Novel Benzo[b]quinolizinium Cations as Uncompetitive N-Methyl-D-aspartic Acid (NMDA) Antagonists: The Relationship between log D and Agonist Independent (Closed) NMDA Channel Block

A series of permanently charged benzo[b]quinolizinium cations having lower lipophilicity than MK-801 or phencyclidine (PCP) were synthesized. Data relating agonist independent block of N-methyl-D-aspartic acid (NMDA) ion channels to log D are described. Closed channel access is predicted to result in a more noncompetitive profile of antagonism compared to selective open channel blockers, which are uncompetitive inhibitors. Reduced closed channel block may underlie the absence of PCP or MK-801-like behavioral side effects observed for benzo[b]-quinolizinium cations.