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.