Calcium/calmodulin-dependent kinase II is involved in the facilitating effect of clozapine on NMDA- and electrically evoked responses in the medial prefrontal cortical pyramidal cells

Using the method of intracellular recording in in vitro brain slices, we investigated whether calcium/calmodulin-dependent kinase II (CaMKII) is involved in the facilitating action produced by the atypical antipsychotic drug (APD) clozapine on N-methyl-D-aspartate (NMDA)-induced inward currents and electrically evoked excitatory postsynaptic currents (EPSCs) in pyramidal cells of the medial prefrontal cortex (mPFC). The CaMKII inhibitor, KN-93 (N-[2-(N-(4-Chlorocinnamyl)-N-methylaminomethyl)phenyll-N-[2-hydroxyethyl]-4-methoxybenzenesulfonamide), but not the inactive isomer, KN-92 (2-[N-(4-Methoxybenzenesulfonyl)]amino-N-(4-chlorocinnamyl)-N-methylbenzylamine, phosphate), blocked clozapine's augmenting effect on NMDA-evoked responses in pyramidal cells of the rat mPFC. KN-93 also inhibited the facilitatory effect of clozapine on electrically evoked responses in the pyramidal cells, while KN-92 did not show any effect. Similarly, the calmodulin antagonist W-7 (N-(6-Aminohexyl)-5-chloro-1-naphthalenesulfonamide) inhibited the augmenting effect of clozapine on NMDA- and electrically evoked responses in the pyramidal cells. To further test the role of CaMKII in mediating the augmenting action of clozapine, we performed experiments in alpha-CaMKII mutant and wild-type mice. In contrast to results in pyramidal cells from rats or wild-type mice, clozapine was not able to potentiate NMDA-induced currents in the mPFC pyramidal cells from the CaMKII mutant mouse. Both KN-93 and W-7, but not KN-92, inhibited the augmenting action of clozapine in the pyramidal cells of wild-type mice. Taken together, these results suggest that the facilitating action of clozapine on the NMDA- and electrically evoked responses in pyramidal cells of the mPFC requires activation of CaMKII enzyme.