receptor-2 in the hypothalamic paraventricular nucleus of hyperphagic maternally separated rats

Early-life stress induces endocrine and metabolic alterations that increase food intake and overweight in adulthood. The stress response activates the corticotropin-releasing hormone (CRH) and urocortins' (Ucns) system in the hypothalamic paraventricular nucleus (PVN). These peptides induce anorexic effects through CRH-R2 receptor activation; however, chronic stressed animals develop hyperphagia despite of high PVN CRH expression.We analyzed this paradoxical behavior in adult rats subjected to maternal separation (MS) for 180min/daily during post-natal days 2–14, evaluating their body weight gain, food intake, serum corticosterone and vasopressin concentrations, PVN mRNA expression of CRH-R1, CRH-R2, CRH, Ucn2, Ucn3, vasopressin and CRH-R2 protein levels.MS adults increased their feeding, weight gain as well as circulating corticosterone and vasopressin levels, evincing chronic hyperactivity of the stress system. MS induced higher PVN CRH, Ucn2 and CRH-R2 mRNA expression and protein levels of CRH-R2 showed a tendency to decrease in the cellular membrane fraction. An intra-PVN injection of the CRH-R2 antagonist antisauvagine-30 in control adults increased receptor's mRNA expression, mimicking the observed PVN receptor's up-regulation of early-life MS adults.An injection of Ucn-2 directly into the PVN reduced food intake and increased PVN pCREB/CREB ratio in control animals; in contrast, Ucn-2 was unable to reduce food intake and enhance phosphorylated-CREB levels in PVN of MS rats.In conclusion, the chronic hyperactivity of the stress axis and PVN CRH-R2 resistance to Ucn2 effects, supported impaired receptor functionality in MS animals, probably due to its chronic stimulation by CRH or Ucn2, induced by early-life stress.

The Effect of Renal Function and Hemodialysis Treatment on Plasma Vasopressin and Copeptin Levels

IntroductionCopeptin is increasingly used in epidemiological studies as a substitute for vasopressin. The effect of renal function per se on copeptin and vasopressin concentrations as well as their ratio have, however, not been well described.MethodsCopeptin and vasopressin levels were measured in 127 patients with various stages of chronic kidney disease, including 42 hemodialysis patients and 16 healthy participants in this observational study. Linear (segmental) regression analyses were performed to assess the association between renal function and copeptin, vasopressin and the C/V ratio. In addition, clearance of copeptin and vasopressin by hemodialysis was calculated.ResultsBoth copeptin and vasopressin levels were higher when renal function was lower, and both showed associations with plasma osmolality. The C/V ratio was stable across renal function in subjects with an eGFR >28 ml/min per 1.73 m2. In contrast, the C/V ratio increased with worsening renal function in patients with eGFR ≤28 ml/min per 1.73 m2. During hemodialysis, the initial decrease in vasopressin levels was greater compared with copeptin and, consequently, the C/V ratio increased. This was, at least in part, explained by a greater dialytic clearance of vasopressin compared with copeptin.DiscussionOur data indicate that copeptin is a reliable substitute for vasopressin in subjects with an eGFR >28 ml/min per 1.73 m2, whereas at an eGFR ≤28 ml/min per 1.73 m2, that is, CKD stages 4 and 5, a correction for renal function is required in epidemiological studies that use copeptin as a marker for vasopressin. Intradialytic copeptin levels do not adequately reflect vasopressin levels because vasopressin clearance by hemodialysis is higher than that of copeptin.

Inhibition of neuronal nitric oxide synthase activity does not alter vasopressin secretion in septic rats.

During the early phase of sepsis, hypotension is accompanied by increase of plasma vasopressin hormone (AVP) levels, which decline during the late phase. This hypotension is due in part to increase of nitric oxide (NO) synthesis by nitric oxide synthase (NOS) enzyme. Neuronal isoform of this enzyme (nNOS) is present in vasopressinergics neurons of hypothalamus, but its role in vasopressin secretion during sepsis is unknown. We evaluated the role of nNOS in NO production and vasopressin secretion during sepsis. Wistar rats received 7-nitroindazole (50mg/kg, i.p.), an inhibitor of nNOS activity, or vehicle and were submitted to septic stimulus by cecal ligation and puncture (CLP). At the time points 0, 4, 6, 18 and 24h after sepsis induction the animals were decapitated and neurohypophysis and hypothalamus were removed for analysis of vasopressin content and NOS activity, respectively. Hematocrit, serum sodium, osmolality, proteins and plasmatic AVP were quantified. Mortality was not affected by 7-nitroindazole (7-NI). Sodium and plasma proteins levels decreased after CLP and the treatment anticipated the protein loss, and delayed serum sodium decrease. Septic animals treated with 7-NI showed decrease of osmolality 4h after CLP. Nitric oxide synthase activity in hypothalamus increased at 4 and 24h after CLP and was reduced with 7-NI. Neurohypophysis content of AVP diminished after CLP and 7-NI did not alter this parameter. Plasma AVP levels increased at 6h and decreased 18 and 24h after CLP. Treatment with 7-NI did not alter plasma vasopressin levels. We concluded that nNOS does not have a substantial role in vasopressin secretion during experimental sepsis.

Challenges to the Pair Bond: Neural and Hormonal Effects of Separation and Reunion in a Monogamous Primate.

Social monogamy at its most basic is a group structure in which two adults form a unit and share a territory. However, many socially monogamous pairs display attachment relationships known as pair bonds, in which there is a mutual preference for the partner and distress upon separation. The neural and hormonal basis of this response to separation from the adult pair mate is under-studied. In this project, we examined this response in male titi monkeys (Callicebus cupreus), a socially monogamous New World primate. Males underwent a baseline scan, a short separation (48 h), a long separation (approximately 2 weeks), a reunion with the female pair mate and an encounter with a female stranger (with nine males completing all five conditions). Regional cerebral glucose metabolism was measured via positron emission tomography (PET) imaging using [18F]-fluorodeoxyglucose (FDG) co-registered with structural magnetic resonance imaging (MRI), and region of interest (ROI) analysis was carried out. In addition, plasma was collected and assayed for cortisol, oxytocin (OT), vasopressin (AVP), glucose and insulin concentrations. Cerebrospinal fluid (CSF) was collected and assayed for OT and AVP. We used generalized estimating equations (GEE) to examine significant changes from baseline. Short separations were characterized by decreases in FDG uptake, in comparison to baseline, in the lateral septum (LS), ventral pallidum (VP), paraventricular nucleus of the hypothalamus (PVN), periaqueductal gray (PAG), and cerebellum, as well as increases in CSF OT, and plasma cortisol and insulin. Long separations differed from baseline in reduced FDG uptake in the central amygdala (CeA), reduced whole brain FDG uptake, increased CSF OT and increased plasma insulin. The response on encounter with a stranger female depended on whether or not the male had previously reproduced with his pair mate, suggesting that transitions to fatherhood contribute to the neurobiology underlying response to a novel female. Reunion with the partner appeared to stimulate coordinated release of central and peripheral OT. The observed changes suggest the involvement of OT and AVP systems, as well as limbic and striatal areas, during separation and reunion from the pair mate.

Validation of an integrative mathematical model of dehydration and rehydration in virtual humans.

Water homeostasis is one of the body's most critical tasks. Physical challenges to the body, including exercise and surgery, almost always coordinate with some change in water handling reflecting the changing needs of the body. Vasopressin is the most important hormone that contributes to short‐term water homeostasis. By manipulating vascular tone and regulating water reabsorption in the collecting duct of the kidneys, vasopressin can mediate the retention or loss of fluids quickly. In this study, we validated HumMod, an integrative mathematical model of human physiology, against six different challenges to water homeostasis with special attention to the secretion of vasopressin and maintenance of electrolyte balance. The studies chosen were performed in normal men and women, and represent a broad spectrum of perturbations. HumMod successfully replicated the experimental results, remaining within 1 standard deviation of the experimental means in 138 of 161 measurements. Only three measurements lay outside of the second standard deviation. Observations were made on serum osmolarity, serum vasopressin concentration, serum sodium concentration, urine osmolarity, serum protein concentration, hematocrit, and cumulative water intake following dehydration. This validation suggests that HumMod can be used to understand water homeostasis under a variety of conditions.

Dose requirements of alfentanil to eliminate autonomic responses during rapid-sequence induction with thiopental 4 mg/kg and rocuronium 0.6 mg/kg

Study objectiveOpioids are integral part of anesthesia induction, but information on optimal dosing is limited. We aimed to determine doses of alfentanil needed to eliminate increases in 5 autonomic response variables (plasma concentrations of epinephrine, norepinephrine and vasopressin, arterial blood pressure [ABP], and heart rate) during rapid-sequence induction of anesthesia with thiopental 4 mg/kg and rocuronium 0.6 mg/kg. DesignProspective, randomized, observer-blinded, interventional clinical study. SettingLarge academic institution. PatientsEighty-four healthy patients, aged 18 to 55 years, received 1 of 7 assessor-blinded doses of alfentanil (0, 10, 20, 30, 40, 50, and 60 μg/kg) together with thiopental 4 mg/kg and rocuronium 0.6 mg/kg, administered in rapid succession (15 seconds). Laryngoscopy was initiated 40 seconds after rocuronium, and tracheal intubation was concluded within 15 seconds thereafter. MeasurementsAn indwelling radial artery catheter was used for hemodynamic monitoring and blood sampling. Relationships between alfentanil dose and response variables were tested with linear regression, and the influence of covariates (sex, body weight, and age) was determined. Alfentanil dose needed to prevent increases in ABP >10% above baseline with 95% probability was estimated with logistic regression. Main resultsSignificant relationships were determined between alfentanil dose and response variables. Clinically interesting influence of covariates was not found. Alfentanil 55 μg/kg was needed to prevent increases in ABP postintubation >10% above baseline with 95% probability. One individual needed a bolus of vasopressor postintubation. ConclusionsOptimal control of autonomic responses during rapid-sequence induction was achieved with clinically relevant doses of alfentanil in healthy patients anesthetized with thiopental 4 mg/kg and rocuronium 0.6 mg/kg.

Comparison of different levels and lengths of restricted drinking water availability and measurement times with Katahdin sheep and Boer and Spanish goat wethers

Thirty-six yearling Boer goat (BOE), Katahdin sheep (KAT), and Spanish goat wethers (SPA) were used to study conditions for evaluating resilience to restricted drinking water availability. Moderate quality grass hay was consumed ad libitum with concentrate (80% corn, 20% soybean meal) supplemented at 0.5% BW. Baseline conditions were determined in the last 2 wk of a 3-wk period (i.e., 100% level). Thereafter, water availability was decreased by 10% every 1 (1X) or 2 wk (2X) to 40% of baseline intake (i.e., 90, 80, 70, 60, 50, and 40% levels), but also with 2 wk at 40% for the 1X restriction treatment. There was an interaction (P<0.001) between animal type (AT) and restriction level in hay DM intake, with values of 346, 360, 358, 276, 286, 235, and 176g/day for BOE, 656, 592, 592, 469, 522, 407, and 307g/day for KAT, and 392, 390, 368, 273, 298, 298, and 219g/day for SPA at levels of 100, 90, 80, 70, 60, 50, and 40%, respectively (SE=29.1). Moreover, hay DM intake by 2X wethers was much lower in wk 2 vs. 1 at the 40% level (week×level interaction, P=0.008; 409, 369, 345, 377, 336, and 276g/day in wk 1 and 428, 398, 312, 352, 310, and 203g/day in wk 2 at 90, 80, 70, 60, 50, and 40% levels, respectively; SE=23.4). Restriction level affected (P<0.001) plasma cortisol concentration in 2X wethers on the last day at each level (12.4, 14.0, 23.3, 26.4, and 32.6nmol/L for 100, 70, 60, 50, and 40% levels, respectively; SE=3.62). Plasma vasopressin concentration in 2X wethers at the end of each week at 60, 50, and 40% levels was affected by an interaction (P=0.006) between week and level (3.98, 5.61, and 7.84 for wk 1 and 6.40, 7.22, and 7.06pmol/L for wk 2, respectively; SE=0.564). In conclusion, there was some indication that DM intake by KAT was more subject to adverse effects of very low water availability but not mild restriction compared with goats. Based on vasopressin concentration, a length of at least 2 wk rather than 1 with a set level(s) of restricted water availability seems desirable, which might also increase meaningfulness of measures such as BW. Results for DM intake and cortisol concentration suggest appropriateness of a maximum restriction level of 50%.

Serotonin 1A agonism decreases affiliative behavior in pair-bonded titi monkeys

Relatively little is known about serotonergic involvement in pair-bonding despite its putative role in regulating social behavior. Here we sought to determine if pharmacological elevation of serotonin 1A (5-HT1A) receptor activity would lead to changes in social behavior in pair-bonded male titi monkeys (Callicebus cupreus). Adult males in established heterosexual pairs were injected daily with the selective 5-HT1A agonist 8-OH-DPAT or saline for 15days using a within-subjects design. Social behavior with the female pair-mate was quantified, and plasma concentrations of oxytocin, vasopressin, and cortisol were measured. When treated with saline, subjects showed reduced plasma oxytocin concentrations, while 8-OH-DPAT treatment buffered this decrease. Treatment with 8-OH-DPAT also led to decreased plasma cortisol 15minutes post-injection and decreased social behavior directed toward the pair-mate including approaching, initiating contact, lipsmacking, and grooming. The reduction in affiliative behavior seen with increased activity at 5-HT1A receptors indicates a substantial role of serotonin activity in the expression of social behavior. In addition, results indicate that the effects of 5-HT1A agonism on social behavior in adulthood differ between rodents and primates.

Vasopressin Impairment During Sepsis Is Associated with Hypothalamic Intrinsic Apoptotic Pathway and Microglial Activation.

Previous studies have shown that in the early phase of sepsis, the plasma concentration of arginine vasopressin (AVP) is increased, but in the late phase, its levels remain inadequately low, despite of persistent hypotension. One hypothesis suggested for this relative deficiency is apoptosis of vasopressinergic neurons. Here, we investigated apoptosis pathways in the hypothalamus during sepsis, as well as mechanisms underlying this process. Male Wistar rats were submitted to sepsis by cecal ligation and puncture (CLP) or nonmanipulated (naive) as control. After 6 and 24h, the animals were decapitated and brain and blood were collected to assess hypothalamic apoptotic markers, IFN-γ plasma levels, and evidence for breakdown of the blood-brain barrier (BBB). Sepsis caused a decrease in mitochondrial antiapoptotic proteins (Bcl-2, Bcl-xL) in the hypothalamus, but had no effect on markers of cell death mediated by death receptors or immune cells. In the supraoptic nuclei of these animals, microglia morphology was consistent with activation, associated with an increase in plasma IFN-γ. A transitory breakdown of BBB in the hypothalamus was seen at 6h following CLP. The results indicate that the intrinsic but not extrinsic apoptosis pathway is involved in the cell death observed in vasopressinergic neurons, and that this condition is temporally associated with microglial activation and BBB leaking.

The Effects of Vasopressin and Oxytocin on the Fetoplacental Distal Stem Arteriolar Vascular Resistance of the Dual-Perfused, Single, Isolated, Human Placental Cotyledon.

Vasoactive agents administered to counter maternal hypotension at cesarean delivery may theoretically intensify the hypoxemic fetoplacental vasoconstrictor response and, hence, negatively impact transplacental oxygen delivery to the fetus. Yet, this aspect of their pharmacodynamic profiles is seldom mentioned, let alone investigated. We hypothesized that vasopressin, a potent systemic vasoconstrictor, and oxytocin, a uterotonic agent administered routinely at cesarean delivery, which, in contrast to vasopressin, possesses significant systemic vasodilator properties, would not influence distal stem villous arteriolar resistance. The dual-perfused, single, isolated cotyledon, human placental perfusion model was used to examine the resistance response of the fetoplacental circulation to oxytocin and vasopressin in placentae harvested from healthy women. Twelve of a total of 17 individual experiments were conducted successfully during which either oxytocin (n = 6) or vasopressin (n = 6) was introduced into the fetal reservoir in concentration increments of 10 M. Fetoplacental distal stem villous arteriolar perfusion pressure (FAP) was measured continuously. The fetal circuit concentration of either oxytocin or vasopressin was raised in a stepwise fashion from 10 to 10 M or 10 to 10 M, respectively. Both reservoirs were then purged of drug, after which 1-mL 1.0 mM 5-hydroxytryptamine (2.5 µM), an agent well known to manifestly increase fetoplacental distal stem villous arteriolar resistance, was introduced into the fetal circuit. A significant increase in FAP from baseline in response to exposure to 5-hydroxytryptamine confirmed that the fetoplacental vasoconstrictor response remained reactive. The primary outcome of this study was changes in FAP after incremental dosing of vasopressin and oxytocin. No changes in FAP were observed with either oxytocin or vasopressin regardless of the drug concentration tested. For each drug and concentration, a mean pressure change greater than ±10 mm Hg was excluded with 95% confidence. In contrast, 5-hydroxytryptamine significantly increased perfusion pressure in all 12 successful experiments. Oxytocin and vasopressin do not influence human fetoplacental distal stem villous arteriolar resistance. The neutral impact of vasopressin noted here is thus analogous to the reported negligible influence of the drug on human pulmonary arteriolar resistance. Neither drug seems likely to adversely influence the compensatory hypoxemic fetoplacental vasoconstrictor response.

Selective Detection of Oxytocin on Diamond Electrodes in Preparation for Making In Vivo Measurements

<Introduction> It has recently been revealed that oxytocin (OT), a peptide hormone known for its role in lactation and parturition, works as a neurotransmitter as well. Due to a series of findings of positive effects on social behaviors such as trust in human, oxytocin has been of keen interest to neuroscientists. What is required now for further understanding of oxytocin science is a real-time measurement of oxytocin in vivo. On the other hand, in the region where oxytocin is secreted in the hypothalamus, another peptide, vasopressin (VP), is also secreted. Vasopressin is also a nonapeptide with a quite similar structure to oxytocin. Therefore, selective measurement of oxytocin and vasopressin is inevitable. Electrochemical detection allows a real-time measurement in millisecond order with high sensitivity. Compared to conventional electrodes, boron-doped diamond (BDD) electrode has a variety of outstanding properties such as wide potential window and low background current, which have led to a number of reports about sensitive measurement of substances which cannot be detected by other electrodes. Using BDD microelectrodes, in vivomeasurement of biomolecules have been achieved and applied to medical and physiological studies. In addition, surface termination of BDD can be changed from original state (hydrogen termination) to oxygen termination by some oxidation treatment, which enables selective measurement. In the present study, electrochemical detection of oxytocin was investigated using BDD electrodes. Two types of BDD, as-deposited (AD-BDD) and anodically-oxidized (AO-BDD), were used in order to achieve selective measurement. <Experiments> BDD electrodes were prepared by growing polycrystalline BDD thin films on silicon substrates or needle tungsten wires using microwave plasma-assisted chemical vapor deposition (MPCVD) system. Electrochemical measurements were conducted in a three-electrode system with BDD, platinum, and Ag/AgCl (KCl saturated) electrode as a working electrode, counter electrode, and reference electrode, respectively. Phosphate buffer saline (PBS) and Tris buffer were used as buffer solution after adjusted to pH 7.4. Surface transformation of BDD electrodes to oxygen termination was conducted on AD-BDD by means of anodic oxidation of 3.0 V application for 20 minutes in PBS. <Results and discussion>The electrochemical behavior of oxytocin was studied using AD-BDD. Cyclic voltammetry (CV) was performed for 0.1 mM oxytocin in 0.1 M PBS with a scan rate of 100 mV/s. Oxidation peak was observed at 0.7 V (vs. Ag/AgCl). Among the 9 amino acids constructing oxytocin, only tyrosine (Tyr) has been reported to be electrochemically oxidized. Tyrosine also gave oxidation signal at 0.7 V and the shape of voltammogram was quite similar to that of oxytocin. Consequently, it was deduced that oxidation of oxytocin is occurred at tyrosine moiety. When compared to other electrodes, BDD showed 4 times higher signal to background ratio than glassy carbon electrode. No signal was observed in the case of platinum electrode. These results showed that sensitive measurement of oxytocin is possible by using BDD electrode. Since vasopressin also contains tyrosine in its structure, it should show the oxidation signal. CV of vasopressin was compared to that of oxytocin. Exactly the same voltammograms were observed. On the other hand, AO-BDD, which has oxygen-terminated surface, showed apparent difference in voltammograms (Figure). Although the peak potential of vasopressin was maintained at the same position as AD-BDD, oxytocin showed a broad signal shifted to more positive potential region. On-set potential of tyrosine was still higher than that of oxytocin. One possible explanation to the results is the electrostatic interaction between the electrode surface and the molecules. The surface state of AO-BDD rich in C-O functional groups can be expected to have electrostatically negative state. On the other hand, tyrosine is negatively charged, oxytocin is almost neutral, and vasopressin is positively charged in the condition of pH 7.4. These facts and the results of CV well explain the mechanism of electrostatic interaction. Aiming at in vivo and selective measurement, chronoamperometry combined with flow injection analysis (FIA) by BDD microelectrodes was conducted. AD-BDD microelectrode applied at 1.0 V gave high linearity (R2 = 0.994) of the current peaks over the oxytocin concentration range from 0.1 to 10.0 μM with a detection limit of 50 nM (S/N =3). On the other hand, using AO-BDD microelectrode, selective measurement of oxytocin and vasopressin was achieved by the use of applied potential of 0.54 V, which gave the signals of only vasopressin. Consequently, the concentration of oxytocin can be obtained by subtracting the concentration of vasopressin measured on AO-BDD from that of oxytocin + vasopressin measured on AD-BDD. Figure 1