Autonomic dysfunction including orthostatic hypertension (OH) is a major health problem, causing significant morbidity and mortality. Its pathophysiology remains poorly understood and hence its management lacks a solid scientific base. The PPG focuses on the pathophysiology and treatment of autonomic failure. Project 1 (Low) incorporates a novel strategy of cholinesterase inhibition in the treatment of OH, an approach that promises to improve OH without supine hypertension. A second blinded treatment trial will evaluate if sodium chloride will expand plasma volume and if urinary sodium excretion is a suitable surrogate measure of plasma volume status. A series of studies, including the use of microneurography to measure sympathetic impuls3es, will evaluate the pathophysiology of postural tachycardia syndrome (POTS). A novel approach of amplitude modulation of the EEG in POTS shows a selective reduction of a frequency band of 0.02-0.05 Hz; this component is of particular interest since it may have a brainstem origin. The venous capacitance bed will be evaluated (Projects) to determine if there is excessive transcapillary efflux and changes in compliance in POTS and the effects of aging. The relative importance of the mesenteric, systematic and cerebrovascular circulations in OH will be evaluated. Project (Benarroch) will expand its studies on the neurochemical organization of autonomic control regions of the medulla in multiple system atrophy (MSA) and the parkinsonian syndromes. These include quantitative evaluates of new cellular groups (nucleus ambiguus, nuclease retroambiguus) and new receptors (including angiotensin II) that are likely to provide insights into the pathophysiology of autonomic failure in MSA. Project (Joyner) will undertake a detailed evaluation of the effects of denervation (mild in POTS and severe in neurogenic OH) and aging on the venous capacity and compliance. Project (Brimijoin) will focus on the response of the pre-ganglionic neuron to denervation and will study the mechanism of spinal intermediolateral column cell loss, using he model of immune-mediated pre-ganglionic autonomic neuropathy. The roles of apoptosis, excitotoxicity, growth factors, and aging will be evaluated and related to MSA.
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