Noncompetitive N-methyl-d-aspartate receptor antagonists such as phencyclidine and MK-801 are known to impair cognitive function in rodents and humans, and serve as a useful tool to study the cellular basis for pathogenesis of schizophrenia cognitive symptoms. In the present study, we tested in rats the effect of MK-801 on ventral hippocampus (HPC)-medial prefrontal cortex (mPFC) synaptic transmission and the performance in 2 cognitive tasks. We found that single injection of MK-801 (0.1 mg/kg) induced gradual and long-lasting increases of the HPC-mPFC response, which shares the common expression mechanisms with long-term potentiation (LTP). But unlike LTP, its induction required no enhanced or synchronized synaptic inputs, suggesting aberrant characteristics. In parallel, rats injected with MK-801 showed impairments of mPFC-dependent cognitive flexibility and HPC-mPFC pathway-dependent spatial working memory. The effects of MK-801 on HPC-mPFC responses and spatial working memory decayed in parallel within 24 h. Moreover, the therapeutically important subtype 2/3 metabotropic glutamate receptor agonist LY379268, which blocked MK-801-induced potentiation, ameliorated the MK-801-induced impairment of spatial working memory. Our results show a novel form of use-independent long-lasting potentiation in HPC-mPFC pathway induced by MK-801, which is associated with impairment of HPC-mPFC projection-dependent cognitive function.
Keywords: MK-801; NMDA receptor hypofunction; long-term potentiation; prefrontal cortex; schizophrenia.
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