Investigation of alpha2-adrenoreceptors in humans
Article Abstract:
Alpha-2-adrenoreceptors were originally discovered in the central nervous system and were defined by their response to the substance norepinephrine, a close relative of adrenalin. Stimulation of alpha-2-adrenoreceptors lowers blood pressure, but the exact mechanism responsible for the reduction in blood pressure is not known, nor are the precise pharmacologic properties of the alpha-2-adrenoreceptors distributed throughout the body. Although it is believed that alpha-2-adrenoreceptor 'agonists' (substances which activate the receptors and result in lower blood pressure) act through receptors in the central nervous system, the possibility of important effects outside the central nervous system cannot be ruled out. For this reason, differences between central and peripheral alpha-2-adrenoreceptors were examined. Since the use of any pharmacologic agent affects both central and peripheral receptors simultaneously, the level of growth hormone in the blood (which is secreted only by the brain) can be used to monitor central nervous system effects. The blood flow in the skin can be used to monitor peripheral effects, thereby allowing the nonclinical pharmacological researcher to tease apart central and peripheral effects. Appropriate monitoring of physiological responses is necessary in the evaluation of alpha-2-adrenoreceptor agonists. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Medicine
Subject: Health care industry
ISSN: 0002-9343
Year: 1989
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Comparison of organ-specific toxicity of temafloxacin in animals and humans
Article Abstract:
Animal studies have suggested that certain areas in the body may be adversely affected by temafloxacin, a type of fluoroquinolone antibiotic. These areas are the kidneys, eyes, central nervous system, and joints of the young. Although temafloxacin can cause adverse effects in the kidneys of rats and dogs, because of the difference in the ion concentration (pH) of human urine, these effects are not thought to occur in humans. Clinical data do not give any support to the occurrence of these side effects in human kidneys. Clinical studies in humans have not shown any adverse effects in the eyes. Studies in young dogs have suggested damage to joint cartilage after treatment with temafloxacin. Limited studies in humans do not show any adverse effects in children, but further study is needed. Adverse effects in the central nervous system have not been seen in humans treated with temafloxacin. This fluoroquinolone was not found to be mutagenic to developing fetuses. However, it is felt that temafloxacin should not be used by pregnant women or children because of the joint damage found in animal studies. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Medicine
Subject: Health care industry
ISSN: 0002-9343
Year: 1991
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New concepts on the central regulation of blood pressure: alpha-2-adrenoreceptors and "imidazoline receptors"
Article Abstract:
A common explanation for the mechanism by which imidazole compounds, such as clonidine, produce blood-pressure-reducing effects is the stimulation of alpha-2-adrenoreceptors within the brainstem. Experiments on the physiology of rabbits has shown that there is a region of the brainstem, called the medullary nucleus reticularis, which causes a reduction in blood pressure when stimulated by imidazoline drugs, a group of related compounds based on the imidazole molecular structure. The natural stimulating substance which defines alpha-2-adrenoreceptors is norepinephrine, a close relative of adrenalin, yet this substance does not produce a hypotensive effect when administered directly to this part of the brain. Therefore, there are at least some receptors in the central nervous system which bind imidazolines, like clonidine, and yet are not alpha-2-adrenoreceptors. This unknown receptor also binds rilmenidine, a close relative of the imidazolines. The natural ligand for these receptors is not yet known. (Consumer Summary produced by Reliance Medical Information, Inc.)
Publication Name: American Journal of Medicine
Subject: Health care industry
ISSN: 0002-9343
Year: 1989
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