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  • 1
    ISSN: 1432-1912
    Keywords: Malignant hyperthermia ; Inositol phosphates ; Serotonin ; Pigs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recent studies have shown a significant increase of inositol phosphates (IPs) in skeletal muscle during episodes of halothane-induced malignant hyperthermia (MH) in pigs. After treatment with dantrolene and disappearance of MH crisis the IP concentrations returned to basal levels. In order to examine if the increase of IPs during halothane-induced MH may be related to an enhanced IP synthesis in response to activation of 5-HT2 (5-hydroxytryptamine) receptors, the effects of ritanserin, a selective 5-HT2 receptor antagonist, on IP levels were investigated. Biopsies of skeletal muscle of the hindlimbs were obtained in random order and IPs were determined in homozygous MH-susceptible (MHS) and MH-non-susceptible (MHN) swine in the following order: (1) basal, (2) after treatment with ritanserin (2.0 mg/kg), (3) after halothane challenge (3 vol% for 20 min). Basal concentrations of all IPs were higher in MHS than in MHN swine. Ritanserin did not cause any significant changes of IP levels compared to the basal concentrations in MHS and MHN pigs. In MHS pigs, ritanserin did not prevent a halothane-induced MH-crisis. After halothane challenge, 1,3,4-IP3, 1,3,4,6-IP4 and 1,3,4,5-IP4 levels were increased in MHS (during MH crisis) vs. basal concentrations, whereas no changes were found in MHN pigs. Since the increases of IP levels in MHS pigs during MH crisis found in the present study were comparable to those without pretreatment with ritanserin, shown by recent studies, it may be concluded that ritanserin does not prevent the increase of IPs during a halothane-induced MH. Thus, the present data indicate that increases of IP levels during halothane-induced MH in swine are due to other mechanisms than 5-HT mediated enhancement of IP synthesis.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-055X
    Keywords: Schlüsselwörter Maligne Hyperthermie ; Halothan ; Koffein ; Serotonin ; in vitro-Kontrakturtest ; Key words Malignant hyperthermia ; Halothane ; Caffeine ; Serotonin ; In vitro contracture test
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Abstract In pigs genetically susceptible to malignant hyperthermia (MH), it has been shown that serotonin (5-HT2) receptor agonists can induce MH and “psychotic” behaviour. Both can be prevented by 5-HT2 receptor antagonists. Furthermore, free levels of serotonin in plasma increased concomitantly with clinical and laboratory parameters during halothane-induced MH in pigs. In this study the in vitro-effects of the 5-HT2 receptor agonist1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) were investigated in muscle specimens of MH-susceptible (MHS) and normal (MHN) patients. Methods. Muscle biopsies were obtained from 37 patients aged 5–69 years (23.6±5.3 years) with clinical suspicion for MH. The patients were first classified as MHS, MHN or MHE (MH equivocal) by the in vitro contracture test (IVCT) according to the European MH protocol. After MH classification, surplus muscle specimens were subjected to the DOI study. DOI was added to the organ bath in a concentration of 0.02 mmol/l. The in vitro effects on contracture development and muscle twitch were observed for 120 min. Results. Muscle specimens of all patients developed contractures after administration of DOI. However, DOI produced an earlier development of contracture in MHS (17.0±1.8 min; n=17) than in MHN (64.7±5.9 min; n=15) muscles. In MHS muscles, contractures were more distinct than in MHN muscles; at the end of the experiment, contractures had reached a maximum of 12.5±0.9 mN in MHS and 5.1±0.7 mN in MHN muscles. Muscle twitch following DOI administration was reduced significantly in both MHS and MHN muscles. The results of four MHE muscles were comparable with MHS. Conclusion. The present study supports the assumption that an altered serotonin system might be involved in the development of MH. In further studies it should investigated whether 5-HT2 receptors of skeletal muscles from MHS subjects are disordered in function or structure. 5-HT2 receptor agonists should be considered as MH-triggering agents.
    Notes: Zusammenfassung Im Tierexperiment löste die Applikation von Agonisten für Serotonin 2 -Rezeptoren eine maligne Hyperthermie (MH) aus, Antagonisten konnten hingegen die Entwicklung einer MH beim Schwein verhindern. In einer weiteren Studie wurde ein Anstieg des Serotonins im Plasma während einer Halothan-induzierten MH beim Schwein nachgewiesen. Ziel dieser Untersuchung war die Registrierung der in vitro-Effekte des Serotonin 2 -Rezeptoragonisten 1-(2,5-Dimethoxy-4-Iodophenyl)-2-Aminopropan (DOI) auf menschliche Skelettmuskelpräparate von MH-Anlageträgern (MHS) und Nichtanlageträgern (MHN). Nach Gabe von 0,02 mmol/l DOI entwickelten die Muskelpräparate aller 37 Patienten Kontrakturen. Allerdings begann in der MHS-Gruppe (n= 17) die Kontrakturentwicklung mit 17,0±1,8 min signifikant früher als in der MHN-Gruppe (64,7± 5,9 min; n=15). Die Kontrakturen der MHS-Muskeln waren signifikant stärker als in der Vergleichsgruppe. Am Ende des Beobachtungszeitraums von 120 min wurde ein Kontrakturmaximum von 12,5±0,9 mN bei MHS- und von 5,1±0,7 mN bei MHN-Muskeln registriert, die Muskelkontraktionskraft zeigte sich in beiden Gruppen signifikant reduziert. Die Ergebnisse von vier als MHE klassifizierten Muskeln waren vergleichbar mit denen der MHS-Muskeln. Die vorgelegte Studie unterstützt die Vermutung, daß bei der MH ein verändertes Serotoninsystem ursächlich beteiligt sein könnte. In weiteren Studien sollte untersucht werden, ob Serotonin 2 -Rezeptoren der Skelettmuskulatur von MHS Individuen in ihrer Funktion oder Struktur alteriert sind. Serotonin 2 -Rezeptoragonisten sollten als Triggersubstanzen der MH gelten.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-1912
    Keywords: Key words Malignant hyperthermia ; Inositol phosphates ; Serotonin ; Pigs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Recent studies have shown a significant increase of inositol phosphates (IPs) in skeletal muscle during episodes of halothane-induced malignant hyperthermia (MH) in pigs. After treatment with dantrolene and disappearance of MH crisis the IP concentrations returned to basal levels. In order to examine if the increase of IPs during halothane-induced MH may be related to an enhanced IP synthesis in response to activation of 5-HT2 (5-hydroxytryptamine) receptors, the effects of ritanserin, a selective 5-HT2 receptor antagonist, on IP levels were investigated. Biopsies of skeletal muscle of the hindlimbs were obtained in random order and IPs were determined in homozygous MH-susceptible (MHS) and MH-non-susceptible (MHN) swine in the following order: (1) basal, (2) after treatment with ritanserin (2.0 mg/kg), (3) after halothane challenge (3 vol% for 20 min). Basal concentrations of all IPs were higher in MHS than in MHN swine. Ritanserin did not cause any significant changes of IP levels compared to the basal concentrations in MHS and MHN pigs. In MHS pigs, ritanserin did not prevent a halothane-induced MH-crisis. After halothane challenge, 1,3,4-IP3, 1,3,4,6-IP4 and 1,3,4,5-IP4 levels were increased in MHS (during MH crisis) vs. basal concentrations, whereas no changes were found in MHN pigs. Since the increases of IP levels in MHS pigs during MH crisis found in the present study were comparable to those without pretreatment with ritanserin, shown by recent studies, it may be concluded that ritanserin does not prevent the increase of IPs during a halothane-induced MH. Thus, the present data indicate that increases of IP levels during halothane-induced MH in swine are due to other mechanisms than 5-HT mediated enhancement of IP synthesis.
    Type of Medium: Electronic Resource
    Library Location Call Number Volume/Issue/Year Availability
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