Scandinavian journal of rheumatology. Supplement
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Scand. J. Rheumatol. Suppl. · Jan 2000
ReviewFibromyalgia-symptom or diagnosis: a definition of the position.
According to the American College of Rheumatology the diagnosis of fibromyalgia is based on criteria for the classification of fibromyalgia consisting entirely of clinical signs and symptoms. For diagnostic reasons autonomic disturbances and mental features have to be considered. The distinction between fibromyalgia (tender points) and myofascial pain syndrome (trigger points) is essential. ⋯ The myopathological patterns in fibromyalgia are non-specific: type II fiber atrophy, an increase of lipid droplets, a slight proliferation of mitochondria, and a slightly elevated incidence of ragged red fibers. Initial reports on some allelic abnormalities in the serotonin system seem to highlight the important role of serotonin already presumed earlier. Significantly high levels of substance P in the cerebrospinal fluid of FM patients additionally support the impact of these neurotransmitters on both nociceptive and antinociceptive mechanisms.
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Repetitive synaptic excitation or the application of L-glutamate into the vicinity of multireceptive neurons in the dorsal horn of the spinal cord and corresponding structures of the trigeminal nucleus increases neuronal excitability, which is then reflected by an expansion of the receptive field (Fig. 1). Similar alterations of the receptive field of neurons have been observed in various other brain regions. The receptive fields of multireceptive neurons also expand their size following mechanical, chemical, inflammatory or nerve injuries. ⋯ There is evidence from recent research that this facilitatory effect on glutamatergic synaptic transmission involves membrane receptor phosphorylation, and enhances activity-dependent gene expression (Fig. 3). In order to investigate the time-dependent processing of ongoing afferent noxious stimulation in the central nervous system we recently employed the quantitative autoradiographic 14C-2-deoxyglucose technique in a model of chronic monoarthritic pain in the rat. A synopsis of these most recent experimental data and results from previous electrophysiological in vivo and in vitro studies suggests that dorsal horn neurons and probably also other neurons in pain-related structures become spontaneously active and can maintain their activity without further noxious peripheral input.
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Scand. J. Rheumatol. Suppl. · Jan 2000
The use of 5-HT3 receptor antagonists in various rheumatic diseases--a clue to the mechanism of action of these agents in fibromyalgia?
In a pilot study, the action of the 5-HT3 receptor antagonist, tropisetron, on different types of local rheumatic pain and inflammatory effects was studied. With intra-articular injection of tropisetron, an improvement in inflammation and pain was obtained in inflammatory rheumatic diseases and activated osteoarthrosis. ⋯ The effect of the 5-HT3 receptor antagonists is probable primarily to limit the release of substance P, which acts as a pain and inflammatory mediator, and is itself released by the neurogenic inflammation that occurs after the binding of serotonin to its corresponding receptor. These results should be backed up with placebo controlled studies, which if confirmed, might imply that 5-HT3 receptor antagonists could supplement or replace the local administration of corticosteroids.