Gene expression profiling following chronic NMDA receptor blockade-induced learning deficits in rats

Acute treatments with MK-801, a noncompetitive antagonist of the NMDA glutamate receptor, induce spatial memory deficits in rodents. In the present study, we developed a low-dose chronic MK-801 treatment regimen that induced persistent learning deficits (determined by the Morris water maze task) after administration of the drug (0.2 mg/kg) every 12 h for 14 days. To determine the impact of such a treatment, changes in mRNA expression were investigated in the hippocampi and striata of treated animals using a cDNA membrane array followed by Western blots. Genes whose expression levels were found to be most altered included preprolactin (downregulated) and mitogen-activated protein kinase (MAP kinase 1; upregulated) in the hippocampus, and acyl-CoA synthetase (downregulated) and apolipoprotein D (upregulated) in the striatum. Furthermore, MAP kinase 1 and proteosome subunit beta precursor was found to meet selection criteria for upregulation in both the hippocampus and striatum. Among other genes found to be most changed in the hippocampus were protein kinase C beta I and II, protein tyrosine phosphatase 1beta, neuropilin I and II, adenosine receptor A1, and metabotropic glutamate receptor 2/3. The impact of some gene expression alterations on their corresponding protein levels was studied next. In the hippocampus, protein kinase C beta I and II, protein tyrosine phosphatase, neuropilin I and II, adenosine receptor A, metabotropic glutamate receptor 2/3, and in the striatum phosphatidyl inositol 4 kinase, mitogen-activated protein kinase 1, adenylyl cyclase II, dopamine receptors 1A and 2, and cytochrome C oxidase subunit Va gene and protein expression levels were found to be highly correlated. These results suggest the potential involvement of several genes and proteins in the neuropharmacological effects of MK-801 and possibly the persisting cognitive deficits induced by this repeated drug treatment.