Inhibition of N-methyl-d-aspartate-induced hippocampal [³H]norepinephrine release by phencyclidine is dependent on potassium concentration

This study examined the ability of phencyclidine (PCP) to inhibit the responses to N-methyl-d-aspartate (NMDA) in depolarizing concentrations of K⁺. The effects of PCP and Mg²⁺ on NMDA-induced norepinephrine release from hippocampal slices were measured during superfusion with various extracellular concentrations of K⁺. The IC₅₀ values for Mg²⁺ and PCP were significantly higher in K⁺ concentrations above 6 mM. These data are supportive of the hypothesis that PCP produces a voltage-dependent blockade of NMDA-activated ion channels.