Meta-analysis of nonselective versus beta-1 adrenoceptor-selective blockade in prevention of tilt-induced neurocardiogenic syncope.
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Adrenergic beta-Antagonists↗
Biomedical subjects
David S Goldstein
Publications and source records attributed to David S Goldstein.
[Disruption of the D(2) dopamine receptor produces adrenergic and endothelin B receptor-dependent hypertension].
OBJECTIVE: To assess whether D(2) receptors participate in the regulation of genetic hypertension. METHODS: Arterial pressure was measured in mice mutant for the D(2) dopamine receptors, and the interactions between D(2) dopamine receptors and other vasopressor systems were also studied. RESULTS: Both systolic blood pressure (BP) in D(2) mutant (D(2)-/-) and hybrid (D(2)+/-) mice (128 +/- 2 mm Hg, 129 +/- 4 mm Hg) and diastolic BP (107 +/- 2 mm Hg, 108 +/- 3 mm Hg) were higher than in wild-type (D(2)+/+) mice (104 +/- 2 mm Hg, 77 +/- 1 mm Hg). The BP after alpha-adrenergic blockade decreased to a greater extent in D(2)-/- than in D(2)+/+ mice. Epinephrine excretion was greater in D(2)-/- than in D(2)+/+ mice and adrenalectomy decreased blood pressure to a greater extent in D(2)-/- than in D(2)+/+ mice. The non specific endothelin B (ETB) blocker (BQ788) decreased BP in D(2)-/- but had not in D(2)+/+ mice. The ETB1 blocker RES 701 - 1 increased BP in D(2)-/- but not D(2)+/+ mice. ET-1 and the ETB agonist, sarafatoxin S6c increased BP to a greater extent in D(2)+/+ than in D(2)-/- mice. Circulating ET-like immunoreactive peptides were similar in D(2)-/- and D(2)+/+ mice but ETB receptor expression was greater in D(2)-/- than in D(2)+/+ mice. In contrast, blockade of ETA and V(1) vasopressin receptors had no effect on BP in either D(2)-/- and D(2)+/+ mice. The hypotensive effect of the AT(1) antagonist, losartan, was also similar in D(2)-/- and D(2)+/+ mice. The greater basal sodium excretion and lower renal Na(+)/K(+)ATPase activity in D(2)-/- than in D(2)+/+ mice indicate that sodium retention was not the cause of hypertension in these animals. CONCLUSION: Hypertension in the D(2) mutant mice may be caused by absent inhibitory effect of D(2) receptors on sympathetic outflow coupled with increased ETB2 activity.
Animals↗
Biochemical diagnosis of pheochromocytoma: which test is best?
CONTEXT: Diagnosis of pheochromocytoma depends on biochemical evidence of catecholamine production by the tumor. However, the best test to establish the diagnosis has not been determined. OBJECTIVE: To determine the biochemical test or combination of tests that provides the best method for diagnosis of pheochromocytoma. DESIGN, SETTING, AND PARTICIPANTS: Multicenter cohort study of patients tested for pheochromocytoma at 4 referral centers between 1994 and 2001. The analysis included 214 patients in whom the diagnosis of pheochromocytoma was confirmed and 644 patients who were determined to not have the tumor. MAIN OUTCOME MEASURES: Test sensitivity and specificity, receiver operating characteristic curves, and positive and negative predictive values at different pretest prevalences using plasma free metanephrines, plasma catecholamines, urinary catecholamines, urinary total and fractionated metanephrines, and urinary vanillylmandelic acid. RESULTS: Sensitivities of plasma free metanephrines (99% [95% confidence interval [CI], 96%-100%]) and urinary fractionated metanephrines (97% [95% CI, 92%-99%]) were higher than those for plasma catecholamines (84% [95% CI, 78%-89%]), urinary catecholamines (86% [95% CI, 80%-91%]), urinary total metanephrines (77% [95% CI, 68%-85%]), and urinary vanillylmandelic acid (64% [95% CI, 55%-71%]). Specificity was highest for urinary vanillylmandelic acid (95% [95% CI, 93%-97%]) and urinary total metanephrines (93% [95% CI, 89%-97%]); intermediate for plasma free metanephrines (89% [95% CI, 87%-92%]), urinary catecholamines (88% [95% CI, 85%-91%]), and plasma catecholamines (81% [95% CI, 78%-84%]); and lowest for urinary fractionated metanephrines (69% [95% CI, 64%-72%]). Sensitivity and specificity values at different upper reference limits were highest for plasma free metanephrines using receiver operating characteristic curves. Combining different tests did not improve the diagnostic yield beyond that of a single test of plasma free metanephrines. CONCLUSION: Plasma free metanephrines provide the best test for excluding or confirming pheochromocytoma and should be the test of first choice for diagnosis of the tumor.
Adolescent↗
Progressive loss of cardiac sympathetic innervation in Parkinson's disease.
This study addressed whether cardiac sympathetic denervation progresses over time in Parkinson's disease. In 9 patients without orthostatic hypotension, 6-[(18)F]fluorodopamine positron emission tomography scanning was repeated after a mean of 2 years from the first scan. 6-[(18)F]fluorodopamine-derived radioactivity was less in the second scan than in the first scan, by 31% in the left ventricular free wall and 16% in the septum. In Parkinson's disease, loss of cardiac sympathetic denervation progresses in a pattern of loss suggesting a dying-back mechanism.
Disease Progression↗
Pandysautonomia associated with impaired ganglionic neurotransmission and circulating antibody to the neuronal nicotinic receptor.
We report the case of a patient with chronic autonomic failure who had evidence of decreased postganglionic traffic to intact sympathetic nerve terminals. The patient complained mainly of decreased salivation, constipation, dry skin, and orthostatic intolerance. There was no evidence of central neurodegeneration. Autonomic function testing showed orthostatic hypotension without tachycardia and abnormal blood pressure and pulse rate responses to the Valsalva maneuver, indicating combined sympathetic and parasympathetic neurocirculatory failure. In contrast to patients with pure autonomic failure, the patient had normal left ventricular myocardial concentrations of 6-[(18)F]fluorodopamine-derived radioactivity, establishing intact postganglionic sympathetic innervation; and in contrast to patients with multiple system atrophy or baroreflex failure, the patient had a low plasma norepinephrine concentration and brisk norepinephrine response to orthostasis. These findings indicated an impediment to ganglionic neurotransmission. Serologic testing demonstrated a circulating antibody to the ganglionic nicotinic acetylcholine receptor. The findings in this case support the concept that circulating antibodies to this receptor can interfere with ganglionic neurotransmission and produce autoimmune autonomic neuropathy.
Adrenergic alpha-Agonists↗
Local sympathetic function in human skeletal muscle and adipose tissue assessed by microdialysis.
BACKGROUND: In response to stressors and pathophysiologic conditions, sympathetic neuronal outflows can change heterogeneously among body organs and tissues. This study examined the validity of microdialysis and measurements of microdialysate concentrations of catechols, to assess local sympathetic function in skeletal muscle and adipose tissue in humans. METHODS: Based on preliminary experiments, a microdialysate perfusion rate of 3 microl/min and collection duration of 30 minutes were chosen. To assess responses to a stimulus that increases sympathetic outflow to skeletal muscle, microdialysate norepinephrine and dihydroxyphenylglycol concentrations in quadriceps muscle, abdominal subcutaneous adipose tissue, and plasma were measured during orthostasis in 8 healthy normal volunteers. To assess responses to decreased postganglionic sympathetic nerve traffic, norepinephrine and dihydroxyphenylglycol concentrations were measured during i. v. infusion of trimethaphan in 5 volunteers. RESULTS: All subjects had detectable norepinephrine and dihydroxyphenylglycol in microdialysate from both skeletal muscle and adipose tissue. Orthostasis significantly increased microdialysate norepinephrine in skeletal muscle (0.38 +/- (SEM) 0.07 nmol/L supine to 1.48+/-0.24 nmol/L standing, p < 0.01) and in adipose tissue (0.31+/-0.02 nmol/L supine to 0.68+/-0.11 nmol/L standing, p < 0.01). Orthostasis also increased microdialysate dihydroxyphenylglycol in both tissues (1.76+/-0.30 nmol/L to 3.08+/-0.43 nmol/L, p < 0.01; 1.37+/-0.15 nmol/L supine to 1.99+/-0.34 nmol/L standing, p < 0.01). Trimethaphan decreased norepinephrine concentrations in skeletal muscle microdialysate by 50%, adipose tissue by 70%, and antecubital venous plasma 50%, with non-significant decreases in dihydroxyphenylglycol concentrations at each site. CONCLUSIONS: Microdialysate concentrations of norepinephrine and dihydroxyphenylglycol can be detected reliably and respond appropriately during manipulations that increase or decrease the sympathetically mediated release and turnover of norepinephrine. This approach may provide a means to assess sympathetic neuronal function in skeletal muscle and adipose tissue in humans with known or suspected dysautonomias.
Adipose Tissue↗
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.
Adult↗
Allostasis, homeostats, and the nature of stress.
This essay continues discussion of a new formulation of homeostasis that uses the concepts of allostasis and homeostats. The new formulation moves beyond Cannon's concept of "homeostasis," which posits an ideal set of conditions for maintenance of the internal environment. The notion of allostasis recognizes that there is no single ideal set of steady-state conditions in life, and different stressors elicit different patterns of activation of the sympathetic nervous and adrenomedullary hormonal systems. Allostasis reflects active, adaptive processes that maintain apparent steady states, via multiple, interacting effectors regulated by homeostatic comparators--"homeostats." "Allostatic load" refers to the consequences of sustained or repeated activation of mediators of allostasis. From the analogy of a home temperature control system, the temperature can be maintained at any of a variety of levels (allostatic states) by multiple means (effectors), regulated by the thermostat (homeostat). Allostatic load and risks of system breakdown increase when, for example, the front door is left open in the winter. Applying these notions can aid in understanding how acute and chronic stress can exert adverse health consequences via allostatic load.
Homeostasis↗
Diagnostic localization of pheochromocytoma: the coming of age of positron emission tomography.
Pheochromocytoma is a rare but clinically important tumor of catecholamine-secreting chromaffin cells. This tumor constitutes a surgically curable cause of hypertension. Therefore, correct localization of pheochromocytoma is essential for effective management of this tumor. Several conventional and nuclear imaging modalities are currently available to localize pheochromocytoma. Computed tomography (CT) and magnetic resonance imaging (MRI) have good sensitivity but poor specificity for detecting pheochromocytoma, and nuclear imaging approaches such as (131)I-metaiodobenzylguanidine scintigraphy or [(111)In]-DTPA-D-Phe-pentetreotide (Octreoscan) have limited sensitivity. However, specificity of (131)I-metaiodobenzylguanidine scintigraphy is very good and this means of imaging provides a method for confirming that a tumor is a pheochromocytoma and rules out metastatic disease. Recently, we introduced a new imaging method, 6-[(18)F]fluorodopamine positron emission tomography, that can be used successfully for the detection of solitary and metastatic pheochromocytomas. Our preliminary data suggest that this method is superior to other nuclear imaging methods including metaiodobenzylguanidine and octreotide scintigraphy. In this report we provide an update regarding nuclear imaging of primary and metastatic pheochromocytoma, particularly using 6-[(18)F]fluorodopamine positron emission tomographic scanning.
3-Iodobenzylguanidine↗
Chronic hypercortisolemia inhibits dopamine synthesis and turnover in the nucleus accumbens: an in vivo microdialysis study.
Over 60% of patients with Cushing's syndrome suffer from major depression, which frequently abates after correction of the hypercortisolism. The mesolimbic and mesocortical dopaminergic (DAergic) systems are thought to participate in psychiatric disorders. In this study, we investigated whether hypercortisolemia affects indices of DAergic activity in the nucleus accumbens (NAc) and the prefrontal cortex (PFC) of freely moving rats. Cortisol (CORT, 25 mg/kg/day) was infused subcutaneously for 7 days via an osmotic minipump. Microdialysate collection (30-min periods, 2 microl/min) began 24 h after probe placement. Concentrations of dihydroxyphenylalanine (DOPA) in interstitial fluid in the nucleus accumbens (NAc) and perifrontal cortex (PFC) were measured before and after local perfusion with NSD-1015, an irreversible inhibitor of L-aromatic amino acid decarboxylase, to assess local dopamine (DA) biosynthesis. The sum of microdialysate DA, dihydroxyphenylacetic acid, and homovanillic acid was used as an index of local DA turnover. DOPA accumulation after NSD-1015 was markedly attenuated in CORT-treated compared with saline-treated animals (5,703 +/- 1,849 vs. 10,902 +/- 2,454 pg/ml; p < 0.01). In contrast, the two groups did not differ in DOPA accumulation in the PFC. Values for the turnover index of DA were also significantly lower in CORT-treated animals in the NAc but not in the PFC. The results indicate that CORT inhibits DA synthesis and turnover in the NAc but not in the PFC. Region-specific CORT-induced inhibition of DAergic activity may help to explain depressive symptoms in patients with chronic hypercortisolemia and normalization after medical or surgical correction of hypercortisolism.
3,4-Dihydroxyphenylacetic Acid↗
Exaggerated adrenomedullary response to immobilization in mice with targeted disruption of the serotonin transporter gene.
This study examined whether serotonin transporter (5-HTT) gene knockout influences adrenomedullary, sympathoneural, or hypothalamo-pituitary-adrenal responses to acute immobilization. In conscious, cannulated mice, arterial plasma concentrations of catecholamines, ACTH, and corticosterone were measured at baseline and after 15 min of immobilization. Tissue levels of serotonin (5-HT), catecholamines, and hormones were also measured in pituitary and adrenal glands. At baseline, adrenal and pituitary 5-HT concentrations in knockout (5-HTT(-/-)) mice were markedly lower than those in littermate control (5-HTT(+/+)) mice, whereas the groups did not differ in levels of catecholamines or hormones in plasma or tissue. Immobilization increased plasma levels of catecholamines, ACTH, and corticosterone in all genotypes. 5-HTT(-/-) mice had exaggerated responses of plasma epinephrine to immobilization and significant reductions in adrenal epinephrine, norepinephrine, and 5-HT contents compared with values in littermate controls. Pituitary ACTH was significantly reduced after immobilization in 5-HTT(-/-) mice only, but increases in plasma ACTH and corticosterone levels did not differ between genotypes. The results suggest that one 5-HTT function is to restrain adrenomedullary activation in response to immobilization. Exaggerated adrenomedullary responses seem to be an autonomic correlate of the anxiety-like behaviors in 5-HTT knockout mice.
3,4-Dihydroxyphenylacetic Acid↗
Local sympathetic denervation in painful diabetic neuropathy.
This study assessed whether painful diabetic neuropathy is associated with abnormal sympathetic nervous function in the affected limbs. Nine patients with diabetes (four men, five women; age 61 +/- 7 years) and painful peripheral neuropathy of the feet, but without evidence of generalized autonomic neuropathy, underwent intravenous infusion of tritiated norepinephrine (NE) and sampling of arterial and venous blood in both feet and in one arm to quantify the rate of entry of NE into the local venous plasma (NE spillover). In the same patients, positron emission tomography (PET) scanning after intravenous injection of the sympathoneural imaging agent 6-[(18)F]fluorodopamine was used to visualize sympathetic innervation and after intravenous [(13)N]ammonia to visualize local perfusion. The results were compared with those in the feet of normal volunteers and in an unaffected foot of patients with unilateral complex regional pain syndrome (CRPS). In addition, neurochemical results obtained in painful diabetic neuropathy were compared with those obtained in diabetic control patients with painless neuropathy and diabetic control patients without neuropathy. Local arteriovenous difference in plasma NE levels (DeltaNE(AV)) and NE spillover in the arms did not differ across the groups. However, DeltaNE(AV) in the feet was significantly less in the group with painful diabetic neuropathy than in the control groups. Also NE spillover in the feet tended to be lower in painful neuropathy. DeltaNE(AV) of diabetic control patients without neuropathy (n = 6) resembled values in the control groups without diabetes, whereas patients with painless diabetic neuropathy (n = 6) had evidence suggesting partial loss of sympathetic innervation. PET scanning revealed decreased flow-corrected 6-[(18)F]fluorodopamine-derived radioactivity in patients with painful diabetic neuropathy, compared with values in normal volunteers and patients with CRPS. The results provide neurochemical and neuroimaging evidence for regionally selective sympathetic denervation in the painful feet of patients with diabetic neuropathy.
Aged↗
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".
Adrenal Medulla↗
Kinetic model for the fate of 6-[18F]fluorodopamine in the human heart: a novel means to examine cardiac sympathetic neuronal function.
After injection of 6-[18F]fluorodopamine, thoracic positron emission tomographic scanning visualizes the sympathetic innervation of the heart. This report introduces a kinetic model that relates 6-[18F]fluorodopamine positron emission tomographic scanning results to specific aspects of cardiac sympathoneural function. Inputs were the 6-[18F]fluorodopamine concentration in arterial blood and the estimated contribution of circulating metabolites of 6-[18F]fluorodopamine. All of the three compartments in the model were intraneuronal. Two compartments corresponded to vesicles in sympathetic nerves, consistent with the "multiple vesicular pool" hypothesis from preclinical studies. The model successfully fit the empirical time-activity curve for myocardial 6-[18F]fluorodopamine-derived radioactivity and predicted correctly the effects of several neuropharmacological and physiological manipulations on the time-activity curve. Myocardial cell uptake of metabolites of 6-[18F]fluorodopamine from the circulation could explain an immediate peak of 6-[18F]fluorodopamine-derived radioactivity. The model seems useful in predicting effects of altered cardiac sympathetic function on time-activity curves for myocardial 6-[18F]fluorodopamine-derived radioactivity in humans.
Adrenergic Fibers↗
Neuropharmacologic distinction of neurogenic orthostatic hypotension syndromes.
BACKGROUND: Neurogenic orthostatic hypotension (OH) characterizes pure autonomic failure (PAF), multiple system atrophy (MSA), and Parkinson disease (PD) with autonomic failure. We used neuropharmacologic probes that might distinguish these diseases based on loss of sympathetic noradrenergic nerves in PAF and PD + OH but not in MSA, and related the results to neurochemical and neuroimaging findings in the same patients. METHODS: Patients with neurogenic OH (PD + OH; N = 35), MSA (N = 41), and PAF (N = 12) received iv trimethaphan (TRI), which inhibits sympathetic nerve traffic, or yohimbine (YOH), which stimulates sympathetic traffic. Dependent measures included blood pressure, plasma norepinephrine (NE) levels, and interventricular septal myocardial radioactivity after iv injection of the sympathoneural imaging agent, 6-[F]fluorodopamine. RESULTS: The PD + OH and PAF groups had smaller pressor responses to YOH (12 +/- 8 and 13 +/- 1 mm Hg) and depressor responses to TRI (-14 +/- 8 and -17 +/- 7 mm Hg) than did the MSA group (43 +/- 8 mm Hg, -57 +/- 8 mm Hg; P = 0.01, P = 0.03). The PD + OH and MSA groups did not differ in NE responses to YOH and TRI. The depressor response to TRI, the pressor response to YOH, and the blood pressure difference between YOH and TRI all correlated positively with myocardial 6-[F]fluorodopamine-derived radioactivity. CONCLUSIONS: The PD + OH resembles PAF and differs from MSA in hemodynamic responses to drugs that alter NE release from sympathetic nerves. The results fit with sympathetic noradrenergic denervation in PD + OH and PAF but not in MSA.
Blood Pressure↗
L-Dihydroxyphenylserine (L-DOPS): a norepinephrine prodrug.
L-threo-3,4-dihydroxyphenylserine (L-DOPS, droxydopa) is a synthetic catecholamino acid. When taken orally, L-DOPS is converted to the sympathetic neurotransmitter, norepinephrine (NE), via decarboxylation catalyzed by L-aromatic-amino-acid decarboxylase (LAAAD). Plasma L-DOPS levels peak at about 3 h, followed by a monoexponential decline with a half-time of 2 to 3 h. Plasma levels of NE and of its main neuronal metabolite, dihydroxyphenylglycol (DHPG) peak approximately concurrently but at much lower concentrations. The relatively long half-time for disappearance of L-DOPS from plasma, compared to that of NE, explains their very different attained plasma concentrations. In patients with neurogenic orthostatic hypotension, L-DOPS increases blood pressure and ameliorates orthostatic intolerance. Inhibition of LAAAD, such as by treatment with carbidopa, which does not penetrate the blood-brain barrier, prevents the blood pressure effects of the drug, indicating that L-DOPS increases blood pressure by augmenting NE production outside the brain. Patients with pure autonomic failure (which usually entails loss of sympathetic noradrenergic nerves), and patients with multiple system atrophy (in which noradrenergic innervation remains intact) have similar plasma NE responses to L-DOPS. This suggests mainly non-neuronal production of NE from L-DOPS. L-DOPS is very effective in treatment of deficiency of dopamine-beta-hydroxylase (DBH), the enzyme required for conversion of dopamine to NE in sympathetic nerves. L-DOPS holds promise for treating other much more common conditions involving decreased DBH activity or NE deficiency, such as a variety of syndromes associated with neurogenic orthostatic hypotension.
Animals↗