Modulation of glutamate receptors in response to the novel antipsychotic olanzapine in rats

Background: A disturbance in glutamate neurotransmission has been hypothesized in schizophrenia. Hence, the beneficial effects of pharmacological treatment may be related to adaptive changes taking place in this neurotransmitter system. Methods: In this study, we investigated the modulation of ionotropic and metabotropic glutamate receptors in the rat brain following acute or chronic exposure to the novel antipsychotic olanzapine. Results: In accordance with the clear distinction between classical and atypical drugs, olanzapine did not alter glutamate receptor expression in striatum. Chronic, not acute, exposure to olanzapine was capable of up-regulating hippocampal mRNA levels for GluR-B and GluR-C, two α-amino-3-hydroxy-5-methyl-4-isoxazole proprionic acid (AMPA)-forming subunits. This effect could be relevant for the improvement of schizophrenic alterations, which are thought to depend on dysfunction of the glutamatergic transmission within the hippocampal formation. We also found that the expression of group II glutamate metabotropic receptors was up-regulated in the frontal cortex after chronic exposure to clozapine, and to a lesser extent olanzapine, but not with haloperidol. Conclusions: The adaptive mechanisms taking place in glutamatergic transmission might prove useful in ameliorating some of the dysfunction observed in the brain of schizophrenic patients.