Vol. 301, Issue 1, 197-209, April 2002

Differential Effects of Haloperidol and Clozapine on [³H]cAMP Binding, Protein Kinase A (PKA) Activity, and mRNA and Protein Expression of Selective Regulatory and Catalytic Subunit Isoforms of PKA in Rat Brain

Yogesh Dwivedi, Hooriyah S. Rizavi and Ghanshyam N. Pandey

Psychiatric Institute, Department of Psychiatry, University of Illinois at Chicago, Chicago, Illinois

The present study was undertaken to examine whether the mechanism of action of typical and atypical antipsychotics is related in their ability to regulate key phosphorylating enzyme of adenylyl cyclase-cAMP pathway, i.e., protein kinase A (PKA). For this purpose, regulatory (R) and catalytic (Cat) activities of PKA and expression of various isoforms of regulatory and catalytic subunits were examined in rat brain after single or chronic (21-day) treatment with haloperidol (HAL, 1 mg/kg) or clozapine (CLOZ, 20 mg/kg). It was observed that chronic but not acute treatment of CLOZ significantly decreased [³H]cAMP binding to the regulatory subunit of PKA as well as catalytic activity of PKA in particulate and cytosol fractions of the rat cortex, hippocampus, and striatum. In these fractions, CLOZ significantly decreased protein levels of selective RII-, RII-, and Cat-subunit isoforms of PKA. These decreases were accompanied by decreases in their respective mRNA expression. In contrast, chronic but not acute treatment of HAL significantly increased [³H]cAMP binding and the catalytic activity of PKA in particulate and cytosol fractions of only the striatum brain area. In addition, chronic treatment of HAL significantly increased mRNA and protein levels of RII- and RII-subunit isoforms in the striatum. None of the antipsychotics caused any change in the expression of the Cat-, RI-, or RI-subunit isoform. These results, thus, suggest that HAL and CLOZ differentially regulate PKA catalytic and regulatory activities and the expression of selective catalytic and regulatory subunit isoforms of PKA, which may be associated with their mechanisms of action.