Olanzapine and clozapine but not haloperidol reverse subchronic phencyclidine-induced functional hyperactivity of N-methyl-D-aspartate receptors in pyramidal cells of the rat medial prefrontal cortex.

In the present study, we have investigated and compared the ability of olanzapine, clozapine and haloperidol to modulate phencyclidine (PCP)-induced effect in pyramidal cells of the medial prefrontal cortex (mPFC) of rats using the techniques of intracellular recording and voltage-clamp. Subchronic treatment of rats with PCP (2 mg/kg, b.i.d., 7 days, 48-60 h withdrawal) produced: (1) a depolarized resting membrane potential, a decrease of slow after hyperpolarization (sAHP) and spike frequency adaptation, (2) a shift of the concentration response curve of N-methyl-D-aspartate (NMDA), but not (+/-)-alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA), to the left, (3) a decrease of the paired pulse facilitation (PPF) with an increase of excitatory postsynaptic current variance (EPSC variance), and (4) a reduction of the blockade of NMDA response by in vitro application of PCP. Repeated treatment with either olanzapine or clozapine, but not haloperidol, completely prevented the aforementioned subchronic PCP-induced effects. The present results indicate that the atypical antipsychotic drugs (APDs) clozapine and olanzapine share a common property in preventing subchronic PCP-induced functional hyperactivity of NMDA receptors.