Sodium thiopental question

[lemonman]

It says this about Sodium thiopental, but the question is what does Sodium thiopental do to nAChR channel, the 5HT3R channel and the GlyR ??? Thanks.

Sodium thiopental is a member of the barbiturate class of drugs, which are relatively non-selective compounds that bind to an entire superfamily of ligand-gated ion channels, of which the GABA_A receptor channel is one of several representatives. This superfamily of ion channels includes the neuronal nAChR channel, the 5HT3R channel, the GlyR channel and others. Surprisingly, while GABA_A receptor currents are increased by barbiturates (and other general anesthetics), ligand-gated ion channels that are predominantly permeable for cationic ions are blocked by these compounds. For example, neuronal nAChR channels are blocked by clinically relevant anesthetic concentrations of both sodium thiopental and pentobarbital.^[24] Such findings implicate (non-GABA-ergic) ligand-gated ion channels, e.g. the neuronal nAChR channel, in mediating some of the (side) effects of barbiturates.^[25] The GABA_A receptor is an inhibitory channel that decreases neuronal activity, and barbiturates enhance the inhibitory action of the GABA_A receptor.^[26]

 

[Solipsis]

Hi there, it clearly says so in the quote: the receptors you mentioned are blocked by sodium thiopental, so... antagonism which is binding without activation. This seems to contribute to the effects of the drug, or at least at anaesthetic doses.

This is surprising because they are mostly not selective and while it blocks those receptors, it agonizes / enhances GABAa which is in the same ionotropic superfamily.

GlyR is inhibitory so blocking this is disinhibiting in certain ways. nAChR activation is excitatory and regulates various processes and 5-HT3 receptors are also excitatory and quite different from many other serotonergic receptors. 5-HT3 is found in the CNS but is also known for being able to mediate nausea.

The drug is mostly a depressant, GABAa is inhibitory... but things like the 'truth serum' aspect are thought to be a result from disinhibition - this seems like a paradox but part of the inhibition acts on systems that are meant to inhibit and control certain functions. Such is an example of how depressant drugs can have 'activating' aspects.