Plasma levels of catechols and metanephrines in neurogenic orthostatic hypotension

An increase in renal dopamine does not stimulate natriuresis after fava bean ingestion

BACKGROUND

Fava beans (Vicia faba) contain dihydroxyphenylalanine (dopa), and their ingestion may increase dopamine stores. Renal dopamine regulates blood pressure and blood volume via a natriuretic effect.

OBJECTIVE

The objective was to determine the relation between dietary fava beans, plasma and urinary catechols, and urinary sodium excretion in 13 healthy volunteers.

DESIGN

Catechol and sodium data were compared by using a longitudinal design in which all participants consumed a fixed-sodium study diet on day 1 and the fixed-sodium diet plus fava beans on day 2. Blood was sampled at 1, 2, 4, and 6 h after a meal, and 3 consecutive 4-h urine samples were collected.

RESULTS

Mean (±SD) plasma dopa was significantly greater 1 h after fava bean consumption (11,670 ± 5440 compared with 1705 ± 530 pg/mL; P = 0.001) and remained elevated at 6 h. Plasma dopamine increased nearly 15-fold during this period. Fava bean consumption also increased urinary dopamine excretion to 306 ± 116, 360 ± 235, and 159 ± 111 μg/4-h urine sample compared with 45 ± 21, 54 ± 29, and 44 ± 17 μg in the 3 consecutive 4-h samples after the control diet (P ≤ 0.005). These substantial increases in plasma and urinary dopa and dopamine were unexpectedly associated with decreased urinary sodium.

CONCLUSION

The failure of fava bean consumption to provoke natriuresis may indicate that dopa concentrations in commercially available beans do not raise renal dopamine sufficiently to stimulate sodium excretion, at least when beans are added to a moderate-sodium diet in healthy volunteers. This trial was registered at clinicaltrials.gov as NCT01064739.

Skin temperature of the hand in multiple system atrophy and Parkinson's disease

AIM

A previous study on a small number of patients showed that low skin temperature of the hands, the so called "cold hands sign", may be useful for distinguishing multiple system atrophy (MSA) from Parkinson's disease (PD). We have further investigated skin temperature of the hand in a larger number of patients.

METHODS

Skin temperature on the palm was measured in 50 MSA (11 MSA-P and 39 MSA-C patients) and 50 PD patients, and 25 normal healthy subjects.

RESULTS

Palm skin temperature was significantly lower in MSA patients (32.0 ± 2.7 °C) than in controls (34.1 ± 0.9 °C, p = 0.0002), but was not different compared with the PD group (32.9 ± 1.8 °C, p = 0.06). Temperatures of <28 °C were observed in 3 MSA patients (6%) and none of the PD patients and controls. There was no significant difference in palm skin temperature between patients with and without orthostatic hypotension for each patient group, or between MSA-P and MSA-C patients.

CONCLUSION

The cold hand (<28 °C) is a useful marker for distinguishing MSA from PD, but it is not common in MSA patients, and its sensitivity may be low for differentiating between MSA and PD.

Diabetic cardiovascular autonomic neuropathy: clinical implications

Diabetic cardiovascular autonomic neuropathy (DCAN), the impairment of the autonomic balance of the cardiovascular system in the setting of diabetes mellitus (DM), is frequently observed in both Type 1 and 2 DM, has detrimental effects on the quality of life and portends increased mortality. Clinical manifestations include: resting heart rate disorders, exercise intolerance, intraoperative cardiovascular lability, orthostatic alterations in heart rate and blood pressure, QT-interval prolongation, abnormal diurnal and nocturnal blood pressure variation, silent myocardial ischemia and diabetic cardiomyopathy. Clinical tests for autonomic nervous system evaluation, heart rate variability analysis, autonomic innervation imaging techniques, microneurography and baroreflex analysis are the main diagnostic tools for DCAN detection. Aldose reductase inhibitors and antioxidants may be helpful in DCAN therapy, but a regular, more generalized and multifactorial approach should be adopted with inclusion of lifestyle modifications, strict glycemic control and treatment of concomitant traditional cardiovascular risk factors, in order to achieve the best therapeutic results. In the present review, the authors provide aspects of DCAN pathophysiology, clinical presentation, diagnosis and an algorithm regarding the evaluation and management of DCAN in DM patients.

Management approaches to hypertension in autonomic failure

PURPOSE OF REVIEW

Supine hypertension is a common finding in autonomic failure that can worsen orthostatic hypotension and predispose to end-organ damage. This review focuses on nonpharmacologic and pharmacologic approaches to manage hypertension in these patients in the face of disabling orthostatic hypotension.

RECENT FINDINGS

The hypertension of autonomic failure can be driven by sympathetic-dependent or independent mechanisms, contingent on the site of autonomic lesions. Management of supine hypertension should include simple nonpharmacologic approaches including avoiding the supine position during the daytime and sleeping in a head-up tilt position at night. Most patients, however, require pharmacologic treatment. Several antihypertensive therapies lower nighttime pressure in autonomic failure, but none improve nocturnal volume depletion or morning orthostatic tolerance. Regardless, treatment may still be beneficial in some patients but must be decided on an individual basis. Blood pressure monitoring is helpful in this regard, as well as titration of doses, as these patients are hypersensitive to depressor agents due to loss of baroreceptor reflexes.

SUMMARY

Autonomic failure provides a unique opportunity to study blood pressure regulation independent of autonomic influences. Understanding mechanisms driving supine hypertension will have important implications for the treatment of autonomic failure and will improve our knowledge of cardiovascular regulation in other populations, including essential hypertension and elderly hypertensive individuals with comorbid orthostatic hypotension.

Biomarkers, mechanisms, and potential prevention of catecholamine neuron loss in Parkinson disease

This chapter is on biomarkers, mechanisms, and potential treatment of catecholamine neuron loss in Parkinson disease (PD). PD is characterized by a movement disorder from loss of nigrostriatal dopamine neurons. An intense search is going on for biomarkers of the disease process. Theoretically, cerebrospinal fluid (CSF) levels of the deaminated DA metabolite, 3,4-dihydroxyphenylacetic acid (DOPAC), should be superior to other neurochemical indices of loss of central dopamine. CSF DOPAC is low in PD-even in patients with recent onset of Parkinsonism. Cardiac norepinephrine depletion is as severe as the loss of putamen dopamine. PD importantly involves nonmotor manifestations, including anosmia, dementia, REM behavior disorder, and orthostatic hypotension, and all of these nonmotor features are associated with neuroimaging evidence for cardiac sympathetic denervation, which seems to occur independently of the movement disorder and striatal dopaminergic lesion. Analogy to a bank robber's getaway car conveys the catecholaldehyde hypothesis, according to which buildup of the dopamine metabolite 3,4-dihydroxyphenylacetaldehyde (DOPAL), the immediate product of the action of monoamine oxidase on cytosolic dopamine, causes or contributes to the death of dopamine neurons. Decreased vesicular uptake of dopamine and decreased DOPAL detoxification by aldehyde dehydrogenase (ALDH) determine this buildup. Vesicular uptake is also markedly decreased in the heart in PD. Multiple factors influence vesicular uptake and ALDH activity. Evidence is accruing for aging-related induction of positive feedback loops and an autotoxic final common pathway in the death of catecholamine neurons, mediated by metabolites produced continuously in neuronal life. The catecholaldehyde hypothesis also leads to testable experimental therapeutic ideas.

Neurogenic orthostatic hypotension: pathophysiology, evaluation, and management

Neurogenic orthostatic hypotension is a distinctive and treatable sign of cardiovascular autonomic dysfunction. It is caused by failure of noradrenergic neurotransmission that is associated with a range of primary or secondary autonomic disorders, including pure autonomic failure, Parkinson’s disease with autonomic failure, multiple system atrophy as well as diabetic and nondiabetic autonomic neuropathies. Neurogenic orthostatic hypotension is commonly accompanied by autonomic dysregulation involving other organ systems such as the bowel and the bladder. In the present review, we provide an overview of the clinical presentation, pathophysiology, epidemiology, evaluation and management of neurogenic orthostatic hypotension focusing on neurodegenerative disorders.

Cardiovascular dysautonomia in Parkinson disease: from pathophysiology to pathogenesis

Signs or symptoms of impaired autonomic regulation of circulation often attend Parkinson disease (PD). This review covers biomarkers and mechanisms of autonomic cardiovascular abnormalities in PD and related alpha-synucleinopathies. The clearest clinical laboratory correlate of dysautonomia in PD is loss of myocardial noradrenergic innervation, detected by cardiac sympathetic neuroimaging. About 30-40% of PD patients have orthostatic hypotension (OH), defined as a persistent, consistent fall in systolic blood pressure of at least 20 mmHg or diastolic blood pressure of at least 10 mmHg within 3 min of change in position from supine to standing. Neuroimaging evidence of cardiac sympathetic denervation is universal in PD with OH (PD+OH). In PD without OH about half the patients have diffuse left ventricular myocardial sympathetic denervation, a substantial minority have partial denervation confined to the inferolateral or apical walls, and a small number have normal innervation. Among patients with partial denervation the neuronal loss invariably progresses over time, and in those with normal innervation at least some loss eventually becomes evident. Thus, cardiac sympathetic denervation in PD occurs independently of the movement disorder. PD+OH also entails extra-cardiac noradrenergic denervation, but this is not as severe as in pure autonomic failure. PD+OH patients have failure of both the parasympathetic and sympathetic components of the arterial baroreflex. OH in PD therefore seems to reflect a "triple whammy" of cardiac and extra-cardiac noradrenergic denervation and baroreflex failure. In contrast, most patients with multiple system atrophy, which can resemble PD+OH clinically, do not have evidence for cardiac or extra-cardiac noradrenergic denervation. Catecholamines in the neuronal cytoplasm are potentially toxic, via spontaneous and enzyme-catalyzed oxidation. Normally cytoplasmic catecholamines are efficiently taken up into vesicles via the vesicular monoamine transporter. The recent finding of decreased vesicular uptake in Lewy body diseases therefore suggests a pathogenetic mechanism for loss of catecholaminergic neurons in the periphery and brain. Parkinson disease (PD) is one of the most common chronic neurodegenerative diseases of the elderly, and it is likely that as populations age PD will become even more prevalent and more of a public health burden. Severe depletion of dopaminergic neurons of the nigrostriatal system characterizes and likely produces the movement disorder (rest tremor, slowness of movement, rigid muscle tone, and postural instability) in PD. Over the past two decades, compelling evidence has accrued that PD also involves loss of noradrenergic neurons in the heart. This finding supports the view that loss of catecholaminergic neurons, both in the nigrostriatal system and the heart, is fundamental in PD. By the time PD manifests clinically, most of the nigrostriatal dopaminergic neurons are already lost. Identifying laboratory measures-biomarkers-of the disease process is therefore crucial for advances in treatment and prevention. Deposition of the protein, alpha-synuclein, in the form of Lewy bodies in catecholaminergic neurons is a pathologic hallmark of PD. Alpha-synucleinopathy in autonomic neurons may occur early in the pathogenetic process. The timing of cardiac noradrenergic denervation in PD is therefore a key issue. This review updates the field of autonomic cardiovascular abnormalities in PD and related disorders, with emphasis on relationships among striatal dopamine depletion, sympathetic noradrenergic denervation, and alpha-synucleinopathy.

Methods of investigation for cardiac autonomic dysfunction in human research studies

This consensus document provides evidence-based guidelines regarding the evaluation of diabetic cardiovascular autonomic neuropathy (CAN) for human research studies; the guidelines are the result of the work of the CAN Subcommittee of the Toronto Diabetic Neuropathy Expert Group. The subcommittee critically reviewed the limitations and strengths of the available diagnostic approaches for CAN and the need for developing new tests for autonomic function. It was concluded that the most sensitive and specific approaches currently available to evaluate CAN in clinical research are: (1) heart rate variability, (2) baroreflex sensitivity, (3) muscle sympathetic nerve activity, (4) plasma catecholamines, and (5) heart sympathetic imaging. It was also recommended that efforts should be undertaken to develop new non-invasive and safe CAN tests to be used in clinical research, with higher sensitivity and specificity, for studying the pathophysiology of CAN and evaluating new therapeutic approaches.

Sympathetic noradrenergic before striatal dopaminergic denervation: relevance to Braak staging of synucleinopathy

Braak's staging concept of Lewy body disease pathogenesis is based on a spatiotemporal sequence of alpha-synuclein deposition, with autonomic nervous system involvement before synucleinopathy in substantia nigra neurons. A patient with primary chronic autonomic failure underwent biennial brain 6-[(18)F]DOPA and myocardial 6-[(18)F]dopamine scanning over 4 years. Low myocardial radioactivity indicated cardiac noradrenergic denervation that persisted. Striatal 6-[(18)F]DOPA-derived radioactivity initially was normal, 2 years later was decreased subtly, and by 4 years was clearly decreased, accompanied by dementia and parkinsonism. In this case, neuroimaging evidence of cardiac noradrenergic denervation and subsequent progressive striatal dopaminergic denervation fit with Braak staging.

Intra-neuronal vesicular uptake of catecholamines is decreased in patients with Lewy body diseases

Several neurodegenerative disorders, including Parkinson disease (PD), are characterized by the presence of Lewy bodies - cytoplasmic inclusions containing α-synuclein protein aggregates - in the affected neurons. A poorly understood feature of Lewy body diseases is loss of sympathetic nerves in the heart and other organs, manifesting as orthostatic hypotension (OH; also known as postural hypotension). We asked whether sympathetic denervation is associated with decreased uptake of catecholamines, such as dopamine and norepinephrine, into storage vesicles within sympathetic neurons. We used 6-[18F]-dopamine (18F-DA) to track myocardial uptake and retention of catecholamines. Concurrently, the fate of intra-neuronal 18F-DA was followed by assessment of arterial plasma levels of the 18F-DA metabolite 18F-dihydroxyphenylacetic acid (18F-DOPAC). The ratio of myocardial 18F-DA to arterial 18F-DOPAC provided an index of vesicular uptake. Tracer concentrations were measured in patients with PD with or without orthostatic hypotension (PD+OH, PD-No-OH); in patients with pure autonomic failure (PAF, a Lewy body disease without parkinsonism); in patients with multiple system atrophy (MSA, a non-Lewy body synucleinopathy); and in normal controls. Patients with PD+OH or PAF had decreased vesicular 18F-DA uptake and accelerated 18F-DA loss, compared with MSA and control subjects. PD-No-OH patients could be subtyped into one of these categories based on their initial 18F-DA uptake. We conclude that sympathetic denervation in Lewy body diseases is associated with decreased vesicular uptake of neuronal catecholamines, suggesting that vesicular monoamine transport is impaired. Vesicular uptake may constitute a novel target for diagnosis, treatment, and prevention.

Catecholamines 101

This review of clinical catecholamine neurochemistry is based on the Streeten Memorial Lecture at the 19th annual meeting of the American Autonomic Society and lectures at a satellite of the 6th Congress of the International Society of Autonomic Neuroscience. Here I provide historical perspective, describe sources and meanings of plasma levels of catecholamines and their metabolites, present a model of a sympathetic noradrenergic neuron that conveys how particular aspects of sympathetic nervous function affect plasma levels of catecholamines and their metabolites, and apply the model to understand plasma neurochemical patterns associated with some drugs and disease states.

Clinostatic hypertension and orthostatic hypotension

BACKGROUND

The association of clinostatic hypertension (CH) and orthostatic hypotension (OH) is described as the "Hyp-Hyp phenomenon," and it has been found in about 5.5% of hypertensive patients and in up to 50% of patients with OH. The importance of CH/OH in clinical practice is mainly due to the presence of troublesome symptoms, end-organ damage, and difficulties in its clinical management.

HYPOTHESIS

The review focuses on the clinical problem of CH and review the international literature for the best management, including the diagnostic work-up and the taylored treatment for this kind of patients.

METHODS

A systematic review of the literature was conducted through MEDLINE research to focus the main controversial issues about CH/OH. Included topics: (1) the diagnostic work-up, (2) the association with dysautonomic failure and syncope, and (3) the treatment options and prevention of end-organ damage.

RESULTS

Current standard reference for OH diagnosis includes functional assessment of the cardiac vagal nervous system and the sympathetic adrenergic system. The association with dysautonomic failure and with syncope needs further investigation. Pharmacologic treatment of OH is aimed at controlling symptoms rather than restoring normotension. Midodrine is the only medication that has been put to multicenter placebo-controlled trial and subsequently approved by the U.S. Food and Drug Administration (FDA) for OH treatment. Short-acting oral antihypertensive agents at bedtime should be considered in patients with severe, sustained CH.

CONCLUSIONS

Data obtained from the literature review showed that clinical diagnosis of the Hyp-Hyp phenomenon is relatively simple, but it remains more difficult to establish the causal disease. In our opinion, it is advisable to define simple diagnostic standards for the selection of patients at risk of dysautonomic impairment so that a subsequent highly specific diagnostic work-up could be initiated.

Pioneer Award Address: ignorance isn't biased: comments on receiving the Pioneer Award

Researchers ordinarily work by deriving testable hypotheses from theories using a deductive process. Hypothesis testing is inherently biased, however, because of the practical requirements of finding and publishing positive results. In contrast, ignorance isn't biased. The combination of relevant new technology, sufficient mastery of the topic to know what is not yet known, and access to patients with rare but informative disorders sets the stage for discoveries about disease mechanisms based on induction from observations. Patient-oriented research is a strength of heart-brain medicine. Patients are a unique scientific resource because they tell us the truth. We experience the joy and thrill of a "sparkle of insight" when we realize what they teach.

Generalized and neurotransmitter-selective noradrenergic denervation in Parkinson's disease with orthostatic hypotension

Patients with Parkinson's disease (PD) often have manifestations of autonomic failure. About 40% have neurogenic orthostatic hypotension (NOH), and among PD+NOH patients virtually all have evidence of cardiac sympathetic denervation; however, whether PD+NOH entails extra-cardiac noradrenergic denervation has been less clear. Microdialysate concentrations of the main neuronal metabolite of norepinephrine (NE) and dihydroxyphenylglycol (DHPG) were measured in skeletal muscle, and plasma concentrations of NE and DHPG were measured in response to i.v. tyramine, yohimbine, and isoproterenol, in patients with PD+NOH, patients with pure autonomic failure (PAF), which is characterized by generalized catecholaminergic denervation, and control subjects. Microdialysate DHPG concentrations were similarly low in PD+NOH and PAF compared to control subjects (163 +/- 25, 153 +/- 27, and 304 +/- 27 pg/mL, P < 0.01 each vs. control). The two groups also had similarly small plasma DHPG responses to tyramine (71 +/- 58 and 82 +/- 105 vs. 313 +/- 94 pg/mL; P < 0.01 each vs. control) and NE responses to yohimbine (223 +/- 37 and 61 +/- 15 vs. 672 +/- 130 pg/mL, P < 0.01 each vs. control), and virtually absent NE responses to isoproterenol (20 +/- 34 and 14 +/- 15 vs. 336 +/- 78 pg/mL, P < 0.01 each vs. control). Patients with PD+NOH had normal bradycardia responses to edrophonium and normal epinephrine responses to glucagon. The results support the concept of generalized noradrenergic denervation in PD+NOH, with similar severity to that seen in PAF. In contrast, the parasympathetic cholinergic and adrenomedullary hormonal components of the autonomic nervous system seem intact in PD+NOH.

Olfactory dysfunction in pure autonomic failure: Implications for the pathogenesis of Lewy body diseases

BACKGROUND

Pure autonomic failure (PAF) and Parkinson disease (PD) both are Lewy body diseases, and both entail substantia nigra dopaminergic, locus ceruleus noradrenergic, and cardiac sympathetic denervation. Multiple system atrophy (MSA) is a non-Lewy body disease in which alpha-synuclein accumulates in glial cells, with central catecholamine deficiency but preserved cardiac sympathetic innervation in most patients. PD is associated with more severe and consistent olfactory dysfunction than in MSA; whether PAF entails olfactory dysfunction has been unknown. In this study we assessed olfactory function in PAF in comparison with the two other synucleinopathies and whether olfactory dysfunction correlates with neuroimaging evidence of cardiac noradrenergic or nigrostriatal dopaminergic denervation.

METHOD

The University of Pennsylvania Smell Identification Test (UPSIT) was administered to 8 patients with PAF, 23 with PD, and 20 with MSA. 6-[(18)F]Fluorodopamine positron emission tomographic (PET) scanning was used to indicate cardiac noradrenergic innervation and the putamen:occipital cortex (PUT:OCC) and substantia nigra (SN):OCC ratios of 6-[(18)F]fluorodopa-derived radioactivity to indicate nigrostriatal dopaminergic innervation.

RESULTS

The PAF group had a low mean UPSIT score (22+/-3), similar to that in PD (20+/-2) and lower than in MSA (31+/-2, p=0.004). Individual UPSIT scores correlated positively with cardiac 6-[(18)F]fluorodopamine-derived radioactivity (r=0.63 in the septum, p<0.0001; r=0.64 in the free wall, p<0.0001) but not with PUT:OCC or SN:OCC ratios of 6-[(18)F]fluorodopa-derived radioactivity.

DISCUSSION

In synucleinopathies, olfactory dysfunction is related to Lewy body pathology and cardiac sympathetic denervation, independently of parkinsonism or striatal dopamine deficiency.

Clinical laboratory evaluation of autoimmune autonomic ganglionopathy: Preliminary observations

Several forms of chronic autonomic failure manifest as neurogenic orthostatic hypotension, including autoimmune autonomic ganglionopathy (AAG) and pure autonomic failure (PAF). AAG and PAF are thought to differ in pathogenesis, AAG reflecting decreased ganglionic neurotransmission due to circulating antibodies to the neuronal nicotinic receptor and PAF being a Lewy body disease with prominent loss of sympathetic noradrenergic nerves. AAG therefore would be expected to differ from PAF in terms of clinical laboratory findings indicating post-ganglionic noradrenergic denervation. Both diseases are rare. Here we report preliminary observations about clinical physiologic, neuropharmacologic, neurochemical, and neuroimaging data that seem to fit with the hypothesized pathogenetic difference between AAG and PAF. Patients with either condition have evidence of baroreflex-sympathoneural and baroreflex-cardiovagal failure. Both disorders feature low plasma levels of catecholamines during supine rest, but plasma levels of the other endogenous catechols, dihydroxyphenylalanine (DOPA), dihydroxyphenylacetic acid (DOPAC), and dihydroxyphenylglycol (DHPG), seem to be lower in PAF than in AAG, probably reflecting decreased norepinephrine synthesis and turnover in PAF, due to diffuse sympathetic noradrenergic denervation. PAF entails cardiac sympathetic denervation, whereas cardiac sympathetic neuroimaging by thoracic 6-[(18)F]fluorodopamine scanning indicates intact myocardial sympathetic innervation in AAG.

Neuronal source of plasma dopamine

BACKGROUND

Determinants of plasma norepinephrine (NE) and epinephrine concentrations are well known; those of the third endogenous catecholamine, dopamine (DA), remain poorly understood. We tested in humans whether DA enters the plasma after corelease with NE during exocytosis from sympathetic noradrenergic nerves.

METHODS

We reviewed plasma catecholamine data from patients referred for autonomic testing and control subjects under the following experimental conditions: during supine rest and in response to orthostasis; intravenous yohimbine (YOH), isoproterenol (ISO), or glucagon (GLU), which augment exocytotic release of NE from sympathetic nerves; intravenous trimethaphan (TRI) or pentolinium (PEN), which decrease exocytotic NE release; or intravenous tyramine (TYR), which releases NE by nonexocytotic means. We included groups of patients with pure autonomic failure (PAF), bilateral thoracic sympathectomies (SNS-x), or multiple system atrophy (MSA), since PAF and SNS-x are associated with noradrenergic denervation and MSA is not.

RESULTS

Orthostasis, YOH, ISO, and TYR increased and TRI/PEN decreased plasma DA concentrations. Individual values for changes in plasma DA concentrations correlated positively with changes in NE in response to orthostasis (r = 0.72, P < 0.0001), YOH (r = 0.75, P < 0.0001), ISO (r = 0.71, P < 0.0001), GLU (r = 0.47, P = 0.01), and TYR (r = 0.67, P < 0.0001). PAF and SNS-x patients had low plasma DA concentrations. We estimated that DA constitutes 2%-4% of the catecholamine released by exocytosis from sympathetic nerves and that 50%-90% of plasma DA has a sympathoneural source.

CONCLUSIONS

Plasma DA is derived substantially from sympathetic noradrenergic nerves.

Cardiac sympathetic denervation preceding motor signs in Parkinson disease

There is substantial interest in identifying biomarkers to detect early Parkinson disease (PD). Cardiac noradrenergic denervation and attenuated baroreflex-cardiovagal function occur in de novo PD, but whether these abnormalities can precede PD has been unknown. Here we report the case of a patient who had profoundly decreased left ventricular myocardial 6-[(18)F]fluorodopamine-derived radioactivity and low baroreflex-cardiovagal gain, 4 years before the onset of symptoms and signs of PD. The results lead us to hypothesize that cardiac noradrenergic denervation and decreased baroreflex-cardiovagal function may occur early in the pathogenesis of PD.

Hemodynamic, autonomic and neurohormonal behaviour of familial amyloidotic polyneuropathy and neurally mediated syncope patients during supine and orthostatic stress

Orthostatic intolerance (OI) syndromes are frequent and share symptoms like dizziness and orthostatic syncope. Their pathophysiology however seems to be different. The aim of our work was to evaluate autonomic and hemodynamic behaviour in patients with familial amyloidotic polyneuropathy and neurally mediated syncope in supine position and after acute orthostatic passive stress. We studied 12 patients with autonomic failure (group A), 12 patients with neurally mediated syncope (group B) and 16 aged matched normal controls (group C), in supine position and during the first 10 min of head-up tilt test (HUTT). Beat-by-beat blood pressure and heart rate were continuously monitored and digitised at 500 Hz. The baroreceptor alfa-index gain (vagal reflex-BRG), high frequency of RR variability (HFRR, vagal tonus) and low frequency of systolic arterial pressure variability (LFSAP, sympathetic tone) were calculated. Catecholamines, plasma brain (BNP) and atrial natriuretic (ANP) peptides were also measured. Hemodynamic data were derived and calculated by the non-invasive modelflow method. During supine position, cardiac output (CO) and stroke volume (SV) were similar in all groups. Mean arterial pressure (MAP) and BNP were higher in group A. Noradrenaline (NOR), BRG, HFRR and LFSAP were extremely low in this group. BRG and adrenaline (ADR) were higher in group B than in controls. Within the first 10 min of HUTT, there was a huge drop of CO, SV and MAP in group A, maintenance of very low levels of neurohormones and lack of autonomic function. HR, LFSAP and ADR had a higher rise at HUTT in group B compared with controls (p<0.01) but a significant decrease of BRG was noted (p<0.05). ANP or BNP did not change with tilt in any group. Different orthostatic intolerance syndromes may show important hormonal, autonomic and hemodynamic differences during supine rest and enhanced after passive orthostatism.

Transient left ventricular apical ballooning at the onset of multiple system atrophy

A 64-year-old woman was admitted to our hospital for persistent lipothymia and exertional dyspnoea and was treated for worsening asthma. During hospital stay, she manifested typical chest pain, with electrocardiographic and echocardiographic abnormalities suggesting acute myocardial infarction. Coronary angiography demonstrated normal coronary arteries and left ventriculography revealed apical akinesis. Creatine kinase levels showed a slight increase in spite of the severe ventricular abnormalities. The electrocardiographic and echocardiographic evolution, along with the favourable outcome, led us to diagnose tako-tsubo cardiomyopathy. Afterwards, severe autonomic dysfunction with multiple system atrophy was diagnosed. Impaired multivessel coronary microcirculation is thought to be one causative mechanism of tako-tsubo-like left ventricular dysfunction, and catecholamines are likely to play a role. In our case, sympathetic neurocirculatory failure was indicative of altered sympathoneural activity. We suggest that the prescribed therapy contributed to the development of this syndrome; in particular dopamine for hypotension and corticosteroids for suspected asthma stimulated heart sympathetic terminals.

Reduced stress- and cold-induced increase in energy expenditure in interleukin-6-deficient mice

Interleukin-6 (IL-6) deficient (-/-) mice develop mature onset obesity. Pharmacological studies have shown that IL-6 has direct lipolytic effects and when administered centrally increases sympathetic outflow. However, the metabolic functions of endogenous IL-6 are not fully elucidated. We aimed to investigate the effect of IL-6 deficiency with respect to cold exposure and cage-switch stress, that is, situations that normally increase sympathetic outflow. Energy metabolism, core temperature, heart rate, and activity were investigated in young preobese IL-6-/- mice by indirect calorimetry together with telemetry. Baseline measurements and the effect of cage-switch stress were investigated at thermoneutrality (30 degrees C) and at room temperature (20 degrees C). The effect of cold exposure was investigated at 4 degrees C. At 30 degrees C, the basal core temperature was 0.6 +/- 0.24 degrees C lower in IL-6-/- compared with wild-type mice, whereas the oxygen consumption did not differ significantly. The respiratory exchange ratio at 20 degrees C was significantly higher and the calculated fat utilization rate was lower in IL-6-/- mice. In response to cage-switch stress, the increase in oxygen consumption at both 30 and 20 degrees C was lower in IL-6-/- than in wild-type mice. The increase in heart rate was lower in IL-6-/- mice at 30 degrees C. At 4 degrees C, both the oxygen consumption and core temperature were lower in IL-6-/- compared with wild-type mice, suggesting a lower cold-induced thermogenesis in IL-6-/- mice. The present results indicate that endogenous IL-6 is of importance for stress- and cold-induced energy expenditure in mice.

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.

Assessment of cardiovascular autonomic function

Autonomic assessment has played an important role in elucidating the role of the autonomic nervous system in diverse clinical and research settings. The techniques most widely used in the clinical setting entail the measurement of an end-organ response to a physiological provocation. The non-invasive measures of cardiovascular parasympathetic function involve the analysis of heart rate variability while the measures of cardiovascular sympathetic function assess the blood pressure response to physiological stimuli. Prolonged tilt-table testing, with or without pharmacological provocation, has become an important tool in the investigation of a predisposition to neurally mediated (vasovagal) syncope. Frequency domain analyses of heart rate and blood pressure variability, microneurography, occlusion plethysmography, laser Doppler imaging and flowmetry, and cardiac sympathetic imaging are currently research tools but may find a place in the clinical assessment of autonomic function in the future.

Neurocirculatory Abnormalities in Parkinson Disease With Orthostatic Hypotension

Patients with Parkinson disease often have orthostatic hypotension. Neurocirculatory abnormalities underlying orthostatic hypotension might reflect levodopa treatment. Sixty-six Parkinson disease patients (36 with orthostatic hypotension, 15 off and 21 on levodopa; 30 without orthostatic hypotension) had tests of reflexive cardiovagal gain (decrease in interbeat interval per unit decrease in systolic pressure during the Valsalva maneuver; orthostatic increase in heart rate per unit decrease in pressure); reflexive sympathoneural function (decrease in pressure during the Valsalva maneuver; orthostatic increment in plasma norepinephrine); and cardiac and extracardiac noradrenergic innervation (septal myocardial 6-[ 18 F]fluorodopamine-derived radioactivity; supine plasma norepinephrine). Severity of orthostatic hypotension did not differ between the levodopa-untreated and levodopa-treated groups with Parkinson disease and orthostatic hypotension (−52±6 [SEM] versus −49±5 mm Hg systolic). The 2 groups had similarly low reflexive cardiovagal gain (0.84±0.23 versus 1.33±0.35 ms/mm Hg during Valsalva; 0.43±0.09 versus 0.27±0.06 bpm/mm Hg during orthostasis); and had similarly attenuated reflexive sympathoneural responses (97±29 versus 71±23 pg/mL during orthostasis; −82±10 versus −73±8 mm Hg during Valsalva). In patients off levodopa, plasma norepinephrine was lower in those with (193±19 pg/mL) than without (348±46 pg/mL) orthostatic hypotension. Low values for reflexive cardiovagal gain, sympathoneural responses, and noradrenergic innervation were strongly related to orthostatic hypotension. Parkinson disease with orthostatic hypotension features reflexive cardiovagal and sympathoneural failure and cardiac and partial extracardiac sympathetic denervation, independent of levodopa treatment.

Management of Hypertension in the Setting of Autonomic Failure

We discuss 2 cases presenting clinically with disabling orthostatic hypotension and severe supine hypertension. This is a common presentation of autonomic failure, and one that challenges conventional treatment. Clinical findings of isolated autonomic failure were the most prominent manifestation in case 1, whereas a movement disorder was the key finding in case 2. The differential diagnosis and treatment of orthostatic hypotension is discussed from a pathophysiological approach. Understanding of the underlying mechanisms of disorders of the autonomic nervous system is fundamental for an effective management of these patients and provides insight into more common disorders such as essential hypertension.

Increased norepinephrine-associated adrenomedullary inclusions in Parkinson's disease

The association with Parkinson's disease (PD) of adrenomedullary inclusions, known as 'hyaline globules' or 'adrenal bodies', has been reported for over 35 years. However, the common perception has been that adrenomedullary chromaffin cells cannot be recognized as pathological cells in PD. In the present study, we discovered that the number of adrenomedullary inclusions per unit area of the adrenal medulla was larger in PD and other Lewy body disorders (LBD) than in other neurological diseases and controls without any autonomic dysfunctions, and correlated with the duration of LBD. We also showed that the cells with adrenomedullary inclusions are all norepinephrine-secreting chromaffin cells. This was detected by PAS reaction following peroxidase immunohistochemistry of four proteins: chromogranin A, phenylethanolamine N-methyltransferase, S-100 protein and neurofilament protein. We also proved that the components of adrenomedullary inclusions are immunocytochemically different from those of Lewy bodies and Lewy-related neurites, as adrenomedullary inclusions were immunonegative to ubiquitin and alpha-synuclein as well as to the above four proteins. Therefore, contrary to current opinion, the norepinephrine-secreting adrenomedullary chromaffin cell is indeed another type of pathological cell in PD and other LBD.

Postural Blood Pressure Changes and Orthostatic Hypotension in the Elderly Patient

With age our ability to maintain haemodynamic homeostasis during position changes becomes less effective. This predisposes elderly patients to significant changes in blood pressure upon standing and orthostatic hypotension (OH). The prevalence of OH varies according to the population being studied. A range of between 5% and 60% has been reported with the lower rate in elderly individuals living in the community and higher rates in those living in an institution or in the acute-care setting. Multiple factors have been linked to OH including age, bed rest, low body mass index and medications. Although antihypertensive medications can theoretically, as a group, worsen OH, the majority of cross-sectional studies have found no association. In addition, prospective randomised trials have demonstrated an improvement in postural blood pressure (PBP) changes with antihypertensive medications. When considering the individual classes, peripheral vasodilators, specifically alpha-adrenoceptor antagonists and nondihydropyridine calcium channel antagonists, can exacerbate PBP changes and lead to OH. ACE inhibitors, angiotensin-receptor antagonists and beta-adrenoceptor antagonists with intrinsic sympathomimetic activity are less likely to worsen OH. Careful management of electrolyte disturbance can decrease the risk of developing OH with diuretic use. With the aging population, this problem will be encountered by the clinicians at a much higher rate. A detailed patient history, an accurate orthostatic blood pressure measurement and careful evaluation of the autonomic nervous system can provide clinical guidance for management of OH. In hypertensive individuals with no pre-treatment OH, the use of antihypertensive medication can be safe and lead to a low risk of developing OH. In individuals with pre-treatment OH or who develop OH while on antihypertensive medications avoidance of the classes that may exacerbate OH and a judicious use of antihypertensive classes that may improve PBP changes may be safe and adequate treatment.

Pharmacology of orthostatic hypotension in Parkinson's disease: from pathophysiology to management

Orthostatic hypotension is highly prevalent in the elderly, and affects up to 20% of patients with Parkinson's disease. Pharmacological approaches help to demonstrate that Parkinson's disease is a primary autonomic failure with involvement of the peripheral autonomic nervous system as shown by decreased [(123)I] meta-iodobenzylguanidine cardiac uptake and preserved growth hormone response to clonidine. No specific clinical trial has evaluated efficacy of antihypotensive drugs in Parkinson's disease. End point of treatment should be a reduction in postural symptoms. Midodrine (Proamatin), Roberts Pharmaceutical), a vasoconstrictor and fludrocortisone (Florinef), Bristol-Myers Squibb), a volume expander are first choice drugs. No data are available on their effects on orthostatic hypotension-related morbidity. The usefulness of other drugs remains to be demonstrated. This review will highlight the importance of nonpharmacological measures in the management of orthostatic hypotension in Parkinson's disease.

Functional Neuroimaging of Sympathetic Innervation of the Heart

Many concepts about acute and chronic effects of stress depend on alterations in sympathetic nerves supplying the heart. Physiologic, pharmacologic, and neurochemical approaches have been used to evaluate cardiac sympathetic function. This article describes a fourth approach that is based on nuclear scanning to visualize cardiac sympathetic innervation and function and relationships between the neuroimaging findings and those from other approaches. Multiple-system atrophy with orthostatic hypotension (formerly the Shy-Drager syndrome) features normal cardiac sympathetic innervation and normal entry of norepinephrine into the coronary sinus (cardiac norepinephrine spillover), in contrast to Parkinson disease with orthostatic hypotension, which features neuroimaging and neurochemical evidence for loss of cardiac sympathetic nerves. This difference may have important implications not only for diagnosis but also for understanding the etiology of Parkinson disease. By analysis of curves relating myocardial radioactivity with time (time-activity curves) after injection of a sympathoneural imaging agent, it is possible to obtain information about cardiac sympathetic function. Abnormal time-activity curves are seen in common disorders such as heart failure and diabetic neuropathy and provide an independent, adverse prognostic index. Analogous abnormalities might help explain increased cardiovascular risk in psychiatric disorders such as melancholic depression.

Dysautonomia in Parkinson's disease: neurocardiological abnormalities

Symptoms of abnormal autonomic-nervous-system function occur commonly in Parkinson's disease (PD). Orthostatic hypotension in patients with parkinsonism has been thought to be a side-effect of treatment with levodopa, a late stage in the disease progression, or, if prominent and early with respect to disordered movement, an indication of a different disease, such as multiple system atrophy. Instead, patients with PD and orthostatic hypotension have clear evidence for baroreflex failure and loss of sympathetic innervation, most noticeably in the heart. By contrast, patients with multiple system atrophy, which is difficult to distinguish clinically from PD, have intact cardiac sympathetic innervation. Post-mortem studies confirm this distinction. Because PD involves postganglionic sympathetic noradrenergic lesions, the disease seems to be not only a movement disorder with dopamine loss in the nigrostriatal system of the brain, but also a dysautonomia, with norepinephrine loss in the sympathetic nervous system of the heart.