Clozapine inhibits strychnine-sensitive glycine receptors in rat hippocampal neurons

Seizure is one kind of severe side effects during clozapine (Clo) treatment. However, the mechanism of seizure associated with Clo therapy is not completely clear. Strychnine-sensitive glycine receptors (GlyRs) play an important role in regulating the excitability in the hippocampus. In the present study, we investigated the effect of Clo on GlyRs in cultured hippocampal neurons of rats. Clo reversibly inhibited the glycine-induced chloride currents (IGly) in a concentration-dependent manner. The half-maximal effect concentration (EC50) for glycine alone was 25.6 ± 0.7 μM with the Hill coefficient 1.5 ± 0.1; in the presence of Clo, the EC50 and the Hill coefficient were 28.9 ± 6.3 μM and 1.2 ± 0.3 respectively, which were not significantly affected by Clo. In addition, Clo inhibition of IGly was not influenced by blocking D1 and D2 dopamine receptors with haloperidol (Hal). Taken together, these results suggest that Clo is a non-competitive antagonist of GlyR independent of its activation of dopamine receptors, which may contribute to seizure associated with Clo therapy.