Microinjections of phencyclidine (PCP) and related drugs into nucleus accumbens shell potentiate medial forebrain bundle brain stimulation reward

Microinjections of phencyclidine (PCP) into the ventro-medial portion of nucleus accumbens in rats potentiated the rewarding impact of lateral hypothalamic brain stimulation. Similar effects were found with nomifensine, which shares with PCP the ability to block dopamine uptake and thus elevate synaptic dopamine levels but does not share with PCP the ability to block NMDA receptors. Similar effects were also seen with dizocilpine (MK-801) and [3-((+/-)2-carboxypiperazin-4-yl)propyl-1-phosphonate] (CPP), which share with PCP the ability to block NMDA receptors but not to block dopamine uptake. Thus PCP's properties as a dopamine uptake inhibitor and as an NMDA receptor antagonist each appear capable of producing reward-related actions in this brain region. The common denominator of these two PCP actions is decreased output of medium spiny neurons; these neurons are tonically activated by a glutamate projection from prefrontal cortex (PCP blocks this source of activation) and are tonically inhibited by a dopaminergic projection from the ventral tegmental area (PCP au this inhibition).