Ketamine inhibits monoamine transporters expressed in human embryonic kidney 293 cells.
BACKGROUND
Ketamine has been characterized as having psychotomimetic and sympathomimetic effects. These symptoms have raised the possibility that ketamine affects monoaminergic neurotransmission. To elucidate the relation between ketamine and monoamine transporters, the authors constructed three cell lines that stably express the norepinephrine, dopamine, and serotonin transporters and investigated the effects of ketamine on these transporters.


METHODS
Human embryonic kidney cells were transfected using the Chen-Okayama method with the human norepinephrine, rat dopamine, and rat serotonin transporter cDNA subcloned into the eukaryotic expression vector. Using cells stably expressing these transporters, the authors investigated the effects of ketamine on the uptake of these compounds and compared them with those of pentobarbital.


RESULTS
Inhibition analysis showed that ketamine significantly inhibited the uptake of all three monoamine transporters in a dose-dependent manner. The Ki (inhibition constant) values of ketamine on the norepinephrine, dopamine, and serotonin transporters were 66.8 microM, 62.9 microM, and 162 microM, respectively. Pentobarbital, a typical general anesthetic agent with no psychotic symptoms, did not affect the uptake of monoamines, however. Further, neither the glycine transporter 1 nor the glutamate/aspartate transporter was affected by ketamine, indicating that ketamine preferentially inhibits monoamine transporters.


CONCLUSIONS
Ketamine inhibited monoamine transporters expressed in human embryonic kidney cells in a dose-dependent manner. This result suggests that the ketamine-induced inhibition of monoamine transporters might contribute to its psychotomimetic and sympathomimetic effects through potentiating monoaminergic neurotransmission.
Nishimura
M
M
Department of Anesthesiology, Osaka University Medical School, Suita, Japan.
Sato
K
K
Okada
T
T
Yoshiya
I
I
Schloss
P
P
Shimada
S
S
Tohyama
M
M
D018528:ATP-Binding Cassette Transporters / Q000187:drug effects*; D027322:Amino Acid Transport System X-AG; D026921:Amino Acid Transport Systems, Neutral; D000778:Anesthetics, Dissociative / Q000494:pharmacology*; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002352:Carrier Proteins / Q000187:drug effects*; D002460:Cell Line; D050483:Dopamine Plasma Membrane Transport Proteins; D050487:Glycine Plasma Membrane Transport Proteins; D006801:Humans; D007649:Ketamine / Q000494:pharmacology*; D008562:Membrane Glycoproteins / Q000187:drug effects; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D050484:Norepinephrine Plasma Membrane Transport Proteins; D051381:Rats; D011994:Recombinant Proteins; D050486:Serotonin Plasma Membrane Transport Proteins; D027981:Symporters
D018528:ATP-Binding Cassette Transporters; D027322:Amino Acid Transport System X-AG; D026921:Amino Acid Transport Systems, Neutral; D000778:Anesthetics, Dissociative; D002352:Carrier Proteins; D050483:Dopamine Plasma Membrane Transport Proteins; D050487:Glycine Plasma Membrane Transport Proteins; D008562:Membrane Glycoproteins; D026901:Membrane Transport Proteins; D009419:Nerve Tissue Proteins; D050484:Norepinephrine Plasma Membrane Transport Proteins; D011994:Recombinant Proteins; C493227:SLC6A2 protein, human; C493230:SLC6A4 protein, human; C493268:SLC6A9 protein, human; D050486:Serotonin Plasma Membrane Transport Proteins; C493226:Slc6a2 protein, rat; C493232:Slc6a4 protein, rat; C493266:Slc6a9 protein, rat; D027981:Symporters; D007649:Ketamine