5-Hydroxytryptamine causes depression of twitch height in the partially curarized rat phrenic nerve hemidiaphragm preparation.
5-Hydroxytryptamine (5-HT) has significant effects on the skeletal neuromuscular junction. We have evaluated the potential neuromodulatory effects of 5-HT on the rat hemidiaphragm using a non-fatiguing pattern of stimulation (0.3 Hz) in a partially curarized preparation using tubocurarine (EC50 = 560 (range 400-650) nmol litre-1). 5-HT was added to the partially curarized preparation in the following concentrations: 0, 12.5, 25, 50, 100, 200 and 400 nmol litre-1 and the twitch response was recorded at each concentration. These measurements were expressed as a ratio of control values, plotted against time and the area under the curve (AUC) calculated. The AUC values for test and control hemidiaphragms were compared by paired t test analysis accepting a 5% significance level. The mean AUC for test (3327 mm2) and control (4102 mm2) preparations were significantly different (P = 0.003). We have shown that the addition of low concentrations of 5-HT to the indirectly stimulated partially curarized rat diaphragm preparation caused depression of twitch height.
Hindle
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AT
Academic Unit of Anaesthesia, St James's University Hospital, Leeds.
Hopkins
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PM
D000818:Animals; D046508:Culture Techniques; D003964:Diaphragm / Q000187:drug effects / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D008297:Male; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000502:physiology; D009469:Neuromuscular Junction / Q000187:drug effects* / Q000502:physiology; D003473:Neuromuscular Nondepolarizing Agents / Q000494:pharmacology; D010791:Phrenic Nerve / Q000187:drug effects* / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012701:Serotonin / Q000494:pharmacology*; D014403:Tubocurarine / Q000494:pharmacology
D003473:Neuromuscular Nondepolarizing Agents; D012701:Serotonin; D014403:Tubocurarine