Cerebrospinal Fluid Arginine Vasopressin Research Articles

Naturally occurring low sociality in female rhesus monkeys: A tractable model for autism or not?

BackgroundAutism spectrum disorder (ASD) is characterized by persistent social interaction impairments and is male-biased in prevalence. We have established naturally occurring low sociality in male rhesus monkeys as a model for the social features of ASD. Low-social male monkeys exhibit reduced social interactions and increased autistic-like trait burden, with both measures highly correlated and strongly linked to low cerebrospinal fluid (CSF) arginine vasopressin (AVP) concentration. Little is known, however, about the behavioral and neurochemical profiles of female rhesus monkeys, and whether low sociality in females is a tractable model for ASD.MethodsSocial behavior assessments (ethological observations; a reverse-translated autistic trait measurement scale, the macaque Social Responsiveness Scale-Revised [mSRS-R]) were completed on N = 88 outdoor-housed female rhesus monkeys during the non-breeding season. CSF and blood samples were collected from a subset of N = 16 monkeys across the frequency distribution of non-social behavior, and AVP and oxytocin (OXT) concentrations were quantified. Data were analyzed using general linear models.ResultsNon-social behavior frequency and mSRS-R scores were continuously distributed across the general female monkey population, as previously found for male monkeys. However, dominance rank significantly predicted mSRS-R scores in females, with higher-ranking individuals showing fewer autistic-like traits, a relationship not previously observed in males from this colony. Females differed from males in several other respects: Social behavior frequencies were unrelated to mSRS-R scores, and AVP concentration was unrelated to any social behavior measure. Blood and CSF concentrations of AVP were positively correlated in females; no significant relationship involving any OXT measure was found.LimitationsThis study sample was small, and did not consider genetic, environmental, or other neurochemical measures that may be related to female mSRS-R scores.ConclusionsDominance rank is the most significant predictor of autistic-like traits in female rhesus monkeys, and CSF neuropeptide concentrations are unrelated to measures of female social functioning (in contrast to prior CSF AVP findings in male rhesus monkeys and male and female autistic children). Although preliminary, this evidence suggests that the strong matrilineal organization of this species may limit the usefulness of low sociality in female rhesus monkeys as a tractable model for ASD.

Autism-associated biomarkers: test\u2013retest reliability and relationship to quantitative social trait variation in rhesus monkeys

BackgroundRhesus monkeys (Macaca mulatta) exhibit pronounced individual differences in social traits as measured by the macaque Social Responsiveness Scale-Revised. The macaque Social Responsiveness Scale was previously adapted from the Social Responsiveness Scale, an instrument designed to assess social and autistic trait variation in humans. To better understand potential biological underpinnings of this behavioral variation, we evaluated the trait-like consistency of several biological measures previously implicated in autism (e.g., arginine vasopressin, oxytocin, and their receptors, as well as ERK1/2, PTEN, and AKT(1–3) from the RAS-MAPK and PI3K-AKT pathways). We also tested which biological measures predicted macaque Social Responsiveness Scale-Revised scores.MethodsCerebrospinal fluid and blood samples were collected from N = 76 male monkeys, which, as a sample, showed a continuous distribution on the macaque Social Responsiveness Scale-Revised. In a subset of these subjects (n = 43), samples were collected thrice over a 10-month period. The following statistical tests were used: “Case 2A” intra-class correlation coefficients of consistency, principal component analysis, and general linear modeling.ResultsAll biological measures (except AKT) showed significant test–retest reliability within individuals across time points. We next performed principal component analysis on data from monkeys with complete biological measurement sets at the first time point (n = 57), to explore potential correlations between the reliable biological measures and their relationship to macaque Social Responsiveness Scale-Revised score; a three-component solution was found. Follow-up analyses revealed that cerebrospinal fluid arginine vasopressin concentration, but no other biological measure, robustly predicted individual differences in macaque Social Responsiveness Scale-Revised scores, such that monkeys with the lowest cerebrospinal fluid arginine vasopressin concentration exhibited the greatest social impairment. Finally, we confirmed that this result held in the larger study sample (in which cerebrospinal fluid arginine vasopressin values were available from n = 75 of the subjects).ConclusionsThese findings indicate that cerebrospinal fluid arginine vasopressin concentration is a stable trait-like measure and that it is linked to quantitative social trait variation in male rhesus monkeys.

Arginine Vasopressin-Containing Neurons of the Suprachiasmatic Nucleus Project to CSF.

While it is well established that there are robust circadian rhythms of arginine vasopressin (AVP) in the cerebrospinal fluid (CSF), the route whereby the peptide reaches the CSF is not clear. A , AVP neurons constitute the largest fraction of the SCN neuronal population. Here, we show that processes of AVP-expressing SCN neurons cross the epithelium of the 3rd ventricular wall to reach the CSF (black arrows). Additionally, we report rostro-caudal differences in AVP neuron size and demonstrate that the localization of cells expressing the clock protein PER2 extend beyond the AVP population, thereby indicating that the size of this nucleus is somewhat larger than previously understood. B , Following lateral ventricle (LV) injection of cholera toxin β subunit (CTβ ; magenta) the retrograde tracer is seen in AVP neurons of the SCN, supporting the anatomical evidence that AVP neuronal processes directly contact the CSF.Arginine vasopressin (AVP) expressing neurons form the major population in the brain's circadian clock located in the hypothalamic suprachiasmatic nucleus (SCN). They participate in inter-neuronal coupling and provide an output signal for synchronizing daily rhythms. AVP is present at high concentrations in the cerebrospinal fluid (CSF) and fluctuates on a circadian timescale. While it is assumed that rhythms in CSF AVP are of SCN origin, a route of communication between these compartments has not been delineated. Using immunochemistry (ICC) and cell filling techniques, we determine the morphology and location of AVP neurons in mouse and delineate their axonal and dendritic processes. Cholera toxin β subunit (CTβ) tracer injected into the lateral ventricle tests whether AVP neurons communicate with CSF. Most importantly, the results indicate that AVP neurons lie in close proximity to the third ventricle, and their processes cross the ventricular wall into the CSF. We also report that contrary to widely held assumptions, AVP neurons do not fully delineate the SCN borders as PER2 expression extends beyond the AVP region. Also, AVP neurons form a rostral prong originating in the SCN medial-most and ventral-most aspect. AVP is lacking in the mid-dorsal shell but does occur at the base of the SCN just above the optic tract. Finally, neurons of the rostral SCN are smaller than those lying caudally. These findings extend our understanding of AVP signaling potential, demonstrate the heterogeneity of AVP neurons, and highlight limits in using this peptide to delineate the mouse SCN.

Neonatal CSF vasopressin concentration predicts later medical record diagnoses of autism spectrum disorder

Autism spectrum disorder (ASD) is a brain disorder characterized by social impairments. ASD is currently diagnosed on the basis of behavioral criteria because no robust biomarkers have been identified. However, we recently found that cerebrospinal fluid (CSF) concentration of the "social" neuropeptide arginine vasopressin (AVP) is significantly lower in pediatric ASD cases vs. controls. As an initial step in establishing the direction of causation for this association, we capitalized upon a rare biomaterials collection of newborn CSF samples to conduct a quasi-prospective test of whether this association held before the developmental period when ASD first manifests. CSF samples had been collected in the course of medical care of 0- to 3-mo-old febrile infants (n = 913) and subsequently archived at -70 °C. We identified a subset of CSF samples from individuals later diagnosed with ASD, matched them 1:2 with appropriate controls (n = 33 total), and quantified their AVP and oxytocin (OXT) concentrations. Neonatal CSF AVP concentrations were significantly lower among ASD cases than controls and individually predicted case status, with highest precision when cases with comorbid attention-deficit/hyperactivity disorder were removed from the analysis. The associations were specific to AVP, as ASD cases and controls did not differ in neonatal CSF concentrations of the structurally related neuropeptide, OXT. These preliminary findings suggest that a neurochemical marker of ASD may be present very early in life, and if replicated in a larger, prospective study, this approach could transform how ASD is detected, both in behaviorally symptomatic children, and in infants at risk for developing it.

Journal Digest

Journal Digest

Arginine vasopressin in cerebrospinal fluid is a marker of sociality in nonhuman primates

Autism spectrum disorder (ASD) is a neurodevelopmental condition characterized by core social impairments. ASD remains poorly understood because of the difficulty in studying disease biology directly in patients and the reliance on mouse models that lack clinically relevant, complex social cognition abilities. We use ethological observations in rhesus macaques to identify male monkeys with naturally occurring low sociality. These monkeys showed differences in specific neuropeptide and kinase signaling pathways compared to socially competent male monkeys. Using a discovery and replication design, we identified arginine vasopressin (AVP) in cerebrospinal fluid (CSF) as a key marker of group differences in monkey sociality; we replicated these findings in an independent monkey cohort. We also confirmed in an additional monkey cohort that AVP concentration in CSF is a stable trait-like measure. Next, we showed in a small pediatric cohort that CSF AVP concentrations were lower in male children with ASD compared to age-matched male children without ASD (but with other medical conditions). We demonstrated that CSF AVP concentration was sufficient to accurately distinguish ASD cases from medical controls. These data suggest that AVP and its signaling pathway warrant consideration in future research studies investigating new targets for diagnostics and drug development in ASD.

Plasma vasopressin concentrations positively predict cerebrospinal fluid vasopressin concentrations in human neonates

Central arginine vasopressin (AVP) plays a critical role in mammalian social behavior and has been hypothesized to be a biomarker of certain human neurodevelopmental disorders, including autism. However, opportunities to collect post-mortem brain tissue or cerebrospinal fluid (CSF) from children are extremely limited, and the use of less invasive peripheral assessments (e.g., blood, urine, or saliva) of AVP as a proxy for more invasive central measures has not been well validated. Further, almost nothing is known about AVP biology in very young infants. Therefore in the present study we concomitantly collected basal CSF and plasma samples from N=20 neonates undergoing clinical sepsis evaluation (all were sepsis negative) and quantified AVP concentrations via well-validated enzyme-immunoassay methodology. Plasma AVP concentrations significantly and positively predicted CSF AVP concentrations (r=0.73, p=0.0021), and this relationship persisted when variance attributed to sex, gestational age, and sample collection time was controlled for in the statistical model (r=0.75, p=0.0047). These findings provide preliminary support for the use of basal plasma AVP measurement as a proxy for basal brain AVP activity in pediatric populations. Future studies are now required to determine the relationship between behavioral measures and AVP concentrations in both central and peripheral compartments in young infants and older children.

Effect of intranasal arginine vasopressin on human headache

Arginine vasopressin (AVP), a nonapeptide hormone of posterior pituitary, reaches the central nervous system from systemic blood circulation with a difficulty because of the blood–brain barrier (BBB). The interest has been expressed in the use of the nasal route for delivery of AVP to the brain directly, exploiting the olfactory pathway. Our previous study has demonstrated that AVP in the brain rather than the spinal cord and blood circulation plays an important role in rat pain modulation. For understanding the role of AVP on pain modulation in human, the communication tried to investigate the effect of intranasal AVP on human headache. The results showed that (1) AVP concentration in both plasma and cerebrospinal fluid (CSF) increased significantly in headache patients, who related with the headache level; (2) there was a positive relationship between plasma and CSF AVP concentration in headache patients; and (3) intranasal AVP could relieve the human headache in a dose-dependent manner. The data suggested that intranasal AVP, which was delivered to the brain through olfactory region, could treat human headache and AVP might be a potential drug of pain relief by intranasal administration.

Early change of plasma and cerebrospinal fluid arginine vasopressin in traumatic subarachnoid hemorrhage

Objective To investigate the changes and effects of arginine vasopressin (AVP) in patients with acute traumatic subarachnoid hemorrhage (tSAH). Methods The plasma and cerebrospinal fluid (CSF) level of AVP, and intracranial pressure (ICP) were measured in a total of 21 patients within 24 hours after tSAH. The neurological status of the patients was evaluated by Glasgow Coma Scale (GCS). Correlation between AVP and ICP, GCS was analyzed respectively. Meanwhile, 18 healthy volunteers were recruited as control group. Results Compared with control group, the levels (pg/ml) of AVP in plasma and CSF (x±s) in tSAH group were significantly increased within 24 hours (38.72±24.71 vs 4.54±1.38 and 34.61±21.43 vs 4.13±1.26, P <0.01), and was remarkably higher in GCS≤8 group than GCS>8 group (50.96±36.81 vs 25.26±12.87 and 44.68±31.72 vs 23.53±10.94, P 0.05). The CSF AVP level was correlated with ICP ( r = 0.46, P<0.05), but no statistically significant correlation was found between plasma AVP, CSF AVP and initial GCS ( r = −0.29, P>0.05 and r= −0.32, P>0.05, respectively). The ICP (mm Hg) in tSAH patients was elevated and higher in GCS=8 group than in GCS≤8 gro up (25.9±9.7 vs 17 .6±5.2, P<0. 05). Conclusion Our research suggests that AVP is correlated with the severity of tSAH, and may be involved in the pathophysiological process of brain damage in the early stage after tSAH. It seems that compared with the plasma AVP concentration, CSF AVP is more related to the severity of tSAH.

Deletion of N-type Ca2+ Channel Cav2.2 Results in Hyperaggressive Behaviors in Mice

Voltage-dependent N-type Ca(2+) channels play important roles in the regulation of diverse neuronal functions in the brain, but little is known about its role in social aggressive behaviors. Mice lacking the alpha1B subunit (Ca(v)2.2) of N-type Ca(2+) channels showed markedly enhanced aggressive behaviors to an intruder mouse in the resident-intruder test. The dorsal raphe nucleus (DRN), which contains serotonin neurons, is known to be involved in aggression in animals. We thus examined the DRN neurons in the Ca(v)2.2-deficient (Ca(v)2.2(-/-)) mice. Microinjection of omega-conotoxin GVIA, an N-type Ca(2+) channel-specific blocker, into the DRN of wild type mice resulted in escalated aggression, mimicking the phenotypes of Ca(v)2.2(-/-). Electrophysiological analysis showed increased firing activity of serotonin neurons with a reduced inhibitory neurotransmission in the Ca(v)2.2(-/-) DRN. Ca(v)2.2(-/-) mice showed an elevated level of arginine vasopressin, an aggression-related hormone, in the cerebrospinal fluid. In addition, Ca(v)2.2(-/-) mice showed an increase of serotonin in the hypothalamus. These results suggest that N-type Ca(2+) channels at the DRN have a key role in the control of aggression.

Vasopressin in CSF and plasma in depressed suicide attempters: preliminary results

Increased plasma arginine vasopressin (AVP) concentrations have been reported in depressed suicide attempters. Plasma AVP is primarily produced by the magnocellular system in response to increased plasma osmolality, and central AVP may be independently regulated. In the present study we investigated cerebrospinal fluid (CSF) and plasma AVP concentrations in depressed patients and controls. Nineteen drug-free depressed psychiatric inpatients (nine suicide attempters) and nine neurological control subjects underwent lumbar puncture and psychiatric evaluation. CSF and plasma concentrations of AVP, serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), homovanillic acid (HVA), and cortisol were assayed. In 15 depressed patients (eight suicide attempters), the combined dexamethasone/corticotropin-releasing hormone (Dex/CRH) test was performed to examine the hypothalamic–pituitary–adrenocortical (HPA) system. There were no differences between depressed subjects and controls in all parameters measured. Suicide attempters did not differ from nonattempters. In depressed patients, plasma AVP correlated positively with cortisol. There was no relationship between CSF AVP and monoamine metabolites in CSF.

Cerebrospinal fluid vasopressin levels: correlates with aggression and serotonin function in personality-disordered subjects.

Animal studies suggest that central vasopressin plays a facilitatory role in aggressive behavior. To examine this possibility in humans, the relationship between cerebrospinal fluid (CSF) arginine vasopressin (AVP) and indices of aggression and central serotonin system function was examined in personality-disordered subjects. We used CSF (AVP), CSF 5-hydroxyindoleacetic acid, and the prolactin response to d-fenfluramine challenge (PRL[d-FEN]) as central indices of vasopressin and serotonergic system function, respectively, in 26 subjects who met the DSM-IV criteria for personality disorder. Measures of aggression and impulsivity included the Life History of Aggression assessment and the Barratt Impulsiveness Scales. The CSF AVP level was correlated directly with life history of general aggression and aggression against persons and inversely with PRL[d-FEN] responses (but not with CSF 5-hydroxyindoleacetic acid), which in turn was correlated inversely with these 2 measures of life history of aggression. The positive relationship between CSF AVP and life history of aggression remained even when the variance associated with PRL[d-FEN] responses in these subjects was accounted for. Central AVP may play a role in enhancing, while serotonin plays a role in inhibiting, aggressive behavior in personality-disordered individuals. In addition to the possibility of central AVP and serotonin interacting to influence human aggression, central AVP may also influence human aggressive behavior through a mechanism independent of central serotonin in personality-disordered subjects.

Role of serotonin in obsessive-compulsive disorder

Serotonin may play a role in the pathophysiology of obsessive-compulsive disorder (OCD) because of the anti-obsessional effect of selective serotonin reuptake inhibitors (SSRIs). The literature is reviewed on knowledge of the role of serotonergic neurons in brain function, studies on monoamine metabolites in cerebrospinal fluid (CSF), various stress neuropeptides, neuroendocrine and behavioural challenge after administration of direct and indirect serotomimetic compounds, and neuroanatomical data on brain circuits organising behaviour. In most of the OCD cases analysed, CSF 5-hydroxyindoleacetic acid and homovanillic acid concentrations do not significantly differ from age-corrected controls. However, a relationship appears to exist between pre-treatment levels of these metabolites and clinical response to drugs acting on the serotonin transporter. Abnormalities in CSF arginine vasopressin, corticotropin-releasing hormone, oxytocin and somatostatin levels have been reported in OCD. Long-term treatment with high-doses of clomipramine, fluvoxamine, and fluoxetine tend to correct these neuropeptide abnormalities. We hypothesise that continuous treatment with SSRIs alters serotonin turnover and neuropeptide expression patterns in OCD-entertaining functional forebrain/midbrain circuits.

Vasopressin in the cerebrospinal fluid of febrile children with or without seizures

Immaturity in water and electrolyte balance in the brain has been considered to increase the susceptibility of young animals and children to febrile convulsions (FCs). Arginine-vasopressin (AVP) is involved in the regulation of several centrally mediated events such as modulation of fever and the ease with which water permeates into and out of the brain. To evaluate the possible role of AVP in the control of water balance and susceptibility to convulsions during fever we measured the AVP concentration in the cerebrospinal fluid (CSF) and plasma of febrile children with or without convulsions. The febrile population consisted of 47 children, of whom 29 experienced seizures during fever. Seven children with epileptic symptoms and 18 children without seizures were included as nonfebrile controls. The CSF AVP concentration in febrile children without seizures and in nonfebrile convulsive children was significantly lower (0.60 ± 0.07 pmol / 1, mean ± SEM, P < 0.01 and 0.65 ± 0.19 pmol/l, P < 0.05, respectively) than in nonfebrile children without convulsions (0.83 ± 0.06 pmol/1). However, the levels of CSF AVP were not significantly different in children with FCs (0.71 ± 0.06 pmol/1) compared with other groups. CSF AVP correlated with the CSF osmolality ( r = 0.33, P = 0.02). No statistical differences in plasma AVP levels between the groups could be found. The present data provide support for the hypothesis of synchronous regulation of osmolality and AVP concentration in CSF. During fever the concentration of CSF AVP was lower in nonconvulsive children compared with nonfebrile nonconvulsive children. CSF AVP levels were not affected in febrile children by convulsions.

Oral physostigmine in alzheimer's disease: Effects on norepinephrine and vasopressin in cerebrospinal fluid and plasma

Physostigmine is a cholinesterase inhibitor which enhances central and peripheral cholinergic activity. In this study, we explored in persons with Alzheimer's disease (AD) the effects of an acute dose of physostigmine in patients receiving chronic physostigmine treatment on the activity of the cholinergically regulated noradrenergic and arginine vasopressin (AVP) systems. Specifically, we estimated the effects of sustained release oral physostigmine on central and peripheral noradrenergic and AVP systems by measuring norepinephrine (NE) and AVP in cerebrospinal fluid (CSF) and plasma. Lumbar punctures were performed in both physostigmine and no drug treatment conditions. In some subjects the effects of physostigmine on the plasma AVP response to the osmolar stimulus of a hypertonic saline infusion also were measured. NE concentrations in both CSF and plasma were significantly lower in the physostigmine than in the no drug condition. AVP concentrations did not differ between conditions in either compartment, nor did physostigmine affect the AVP response to hypertonic saline. Physostigmine appears to decrease both central and peripheral noradrenergic activity in AD.

Impaired water metabolism and cerebral oedema following experimental subarachnoid haemorrhage in rats1

The acute phase of subarachnoid haemorrhage (SAH) is frequently associated with an impaired water metabolism and a disposition to cerebral oedema. For study of the pathogenesis of brain oedema following SAH, an experimental model of SAH was created in the rat The diuretic curves after water loading, the brain water and electrolyte contents and the plasma and cerebrospinal fluid arginine vasopressin (AVP) levels were examined in rats with SAH. Following a water load, a significant water retention and increases in brain water and sodium contents were observed after subarachnoid bleeding. Plasma and cerebrospinal fluid AVP levels were also elevated following SAH. It can be concluded that AVP plays important roles in the development of antidiuresis after water loading and in the disturbance of the brain water and electrolyte balance following experimental SAH.

Plasma and cerebrospinal fluid arginine vasopressin in patients with and without fever.

Hyponatraemia has been described in association with a number of acute infectious diseases, mainly bacterial and tuberculous meningitis and pneumonia, and has been attributed to inappropriate secretion of arginine vasopressin (AVP). The mechanism of inappropriate AVP production is uncertain, but there is experimental evidence to suggest that fever may stimulate secretion of AVP into plasma and cerebrospinal fluid. In this study, AVP concentrations in plasma and cerebrospinal fluid from 37 febrile children with infections have been compared with those from 27 afebrile control subjects. Ten of the febrile children had meningitis (eight bacterial, two viral) and the remainder a variety of other infectious diseases. Seventy four per cent of febrile infected children were hyponatraemic (serum sodium less than 135 mmol/l) compared with only 8% of the afebrile controls. Plasma AVP concentrations were significantly higher in the febrile patients (median 2.92 pmol/l, range 1.0-23.25, n = 28) than in controls (median 1.67 pmol/l, range 0.57-6.0, n = 14) but there was no significant difference in cerebrospinal fluid AVP concentrations. There was no difference in plasma AVP concentrations between patients with meningitis and those with infections not involving the central nervous system. Careful attention should be paid to fluid and electrolyte balance in all children with acute infections.

Arginine vasopressin concentrations in the cerebrospinal fluid of children

Cerebrospinal fluid (CSF) arginine vasopressin (AVP) levels are reported in a group of 22 children (median age 24 months) investigated for possible bacterial meningitis and subsequently found not to be suffering from this disease. The mean CSF AVP concentration was 0.80 +/- 0.33 pg/ml. The results obtained in patients suffering from febrile convulsions (mean 0.71 pg/ml), other convulsive disorders (mean 0.80 pg/ml) and miscellaneous infectious diseases (mean 0.85 pg/ml) did not differ significantly from one another. Our findings confirm the presence of AVP in the CSF of children and provide reference values for further investigations into the functions of CSF AVP in children.

Cerebrospinal fluid and plasma concentrations of oxytocin and vasopressin during parturition and vaginocervical stimulation in the sheep

Simultaneous blood and Cerebrospinal fluid (CSF) samples were taken from conscious sheep before, during and after parturition. Concentrations of plasma and CSF oxytocin were significantly elevated during contractions and particularly at birth. Mean prepartum CSF concentrations of oxytocin were around 55% of those found in plasma but postpartum they were up to 2-fold higher than those in plasma. Plasma concentrations of oxytocin were only significantly elevated, compared to prepartum levels, for 15 min postpartum whereas those in CSF were increased for the whole of the 120 min postpartum sampling period. Plasma, but not CSF, concentrations of arginine-vasopressin (AVP) were significantly raised during contractions and birth, and for 15 min postpartum. During the prepartum period CSF AVP concentrations were 67% of those found in plasma whereas at birth plasma levels were 10-fold higher than in CSF. In a separate experiment it was shown that 5 min of mechanical vaginocervical stimulation also stimulated significant increases in CSF and plasma oxytocin concentrations and in plasma vasopressin. Results support previous work suggesting an important role for central oxytocin release in the postpartum induction of maternal behavior and demonstrate that elevated concentrations of oxytocin in the CSF are present for a greater period than in blood. Elevated plasma AVP concentrations during contractions, birth or vaginocervical stimulation may be stimulated by stress associated with these stimuli.

Yohimbine Increases Cerebrospinal Fluid and Plasma Norepinephrine but Not Arginine Vasopressin in Humans

Previous studies have demonstrated alpha 2-inhibitory regulation of central nervous system (CNS) noradrenergic and arginine vasopressinergic systems. We tested the hypothesis that alpha 2-inhibition of CNS noradrenergic and vasopressinergic systems is tonic in nature by measuring the response of cerebrospinal fluid (CSF) norepinephrine (NE) and arginine vasopressin (AVP) to the alpha 2-antagonist yohimbine in 7 young normal male human subjects. We also evaluated the tonic nature of alpha 2-inhibition of the sympathetic nervous system (SNS) and of AVP release into plasma by measuring the response of plasma NE and plasma AVP to yohimbine. CSF NE was significantly higher following yohimbine as compared to placebo. In contrast CSF AVP did not differ between yohimbine and placebo conditions. Similarly, plasma NE was significantly higher following yohimbine as compared to placebo, while plasma AVP was unchanged. These results support a tonic alpha 2-inhibitory regulatory mechanism for both CNS noradrenergic systems and sympathetic outflow. Such tonic alpha 2-inhibition could not be demonstrated for regulation of AVP levels in CSF or plasma in humans.