What is the primary mechanism of action of sodium thiopental?

What is the primary mechanism of action of sodium thiopental?

• A. Inhibition of acetylcholinesterase
• B. Dopamine receptor blockade
• C. GABA-A receptor activation leading to CNS depression
• D. NMDA receptor antagonism

Answer: (C)

Sodium thiopental induces anesthesia mainly by boosting GABAergic inhibition in the brain. As a barbiturate, it binds to it enhances the activity of the GABA-A receptor, increasing chloride ion influx and hyperpolarizing neurons. This heightened inhibitory effect quiets neuronal activity, producing rapid CNS depression and anesthesia. At usual doses it acts as a positive allosteric modulator, making GABA’s action more effective and prolonging the chloride channel opening. At higher doses it can directly activate the receptor even without GABA, leading to deeper CNS depression. Its rapid onset after IV injection comes from high lipid solubility, which allows swift brain entry for induction. It does not work by inhibiting acetylcholinesterase, blocking dopamine receptors, or antagonizing NMDA receptors, so those mechanisms don’t describe how it produces anesthesia.

Sodium thiopental induces anesthesia mainly by boosting GABAergic inhibition in the brain. As a barbiturate, it binds to it enhances the activity of the GABA-A receptor, increasing chloride ion influx and hyperpolarizing neurons. This heightened inhibitory effect quiets neuronal activity, producing rapid CNS depression and anesthesia. At usual doses it acts as a positive allosteric modulator, making GABA’s action more effective and prolonging the chloride channel opening. At higher doses it can directly activate the receptor even without GABA, leading to deeper CNS depression. Its rapid onset after IV injection comes from high lipid solubility, which allows swift brain entry for induction. It does not work by inhibiting acetylcholinesterase, blocking dopamine receptors, or antagonizing NMDA receptors, so those mechanisms don’t describe how it produces anesthesia.