Study on Molecular Pathophysiology of Schizophrenia

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Several lines of evidence suggest that dysfunction of glutamatergic transmission via NMDA receptor play a role in the pathophysiology of schizophrenia. Therefore, NMDA receptor antagonist phencyclidine (PCP) have been widely used as animal model of schizophrenia. We reported that PCP-induced cognitive deficits in mice could be attenuated by subsequent subchronic administration of clozapine, but not haloperidol.This study was undertaken to examine the effects of the selective serotonin reuptake inhibitor fluvoxamine on cognitive deficits in mice after repeated administration of the NMDA receptor antagonist phencyclidine (PCP). In the novel object recognition test, repeated administration of PCP (10 mg/kg/day, 10 days) significantly decreased the exploratory preference in the retention test session, but not in the training test session. PCP-induced cognitive deficits were significantly improved by subsequent subchronic (2-week) administration of fluvoxamine (20 mg/kg/day). Furthermore, t … More he effect of fluvoxamine on PCP-induced cognitive deficits was antagonized by co-administration of the selective sigma-1 receptor antagonist NE-100 (1 mg/kg/day). Moreover, PCP-induced cognitive deficits were also significantly improved by subsequent subchronic (2-week) administration of the selective sigma-1 receptor agonist SA4503 (1 mg/kg/day) or neurosteroid dehydroepiandrosterone 3-sulfate (DHEA-S ; 25 mg/kg/day). The effects of SA4503 or DHEA-S were also antagonized by co-administration of NE-100 (1 mg/kg/day), suggesting the role of sigma-1 receptors in the active mechanisms of these drugs. In contrast, acute single administration of these drugs (fluvoxamine, paroxetine, SA4503) alone or combination with NE-100 did not alter PCP-induced cognitive deficits. The present study suggests that agonistic activity of fluvoxamine at sigma-1 receptors plays a role in the active mechanisms of fluvoxamine on PCP-induced cognitive deficits in mice.Next, we examined the effects of tropisetron, a 5-hydroxytryptamine (5-HT3) receptor antagonist and α7 nicotinic receptor agonist, on cognitive deficits in mice after repeated administration of the NMDA receptor antagonist phencyclidine (PCP). PCP (10 mg/kg/day for 10 days)-induced cognitive deficits were significantly improved by subsequent subchronic (2-weeks) administration of tropisetron, but not ondansetron. Effects of tropisetron were significantly antagonized by co-administration of the α7 nicotinic receptor antagonist methyllycaconitine, suggesting the role of α7 nicotinic receptors in the active mechanisms of tropisetron. These findings suggest that sigma-1 receptor agonists and α7 nicotinic receptor agonists such as tropisetron could be a potential therapeutic drug for cognitive deficits in schizophrenic patients. Less