Increased Plasma Norepinephrine Research Articles

Norepinephrine induces apoptosis in neonatal rat endothelial cells via down-regulation of Bcl-2 and activation of beta-adrenergic and caspase-2 pathways.

Heart failure is associated with increased plasma norepinephrine (NE) and endothelial apoptosis. Recent reports have suggested that endothelial dysfunction is an important target for future therapies of heart failure. However, whether NE can induce endothelial apoptosis and its mechanism remains unknown. Endothelial cells from neonatal rat heart were treated with various concentrations of NE for different durations. Apoptosis was assessed by terminal deoxynucleotidyl transferase-mediated nick end-labeling (TUNEL) and DNA fragmentation assays. Caspase activity was measured using specific fluorogenic substrates. Proteins of Bcl-2 family and cytochrome c were assayed by Western blotting. NE induced endothelial apoptosis in a dose- and time-dependent manner. After treatment for 48 h, increasing NE concentration from 5, 10, 50, 100 to 200 microM resulted in 6+/-3%, 14+/-5%, 43+/-4%, 66+/-5%, and 89+/-6% apoptotic cells, respectively. The apoptosis was accompanied by down-regulation of Bcl-2 protein synthesis but not by cytosolic cytochrome c translocation. Caspase-2, -3, -6 and -9 were activated during apoptosis and caspase-2 inhibitor (Z-VDVAD-FMK) and caspase-3 inhibitor (Z-DEVD-FMK) significantly attenuated the apoptosis. Overexpression of Bcl-2 inhibited caspase activity and decreased the apoptosis. Moreover, the NE-mediated apoptotic effect was attenuated by beta- (beta2>beta>beta1) adrenergic antagonists (ICI-118,551>propranolol>atenolol) but was not affected by alpha1- or alpha2-adrenergic antagonists (prazosin or yohimbine). Our study is the first report documenting that NE induces apoptosis in neonatal rat endothelial cells mainly through down-regulation of Bcl-2 protein and activation of the beta-adrenergic (beta2>beta1) and caspase-2 pathways. beta-Adrenergic antagonists and caspases inhibitors may be useful in the prevention and management of NE-mediated endothelial apoptosis during heart failure.

Serial Alterations of .BETA.-Adrenergic Signaling in Dilated Cardiomyopathic Hamsters-Possible Role of Myocardial Oxidative Stress-

The relationship between enhanced myocardial oxidative stress and impaired beta-adrenergic signaling remains to be characterized during the development of dilated cardiomyopathy. Alterations in myocardial oxidative stress and beta-adrenergic signaling, as well as left ventricular (LV) functional and structural changes, were evaluated during the development of cardiomyopathy in TO-2 hamsters; F1B hamsters served as controls. LV dysfunction was first apparent at 8 weeks of age and deteriorated thereafter in the TO-2 hamsters. At 32 weeks, the animals exhibited heart failure with an increased plasma norepinephrine concentration. Cardiac myolysis, as demonstrated by elevated plasma concentration of cardiac troponin T, peaked at 8 weeks. The glutathione redox ratio revealed increased oxidative stress in the LV myocardium in TO-2 hamsters even at 4 weeks and became manifest after 8 weeks. The hearts of TO-2 hamsters had significantly reduced superoxide dismutase activity from 8 weeks onward compared with control hamsters. However, glutathione peroxidase activity was unchanged at any time point. The LV functional response to isoproterenol was markedly reduced at 8 weeks, without any apparent changes in the amount of beta-adrenergic signaling molecules, and it deteriorated thereafter. Adenylyl cyclase activity was significantly decreased, despite increased amounts of both G(s) alpha mRNA and protein, in the LV myocardium at 18 weeks. Myocardial oxidative stress is actually enhanced in the initial development of LV dysfunction. Both activation of myocardial oxidative stress and impairment of beta-adrenergic signaling become prominent at the stage of severe LV dysfunction. Myocardial oxidative stress may be involved in the development of beta-adrenergic desensitization.

Inducible nitric oxide synthase is involved in corticotropin-releasing hormone-mediated central sympatho-adrenal outflow in rats

Brain nitric oxide (NO), recognized as a neurotransmitter or a neuromodulator, is mainly generated either by neuronal NO synthase (NOS) or by inducible NOS. NO has been shown to activate cyclooxygenase (a prostaglandin-forming enzyme) in addition to guanylate cyclase. Recently, we reported that the intracerebroventricularly (i.c.v.) administered corticotropin-releasing hormone (CRH) increases plasma catecholamines through brain cyclooxygenase-dependent mechanisms in rats [Eur. J. Pharmacol. 419 (2001) 183]. In the present experiments, therefore, we examined whether NO is involved in the CRH-induced increase of plasma catecholamines using urethane-anesthetized rats. I.c.v. administered CRH increased plasma noradrenaline and adrenaline in a dose-dependent manner (0.5, 1.5, and 3.0 nmol/animal). The CRH (1.5 nmol/animal, i.c.v.)-induced increase of plasma catecholamines was reduced by N ω-nitro- l-arginine methyl ester (a non-selective inhibitor of NOS) [111 nmol (30 μg)/animal, i.c.v.], but not by the same dose of N ω-nitro- d-arginine methyl ester (an inactive isomer of N ω-nitro- l-arginine methyl ester). The CRH-induced increase of plasma catecholamines was also reduced either by cycloheximide (an inhibitor of protein synthesis) [107 nmol (30 μg)/animal, i.c.v.] or by S-methylisothiourea (an inhibitor of inducible NOS) [71 nmol (20 μg) and 711 nmol (200 μg)/animal, i.c.v.]. These results suggest the involvement of brain inducible NOS in the CRH-induced activation of the central sympatho-adrenomedullary outflow in rats.

ACE inhibition does not exaggerate the blood pressure decrease in the early phase of spinal anaesthesia

This study investigates whether long-term treatment with an angiotensin converting enzyme inhibitor (ACEI) impairs the hemodynamic regulation during the early phase of spinal anaesthesia. Forty-two patients undergoing minor surgery were studied. Twenty-one patients were long-term treated (ACEI group), while the other patients served as controls (nonACEI group). All patients received a balanced electrolyte solution (6 ml kg(-1)) 20 min before spinal anaesthesia. Mean arterial blood pressure decreased 19% in both groups within 20 min after spinal anaesthesia. Heart rate did not change in either group. Plasma renin concentration increased from 7.3 +/- 2.1 to 12.8 +/- 4 pg ml(-1) during spinal anaesthesia in nonACEI patients (P < 0.05), whereas an elevated plasma renin level remained unchanged in the nonACEI group. The angiotensin II concentration increased in both groups during spinal anaesthesia (P < 0.05). The vasopressin concentration did not change during spinal anaesthesia in the ACEI group, but increased from 1.2 +/- 0.3 to 2.2 +/- 0.5 pg ml(-1) in patients with ACEI treatment (P < 0.05). The norepinephrine concentration increased transiently 5 min after spinal anaesthesia in both groups, and returned to baseline levels within 15 min. Long-term ACEI treatment does not further exaggerate the blood pressure decrease in the early phase of spinal anaesthesia. The increase in vasopressin concentrations in ACEI treated patients seems to be sufficient to compensate for the inhibited renin-angiotensin system. In addition, the transient increase in plasma norepinephrine, which occurs independent of preoperative ACEI treatment, seems to be involved in blood pressure regulation during spinal anaesthesia.

Change in mitochondrial membrane potential in peripheral blood lymphocytes, especially in natural killer cells, is a possible marker for surgical stress on the immune system.

There is accumulating evidence that surgical stresses cause impairment of systemic immune responses, which may promote susceptibility to infection as well as growth of remnant cancer cells in cancer patients. Although alterations in numbers, populations, and functions of lymphocytes have been extensively studied to assess modulation of the immune system, the precise mechanisms of immunosuppression caused by surgical stresses have not been identified, nor have methods been developed to estimate the magnitude of surgical stresses on the immune system. In the present study, to evaluate the effects of surgical procedures on the immune system, the mitochondrial membrane potential (Delta Psi(m)) of peripheral blood lymphocytes (PBL) from 25 patients who underwent various types of operation was measured by flow cytometry using 3,3'-dihexiloxacarbocyanine iodide (DiOC(6)(3)) on the day before operation and on postoperative day (POD) 1, POD 3, and POD 7. The Delta Psi(m) in PBL, especially in natural killer (NK) cell population, was reduced after major surgery. In particular, the reduction of Psi Delta(m) in NK cells appeared to be proportional to the severity of the surgical procedures and reflected the impairment of cellular function. Interestingly, the Delta Psi(m) in NK cells was also negatively correlated with the level of plasma noradrenaline after major surgery, suggesting that the reduction of Delta Psi(m) in NK cells induced by surgical stresses may be mediated, at least in part, by the accompanying increase in plasma noradrenaline. Monitoring of Delta Psi(m) in PBL after operation may be one of the useful markers for estimating the magnitude of surgical stresses on the immune system.

Efficacy of losartan in hypertensive obese patients

Aim of the study was to compare the effect of losartan and felodipine on blood pressure (BP) and plasma norepinephrine (pNE) in hypertensive patients with obesity, a condition characterized by increased sympathetic activity. Fifty-four obese patients (BMI > 30 Kg/m2) with mild to moderate hypertension (DBP evaluated with appropriate size cuff ≥ 95 mmHg < 110 mmHg) aged 32-58 years after a 4 week placebo period were randomized to Losartan 50 mg (n = 27) or to felodipine 5 mg(n = 27) for 16 weeks; after the first 4 weeks of treatment there was a titration with dose doubling in non responder (DBP > 90 mmHg) patients. At the end of the placebo period and of each treatment period BP and BMI were evaluated and a venous sample was drawn in the morning at the same hour to evaluate pNE. No dietary advice was prescribed for the duration of the study. The main results are shown in the table. Main Results *P < 0.05; **P < 0.01 vs placebo Main Results *P < 0.05; **P < 0.01 vs placebo Both losartan and felodipine significantly decreased BP withouth any differences between the two treatments, however felodipine increased plasma norepinephrine and had no effect on body weight, while Losartan induced a small but significant BMI reduction. These data suggest that Angiotensin II antagonists could be drugs of choice for the treatment of hypertension in obese patients.

The response of endocrine system to stress loads during space flight in human subject

The responses of endocrine system to the exposure to stress-work load and hormonal changes during oral glucose tolerance tests were studied in the Slovak astronaut before (three weeks before flight), during (on the 4th and the 6th days of space flight), and after space flight (1–3 days and 15–17 days after space flight) on board of space station MIR. Blood samples during the tests were collected via cannula inserted into cubital vein, centrifuged in the special appliance Plasma-03, frozen in Kryogem-03, and at the end of the 8-day space flight transforred to Earth in special container for hormonal analysis. Preflight workload produced an increase of plasma norepinephrine and a moderate elevation of epinephrine levels. Plasma levels of insulin, growth hormone, prolactin and cortisol were not markedly changed immediately or 10 min after the end of work load. The higher increases of plasma growth hormone, prolactin and catecholamine levels were noted after workload during space flight as compared to preflight response. The higher plasma glucose and insulin levels were noted during the oral glucose tolerance test in space flight and also in the post flight period. Plasma epinephrine levels were slightly decreasing during glucose tolerance test; however, plasma norepinephrine levels were not changed. The similar patterns of catecholamine levels during glucose tolerance test were found when compared the preflight, in-flight and post flight values. These data demonstrate the changes of the dynamic responses of endocrine system to stress-work and metabolic loads during space flight in human subject.

Selegiline attenuates cardiac oxidative stress and apoptosis in heart failure: association with improvement of cardiac function

We have shown recently that selegiline exerts a cardiac neuroprotective effect in chronic heart failure. Since selegiline has an antioxidant antiapoptotic effect, we proposed to determine whether selegiline attenuates cardiac oxidative stress and myocyte apoptosis in chronic heart failure by modulating Bcl-2 and Bax protein expression, and whether the effects are associated with the improvement of cardiac function. Rabbits with rapid cardiac pacing (360 beats/min) and sham operation without pacing were randomized to receive oral selegiline (1 mg/day) or placebo for 8 weeks. Echocardiography was used to measure left ventricular fractional shortening. After 8 weeks of treatment, animals were studied for arterial norepinephrine and left ventricular systolic function (fractional shortening and d P/d t), and were then sacrificed for measuring the stable oxidative product of myocardial mitochondrial DNA (mtDNA) 8-oxo-7,8-dihydro-2′-deoxyguanosine (8-oxo-dG), myocyte apoptosis by monoclonal antibody to single stranded DNA, and Bcl-2 and Bax protein expression by Western blot and immunohistochemistry. Rapid cardiac pacing increased plasma norepinephrine, cardiac oxidative stress and myocyte apoptosis, reduced Bcl-2 and the Bcl-2 to Bax ratio. These changes were associated with decreased left ventricular fractional shortening and d P/d t. Selegiline treatment in chronic heart failure animals reduced plasma norepinephrine, cardiac oxidative stress and myocyte apoptosis, prevented the changes of Bcl-2 and Bcl-2 to Bax ratio, and improved left ventricular fractional shortening and d P/d t. The findings suggest that the reduction by selegiline of myocyte apoptosis is related to the decrease of cardiac oxidative stress and the modulation of apoptotic and antiapoptotic proteins. The antioxidant antiapoptotic effects of selegiline are potentially beneficial in the improvement of cardiac function in chronic heart failure.

Neurohormonal determinants of peak oxygen uptake in patients with chronic heart failure.

Chronic heart failure (CHF) is characterized by the activation of neurohormones and cytokines. This study determined whether peak oxygen uptake (VO2) can be predicted by the degree of neurohormonal and cytokine activations in CHF. Plasma norepinephrine. epinephrine, renin-angiotensin system activity, ANP, BNP, and serum interleukin-6 (IL-6) and tumor necrosis factor (TNF)-alpha were measured in 84 CHF patients (age, 59 +/- 1 years, LVEF, 36 +/- 1%) and 34 controls. Maximal cardiopulmonary exercise testing was performed. Peak VO2 (Controls vs CHF: 27.8 +/- 1.3 vs 18.2 +/- 0.5 mL/min/kg, P < 0.0001) was lower in CHF. Patients with CHF had increased plasma norepinephrine (211 +/- 11 vs 315 +/- 24 pg/mL), renin activity (1.2 +/- 0.2 vs 6.2 +/- 1.1 ng/mL/hr), ANP (22 +/- 3 vs 72 +/- 7 pg/mL), and BNP levels (18 +/- 3 vs 200 +/- 25 pg/mL) (all P < 0.01). Serum IL-6 (1.1 0.1 vs 2.4 +/- 0.3 pg/mL) and TNF-alpha (2.7 +/- 0.2 vs 4.0 +/- 0.3 pg/mL) levels were higher in CHF (both P < 0.001). Univariate analysis revealed that age (P < 0.001), cardiothoracic ratio (P < 0.001), norepinephrine (P < 0.0001), ANP (P < 0.001), BNP (P < 0.01), and log IL-6 (P < 0.05) were significantly related with peak VO2. Stepwise regression analysis indicated that plasma norepinephrine and ANP emerged as significant determinants of peak VO2, independent of patient age (overall R = 0.61, P < 0.0001). In summary, patients with CHF exhibited activation of neurohormones and proinflammatory cytokines. Among the elevated hormonal and cytokine markers, plasma norepinephrine and ANP levels were independent predictors of exercise capacity.

Schizophrenic Patients Who Develop Postoperative Confusion Have an Increased Norepinephrine and Cortisol Response to Surgery

The purpose of this study was to investigate the relationship between postoperative confusion and the plasma norepinephrine (NE), adrenocorticotropin (ACTH) or cortisol response to surgery in schizophrenic patients. We studied 50 schizophrenic patients and 35 control patients who underwent orthopedic surgery and perioperatively measured plasma NE, ACTH and cortisol levels. Postoperative confusion during 72 h after the end of the operation occurred in 14 of 50 schizophrenic patients (28%) and in 2 of 35 control patients (6%). Plasma NE levels 15 min after skin incision, the next day, the second day and the third day after operation in schizophrenic patients with postoperative confusion (668.0 ± 59.2, 522.0 ± 96.5, 463.2 ± 71.2 and 398.9 ± 56.2 pg/ml, respectively) were significantly higher than those in schizophrenic patients without confusion (524.1 ± 62.6, 342.4 ± 38.6, 311.2 ± 58.3 and 314.1 ± 77.1 pg/ml, respectively). Plasma cortisol levels 15 min after the skin incision and the next and second days after operation in schizophrenic patients with postoperative confusion (23.6 ± 3.2, 21.1 ± 4.3 and 19.9 ± 4.4 µg/dl, respectively) were significantly higher than those in schizophrenic patients without confusion (15.2 ± 4.5, 14.3 ± 5.1 and 13.8 ± 3.8 µg/ dl, respectively). In conclusion, the occurrence of postoperative confusion in schizophrenic patients is associated with an increase in plasma norepinephrine and cortisol levels during and after surgery.

Effects of Risperidone on the Peripheral Noradrenegic System in Patients with Schizophrenia: A Comparison with Clozapine and Placebo

Risperidone is an atypical antipsychotic drug that increases plasma norepinephrine (NE) levels, but the mechanism behind this effect is unclear. We measured arterial plasma levels of NE and other catechols during intravenous infusion of tritium-labeled NE (3H-NE) in risperidone-treated patients and compared their data with those from patients treated with clozapine or placebo. NE levels in risperidone patients were significantly higher than in placebo patients, but lower than in clozapine patients. Neither drug, however, had significant effect on plasma levels of the main neuronal metabolite of NE, dihydroxyphenylglycol (DHPG), suggesting that adrenoceptors blockade alone would not explain the NE findings. The rate of release of endogenous NE into the bloodstream (spillover) was elevated in both risperidone and clozapine patients in a manner that paralleled their NE levels; the NE clearance in both groups did not differ from placebo. Following 3H-NE infusion in risperidone-treated individuals, production of 3H-DHPG was normal, as it was in the clozapine group, suggesting that risperidone does not impede neuronal uptake or intraneuronal metabolism of NE by monoamine oxidase. Our data suggest that both risperidone and clozapine elevate plasma NE levels via enhanced neurotransmitter spillover, with risperidone producing a smaller effect.

Renal injury caused by intrarenal injection of phenol increases afferent and efferent renal sympathetic nerve activity

Intrarenal injection of phenol in rats causes a persistent elevation in blood pressure (BP) and in norepinephrine (NE) secretion from the posterior hypothalamus (PH), and downregulation of neuronal nitric oxide synthase (nNOS) and interleukin-1β (IL-1β) in the PH. These studies suggest that afferent impulses from the kidney to the brain may be responsible for hypertension associated with renal injury. Downregulation of nNOS and IL-1β, two modulators of sympathetic nervous system (SNS) activity may mediate this activation. In this study we measured the effects of intrarenal phenol injection on peripheral SNS activity by direct renal nerve recording, plasma NE, nNOS, and IL -1β abundance in the brain. We also determined whether renal denervation or administration of clonidine prevented these effects of phenol. Acutely, the phenol injection increased both afferent and efferent renal sympathetic nerve activity, decreased urinary sodium excretion, and increased plasma NE. Three weeks after the phenol injection, BP and plasma NE remained elevated. Renal denervation and pretreatment with clonidine prevented the increase in BP and plasma NE caused by phenol. Chronic renal injury caused by phenol was associated with decreased abundance of IL-1β and nNOS in the PH. These studies have shown that a renal injury caused by phenol injection increases BP and central as well as peripheral SNS activity, which persist long after the injury. Renal denervation and antiadrenergic drugs abolish the effects of phenol on BP and plasma NE. Because NO and IL-1β modulate SNS activity, the stimulatory action of phenol on the SNS could be mediated by downregulation of nNOS and IL-1β in the brain.

Human aquaporin adipose (AQPap) gene. Genomic structure, promoter analysis and functional mutation.

Aquaporin adipose (AQPap), which we identified from human adipose tissue, is a glycerol channel in adipocyte [Kishida et al. (2000) J. Biol. Chem. 275, 20896-20902]. In the current study, we determined the genomic structure of the human AQPap gene, and identified three AQPap-like genes that resembled (approximately 95%) AQPap, with little expression in human tissues. The AQPap promoter contained a putative peroxisome proliferator response element (PPRE) at -46 to -62, and a putative insulin response element (IRE) at -542/-536. Deletion of the PPRE abolished the pioglitazone-mediated induction of AQPap promoter activity in 3T3-L1 adipocytes. Deletion and single base pair substitution analysis of the IRE abolished the insulin-mediated suppression of the human AQPap gene. Analysis of AQPap sequence in human subjects revealed three missense mutations (R12C, V59L and G264V), and two silent mutations (A103A and G250G). The cRNA injection of the missense mutants into Xenopus oocytes revealed the absence of the activity to transport glycerol and water in the AQPap-G264V protein. In the subject homozygous for AQPap-G264V, exercise-induced increase in plasma glycerol was not observed in spite of the increased plasma noradrenaline. We suggest that AQPap is responsible for the increase of plasma glycerol during exercise in humans.

Plasma norepinephrine predicts survival and incident cardiovascular events in patients with end-stage renal disease.

Sympathetic tone is consistently raised in patients with end-stage renal disease (ESRD). We therefore tested the hypothesis that sympathetic activation is associated with mortality and cardiovascular events in a cohort of 228 patients undergoing chronic hemodialysis who did not have congestive heart failure at baseline and who had left ventricular ejection fraction >35%. The plasma concentration of norepinephrine (NE) was used as a measure of sympathetic activity. Plasma NE exceeded the upper limit of the normal range (cutoff 3.54 nmol/L) in 102 dialysis patients (45%). In a multivariate Cox regression model that included all univariate predictors of death as well as the use of sympathicoplegic agents and beta-blockers, plasma NE proved to be an independent predictor of this outcome (hazard ratio [1-nmol/L increase in plasma NE]: 1.07, 95% CI 1.01 to 1.14, P=0.03). Similarly, plasma NE emerged as an independent predictor of fatal and nonfatal cardiovascular events (hazard ratio [1-nmol/L increase in plasma NE] 1.08, 95% CI 1.02 to 1.15, P=0.01) in a model that included previous cardiovascular events, pulse pressure, age, diabetes, smoking, and use of sympathicoplegic agents and beta-blockers. The adjusted relative risk for cardiovascular complications in patients with plasma NE >75th percentile was 1.92 (95% CI 1.20 to 3.07) times higher than in those below this threshold (P=0.006). Sympathetic nerve overactivity is associated with mortality and cardiovascular outcomes in ESRD. Controlled trials with antiadrenergic drugs are needed to determine whether interference with the sympathetic system could reduce the high cardiovascular morbidity and mortality in dialysis patients.

Perinatal malnutrition programs sympathoadrenal and hypothalamic-pituitary-adrenal axis responsiveness to restraint stress in adult male rats.

In humans, an altered control of cortisol secretion was reported in adult men born with a low birth weight making the hypothalamic-pituitary-adrenal (HPA) axis a possible primary target of early life programming. In rats, we have recently shown that maternal food restriction during late pregnancy induces both an intrauterine growth retardation and an overexposure of fetuses to maternal corticosterone, which disturb the development of the HPA axis in offspring. The first aim of this work was to investigate, in adult male rats, whether perinatal malnutrition has long-lasting effects on the HPA axis activity during both basal and stressful conditions. Moreover, as the HPA axis and sympathetic nervous system are both activated by stress, the second aim of this work was to investigate, in these rats, the adrenomedullary catecholaminergic system under basal and stressful conditions. This study was conducted on 4-month-old male rats malnourished during their perinatal life and on age-matched control animals. Under basal conditions, perinatal malnutrition reduced body weight and plasma corticosteroid-binding globulin (CBG) level but increased mineralocorticoid receptor (MR) gene expression in CA1 hippocampal area. After 30 min of restraint, perinatally malnourished (PM) rats showed increased plasma noradrenaline, adrenocorticotropin hormone (ACTH) and corticosterone concentrations similarly as controls, but calculated plasma-free corticosterone concentration was significantly higher and adrenaline level lower than controls. During the phase of recovery, PM rats showed a rapid return of plasma ACTH and corticosterone concentrations to baseline levels in comparison with controls. These data suggest that in PM rats, an elevation of basal concentrations of corticosterone, in face of reduced CBG and probably increased hippocampal MR lead to a much larger impact of corticosterone on target cells that mediate the negative-feedback mechanism on the activities of both the HPA axis and sympathoadrenal one.

Loss of cardiac sympathetic neurotransmitters in heart failure and NE infusion is associated with reduced NGF.

Sympathetic neurotransmitters are diminished in cardiac efferent nerve endings in congestive heart failure (CHF). Similar changes occur after exogenous norepinephrine (NE) infusion. Since NE reduces nerve growth factor (NGF) in cultured cardiomyocytes, we proposed to determine whether the loss of noradrenergic transmitters in the failing heart is caused by the NE-mediated reduction of NGF or its neurotrophic receptor tyrosine kinase A (TrKA). Dogs were assigned to receive either rapid ventricular pacing (225 beats/min) or NE infusion (0.5 microg/kg/min) for 8 wk. Control animals received either cardiac pacing of 100 beats/min or saline infusion. We measured NGF and TrKA proteins by Western blot and immunocytochemistry and measured NGF and TrKA mRNAs by reverse transcription polymerase chain reaction, neuronal catecholaminergic histofluorescence, tyrosine hydroxylase-immunostained profiles, and plasma NE. Rapid ventricular pacing produced CHF with increased plasma NE, decreased myocardial NGF protein (0.61 +/- 0.07 vs. 1.04 +/- 0.04, P < 0.05), TrKA protein (0.75 +/- 0.08 vs. 0.98 +/- 0.06, P < 0.05), NGF and TrKA mRNAs and reduced catecholaminergic histofluorescence (197 +/- 23 vs. 485 +/- 43, P < 0.05), and tyrosine hydroxylase profiles (360 +/- 51 vs. 773 +/- 36, P < 0.05). Decreases in tissue NGF and TrKA protein were also noted by immunocytochemistry. Similar changes occurred in NE-treated animals. Tissue NGF and TrKA levels correlated closely with the noradrenergic transmitter profiles. We conclude that cardiac NGF and TrKA are reduced by rapid ventricular pacing and NE infusion, and that these changes correlate with decreases of cardiac catecholaminergic and tyrosine hydroxylase profiles. Findings indicate that decrease of cardiac sympathetic transmitters in heart failure is associated with NE-mediated reduction of NGF and TrKA.

Sleep Deprivation in the Rat: X. Integration and Discussion of the Findings

The results of a series of studies on total and selective sleep deprivation in the rat are integrated and discussed. These studies showed that total sleep deprivation, paradoxical sleep deprivation, and disruption and/or deprivation of non-rapid eye movement (NREM) sleep produced a reliable syndrome that included death, debilitated appearance, skin lesions, increased food intake, weight loss, increased energy expenditure, decreased body temperature during the late stages of deprivation, increased plasma norepinephrine, and decreased plasma thyroxine. The significance of this syndrome for the function of sleep is not entirely clear, but several changes suggested that sleep may be necessary for effective thermoregulation.

Association Analysis of Arg16Gly Polymorphism of the β 2 -Adrenergic Receptor Gene in Offspring from Hypertensive and Normotensive Families

Objective: Since g 2 -adrenergic receptors ( g 2 AR) can influence blood pressure not only by vasodilation, but also participate in noradrenaline release from sympathetic nerve endings, we have studied whether Arg16Gly polymorphism of the g 2 AR gene is associated with predisposition to essential hypertension and increased plasma noradrenaline concentration in offspring from normotensive (SN) and hypertensive parents (SH). Design and methods: The study population consisted of 105 young SN and 101 SH subjects matched for age and body mass index. Arg16Gly polymorphism of the g 2 AR gene was determined by polymerase chain reaction (PCR) technique and subsequent incubation with NcoI restriction enzyme. Resulting fragments were separated using electrophoresis on a 4.2% Metaphor agarose gel. Results: SH already had significantly higher systolic BP, and a tendency to higher diastolic BP than the SN group. The frequency of Arg/Arg homozygotes was significantly increased in SH when compared to SN (25% vs 15%). Results of logistic regression analysis showed the highest relative risk for the Arg/Arg genotype and suggested a recessive action of the Arg16 variant. There was an increased diastolic BP in Arg/Arg homozygotes of the SN group ( p = 0.029). This genotype also had a tendency to increased heart rate in both groups ( p = 0.049). There was no relationship of this polymorphism with plasma noradrenaline concentration. Conclusion: Our findings suggest that genetic variability of the g 2 AR gene is implicated in predisposition to essential hypertension. However, the contradictory results between individual studies indicate that the action of the g 2 AR gene is indirect, through multiple intermediate phenotypes and gene interactions.

Threshold for adrenomedullary activation and increased cardiac work during mild core hypothermia

Postoperative hypothermia increases the incidence of ischaemic cardiac events in patients at risk, but the underlying mechanism is unclear. One possibility is increased cardiac work related to the sympathoneural or adrenomedullary hormonal responses. In awake human volunteers, the present study assessed the effects of mild core hypothermia on these responses, and on the associated changes in indices of cardiac work. A total of 11 healthy men were studied on two separate days. On one day, core temperature (T(c)) was decreased by the intravenous infusion of cold normal saline (4 degrees C; 60 ml/kg over 30 min) through a central venous catheter. On the other day (normothermic control), warm normal saline (37 degrees C; 60 ml/kg over 30 min) was given intravenously. Transthoracic echocardiograms, the sympathoneural response (noradrenaline) and the adrenomedullary response (adrenaline) were evaluated before, during and after the intravenous infusions. Echocardiography was used to measure left ventricular function and cardiac output. Compared with the normothermic control treatment, core cooling of 0.7 degrees C was associated with increased plasma noradrenaline (220% increase; P=0.001), whereas adrenaline, cardiac output, heart rate and the rate-pressure product were unchanged. After core cooling of 1.0 degrees C, increases in noradrenaline (by 230%; P=0.001), adrenaline (by 68%; P=0.05), cardiac output (by 23%; P=0.04), heart rate (by 16%; P=0.04) and rate-pressure product (by 25%; P=0.007) were all significant compared with the normothermic control treatment. In conclusion, there is a T(c) threshold, below which an adrenomedullary (adrenaline) response is triggered in addition to the sympathoneural (noradrenaline) response. This T(c) threshold (approximately 1 degrees C below the normothermic baseline) is also associated with an increase in haemodynamic indices of cardiac work. Mild core hypothermia therefore constitutes a catecholamine-mediated cardiovascular "stress test".

Threshold for adrenomedullary activation and increased cardiac work during mild core hypothermia

Postoperative hypothermia increases the incidence of ischaemic cardiac events in patients at risk, but the underlying mechanism is unclear. One possibility is increased cardiac work related to the sympathoneural or adrenomedullary hormonal responses. In awake human volunteers, the present study assessed the effects of mild core hypothermia on these responses, and on the associated changes in indices of cardiac work. A total of 11healthy men were studied on two separate days. On one day, core temperature (Tc) was decreased by the intravenous infusion of cold normal saline (4°C; 60ml/kg over 30min) through a central venous catheter. On the other day (normothermic control), warm normal saline (37°C; 60ml/kg over 30min) was given intravenously. Transthoracic echocardiograms, the sympathoneural response (noradrenaline) and the adrenomedullary response (adrenaline) were evaluated before, during and after the intravenous infusions. Echocardiography was used to measure left ventricular function and cardiac output. Compared with the normothermic control treatment, core cooling of 0.7°C was associated with increased plasma noradrenaline (220% increase; P = 0.001), whereas adrenaline, cardiac output, heart rate and the rate-pressure product were unchanged. After core cooling of 1.0°C, increases in noradrenaline (by 230%; P = 0.001), adrenaline (by 68%; P = 0.05), cardiac output (by 23%; P = 0.04), heart rate (by 16%; P = 0.04) and rate-pressure product (by 25%; P = 0.007) were all significant compared with the normothermic control treatment. In conclusion, there is a Tc threshold, below which an adrenomedullary (adrenaline) response is triggered in addition to the sympathoneural (noradrenaline) response. This Tc threshold (≈ 1°C below the normothermic baseline) is also associated with an increase in haemodynamic indices of cardiac work. Mild core hypothermia therefore constitutes a catecholamine-mediated cardiovascular ‘stress test’.