Dopamine receptor contribution to the action of PCP,
LSD and ketamine psychotomimetics

by
Seeman P, Ko F, Tallerico T.
Department of Pharmacology,
University of Toronto,
Toronto, Ontario, Canada.
philip.seeman@utoronto.ca
Mol Psychiatry. 2005 Sep;10(9):877-83.


ABSTRACT

Although phencyclidine and ketamine are used to model a hypoglutamate theory of schizophrenia, their selectivity for NMDA receptors has been questioned. To determine the affinities of phencyclidine, ketamine, dizocilpine and LSD for the functional high-affinity state of the dopamine D2 receptor, D2High, their dissociation constants (Ki) were obtained on [3H]domperidone binding to human cloned dopamine D2 receptors. Phencyclidine had a high affinity for D2High with a Ki of 2.7 nM, in contrast to its low affinity for the NMDA receptor, with a Ki of 313 nM, as labeled by [3H]dizocilpine on rat striatal tissue. Ketamine also had a high affinity for D2High with a Ki of 55 nM, an affinity higher than its 3100 nM Ki for the NMDA sites. Dizocilpine had a Ki of 0.3 nM at D2High, but a Kd of 1.8 nM at the NMDA receptor. LSD had a Ki of 2 nM at D2High. Because the psychotomimetics had higher potency at D2High than at the NMDA site, the psychotomimetic action of these drugs must have a major contribution from D2 agonism. Because these drugs have a combined action on both dopamine receptors and NMDA receptors, these drugs, when given in vivo, test a combined hyperdopamine and hypoglutamate theory of psychosis.

LSD
Ketamine
Dopamine
Phencyclidine
Beyond the K-hole
Ketamine and opiate withdrawal
Ketamine and the nucleus accumbens
Ketamine: medical and non-medical use
The role of ketamine in pain management
Ketamine and the glutaminergic hypothesis of schizophrenia
Low-dose ketamine as a fast-onset, long-acting antidepressant


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