Reduced plasma nitric oxide metabolites before and after antipsychotic treatment in patients with schizophrenia compared to controls

Available online at www.sciencedirect.com

Schizophrenia Research 104 (2008) 36 – 43 www.elsevier.com/locate/schres

Reduced plasma nitric oxide metabolites before and after antipsychotic treatment in patients with schizophrenia compared to controls Bun-Hee Lee a , Yong-Ku Kim a,b,⁎ a

Department of Psychiatry, Korea University Ansan Hospital, 516, Gojan Dong, Ansan, Kyunggi, 425-707, Republic of Korea b Division of Brain Korea 21 Biomedical Science, Korea University, Republic of Korea Received 24 January 2008; received in revised form 29 May 2008; accepted 9 June 2008 Available online 18 July 2008

Abstract Background: Nitric oxide (NO) is believed to have a role in the pathophysiology of schizophrenia. We examined plasma levels of NO metabolites in patients with schizophrenia and normal controls. We also determined the impact of 6-week risperidone treatment on circulating NO metabolites in patients with schizophrenia. Method: Plasma NO metabolite (NOx) levels were measured in 55 schizophrenia patients before and after 6-week treatment with risperidone and in 55 normal controls. Severity of schizophrenia and response to treatment were assessed with the positive and negative syndrome scale (PANSS) for schizophrenia. NOx levels were estimated by the Griess method. Results: Pre-treatment plasma NOx levels in schizophrenia patients (8.97 ± 6.74 µmol/L) were lower than those of normal controls (14.51 ± 6.30 µmol/L) (p b 0.01). Schizophrenia patients had lower post-treatment NOx levels (10.99 ± 8.31 µmol/L) than those of normal controls (p b 0.01). There was marginal significant change between plasma NOx levels before and after 6-week treatment (p = 0.056). Moreover, in 37 treatment responders (≥ 30% improvement in PANSS score), post-treatment plasma NOx significantly increased in comparison to pre-treatment NOx (p = 0.028). Conclusions: Plasma levels of NOx in patients with schizophrenia were significantly lower than normal controls both before and after the treatment. Our findings suggest that the improvement of psychiatric symptoms can lead to partially normalize a deficiency of NO after treatment in schizophrenia patients. Our findings support the hypothesis that the NO system is dampened in schizophrenia. © 2008 Elsevier B.V. All rights reserved. Keywords: Nitric oxide; Risperidone; Schizophrenia

1. Introduction ⁎ Corresponding author. Department of Psychiatry, Korea University Ansan Hospital, 516, Gojan Dong, Ansan City, Kyunggi Province, 425-707, Republic of Korea. Tel.: +82 31 412 5140; fax: +82 31 412 5144. E-mail addresses: [email protected] (B.-H. Lee), [email protected] (Y.-K. Kim). 0920-9964/$ - see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.schres.2008.06.005

The biologically active molecule nitric oxide (NO) is a membrane-permeable gas with unique chemistry. NO is synthesized from L-arginine by a family of enzyme isoforms known as NO synthases (NOS). There are three isoforms of NOS, including a neuronal isoform in neuronal tissue (nNOS), an inducible isoform in macrophages

B.-H. Lee, Y.-K. Kim / Schizophrenia Research 104 (2008) 36–43

(iNOS), and an endothelial isoform in the endothelial tissue of blood vessels (eNOS) (Barañano and Snyder, 2001). In the brain, NO has multiple functions in brain circuits and plasticity, neuroprotection and neurotoxicity, and behavior (Bonfoco et al., 1995; Nelson et al., 1997; Yermolaieva et al., 2000). NO is known to have effects on the storage, uptake and/or release of most neurotransmitters in the central nervous system (Montague et al., 1994; Pogun and Kuhar, 1994; Yamada et al., 1995). Several studies indicate that the NO system is involved in the pathogenesis of neuropsychiatric disorders or neurologic disorders such as schizophrenia, depression, Alzheimer disease, Huntington disease, and stroke (Bernstein et al., 2005; Guix et al., 2005; McLeod et al., 2001). However, findings about NO metabolites or NOS activities in schizophrenic patients have been inconsistent. Das et al. showed increased NOS activity in the platelets of drug-free patients with schizophrenia (Das et al., 1995); however, they later reported decreased nitrate levels in plasma and skin fibroblasts of drug-free patients with schizophrenia (Das et al., 1996; Das et al., 1998). Postmortem studies showed increased nNOS and NO radicals in the brain from schizophrenia patients (Baba et al., 2004; Yao et al., 2004), while calcium-dependent constitutive NOS (cNOS) activity was reported to be reduced in the postmortem brains of patients with schizophrenia (Xing et al., 2002). In the present study, we examined whether NO production is increased or decreased in schizophrenia patients by comparing plasma levels of NO metabolites (NOx, nitrite and nitrate) in schizophrenia patients with those in normal controls. Also, we determined the changes of plasma NOx levels in patients with schizophrenia after 6-week risperidone treatment.

37

laboratory baseline values. This study was approved by the Institutional Review Board of Korea University, Ansan Hospital. All patients gave written informed consent to participate. The 55 schizophrenia participants (male: female = 24: 31, 33.6 ± 9.9 years) were treated with risperidone, with a flexible dosage based on their psychiatric symptoms. Their dose range was from 3 to 11 mg/day (mean ± SD = 5.7 ± 2.1) at the end of the 6-week study. No other drugs were permitted except benztropine and lorazepam. Of 55 patients, 47 patients were medicated with benztropine (dose range, 0.5–2 mg/day) for extrapyramidal symptoms and 44 patients with lorazepam (dose range, 0.5–2 mg/day) for anxiety or sleep disturbance. Patients were found to have a normal physical state as seen from normal values of blood and urine tests, such as SGOT, SGPT, hemoglobin, hematocrit, serum electrolytes, blood urea, and creatine and normal findings of electrocardiogram (EKG) and electroencephalogram (EEG) at baseline and the end of week 6. Healthy controls were recruited among patients who came for regular health screening at the same hospital during the years of 2003–2004. Among them, 55 healthy adults (male: female = 24: 31, 33.5 ± 9.9 years) were ageand sex-matched to the schizophrenia patients. Each control subject was given a Structured Clinical Interview for DSM-IV (First et al., 1998). Subjects with any personal or familial history of psychiatric illness or substance or alcohol abuse were excluded. All subjects were free of chronic and acute physical illness within the 4 weeks before this enrollment. They showed normal laboratory findings in blood chemistry, renal function, thyroid function, liver function, EKG, and EEG. Table 1 lists the demographic data for the 110 study subjects.

2. Methods 2.2. Assessments 2.1. Subjects The study subjects were 55 Korean schizophrenia inpatients in the Department of Psychiatry, Ansan Hospital, College of Medicine, Korea University, Kyunggi, Korea. All of them were interviewed by Structured Clinical Interview for DSM-IV (First et al., 1998) and fulfilled the DSM-IV (APA, 1994) criteria for schizophrenia. They were either medication-naïve or had administered no oral or injected medication for at least 4 weeks. We excluded patients who had any past history of Axis I psychiatric disorders other than schizophrenia, such as mood disorder, alcohol or substance dependence, or who had any serious medical illness. We also excluded patients who had past history of chronic adverse effects such as tardive dyskinesia or who had abnormal

2.2.1. Clinical evaluation The psychopathological status of the patients was assessed by a trained psychiatrist using the positive and negative syndrome scale (PANSS) (Kay et al., 1987) for all the patients with schizophrenia at baseline and at the end of week 6 of treatment. To evaluate the responsiveness to the treatment, ‘response’ was defined as at least 30% improvement in PANSS score at endpoint over baseline. Among all the patients, 37 (67.3%) were responders, and 18 (32.7%) were non-responders. 2.2.2. Plasma nitric oxide metabolite (NOx) assays Following an overnight fast, blood samples were withdrawn between 8:00 and 9:00 a.m. Approximately 5 mL of blood was collected and placed in a vacuum

38

B.-H. Lee, Y.-K. Kim / Schizophrenia Research 104 (2008) 36–43

Table 1 Demographic data and clinical characteristics of study subjects Normal controls (n = 55) Schizophrenia (n = 55) Statistical value Sex (male/female) Age (years) BMI (kg/m2)

24/31 33.5 ± 9.9 22.5 ± 3.0

24/31 33.6 ± 9.9 22.1 ± 3.6

t = − 0.010, df = 108, p = 0.992 t = 0.541, df = 108, p = 0.590

Total (n = 55)

Responders (n = 37)

Non-responders (n = 18)

Statistical value a

9/9 30.8 ± 11.9 22.8 ± 3.4 24.9 ± 8.5 71.9 ± 67.8

χ2 = 0.691, df = 1, p = 0.406 t = 1.419, df = 53, p = 0.162 t = −0.532, df = 53, p = 0.598 t = 1.544, df = 53, p = 0.129 t = −0.347, df = 53, p = 0.730

11/7

χ2 = 2.096, df = 1, p = 0.148

15/3

χ2 = 0.028, df = 1, p = 0.867

6.3 ± 2.2

t = −1.124, df = 55, p = 0.267

106.1 ± 30.0 25.8 ± 7.6 27.1 ± 9.5 53.2 ± 14.7

t = −1.279, df = 53, p = 0.207 t = 0.166, df = 53, p = 0.869 t = −1.486, df = 53, p = 0.144 t = −1.532, df = 53, p = 0.132

88.2 ± 25.9 20.4 ± 6.7 25.8 ± 9.2 42.0 ± 13.1

t = −5.126, df = 53, p b 0.01 t = −5.183, df = 53, p b 0.01 t = −4.869, df = 53, p b 0.01 t = −4.472, df = 53, p b 0.01

Schizophrenic patients

Sex (male/female) 24/31 15/22 Age (years) 33.6 ± 9.9 35.4 ± 9.3 BMI (kg/m2) 22.1 ± 3.6 22.0 ± 3.9 Age of onset (years) 27.5 ± 9.5 (15–55) 29.6 ± 9.6 Duration of total illness (months) 67.2 ± 63.1 (1–228) 64.6 ± 65.0 Medication status on admission (medication-naïve/medication-free) 31/24 20/17 Subtypes (paranoid/undifferentiated) 47/8 32/5 Dose of risperidone at 6 weeks (mg/day) 5.5 ± 2.3 5.5 ± 2.1 Psychopathology score PANSS at admission Total score 99.1 ± 22.9 96.7 ± 19.8 Positive score 26.12 ± 6.8 26.2 ± 6.7 Negative score 24.0 ± 8.7 22.9 ± 8.3 General score 49.0 ± 11.5 47.5 ± 10.1 PANSS at 6 weeks Total score 59.3 ± 25.3 49.2 ± 15.4 Positive score 13.9 ± 6.5 11.6 ± 4.7 Negative score 16.0 ± 8.8 12.6 ± 5.6 General score 29.4 ± 11.6 24.9 ± 7.0 PANSS the positive and negative syndrome scale for schizophrenia. a Responders vs. non-responders to treatment among schizophrenic patients.

tube without additives. For schizophrenia patients, blood was sampled both on admission and 6 weeks later. Plasma NOx metabolite level was measured by the Griess reaction as the nitrite concentration after nitrate reduction to nitrite (Fiddler, 1977). Briefly, 50 µL of 1% sulfanilamide was added to the samples, incubated for 5– 10 min, and then 50 µL of 0.1% N-1-naphthylethylenediamine dihydrochloride was added. The reaction was incubated at room temperature for 5–10 min, and absorbance at 540 nm was measured, using sodium nitrite solution as standard. The intra-assay coefficient of variation of the plasma NOx level analysis was determined to be b 10%. The inter-assay coefficient of variation was determined to be b 10%. Levels of plasma NOx are reported in µmol/L. 2.3. Statistical analysis Study groups were compared for continuous variates by a two-tailed t-test. For discrete variates, study groups were compared by a chi-square test. For NO metabolites, log

transformations were used to normalize the distribution of the data. The pre- and post-treatment plasma levels of NOx or PANSS scores of schizophrenia patients were compared by paired t-test or Wilcoxon signed ranks test. Pearson's or Spearman's product moment correlation coefficients were calculated to examine the relationships between the plasma NOx and clinical variables. The null hypothesis was rejected at p b 0.05. The statistical package used for the analysis was SPSS 12.0. 3. Results 3.1. Plasma NOx levels in schizophrenia patients and normal controls Mean plasma NOx levels were 8.97± 6.74 µmol/L at baseline in schizophrenia patients and 14.51 ± 6.30 µmol/L in matched normal controls. Mean plasma NOx levels were significantly lower in patients with schizophrenia than normal controls (t= 5.920, df= 108, p b 0.01) (Table 2). Plasma NOx in male control subjects was significantly

B.-H. Lee, Y.-K. Kim / Schizophrenia Research 104 (2008) 36–43

higher than in female subjects (t =2.850, df =53, p= 0.006). However, NOx in schizophrenia patients had no significant difference between males and females (t =1.488, df= 53, p= 0.143). There were no significant correlations between plasma NOx and age or BMI among all subjects. There were no significant correlations between plasma NOx of patients with schizophrenia and any clinical variable including age of onset, duration of illness, schizophrenic subtype, PANSS scores, or dose of risperidone (data not shown). 3.2. Changes in PANSS scores and plasma NOx levels before and after 6 weeks of treatment in schizophrenia patients Mean total PANSS scores of patients were 99.1 ± 22.9 at baseline and 59.3 ± 25.3 at the end of 6-week treatment (t = 13.477, df = 54, p b 0.01). Plasma NOx levels at the end of 6 weeks in patients were 10.99 ± 8.31 µmol/L, which were significantly lower than those of normal controls (t = 3.887, df = 108, p b 0.01). There were marginal significant changes of the plasma NOx between the baseline and the end of 6-week treatment in patients with schizophrenia (t = − 1.952, df = 54, p = 0.056). There were no significant correlations between the changes in plasma NO products and the changes in total scores or subscores of PANSS (data not shown). 3.3. Comparisons of plasma NOx levels between responders and non-responders to treatments We compared plasma NOx levels between 37 responders and 18 non-responders to treatments among patients with schizophrenia. The means of plasma NOx levels at baseline were 8.77± 7.41 µmol/L in responders and 9.62 ± 5.06 µmol/L in non-responders. Plasma NOx measured at the end of 6-week treatment were 12.03 ± 9.60 µmol/L in responders and 8.83± 4.47 µmol/L in non-responders. Both pre- and post-treatment plasma NOx had no significant differences between responders and non-responders (pretreatment, t = −0.783, df = 53, p = 0.437; post-treatment, t = 1.052, df = 53, p = 0.298, respectively) (Table 2). There were no significant differences of most demographic and clinical variables between responders and nonresponders (Table 1). Total scores and subscores of the baseline PANSS did not differ between them, while total scores and subscores of the 6-week treatment PANSS had significant differences between 2 groups (Table 1). In the 37 responders, plasma NOx levels after treatment significantly increased when compared with

39

Table 2 Pre- and post-treatment plasma NOx levels in normal controls and patients with schizophrenia Normal controls NOx (µmol/L)/log NOx Total 14.51 ± 6.30/ 2.59 ± 0.42 Male 16.74 ± 6.39/ 2.76 ± 0.33 a Female 12.78 ± 5.75/ 2.45 ± 0.44 a

Schizophrenia

Statistical value

8.97 ± 6.74/ 2.01 ± 0.59 10.59 ± 8.79/ 2.14 ± 0.65 b 7.72 ± 4.33/ 1.91 ± 0.51 b

t = 5.920, df = 108, p b 0.01 t = 4.119, df = 46, p b 0.01 t = 4.481, df = 60, p b 0.01

Schizophrenic patients Total (n = 55)

Responders Non-responders Statistical (n = 37) (n = 18) value c

At baseline Plasma NOx 8.97 ± 6.74 8.77 ± 7.41 9.62 ± 5.06 (µmol/L) log NOx 2.01 ± 0.59 1.98 ± 0.58 2.13 ± 0.56

After 6 weeks of treatment Plasma NOx 10.99 ± 8.31 12.03 ± 9.60 8.83 ± 4.47 (µmol/L) log NOx 2.21 ± 0.58 2.27 ± 0.63 2.07 ± 0.50

t = − 0.783, df = 53, p = 0.437

t = 1.052, df = 53, p = 0.298

NOx: Nitric Oxide metabolite. Data are presented as mean ± SD. a Plasma NOxNOx levels of normal controls were significantly higher in males than in females (t = 2.850, df = 53, p = 0.006). b Plasma NOxNOx levels of schizophrenic patients were higher in males than in females, but not significantly (t=1.488, df=53, p=1.143). c Responders vs. non-responders to treatment among patients with schizophrenia.

those at baseline (t = − 2.286, df = 36, p = 0.028). However, there was no significant change of plasma NOx in the non-responders (Z = − 0.035, p = 0.972) (Fig. 1). 4. Discussion Our data show that plasma NO metabolite levels among schizophrenia patients are significantly lower than among normal controls. This result is consistent with previous studies. Some reports found that plasma nitrate levels of schizophrenia patients with deficit syndrome were lower than those with non-deficit syndrome (Suzuki et al., 2003) and that nitrite content in the polymorphonuclear leukocytes of schizophrenia patients was reduced in comparison to normal controls (Srivastava et al., 2001). Levels of NO metabolite in the cerebrospinal fluid were found to be lower in schizophrenia patients than in patients with other neurological disorders (Ramirez et al., 2004). However,

40

B.-H. Lee, Y.-K. Kim / Schizophrenia Research 104 (2008) 36–43

Fig. 1. Changes in plasma NOx levels in schizophrenia patients before and after 6 weeks of treatment. NOx: nitric oxide metabolite. There were marginally significant changes of plasma NOx between the baseline and 6-weeks treatment in all patients (t = − 1.95, df = 54, p = 0.056). The treatment responders had significantly increased plasma NOx after 6-week treatment (t = −2.28, df = 36, p = 0.028), while the non-responders had no significant change (t = 0.30, df = 17, p = 0.768). The central box represents the values from the lower to upper quartile (25 to 75 percentile). The middle line represents the median. A line extends from the minimum to the maximum value. The blue line between the boxes shows the changes of the mean plasma NOxNOx levels between the baseline and 6-weeks treatment. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)

in other reports, increases of NOS activity and plasma NO metabolites were found in patients with schizophrenia (Das et al., 1995; Herken et al., 2001; Taneli et al., 2004). Recently, Richardson et al. reported a deficiency of tetrahydrobiopterin (BH4), a vital cofactor regulating the synthesis of NO and stimulating and modulating the glutamatergic system, in schizophrenia (Richardson et al., 2005; Richardson et al., 2007). They showed that plasma total biopterin levels (a measure of BH4) were significantly lower in schizophrenia patients than in normal controls, which supports a deficiency of NO activity in schizophrenia. It is well known that NO exerts a strong influence on glutamatergic neurotransmission by directly interacting with NMDA receptors. nNOS increases NO production following activation of NMDA receptors (Brenman and Bredt, 1997). Thus, the level of endogenously produced NO around NMDA synapses reflects the activity of glutamate-mediated neurotransmission (Akyol et al., 2004). The phencyclidine (PCP) model has contributed to a hypothesis for the pathophysiology of schizophrenia (Sams-Dodd, 1998). PCP acts as a noncompetitive NMDA receptor antagonist in the CNS, and this property has contributed to the postulation of a glutamate deficiency model in schizophrenia (Carlsson et al., 1999). PCP was reported to be an effective inhibitor of NOS in the brain (Osawa and Davila, 1993).

Animal studies reported that PCP-induced behaviors were suppressed by NO donors and were potentiated by NOS inhibitors (Bujas-Bobanovic et al., 2000a; BujasBobanovic et al., 2000b). However, another study showed that NOS inhibitors normalize PCP-induced behavior (Klamer et al., 2005b). PCP-induced behavioral effects and neuronal activity are reduced in nNOS knockout mice, suggesting that the NO system in the brain is necessary for PCP-induced effects (Bird et al., 2001; Klamer et al., 2005a). Taken together, the NO system or the interaction of NO and NMDA might contribute to the pathogenesis of schizophrenia. Another possible explanation of decreased plasma NOx in our schizophrenia patients is related to previous findings of altered or reduced regional cerebral blood flow in patients with schizophrenia (Andreasen et al., 1992; Liddle et al., 1992) by considering the role of NO as a vasodilator. Moreover, several reports indicated that antipsychotic drugs improve regional cerebral blood flow in schizophrenia patients (Vita and De Peri, 2007). Some findings showed increased regional cerebral blood flow in frontal or anterior cingulate cortex after 4-week or 8-week antipsychotic treatments (including risperidone) compared to before treatment among medication-naïve patients with first-episode schizophrenia (Brewer et al., 2007; Snitz et al., 2005). Those findings are comparable with our finding which indicated that plasma NOx increased after 6-week

B.-H. Lee, Y.-K. Kim / Schizophrenia Research 104 (2008) 36–43

treatment in patients or responders with schizophrenia. Our data demonstrated increased post-treatment plasma NOx levels compared to pre-treatment NOx in patients with schizophrenia, which was marginally significant (p= 0.056). Moreover, the treatment responders among our patients had significantly increased plasma NOx after treatment (p= 0.028), while the non-responders had no significant change (p =0.768) (Fig. 1). One animal study found that 28-day treatment with antipsychotics increased iNOS mRNA in rat brain (Suzuki et al., 2002). However, there have been different reports about the effect of risperidone or antipsychotics on NO system. Long-term (28 days) treatment with atypical antipsychotic drugs, including risperidone, olanzapine, and quetiapine, was reported not to influence nNOS in rat brain (Tarazi et al., 2002). A clinical study also showed that 6-week treatments with atypical antipsychotics had no significant effects on serum NO metabolites in schizophrenia (Taneli et al., 2004). The other animal study reported that risperidone inhibited the production of NO and proinflammatory cytokines by interferon-γinduce mice microglial activation in vitro (Kato et al., 2007). Considering various findings, partial normalized plasma NOx in responders with schizophrenia might be associated with the improvement of psychiatric symptoms, not with the direct effect of risperidone. Plasma NOx levels reported in our study were lower than reported in some previous studies using the same method to measure NO x. Explanations for these differences of NOx between them are detailed in a recent review (Tsikas, 2007). Factors, which could account for these differences, include preparation of blood prior to the Griess reaction such as sample handling and storage procedures, stability of reaction intermediates, formation of more than one dye, pH and temperature. However, we processed and analyzed our samples from patients and healthy controls in a standardized manner in this study. This study is limited in that the source of NOx levels measured could not be attributed specially to the CNS or the peripheral vascular system. Experimental studies have suggested that centrally increased nitrite and nitrate can overflow into plasma (Suzuki et al., 2001). Another limitation is that we used an open flexible dose regimen of risperidone, and some patients took benztropine and/ or lorazepam. Further studies are therefore warranted to confirm our findings. Suzuki et al. (2002) demonstrated that antidepressant, antipsychotic, and benzodiazepine agents induced iNOS mRNA in rat brain. However, antipsychotics had greater effect on induced iNOS mRNA than benzodiazepine. Therefore, the effect of risperidone on plasma NOx is possible to be greater than the effect of lorazepam although medications with

41

risperidone and/or lorazepam in our study could increase plasma NOx. A third limitation is to evaluate the severity of schizophrenia and the responsiveness to the treatment only by using PANSS. Further study will require using various instruments, e.g. PANSS, Scale for the Assessment of Negative Symptoms (SANS), Scale for the Assessment of Positive Symptoms (SAPS), the Schedule for the Deficit Syndrome (SDS), or CGI (the Clinical Global Impression), and measuring plasma risperidone or risperidone metabolite. In conclusion, plasma levels of NO metabolite in patients with schizophrenia were significantly lower than normal controls. Our findings suggest that the improvement of psychiatric symptoms can lead to partially normalize a deficiency of NO after treatment in patients with schizophrenia. These findings support the hypothesis that the NO system is dampened in schizophrenia. However, further studies with larger sample size will be required to further elucidate the role of the NO system in schizophrenia. Role of funding source Funding for this study was provided by a grant from the Korea Health 21 R&D Project, Ministry of Health and Welfare, Republic of Korea (A040042); the Korea Health 21 R&D Project had no further role in study design; in the collection, analysis and interpretation of data; in the writing of the report; and in the decision to submit the paper for publication. Contributors Authors Bun-Hee Lee and Yong-Ku Kim designed the study, wrote the protocol, and managed the literature searches and analyses. Author Bun-Hee Lee undertook the statistical analysis and wrote the first draft of the manuscript. All authors contributed to and have approved the final manuscript. The conflict of interest Bun-Hee Lee and Yong-Ku Kim declare to have no conflicts of interests. Acknowledgments We thank Ji-Won Hur and Ae-Ra Lee for their effort in recruitment and handling of patients at the Korea University Ansan Hospital throughout the study period.

References Akyol, O., Zoroglu, S.S., Armutcu, F., Sahin, S., Gurel, A., 2004. Nitric oxide as a physiopathological factor in neuropsychiatric disorders. In Vivo 18 (3), 377–390. Andreasen, N.C., Rezai, K., Alliger, R., Swayze, V.W.n., Flaum, M., Kirchner, P., Cohen, G., O'Leary, D.S., 1992. Hypofrontality in neuroleptic-naive patients and in patients with chronic schizophrenia. Assessment with xenon 133 single-photon emission computed tomography and the Tower of London. Arch. Gen. Psychiatry 49 (12), 943–958.

42

B.-H. Lee, Y.-K. Kim / Schizophrenia Research 104 (2008) 36–43

American Psychiatric Association, 1994. DSM-IV:Diagnostic and Statistical Manual of Mental Disorders, Fourth ed. American Psychiatric Press, Washington DC. Baba, H., Suzuki, T., Arai, H., Emson, P.C., 2004. Expression of nNOS and soluble guanylate cyclase in schizophrenic brain. Neuroreport 15 (4), 677–680. Barañano, D.E., Snyder, S.H., 2001. Neural roles for heme oxygenase: contrasts to nitric oxide synthase. Proc. Natl. Acad. Sci. U. S. A. 98 (20), 10996–11002. Bernstein, H.G., Bogerts, B., Keilhoff, G., 2005. The many faces of nitric oxide in schizophrenia. A review. Schizophr. Res. 78 (1), 69–86. Bird, D.C., Bujas-Bobanovic, M., Robertson, H.A., Dursun, S.M., 2001. Lack of phencyclidine-induced effects in mice with reduced neuronal nitric oxide synthase. Psychopharmacology (Berl) 155 (3), 299–309. Bonfoco, E., Krainc, D., Ankarcrona, M., Nicotera, P., Lipton, S.A., 1995. Apoptosis and necrosis: two distinct events induced, respectively, by mild and intense insults with N-methyl-D-aspartate or nitric oxide/ superoxide in cortical cell cultures. Proc. Natl. Acad. Sci. U. S. A. 92, 7162–7166. Brenman, J.E., Bredt, D.S., 1997. Synaptic signaling by nitric oxide. Curr. Opin. Neurobiol. 7 (3), 374–378. Brewer, W.J., Yücel, M., Harrison, B.J., McGorry, P.D., Olver, J., Egan, G.F., Velakoulis, D., Pantelis, C., 2007. Increased prefrontal cerebral blood flow in first-episode schizophrenia following treatment: longitudinal positron emission tomography study. Aust. N. Z. J. Psychiatry 41 (2), 129–135. Bujas-Bobanovic, M., Bird, D.C., Robertson, H.A., Dursun, S.M., 2000a. Blockade of phencyclidine-induced effects by a nitric oxide donor. Br. J. Pharmacol. 130 (5), 1005–1012. Bujas-Bobanovic, M., Robertson, H.A., Dursun, S.M., 2000b. Effects of nitric oxide synthase inhibitor N(G)-nitro-L-arginine methyl ester on phencyclidine-induced effects in rats. Eur. J. Pharmacol. 409 (1), 57–65. Carlsson, A., Hansson, L.O., Waters, N., Carlsson, M.L., 1999. A glutamatergic deficiency model of schizophrenia. Br. J. Psychiatr., Suppl. (37), 2–6. Das, I., Khan, N.S., Puri, B.K., Hirsch, S.R., 1996. Elevated endogenous nitric oxide synthase inhibitor in schizophrenic plasma may reflect abnormalities in brain nitric oxide production. Neurosci. Lett. 215 (3), 209–211. Das, I., Khan, N.S., Puri, B.K., Sooranna, S.R., Belleroche, J.d., Hirsch, S.R., 1995. Elevated platelet calcium mobilization and nitric oxide synthase activity may reflect abnormalities in schizophrenic brain. Biochem. Biophys. Res. Commun. 212 (2), 375–380. Das, I., Ramchand, C.N., Gliddon, A., Hirsch, S.R., 1998. Nitric oxide, free radicals and polyamines may have a role in the membrane pathology of schizophrenia. Neuropsychobiology 37 (2), 65–67. Fiddler, R.M., 1977. Collaborative study of modified AOAC method of analysis for nitrite in meat and meat products. J. AOAC 60, 594. First, M., Spitzer, R.L., Gibbon, M., William, J.B., 1998. Structured Clinical Interview for DSM-IV Axis I Disorder — Patient Edition (SCID-I/P, version 2.0). Biometrics Research Department, New York State Psychiatric Institute, New York. Guix, F.X., Uribesalgo, I., Coma, M., Munoz, F.J., 2005. The physiology and pathophysiology of nitric oxide in the brain. Prog. Neurobiol. 76 (2), 126–152. Herken, H., Uz, E., Ozyurt, H., Akyol, O., 2001. Red blood cell nitric oxide levels in patients with schizophrenia. Schizophr. Res. 52 (3), 289–290. Kato, T., Monji, A., Hashioka, S., Kanba, S., 2007. Risperidone significantly inhibits interferon-gamma-induced microglial activation in vitro. Schizophr. Res. 92 (1–3), 108115.

Kay, S.R., Fiszbein, A., Opler, L.A., 1987. The positive and negative syndrome scale (PANSS) for schizophrenia. Schizophr. Bull 13 (2), 261–276. Klamer, D., Engel, J.A., Svensson, L., 2005a. Effects of phencyclidine on acoustic startle and prepulse inhibition in neuronal nitric oxide synthase deficient mice. Eur. Neuropsychopharmacol. 15 (5), 587–590. Klamer, D., Zhang, J., Engel, J.A., Svensson, L., 2005b. Selective interaction of nitric oxide synthase inhibition with phencyclidine: behavioural and NMDA receptor binding studies in the rat. Behav. Brain. Res. 159 (1), 95–103. Liddle, P.F., Friston, K.J., Frith, C.D., Hirsch, S.R., Jones, T., Frackowiak, R.S., 1992. Patterns of cerebral blood flow in schizophrenia. Br. J. Psychiatry 160, 179–186. McLeod, T.M., Lopez-Figueroa, A.L., Lopez-Figueroa, M.O., 2001. Nitric oxide, stress, and depression. Psychopharmacol. Bull. 35 (1), 24–41. Montague, P.R., Gancayco, C.D., Winn, M.J., Marchase, R.B., Friedlander, J., 1994. Role of NO production in NMDA receptor-mediated neurotransmitter release in cerebral cortex. Science 263, 973–977. Nelson, R.J., Kriegsfeld, L.J., Dawson, V.L., Dawson, T.M., 1997. Effects of nitric oxide on neuroendocrine function and behavior. Front. Neuroendocrinol. 18, 463–491. Osawa, Y., Davila, J.C., 1993. Phencyclidine, a psychotomimetic agent and drug of abuse, is a suicide inhibitor of brain nitric oxide synthase. Biochem. Biophys. Res. Commun. 194 (3), 1435–1439. Pogun, S., Kuhar, M.J., 1994. Regulation of neurotransmitter reuptake by nitric oxide. Ann. N. Y. Acad. Sci. 738, 305–315. Ramirez, J., Garnica, R., Boll, M.C., Montes, S., Rios, C., 2004. Low concentration of nitrite and nitrate in the cerebrospinal fluid from schizophrenic patients: a pilot study. Schizophr. Res. 68 (2–3), 357–361. Richardson, M.A., Read, L.L., Clelland, C.L.T., Reilly, M.A., Chao, H.M., Guynn, R.W., Suckow, R.F., Clelland, J.D., 2005. Evidence for a tetrahydrobiopterin deficit in schizophrenia. Neuropsychobiology 52 (4), 190–201. Richardson, M.A., Read, L.L., Reilly, M.A., Clelland, J.D., Clelland, C.L., 2007. Analysis of plasma biopterin levels in psychiatric disorders suggests a common BH4 deficit in schizophrenia and schizoaffective disorder. Neurochem. Res. 32 (1), 107–113. Sams-Dodd, F., 1998. Effects of continuous D-amphetamine and phencyclidine administration on social behaviour, stereotyped behaviour, and locomotor activity in rats. Neuropsychopharmacology 19 (1), 18–25. Snitz, B.E., MacDonald 3rd, A., Cohen, J.D., Cho, R.Y., Becker, T., Carter, C.S., 2005. Lateral and medial hypofrontality in firstepisode schizophrenia: functional activity in a medication-naive state and effects of short-term atypical antipsychotic treatment. Am. J. Psychiatry 162 (12), 2322–2329. Srivastava, N., Barthwal, M.K., Dalal, P.K., Agarwal, A.K., Nag, D., Srimal, R.C., Seth, P.K., Dikshit, M., 2001. Nitrite content and antioxidant enzyme levels in the blood of schizophrenia patients. Psychopharmacology (Berl) 158 (2), 140–145. Suzuki, E., Yagi, G., Nakaki, T., Kahba, S., Asai, M., 2001. Elevated plasma nitrate levels in depressive states. J. Affect. Disord. 63, 221–224. Suzuki, E., Nakaki, T., Shintani, F., Kanba, S., Miyaoka, H., 2002. Antipsychotic, antidepressant, anxiolytic, and anticonvulsant drugs induce type II nitric oxide synthase mRNA in rat brain. Neurosci. Lett. 333 (3), 217–219. Suzuki, E., Nakaki, T., Nakamura, M., Miyaoka, H., 2003. Plasma nitrate levels in deficit versus non-deficit forms of schizophrenia. J. Psychiatry Neurosci. 28 (4), 288–292.

B.-H. Lee, Y.-K. Kim / Schizophrenia Research 104 (2008) 36–43 Taneli, F., Pirildar, S., Akdeniz, F., Uyanik, B.S., Ari, Z., 2004. Serum nitric oxide metabolite levels and the effect of antipsychotic therapy in schizophrenia. Arch. Med. Res. 35 (5), 401–405. Tarazi, F.I., Zhang, K., Baldessarini, R.J., 2002. Long-term effects of newer antipsychotic drugs on neuronal nitric oxide synthase in rat brain. Nitric Oxide 7 (4), 297–300. Tsikas, D., 2007. Analysis of nitrite and nitrate in biological fluids by assays based on the Griess reaction: appraisal of the Griess reaction in the L-arginine/nitric oxide area of research. J. Chromatogr. B Analyt. Technol. Biomed. Life Sci. 851 (1–2), 51–70. Vita, A., De Peri, L., 2007. The effects of antipsychotic treatment on cerebral structure and function in schizophrenia. Int. Rev. Psychiatry 19 (4), 429–436. Xing, G., Chavko, M., Zhang, L.X., Yang, S., Post, R.M., 2002. Decreased calcium-dependent constitutive nitric oxide synthase

43

(cNOS) activity in prefrontal cortex in schizophrenia and depression. Schizophr. Res. 58 (1), 21–30. Yamada, K., Noda, Y., Nakayama, S., Komori, Y., Sugihara, H., Hasegawa, T., Nabeshima, T., 1995. Role of nitric oxide in learning and memory and in monoamine metabolism in the rat brain. Br. J. Pharmacol. 115, 852–858. Yao, J.K., Leonard, S., Reddy, R.D., 2004. Increased nitric oxide radicals in postmortem brain from patients with schizophrenia. Schizophr. Bull. 30 (4), 923–934. Yermolaieva, O., Brot, N., Weissbach, H., Heinemann, S.H., Hoshi, T., 2000. Reactive oxygen species and nitric oxide mediate plasticity of neuronal calcium signaling. Proc. Natl. Acad. Sci. U. S. A. 97, 448–453.