Ketamine receptors have GABAA receptor agonistic properties. Subanaesthetic doses of Ketamine receptors inhibits tonic convulsions induced by the GABAA receptor antagonist bicuculline.
The GABAA receptor agonist, muscimol, potentiates ketamin induced anesthesia whereas, bicuculline antagonizes it.
Opioid Receptors : Ketamine receptors has been reported to interact with opioid receptors in clinically relevant concentration. Other studies have suggested an agonist action at kappa receptors.
Studies shows S(+)-ketamine to be three times more potent than R(-)-ketamine at mu and kappa receptors. It improves opioid efficacy and reduces postoperative opioid requirement.
The antinociceptive action of Ketamine receptors may involve descending inhibitory monoaminergic pain pathways. Systemic administration of ketamine perioperatively suppresses early-stage postoperative pain via monoaminergic descending inhibitory pathways.
Muscarinic and Nicotinic Receptors :
Ketamine receptors inhibits muscarinic receptor (M,) which may explain some of its anticholinergic effects on memory and consciousness, prominent sympathetic tone, bronchodilation, and mydriasis. However, the muscaririic inhibitory action of ketamine isomers is not stereoselective.
A significant fraction of this muscarinic inhibitory action of ketamine may be due to the preservative benzethonium. Ketamine also antagonizes the actions of anticholinesterases like neostigmine. Ketamine-like volatile anesthetics inhibit neuronal nicotinic acetylcholine receptors in clinically relevant concentration range, which may play a role in ketamine’s analgesic action.
Effects on Voltage Gated Channels :
Ketamine receptors blocks Na and K(DR) channels in superficial dorsal horn neurons of the lumbar spinal cord at clinically relevant concentrations for local and intrathecal application, reducing the excitability of the neurons, which may play an important role in the complex mechanism of its action during spinal anaesthesia.
Similar to local anesthetics, it interacts with voltage-gated sodium channels sharing a binding site with local anesthetics.