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Interaction of i.v. anaesthetic agents with 5-HT3 receptors
1University Department of Anaesthesia, Leicester Royal Infirmary.
Abstract:
Using N1E-115 neuroblastoma cells as an experimental model, we have examined if four commonly used i.v. anaesthetic induction agents interact with 5-HT3 receptors. Specifically, we tested the hypothesis that the antiemetic effects of propofol may result from 5-HT3 receptor antagonism. Binding of tropisetron (a 5-HT3 selective reference compound), etomidate, ketamine, thiopentone and propofol to 5-HT3 receptors was assessed by measuring the displacement of [3H]BRL 43694 from whole N1E-115 cells. The rank order potency (Ki) was tropisetron (1.7 (SEM 0.2) nmol litre-1) >> etomidate (83.(4) mumol litre-1) > or = ketamine (97 (4) mumol litre-1) > thiopentone (177 (9) mumol litre-1) > propofol (819 (171) mumol litre-1). With the exception of thiopentone these effects were outside the clinical range and suggest that anaesthetic agents are unlikely to interact directly with 5-HT3 receptors, and that other mechanism(s) must underlie the antiemetic effects of propofol.
Insights
Common anesthetic agents like propofol do not directly interact with 5-HT3 receptors at clinical concentrations. Therefore, propofol's antiemetic effects likely stem from alternative biological mechanisms, not 5-HT3 receptor antagonism.
Area of Science:
- Neuroscience
- Pharmacology
Background:
- 5-HT3 receptors play a role in nausea and vomiting.
- Propofol is known for its antiemetic properties, but the underlying mechanism is not fully understood.
Purpose of the Study:
- To investigate whether common intravenous anesthetic induction agents interact with 5-HT3 receptors.
- To test the hypothesis that propofol's antiemetic effects are due to 5-HT3 receptor antagonism.
Main Methods:
- N1E-115 neuroblastoma cells were used as an experimental model.
- Binding assays were performed to measure the displacement of [3H]BRL 43694 from 5-HT3 receptors by tropisetron, etomidate, ketamine, thiopentone, and propofol.
Main Results:
- The rank order of 5-HT3 receptor affinity was tropisetron >> etomidate > ketamine >= thiopentone > propofol.
- The inhibitory concentrations (Ki) for etomidate, ketamine, thiopentone, and propofol were significantly outside the clinical range.
- Tropisetron demonstrated high affinity for the 5-HT3 receptor.
Conclusions:
- Intravenous anesthetic agents, excluding thiopentone, show negligible interaction with 5-HT3 receptors at clinically relevant concentrations.
- The antiemetic effects of propofol are unlikely to be mediated by direct 5-HT3 receptor antagonism.
- Alternative mechanisms must be responsible for the observed antiemetic properties of propofol.