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Hermann (Hugh) Blaschko was a biochemical pharmacologist best known for discovering how adrenaline (epinephrine), noradrenaline (norepinephrine), and dopamine were synthesized, stored, and metabolized in adrenomedullary cells and sympathetic nerves. Blaschko's work not only supported the validity of the concept of neurochemical synaptic transmission but he also made fundamental contributions to the development of drugs used in clinical medicine to treat diseases such as depression, hypertension, and Parkinson's Disease.

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The prominence of catecholamines and their congeners in allergic diseases rests chiefly on their use in asthma and acute hypersensitivity reactions, such as anaphylaxis. They act in these indications by activating both α- and ß-adrenoceptors. Adrenaline, the prototype, was discovered in the adrenals in 1893/1894. In 1939, dopa decarboxylase was the first enzyme in the biosynthesis of catecholamines to be described. Later other catecholamines like noradrenaline and dopamine were characterized. The identification of the active chemicals went along with studies regarding catecholamine receptors. It took until 1948 before the existence of at least two different receptors for the different effects was accepted. Meanwhile, genes from all mammalian catecholamine receptors have been cloned.

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PURPOSE: To define some of the most common characteristics of vascular hyporesponsiveness to catecholamines during septic shock and outline current therapeutic approaches and future perspectives. METHODS: Source data were obtained from a PubMed search of the medical literature with the following MeSH terms: Muscle, smooth, vascular/physiopathology; hypotension/etiology; shock/physiopathology; vasodilation/physiology; shock/therapy; vasoconstrictor agents. RESULTS: NO and peroxynitrite are mainly responsible for vasoplegia and vascular hyporeactivity while COX 2 enzyme is responsible for the increase in PGI2, which also contributes to hyporeactivity. Moreover, K+ATP and BKCa channels are over-activated during septic shock and participate in hypotension. Finally, other mechanisms are involved in vascular hyporesponsiveness such as critical illness-related corticosteroid insufficiency, vasopressin depletion, dysfunction and desensitization of adrenoreceptors as well as inactivation of catecholamines by oxidation. CONCLUSION: In animal models, several therapeutic approaches, targeted on one particular compound have proven their efficacy in preventing or reversing vascular hyporesponsiveness to catecholamines. Unfortunately, none have been successfully tested in clinical trials. Nevertheless, very high doses of catecholamines ( > 5 µg/kg/min), hydrocortisone, terlipressin or vasopressin could represent an alternative for the treatment of refractory septic shock.

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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.

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This review examines the history of discoveries that contributed to development of the dopamine hypothesis of schizophrenia. The origin of the hypothesis is traced to the recognition that neuroleptic drugs interfere with brain dopamine function. This insight was derived from two distinct lines of research. The first line originated from the discovery in 1956 that reserpine depletes brain serotonin. This finding resulted in a sequence of studies that led to the discovery that brain dopamine is involved in neuroleptic-induced extrapyramidal motor disturbances. The second line of research was aimed at determining the mechanism of action of psychomotor stimulants. This research produced evidence that stimulants directly or indirectly activate brain dopamine receptors. Because nonreserpine neuroleptics such as chlorpromazine block stimulant-induced movement, these findings suggested that neuroleptics were dopamine antagonists. Most previous accounts of the development of the dopamine hypothesis of schizophrenia emphasize the first line of research and ignore the second.

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Although early experiments in animals and humans suggested that digitalis glycosides increased cardiac output only in the failing heart, later studies showed that these cardiotonic agents increase intraventricular systolic pressure and decrease relaxation time in the normal animal. The controversy concerning the peripheral vascular or direct cardiac effects of digitalis was finally resolved when new methods were applied to the study of the effects of this drug on intraventricular pressures and cardiac contractile force. Other positive inotropic agents, such as the adrenergic agonists, have also been tested for the treatment of heart failure. However, during long-term oral or intravenous therapy, the effectiveness of these drugs appears to diminish. Clinical studies of glucagon, a polypeptide with positive inotropic and chronotropic effects, have revealed its potential for causing side effects and its reduced activity in patients with chronic heart failure. With the discovery of several new types of inotropic agents, i.e., the bipyridines and the imidazole and benzimidazole derivatives, interest in revising our therapeutic approach to congestive heart failure has increased. This review discusses recent developments in this area.

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