Diminished excitatory synaptic transmission correlates with impaired spatial working memory in neurodevelopmental rodent models of schizophrenia

Abstract

Neurodevelopmental abnormalities are associated with cognitive dysfunction in schizophrenia. In particular, deficits of working memory, are consistently observed in schizophrenia, reflecting prefrontal cortex (PFc) dysfunction. To elucidate the mechanism of such deficits in working memory, the pathophysiological properties of PFc neurons and synaptic transmission have been studied in several developmental models of schizophrenia. Given the pathogenetic heterogeneity of schizophrenia, comparison of PFc synaptic transmission between models of prenatal and postnatal defect would promote our understanding on the developmental components of the biological vulnerability to schizophrenia. In the present study, we investigated the excitatory synaptic transmission onto pyramidal cells localized in layer 5 of the medial PFc (mPFc) in two developmental models of schizophrenia: gestational methylazoxymethanol acetate (MAM) administration and post-weaning social isolation (SI). We found that both models exhibited defective spatial working memory, as indicated by lower spontaneous alternations in a Y-maze paradigm. The recordings from pyramidal neurons in both models exhibited decreased spontaneous excitatory postsynaptic current (sEPSC), representing the reduction of excitatory synaptic transmission in the mPFc. Interestingly, a positive correlation between the impaired spontaneous alternation behavior and the decreased excitatory synaptic transmission of pyramidal neurons was found in both models. These findings suggest that diminished excitatory neurotransmission in the mPFc could be a common pathophysiology regardless of the prenatal and postnatal pathogenesis in developmental models of schizophrenia, and that it might underlie the mechanism of defective working memory in those models.