Phencyclidine (PCP)

PCP is well known for its primary action on ionotropic glutamate receptors, such as the NMDA receptor in rats and in rat brain homogenate. As such, PCP is an NMDA receptor antagonist. NMDA receptors mediate excitation, however, studies have shown that PCP unexpectedly produces substantial cortical activation in humans and rodents.  Research also indicates that PCP inhibits nicotinic acetylcholine (nACh) receptors. Analogues of PCP exhibit varying potency at nACh receptors[citation needed] and NMDA receptors. In some brain regions, these effects are believed to act synergistically by inhibiting excitatory activity.PCP, like ketamine, also acts as a D2 receptor partial agonist in rat brain homogenate. This activity may be associated with some of the other more psychotic features of PCP intoxication, which is evidenced by the successful use of D2 receptor antagonists (such as haloperidol) in the treatment of PCP psychosis.