Assessment of sympathoneural activity in clinical research

Titanium-treated surroundings attenuate psychological stress associated with autonomic nerve regulation in office workers with daily emotional stress

Housing mice in the presence of small particles of titanium has been shown to reduce stress-responsive behavior via the autonomic nervous system. Here, we examined the effects of nighttime titanium exposure on stress parameters and autonomic nerve activity in office workers with emotional stress. A randomized double-blind, placebo controlled trial was performed in 24 male subjects with desk jobs, who were randomly allocated to spend 5 nights in rooms with or without titanium. The serum concentrations of stress-responsive hormones (cortisol, adrenocorticotropin, and catecholamine) were measured, and profiles of emotional stress were collected to subjectively assess relaxation. Autonomic nerve activity was examined by power spectra analysis of heart rate variability. In psychological tests, factors related to tension (-14.5%, 95% CI=-15.7--2.1), anger (-11.3%, 95% CI=-13.9--0.7), and emotional stress (-28.5%, 95% CI=-30.0--5.3) were significantly decreased by exposure to titanium. The serum level of adrenocorticotropin was gradually elevated throughout the experimental period in the placebo group (day 4, 80.5%, 95% CI=7.1-37.5 vs. before trial) but not the titanium group. Power spectral analysis of R-R interval data showed a significant elevation in the high-frequency power spectral ratio in subjects housed in titanium rooms (days 1-2, 14.3%, 95% CI=4.7-21.9; days 3-4, 26.8%, 95% CI=4.9-38.7; and days 5-6, 24.1%, 95% CI=5.8-34.0 vs. before trial). These results suggest that sleeping in a room containing titanium lowers physiological and psychological stress.

Effect of esmolol on positive-pressure ventilation-induced variations of arterial pressure in anaesthetized humans

Positive-pressure ventilation-induced variations in arterial pressure have been related to cardiac sympathetic activity in animals. However, the effect of β-adrenoceptor blockade on these variations in anaesthetized humans under positive-pressure ventilation has not yet been investigated. In the present study, RAPV (respiratory-related arterial pressure variability) and %SPV (percentile systolic pressure variation) were determined before and after esmolol treatment in ten mechanically ventilated patients. RAPV and %SPV decreased significantly after intravenous esmolol (1 mg/kg of body weight) treatment (maximal decrease of RAPV, 50% and %SPV, 35%). Linear regression analysis of RAPV and %SPV before and after esmolol treatment both revealed high correlation (r=0.93 and 0.91 respectively). The amplitudes of RAPV and %SPV also significantly increased in a graded way with higher tidal volumes. Thus we propose that esmolol suppresses the variations in arterial pressure induced by positive-pressure mechanical ventilation, and we suggest that RAPV and %SPV may be alternative choices for monitoring cardiac sympathetic regulation in anaesthetized patients under positive-pressure ventilation.

Anxiety and high plasma catecholamines do not impair pharmaco-induced erection of psychogenic erectile dysfunctional patients

The aim of this study was to assess the influence of anxiety and plasma catecholamines on the pharmaco-induced erection of psychogenic erectile dysfunction (ED) patients. A total of 23 patients with psychogenic ED aged from 19 to 43 y were submitted to: (1) anxiety evaluation by the Spielberger's State and Trait Anxiety Inventory-STAI; (2) intracavernous injection of PGE1 10 microg+phentolamine 1 mg with the response monitored by Rigiscan; (3) blood sampling from cavernous bodies and cubital vein for adrenaline and noradrenaline levels determination by high performance liquid chromatography. The whole procedure was done in a single clinical setting at the same day. We found no significant correlation between the erection rigidity and the cavernous or peripheral catecholamines or between erection rigidity and anxiety scores. Some patients showed rigid erections despite high anxiety scores or penile catecholamine levels while others, with incomplete erections, had much smaller levels. These results are suggestive of a more complex mechanism controlling the penile sympathetic responsiveness in psychogenic ED patients.

Role of epinephrine in acute stress

This article presents the likely pathway of stimuli generated by the recognition of high-intensity stressors to ultimately produce a fight-or-flight response. A key element is the recognition that psychological stressors that do not directly alter the internal environment represent the most important etiology of a fight-or-flight response. Adrenomedullary secretion is a critical component of that response; impromptu stimulation of the adrenal medulla can produce plasma epinephrine concentrations greater than 10,000 pg/mL. When these plasma levels reach the hypothalamus to act on the CNS, the result is facilitation of the decision making, and decision execution processes (fight-or-flight), and perhaps further sympathetic stimulation and vasopressin release. Subjects with underlying cardiovascular and/or metabolic pathology may be particularly susceptible to potentially lethal reactions to this neuroendocrine response. Additionally, since this biological reaction may be triggered by sudden changes in the social environment, the coordinated actions of epinephrine, sympathetic stimulation and vasopressin must be directed at not only optimizing the chances for survival, but also at attaining maximal preservation of the individual environmental and social domains.

Early reduction in plasma norepinephrine during beta-blocking therapy with metoprolol in chronic heart failure

BACKGROUND

The possible role exerted by modulation of sympathetic outflow in the clinical effects of beta-blockade in chronic heart failure was tested during short- and long-term treatment.

METHODS AND RESULTS

Oral metoprolol (30-150 mg/day) was added to conventional therapy in 14 patients with idiopathic dilated cardiomyopathy, left ventricular ejection fraction (LVEF) of <0.45, and New York Heart Association class II or III. Norepinephrine plasma levels, which are an index of sympathetic activation, decreased by 27.57 +/- 18.03% after 1 month (P < .005), but returned to pretreatment levels after 6 months. LVEF increased by 7.7 +/- 6.0 ejection fraction units after 6 months (P < .005 vs baseline and P < .05 vs 1 month). Long-term beta-blockade resulted in nonsignificant improvements in functional class, symptom score, and oxygen consumption at peak exercise. After 1 month, the reduction in plasma norepinephrine levels and the changes in LVEF were inversely correlated (P < .01). No other correlation emerged during short- or long-term treatment.

CONCLUSION

In conclusion, the reduction in plasma norepinephrine levels during short-term beta-blockade was not proportional to the clinical benefits and may have been attributed to the direct inhibition of sympathetic outflow. The early reduction in circulating norepinephrine levels may decrease cardiac performance through withdrawal of sympathetic support when the favorable effects of beta-blockade have not had time to occur. The role that sympathetic modulation may exert in the long-term clinical benefits of metoprolol deserves further investigation.

Myocardial interstitial noradrenaline monitoring during occlusion of inferior vena cava in cats

To investigate myocardial interstitial noradrenaline (NA) kinetics during activation of systemic sympathetic nerves, we applied a dialysis technique to the left ventricle of anaesthetised cats and monitored myocardial interstitial NA levels during 6-min occlusion of the inferior vena cava (IVC). Dialysis probes were implanted in the left ventricular wall, and dialysate NA levels as an index of myocardial interstitial NA levels, were measured with high-performance liquid chromatographic-electrochemical detection. During IVC occlusion, dialysate NA levels progressively increased from 110 +/- 17 pmol L-1 in the control and reached 620 +/- 160 pmol L-1 at 4-6 min of IVC occlusion. Local administration of omega-conotoxin GVIA at 10 microM decreased the control dialysate NA level to 35 +/- 0.2 pmol L-1. The IVC occlusion induced increase in dialysate NA was suppressed only at 0-2 min of IVC occlusion. Intravenous injection of omega-conotoxin GVIA (10 micrograms kg-1) did not increase the dialysate NA levels during IVC occlusion. Local administration of desipramine at 100 microM increased the control dialysate NA level to 900 +/- 73 pmol L-1. The IVC occlusion induced progressive increase in dialysate NA was augmented at 2-6 min of IVC occlusion. These results suggest that the early increase in myocardial interstitial NA levels is mainly caused by neuronal release of NA from cardiac sympathetic nerve terminals, and that extraction from the circulation and neuronal NA uptake contribute to changes in myocardial interstitial NA levels after a delay of several minutes.

Effects of locally administered desipramine on myocardial interstitial norepinephrine levels

We investigated whether locally administered neuronal uptake blockade with desipramine (DMI) modified basal myocardial interstitial norepinephrine (NE) levels and stimulation-induced NE responses. Using the dialysis technique, dialysates were sampled from the midwall of the left ventricle in anesthetized cats. Dialysate NE concentrations, as an index of myocardial interstitial NE level, were measured by high performance liquid chromatography. Through the dialysis probe, local administration of DMI (10(-4) mol/l) increased the dialysate NE level from 24.6 +/- 12.2 to 127.8 +/- 37.4 and from 11.9 +/- 5.4 to 64.9 +/- 28.7 pg/ml regardless of whether stellate ganglia were intact or transected. The arterial pressure and heart rate responses to electrical stimulation of the stellate ganglia were not altered by DMI. Control nerve stimulation increased dialysate NE concentrations to 214.5 +/- 100.0 and 57.5 +/- 22.0 pg/ml at 5 Hz and 2 Hz, respectively. During local administration of DMI, nerve stimulation-induced NE response increased to 997.5 +/- 202.0 at 5 Hz and to 436.0 +/- 68.5 pg/ml at 2 Hz. We conclude that local administration of DMI caused marked rises in basal myocardial interstitial NE concentrations and responses to cardiac sympathetic activation.

Routine high-performance liquid chromatographic determination of myocardial interstitial norepinephrine

The present study describes a high-performance liquid chromatographic-electrochemical detection (HPLC-ED) system for routine measurement of the low levels of norepinephrine (NE) found in the myocardial interstitial space. In this system, an in vivo detection limit of 100 fg in a 50-microliters injection was achieved for NE. Using cardiac dialysis technique, 20-microliters dialysates were sampled from the myocardial interstitial space at 2-min intervals. The basal dialysate NE concentration was 16.6 +/- 4.0 pg/ml. This low detection limit allowed the dialysate NE concentration to be monitored for dysfunction of the cardiac sympathetic nerve terminal. This system offers a new possibility for routine analysis of myocardial interstitial NE levels.

Young borderline hypertensives are hyperreactive to mental arithmetic stress: spectral analysis of R-R intervals

To investigate whether sympathetic tone and its reactivity to stress are increased in borderline hypertension, we compared pressor and autonomic nervous responses to mental arithmetic stress in male borderline hypertensives (BH) and normotensive volunteers (NT). Three age groups, 30, 40 and 50-year-old groups, which included 30 to 39, 40 to 49 and 50 to 59-year-old subjects, were studied. Fractional LF (%LF), fractional HF (%HF) and L/H, obtained from the power spectrum of R-R intervals, were used as indices of autonomic nervous function. Baseline autonomic nervous indices did not differ between NT and BH of any age group. Blood pressure rose higher during mental arithmetic stress in 50 than in 30-year-old NT but not in comparable age groups of BH. Pressor responses were augmented in BH compared to NT only in the 30-year-old group. However, the differences were not significant when pressor responses were expressed as percent increases in blood pressure. Both %L and L/H increased during arithmetic stress. The increase in %L did not differ between NT and BH but that in L/H (% delta L/H) was larger in 50 than in 30-year-old NT. % delta L/H was larger in BH than in NT only in the 30-year-old group. These findings suggest that both pressor and autonomic nervous responses to metal arithmetic stress were altered by aging and augmented in BH compared to NT in the 30-year-old group.

Heart rate power spectrum analysis of autonomic dysfunction in adolescents with anorexia nervosa

We studied autonomic modulation of heart rate in 8 females with anorexia nervosa (AN) using power spectral analysis (PSA) of heart rate variability in the supine and standing positions at baseline and after 2 weeks of intensive nutritional rehabilitation, and compared findings with healthy female control subjects. The results indicate that there is a decrease in sympathetic modulation of heart rate, evident by a deficit of low frequency (0.01-0.15 Hz) heart rate power in the supine position in AN compared with control subjects. In addition, parasympathetic modulation of heart rate failed to decrease with standing. A trend toward improvement in autonomic control of heart rate in adolescents with AN occurs in the supine position relatively early in weight rehabilitation. PSA is a sensitive, quantitative, and noninvasive means of determining autonomic control of heart rate and could be a useful tool in monitoring the health of patients with AN.

Plasma neuropeptide Y in healthy children: influence of age, anaesthesia and the establishment of an age-adjusted reference interval

Plasma concentrations of neuropeptide Y, analysed in 112 healthy children, decreased significantly with age, while sex, discomfort induced by the sampling procedure or induction of general anaesthesia did not have a significant influence. An age-adjusted upper reference limit was established and proved to be useful when tested prospectively in 56 children with tumours. Two of 18 children with preliminary diagnosis of rhabdomyosarcoma had elevated plasma neuropeptide Y; both showed malignant ectomesenchymoma (p < 0.01), a mixed tumour with neural crest features. Among 38 children with neural crest derived tumours, all 7 with benign ganglioneuromas had plasma neuropeptide Y concentrations below the reference limit, while 13 of 31 with neuroblastoma had elevated concentrations (p < 0.05). Only neuroblastoma patients with elevated plasma neuropeptide Y had a poor outcome; 10 of 13 died, whereas all with normal concentrations are alive after 3-74 months of follow-up (p < 0.001).