Which intravenous anesthetic agent stimulates NDMA receptors as its mechanism of action?

The correct answer is Ketamine, as it uniquely acts as an NMDA (N-methyl-D-aspartate) receptor antagonist in its mechanism of action. This interaction with NMDA receptors contributes to its anesthetic and analgesic properties, making it particularly effective for inducing dissociative anesthesia. Ketamine not only inhibits the excitatory neurotransmitter pathways but also has a distinct ability to produce profound analgesia and a cataleptic state, which is not seen with the other agents listed.

In contrast, Etomidate, Propofol, and Sodium Thiopental operate primarily through enhancing GABA (gamma-aminobutyric acid) receptor activity, which increases inhibitory neurotransmission in the brain but does not involve the modulation of NMDA receptors. This is why Ketamine stands out as the only intravenous anesthetic agent that directly stimulates NMDA receptors, marking its unique pharmacodynamics in clinical use.