Which property of ketamine is responsible for the dissociative anaesthesia it produces?
- A Potentiation of GABA-A receptor chloride influx
- B Kappa opioid receptor agonism in the cerebral cortex
- C Non-competitive antagonism of the NMDA receptor at the PCP site ✓
- D Activation of sigma receptors causing cataleptic state
Correct answer: C. Non-competitive antagonism of the NMDA receptor at the PCP site
Explanation
Ketamine produces dissociative anaesthesia by non-competitively blocking the NMDA receptor at the phencyclidine (PCP) binding site within the ion channel, interrupting thalamocortical and limbic pathways. This creates a functional and electrophysiological dissociation between the thalamic and limbic systems, manifesting as profound analgesia, sedation, and amnesia while the patient may appear awake with open eyes and preserved laryngeal reflexes. GABA potentiation is the mechanism of benzodiazepines and propofol.
Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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