Mary B

Mary B. parvalbumin, interneurons, NADPH-oxidase, prelimbic Intro Acute exposure in adulthood to subanesthetic doses of NMDA receptor (NMDA-R) antagonists such as phencyclidine (PCP) and ketamine reproduce both negative and positive symptoms of schizophrenia, and offers therefore been used to model its pathophysiological features (Javitt, Clozapine N-oxide 2007). The acute propsychotic Clozapine N-oxide effects of these antagonists are believed to arise from specific effects on inhibitory circuits that lead to disinhibition of excitatory systems (Olney et al., 1999; Tomitaka et al., 2000; Holcomb et al., 2005; Homayoun and Moghaddam, 2007). Although acute exposures to NMDA-R antagonists produce increased rate of metabolism in frontal areas, these effects are transient. Subchronic exposures, however, produce more persistent neurochemical changes that include major depression in mind metabolic activity in the prefrontal cortex (PFC), as well as within constructions of the auditory system and the reticular nucleus of the thalamus, and resemble more closely the alterations observed in schizophrenia individuals (Jentsch and Roth, 1999; Cochran et al., 2003). These subchronic exposures lead to reduced manifestation of the calcium-binding protein parvalbumin (PV) in GABAergic interneurons in rodents and nonhuman primates (Cochran et al., 2003; Keilhoff et al., 2004; Rujescu et al., 2006; Morrow et al., 2007), a deficiency that has been consistently observed in postmortem mind samples of schizophrenic individuals. Initial studies showing decreased manifestation GRK5 of GAD67, the main isoform synthesizing GABA (Akbarian et al., 1995), were subsequently supported by studies showing that the manifestation of PV inside a subset of fast-spiking inhibitory interneurons was also reduced in postmortem samples of schizophrenic individuals (Beasley and Reynolds, 1997; Hashimoto et al., 2003). This loss of GABAergic phenotype in PV-interneurons led to the suggestion that dysfunction of these fast-spiking inhibitory interneurons may be a core feature of the disease (Lewis et al., 2005). We have recently confirmed that prolonged exposure to ketamine and additional NMDA-R antagonists decreases GAD67 and parvalbumin in the same neurons (Kinney et al., 2006), and that exposure to subanesthetic doses on 2 consecutive days is sufficient to induce the loss of phenotype of these interneurons in mouse PFC (Behrens et al., 2007). Accumulating evidence suggests that schizophrenia individuals suffer from diminished antioxidant defenses, and a recent clinical trial showed that increasing these defenses may ameliorate symptoms of the disease (Berk et al., 2008). We have recently demonstrated that the initial disinhibition caused by exposure to ketamine at subanesthetic doses induced the activation of the superoxide-producing enzyme NADPH oxidase (Nox) and and and test for multiple comparisons as indicated in each number. ANOVA results were regarded as significant when < 0.05. Results We have recently demonstrated that exposure to subanesthetic levels of ketamine on 2 consecutive days induces a pronounced increase in mind superoxide through activation of NADPH-oxidase, and that this leads to the loss of phenotype of PV-interneurons in prefrontal cortex (Behrens et al., 2007). The effects of ketamine on PV-interneurons in the prefrontal region were observed only after exposure on 2 consecutive days, and not present 24 h following a solitary exposure (Fig. 1) (main effect of exposure time: < 0.001), while previously reported for rat (Cochran et al., 2002). Furthermore, as previously demonstrated in microdialysis studies in rats 24 h after exposure to a single injection of ketamine (Zuo et al., 2007) we did not observe increase in DHE oxidation in the prelimbic region of mice 24 h after a single injection of ketamine (data not demonstrated). These results support the idea that repeated exposure to NMDA-R antagonists is required to produce persistent changes in PV-interneuron phenotype and function (Cochran et al., 2003; Keilhoff et al., 2004; Rujescu et al., 2006; Behrens et al., 2007; Morrow et al., 2007). To test for the enduring effects of the 2 2 d ketamine Clozapine N-oxide treatment on the loss of phenotype of PV-interneurons, adult male C57BL/6 mice were treated with saline or ketamine (30 mg/kg) Clozapine N-oxide on 2 consecutive days and the PV-interneuronal human population in the prelimbic region was Clozapine N-oxide analyzed on days 1, 3, and 10 after the last ketamine injection. As previously explained (Behrens et al., 2007), a pronounced decrease in the manifestation of PV and GAD67 in PV-interneurons was observed the day after the two ketamine injections (main effect of ketamine: < 0.001 for PV,.