The effects of clonidine on the kidney function in the anesthetized dog

Studies were performed to determine the mechanism by which the antihypertensive agent clonidine increased urine flow. The response of the kidney has been examined in four combinations. The parameters of renal function have been compared during volume expansion by 1.5-2.0% body weight Ringer solution. In the control animals, volume expansion by 2% body weight, resulted in a slight increase in sodium excretion and urine flow. In 10 anesthetized dogs 1.0 microgram/kg/min of clonidine infused i.v. during 30 minutes (the total amount of clonidine infused was 30 micrograms/kg) decreased the arterial blood pressure from 136 +/- 13 mmHg to 127 +/- 12 mmHg and elevated urine flow from 2.95 +/- 1.65 ml/min to 4.34 +/- 1.77 ml/min while the urine osmolality diminished from 399 +/- 107 mosm/l to 265 +/- 90 mosm/l and the glomerular filtration remained constant. In 5 animals 0.1 microgram/kg/min of clonidine was infused into the left renal artery (this dose is corresponding to the renal fraction of the cardiac output) without any effects in the left kidney. 1.0 microgram/kg/min of clonidine infused directly into the left renal artery produced vasoconstriction in the ipsilateral kidney, decreased the glomerular filtration rate and the urine flow. By contrast in the right kidney the urine flow rose without hemodynamic changes, and the urine osmolality became hypoosmotic compared to the plasma. In ten dogs 1.0 microgram/kg/min of clonidine and 1 mU/kg/min of arginine-vasopressin were infused intravenously. The vasopressin infusion superimposed on the clonidine could not inhibit the increase of the urine excretion, and the fall of the urine osmolality. The results suggest that the clonidine increases the renal medullary blood flow possibly via a direct mechanism, decreases the sympathetic outflow to the kidney and via an indirect pathway, mediated by the renin-angiotensin system. The renal medullary flow increase produces a washout of the medullary osmotic gradient, and the water reabsorption diminishes.     

Mitophagy in the basolateral amygdala mediates increased anxiety induced by aversive social experience

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Effect of clonidine on cardiac baroreflex delay in humans and rats

The delay τ between rising systolic blood pressure (SBP) and baroreflex bradycardia has been found to increase when vagal tone is low. The α(2)-agonist clonidine increases cardiac vagal tone, and this study tested how it affects τ. In eight conscious supine human volunteers clonidine (6 μg/kg po) reduced τ, assessed both by cross correlation baroreflex sensitivity and sequence methods (both P < 0.05). Experiments on urethane-anaesthetized rats reproduced the phenomenon and investigated the underlying mechanism. Heart rate (HR) responses to increasing SBP produced with an arterial balloon catheter showed reduced τ (P < 0.05) after clonidine (100 μg/kg iv). The central latency of the reflex was unaltered, however, as shown by the unchanged timing with which antidromically identified cardiac vagal motoneurons (CVM) responded to the arterial pulse. Testing the latency of the HR response to brief electrical stimuli to the right vagus showed that this was also unchanged by clonidine. Nevertheless, vagal stimuli delivered at a fixed time in the cardiac cycle (triggered from the ECG R-wave) slowed HR with a 1-beat delay in the baseline state but a 0-beat delay after clonidine (n = 5, P < 0.05). This was because clonidine lengthened the diastolic period, allowing the vagal volleys to arrive at the heart just in time to postpone the next beat. Calculations indicate that naturally generated CVM volleys in both humans and rats arrive around this critical time. Clonidine thus reduces τ not by changing central or efferent latencies but simply by slowing the heart.     

Assessment of alpha 2 adrenergic autoreceptor function in humans: effects of oral yohimbine

Administration of three oral doses of yohimbine (10 mg, 15 mg, 20 mg) to eight healthy subjects resulted in significant increases in plasma free 3-methoxy-4-hydroxyphenylethyleneglycol (MHPG). The 15 mg and 20 mg yohimbine doses induced modest increases in systolic blood pressure and autonomic symptoms such as piloerection and rhinorrhea. Marked behavioral effects such as anxiety were not observed. These results indicate that determination of the plasma MHPG response to yohimbine may be of value in assessing alpha 2 adrenergic autoreceptor function in humans.     

Sympathetic overactivity in active ulcerative colitis: effects of clonidine

Previous reports suggest that inflammatory bowel diseases may be accompanied by abnormalities in the neural autonomic profile. We tested the hypotheses that 1) an exaggerated sympathetic activity characterizes active ulcerative colitis (UC) and 2) a reduction of sympathetic activity by clonidine would be associated with clinical changes of UC. In 23 patients with UC and 20 controls, muscle sympathetic nerve activity (MSNA), ECG, blood pressure, and respiration were continuously recorded, and plasma catecholamine was evaluated both at rest and during a 75 degrees head-up tilt. Autonomic profile was assessed by MSNA, norepinephrine, epinephrine, spectral markers of low-frequency (LF) cardiac sympathetic (LF(RR); normalized units) and high-frequency (HF) parasympathetic (HF(RR); normalized units) modulation and sympathetic vasomotor control (LF systolic arterial pressure; LF(SAP)), obtained by spectrum analysis of the R-R interval and systolic pressure variability. Among UC patients, 16 agreed to be randomly assigned to 8-wk transdermal clonidine (15 mg/wk, 9 subjects), or placebo (7 patients). An autonomic profile, Disease Activity Index (DAI), and endoscopic pattern were compared before and after clonidine/placebo. At rest, MSNA, heart rate (HR), LF(RR), LF/HF, and LF(SAP) were higher and HF(RR) was lower in patients than in controls. Tilt decreased HF(RR) and increased MSNA and LF(RR) less in patients than in controls. Clonidine decreased HR, MSNA, epinephrine, LF(RR), and increased HF(RR), whereas placebo had no effects. Changes of the autonomic profile after clonidine were associated with reduction of DAI score. An overall increase of sympathetic activity characterized active UC. Normalization of the autonomic profile by clonidine was accompanied by an improvement of the disease.     

Suppression of norepinephrine appearance rate in plasma by diazepam in humans

Studies demonstrating benzodiazepine-induced reductions in plasma norepinephrine (NE) have assumed that changes in circulating plasma NE closely parallel changes in sympathetic nervous system (SNS) activity and that benzodiazepines suppress SNS outflow. However, decreases in plasma NE could also result from increased removal of NE from plasma via neuronal uptake or tissue metabolism. This study used a tritiated norepinephrine ([3H] NE) isotope dilution technique for measurement of plasma NE kinetics to determine if the fall in plasma NE induced by a single dose of diazepam orally administered to eight psychiatrically-healthy volunteers was due to a fall in plasma NE appearance rate or an increase in plasma NE removal. Diazepam decreased plasma NE appearance, but not clearance, and also decreased plasma epinephrine and mean arterial pressure, memory performance and alertness. Plasma levels of diazepam were correlated with drug effects on memory and alertness but not cardiovascular or SNS effects.     

Effects of clonidine and dihydralazine on atrial natriuretic factor and cGMP in humans

The effects of a 1-wk treatment with clonidine (75 micrograms/day twice a day) and dihydralazine (25 mg/day twice a day) on base-line levels of plasma atrial natriuretic factor (ANF) and plasma and urinary guanosine 3',5'-cyclic monophosphate (cGMP) and their changes by acute saline infusion (2 liters) in eight normal subjects were evaluated. Basal ANF was decreased to 65% in the clonidine group compared with both the control and dihydralazine groups. Volume loading increased plasma ANF levels by 30-40% of base-line values in the control and the dihydralazine groups and by 15% in the clonidine group. Basal plasma and urinary cGMP levels were raised by 30 and 90% in the dihydralazine group compared with both other groups. Volume loading increased plasma cGMP levels by 40% in the control and clonidine-treated groups and by 25% in the dihydralazine-treated group. It is concluded that ANF may contribute to hemodynamic effects of clonidine but not to those of dihydralazine. Dihydralazine increases plasma and urinary cGMP, supposedly by direct activation of the soluble guanylate cyclase.     

Norepinephrine transporter expression and function in noradrenergic cell differentiations

The classical view of norepinephrine transporter (NET) function is the re-uptake of released norepinephrine (NE) by mature sympathetic neurons and noradrenergic neurons of the locus ceruleus (LC; [1-3]). In this report we review previous data and present new results that show that NET is expressed in the young embryo in a wide range of neuronal and non-neuronal tissues and that NET has additional functions during embryonic development. Sympathetic neurons are derived from neural crest stem cells. Fibroblast growth factor-2 (FGF-2), neurotrophin-3 (NT-3) and transforming growth factor-1 (TGF-1) regulate NET expression in cultured quail neural crest cells by causing an increase in NET mRNA levels. They also promote NET function in both neural crest cells and presumptive noradrenergic cells of the LC. The growth factors are synthesized by the neural crest cells and therefore are likely to have autocrine function. In a subsequent stage of development, NE transport regulates differentiation of noradrenergic neurons in the peripheral nervous system and the LC by promoting expression of tyrosine hydroxylase (TH) and dopamine--hydroxylase (DBH). Conversely, uptake inhibitors, such as the tricyclic antidepressant, desipramine, and the drug of abuse, cocaine, inhibit noradrenergic differentiation in both tissues. Taken together, our data indicate that NET is expressed early in embryonic development, NE transport is involved in regulating expression of the noradrenergic phenotype in the peripheral and central nervous systems, and norepinephrine uptake inhibitors can disturb noradrenergic cell differentiation in the sympathetic ganglion (SG) and LC.     

The pentylenetetrazol model of anxiety detects withdrawal from diazepam in rats

This experiment tested whether benzodiazepine withdrawal could be detected in an animal model of anxiety. Rats were trained in operant chambers using food reward to press one lever after pentylenetetrazol (PTZ), 20 mg/kg, injection and the other lever after saline injection. Previously, the PTZ cue has been shown to be simulated by anxiogenic drugs and blocked by anxiolytic drugs. After rats reliably performed this discrimination, they were injected with diazepam, 20 mg/kg, from 1 to 4 times a day for six days. For one group of subjects, on the third, fourth and sixth days, they were also injected with 40 mg/kg of RO 15-1788, a benzodiazepine receptor antagonist, and tested for lever selection: 50–80% of the subjects selected the PTZ lever; these results are in contrast to those obtained prior to chronic diazepam treatment in which RO 15-1788 did not generalize to PTZ. A second group of subjects was also injected for six days with diazepam and then allowed to withdraw spontaneously for eight days: PTZ lever selection over this period varied from 20 to 60% of rats. These data indicate that animals trained to discriminate a PTZ cue: 1) generalize the benzodiazepine withdrawal state to the PTZ cue, and 2) discriminate the withdrawal state for long periods of time, agreeing with clinical observations of long-lasting anxiety signs during benzodiazepine withdrawal.     

Protective effects of curcumin towards anxiety and depression-like behaviors induced mercury chloride

The main objective of this work is to analyze the perinatal protective effects of curcumin (Cur) on the toxicity of inorganic mercury (mercuric chloride – HgCl₂) in the developing mice offspring on their behavioral and biochemical changes. Six groups of pregnant mice (consisting of ten animals in each) were allocated in a way that Group I consuming tap water was used as control. Groups II to VI were the experimentally treated groups in which Group II and III received 150 and 300 ppm of curcumin, respectively; Group IV was given 10 ppm of HgCl₂; and Group V and VI were also exposed to 10 ppm of HgCl₂ but concurrently they were also treated with 150 and 300 ppm of curcumin, respectively. Appearance of vaginal plug was considered as the first day of pregnancy and all treatment started from day one of pregnancy until post-natal day 15 (PD 15) and the mothers were switched to plain tap water thereafter. At the age of PD 40, the male pups were subjected to measuring the depression in the light-dark chambers, forced swimming and tail suspension tests and to measuring their anxiety in plus-maze and open-field tests. Subsequently, after behavioral tests, the levels of corticosterone and cortisol hormones were estimated in the plasma of the experimental offspring. Behavioral tests were measured in the HgCl₂ treated offspring for the light-dark chambers; forced swimming test; tail suspension test; plus-maze test; and open –field test showed significant alterations in their depression, anxiety and locomotory activities. Biochemical estimation of corticosterone and cortisol hormones in the plasma of these offspring showed significant depletion in their levels. Treatment of these offspring with curcumin significantly and dose dependently ameliorated all the behavioral and biochemical disruptive effects in the offspring due to HgCl₂ toxicity. In conclusion, curcumin ameliorates the toxic effects of HgCl₂ in the offspring during gestation and lactation periods. Thus, exposure to HgCl₂ to mothers during pregnancy needs careful monitoring for minimizing its toxicity. Curcumin appears to be a promising ameliorating agent for such HgCl₂ toxicity; however, further studies are needed for establishing these preliminary findings.     

Caffeine and theophylline counteract diazepam effects in man

A total of 237 healthy subjects were studied in four placebo-controlled double-blind trials with parallel treatment groups. The subjects ingested a capsule (diazepam or placebo) and decaffeinated coffee with or without added caffeine or theophylline. Diazepam (10 and 20 mg) impaired dose dependently cognitive skills as measured by digit symbol substitution and letter cancellation, the balance of extraocular muscles, flicker fusion, and tapping speed. With diazepam 10 mg statistically significant effects were seen on digit symbols and exophoria only. Theophylline (10 mg/kg) increased tapping speed and heart rate, whereas other objective measurements were negative for the effects of theophylline or caffeine (250 and 500 mg) alone. Subjectively they reduced calmness, and caffeine also increased alertness. Caffeine 250 mg counteracted diazepam induced (10 mg) impairment of cognitive skills and relaxation of extraocular muscles whereas caffeine 500 mg counteracted the same effects of diazepam 20 mg, respectively. Theophylline antagonized diazepam-induced impairment in digit symbol substitution and tapping speed tests. Subjectively, caffeine and theophylline counteracted diazepam induced drowsiness and mental slowness. The results suggest, therefore, that the ample use of methylxanthines compensates various side-effects of benzodiazepines in man. It may also increase the need of sedation and thus the consumption of benzodiazepines.     

Regulation of noradrenergic function by inflammatory cytokines and depolarization

Although the sympathetic neurons innervating the heart are exposed to the inflammatory cytokines cardiotrophin-1 (CT-1), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNFalpha) after myocardial infarction, the effects of these cytokines on noradrenergic function are not well understood. We used cultured sympathetic neurons to investigate the effects of these cytokines on catecholamine content, the tyrosine hydroxylase co-factor, tetrahydrobiopterin (BH4), and norepinephrine (NE) uptake. CT-1, but not IL-6 or TNFalpha, suppressed NE uptake and catecholamines in these neurons, whereas CT-1 and, to a lesser extent, IL-6 decreased BH4 content. CT-1 exerted these effects by decreasing tyrosine hydroxylase, GTP cyclohydrolase (GCH) and NE transporter mRNAs, while IL-6 lowered only GCH mRNA. The neurons innervating the heart are also activated by the central nervous system after myocardial infarction. We examined the combined effect of depolarization and cytokines on noradrenergic function. In CT-1-treated cells, depolarization caused a small increase in BH4 and NE uptake, and a large increase in catecholamines. These changes were accompanied by increased TH, GCH and NE transporter mRNAs. CT-1 and depolarization regulate expression of noradrenergic properties in an opposing manner, and the combined treatment results in elevated cellular catecholamines and decreased NE uptake relative to control cells.     

Controlled study of withdrawal symptoms and rebound anxiety after six week course of diazepam for generalised anxiety.

A group of patients suffering from anxiety, as assessed by general practitioners and psychologists using research criteria for generalised anxiety, were treated with either diazepam or placebo double blind for six weeks. This active treatment period was preceded by a one week single blind placebo "wash in" period and followed by a two week single blind placebo "wash out" period. The results suggest that diazepam can produce rebound anxiety and withdrawal symptoms when used in moderate doses and for what has previously been regarded as a safe length of time. If replicated these results have implications for the therapeutic use of benzodiazepines.     

Effects of propranolol, clonidine and hydrochlorothiazide treatment and abrupt discontinuation on central and peripheral noradrenergic activity in essential hypertension

This study was undertaken to investigate further the CNS actions of commonly employed antihypertensive drugs. Measurements of cerebrospinal fluid (CSF) and plasma catecholamines (CA) were made in an attempt to estimate the activity of central and peripheral noradrenergic neurons during treatment with or after abrupt discontinuation of treatment with clonidine (CLO), propranolol (PRO), hydrochlorothiazide (HCTZ) or placebo, in patients with essential hypertension. A randomized, parallel, placebo-controlled, single-blind design was employed. BP reductions equal to or greater than 10 mmHg were observed with CLO (0.36 +/- 0.07 mg daily), PRO (160 mg +/- 0 mg daily) or HCTZ (70 +/- 12 mg daily). CLO reduced plasma norepinephrine (NE) by 64% and PRO increased it by 25%. Neither HCTZ nor placebo modified plasma NE. Plasma renin activity (PRA) was reduced by PRO (51%, P less than 0.01) and CLO (35%, P less than 0.05). CSF-NE levels (pg/ml) were significantly lower in the CLO group (CLO: 175 +/- 23; PRO: 278 +/- 35; HCTZ: 255 +/- 34; placebo: 203 +/- 7).     

Further confirmation of the association between anxiety and CTNND2: replication in humans

The rat genome sequencing and mapping consortium found evidence for an association between the catenin‐δ2 gene (CTNND2) and anxious behaviour. We replicated these results in humans by carrying out a genetic association test in patients with panic disorder, social phobia, generalized anxiety disorder and/or agoraphobia (N = 1714) and controls (N = 4125). We further explored the association between CTNND2 and other psychiatric disorders based on publicly available genome‐wide association results. A gene‐based test showed that single nucleotide polymorphisms (SNPs) in CTNND2 have a significantly increased signal (P < 1e^?5) and decreased P‐values. Single nucleotide polymorphism rs1012176 showed the strongest association with any anxiety disorder (odds ratio: 0.8128, SE = 0.063, P = 0.00099), but this effect was not significant after correction for multiple testing. In available genome‐wide association results from the Psychiatric Genomics Consortium we found that SNPs in CTNND2 collectively showed an increased signal for schizophrenia (P < 1e^?5) and major depressive disorder (P < 1e^?5), but not for bipolar disorder. These signals remained significant after correction for potential confounders. The association between CTNND2 and anxiety was not strong enough to be picked up in the current generation of human genome‐wide analyses, indicating the usefulness of and need for animal genetic studies to identify candidate genes for further study in human samples .