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Journal of Biomedicine and Biotechnology
Volume 2010, Article ID 859516, 7 pages
http://dx.doi.org/10.1155/2010/859516
Research Article

Expressions of Neuregulin 1 and ErbB4 in Prefrontal Cortex and Hippocampus of a Rat Schizophrenia Model Induced by Chronic MK-801 Administration

1Key Laboratory of Mental Health of National Health Ministry, Institute of Mental Health, Peking University, No. 51 Hua Yuan Bei Road, Haidian District, Beijing 100191, China
2Max Planck Institute of Psychiatry, Kraepelinstr. 2-10, 80804 Munich, Germany

Received 16 January 2010; Accepted 22 February 2010

Academic Editor: Xudong Huang

Copyright © 2010 Yu Feng et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Recent human genetic studies and postmortem brain examinations of schizophrenia patients strongly indicate that dysregulation of NRG1 and ErbB4 may be important pathogenic factors of schizophrenia. However, this hypothesis has not been validated and fully investigated in animal models of schizophrenia. In this study we quantitatively examined NRG1 and ErbB4 protein expressions by immunohistochemistry and Western blot in the brain of a rat schizophrenia model induced by chronic administration of MK-801 (a noncompetitive NMDA receptor antagonist). Our data showed that NRG1 and ErbB4 expressions were significantly increased in the rat prefrontal cortex and hippocampus but in different subregions. These findings suggest that altered expressions of NRG1 and ErbB4 might be attributed to the schizophrenia. Further study in the role and mechanism of NRG1 and ErbB4 may lead to better understanding of the pathophysiology for this disorder.

1. Introduction

Schizophrenia is a complex and severe brain disorder with poorly defined etiology and pathophysiology. Emerging clinical investigations have suggested that there are certain susceptible genes that may be responsible of the pathophysiology of schizophrenia, such as COMT (Catechol-O-methyl transferase), DTNBP1 (Dysbindin), NRG1 (Neuregulin 1), ErbB4, RGS4 (Regulator of G-protein signaling 4), DISC1 (Disrupted-in-schizophrenia 1), and G72 [15]. NRG1 and ErbB4 transgenic mice have shown “schizophrenia-like” behavioral deficits, indicating that NRG1 and its receptor ErbB4 might be two of crucial pathogenic factors for the schizophrenia [68].

Accumulating reports have demonstrated the significance of NRG1 and ErbB4 function in the brain. For example, NRG1 comprises a family of transmembrane or secreted proteins, sharing an epidermal growth factor- (EGF- ) like domain that specifically activates ErbB receptor tyrosine kinases [9, 10]. Among the ErbB receptors, ErbB4 is the major mediator of NRG1 function in the brain [11, 12]. In the central nervous system, NRG1-ErbB4 signaling regulates neural and glial development [13], axon myelination and ensheathment [1417], synaptic plasticity [11, 18], expression and activation of neurotransmitter receptors [2, 18], neurotrophic coupling, and neuroprotection following neurological disorders [11].

Importantly, dysregulation and dysfunction of NRG1 and ErbB4 may be associated with some types of neurological disorders [19]. Clinical evidence has revealed altered NRG1 and its receptor ErB4 expressions in postmortem brains of schizophrenia patients [5, 20, 21]. Since the above tested brain samples of all patients received antipsychotic treatment before death, the association of the altered NRG1 and ErbB4 expressions with schizophrenia pathology or antipsychotic drug effects remains unknown. Therefore, it is fundamentally and clinically significant to investigate the role and mechanism of NRG1 and ErB4 in animal models of schizophrenia. By doing so, for the first step, in this study we aimed to determine whether there is altered expression of NRG1 and ErbB4 in an animal model of schizophrenia.

Among a number of schizophrenia animal models, a very commonly used rat model is induced by chronic dizocilpine maleate (MK-801, a noncompetitive NMDA receptor antagonist) administration, which was selected in this study [22, 23]. This model was based on the key pathological mechanism of NMDA glutamatergic hypofunction in schizophrenia [24]. It has been well documented that repeated administration of NMDA receptor antagonists could induce schizophrenia-like behavioral deficits in normal rats [25, 26]. In this animal model, we examined expressions of NRG1 and ErbB4 proteins in the prefrontal cortex and hippocampus, because the two brain regions are closely related to the pathophysiology of schizophrenia [2729].

2. Materials and Methods

2.1. Animals

Adult male Wistar rats (Vital River, Beijing, China) weighing 185–225 g were group-housed under a 12-hour light/dark cycle with ad libitum access to both food and water. All procedures were performed in accordance with the National Institute of Health’s Guide for the Use and Care of Laboratory Animals and were approved by the Peking University Committee on Animal Care and Use.

2.2. Drug Treatment

MK-801 (St. Louis, MO, USA) was dissolved with normal saline. After a 1-week acclimatization, the rats were randomly divided into two groups, and each rat received intraperitoneal injection of either MK-801 (0.5 mg/kg, = 10) or normal saline (vehicle, = 10) for 4 weeks. The dosage of the MK-801 used in this study was based on other previous studies [30]. All rats received single, daily injection between 09:00 and 11:00 am.

2.3. Immunohistochemistry

The rats ( = 5 per group) were deeply anaesthetized with chloral hydrate (300 mg/kg) and transcardially perfused with 250 mL cool saline solution followed by 300 mL of 4% paraformaldehyde in 0.1 M phosphate buffered saline (PBS, pH 7.4). Brains were immediately removed, postfixed in the same fixative overnight, and cryoprotected in 30% sucrose at for 5 d. After quenching by immersing them in cold N-hexane on dry ice, the brains were stored at until analyzed.

Serial coronal sections of 20  m thickness at various levels (100  m interval) through the prefrontal cortex (bregma 3.72–2.52) and hippocampus (bregma 2.76 to 3.96) [31] were cut on a cryostat (Leica, Wetzlar, Germany) and slide-mounted. After blocking in 10% normal goat serum in 0.1 M PBS containing 0.3% Triton X-100 for 1 hour at room temperature (RT), sections were incubated with NRG1 - (sc-347) or ErbB4- (sc-283, all from Santa Cruz Biotechnology Inc., Santa Cruz, CA, USA) specific antibodies diluted 1  :  100 in 0.1 M PBS overnight at . The next morning, sections were incubated with primary antibodies for an additional 1 hour at RT, followed by incubation with biotinylated secondary antibodies (Santa Cruz Biotechnology Inc.) for 3 hours at RT, and then incubated with avidin-biotin-horseradish peroxidase (Santa Cruz Biotechnology Inc.) for 3 hours at RT. Finally, the sections were developed with a solution of 50% 3, -diaminobenzidine (DAB) and 3% hydrogen peroxide in 0.1 M PBS, dehydrated, and coverslipped.

Four sections (20  m thickness, 100  m interval) from the prefrontal cortex and hippocampus were obtained and immunoreactivity was determined and quantitated as previously described [32]. Briefly, immunoreactive staining was observed and photographed at 40 magnification using an Olympus BX51 microscope fitted with a CoolSNAP MP5 CCD camera (Roper Scientific, Tucson, AZ, USA). Images were converted to grey scale and analyzed with Image Pro-Plus software (Media Cybernetics, Silver Spring, MD, USA). For calculating immunoreactivity of prefrontal cortex, a 1 1 mm2 cursor was placed on the prelimbic cortex (PrL) or the cingulate cortex area 1 (Cg1) plus secondary motor cortex (M2) [31]. Constant background intensity across different sections from each animal was set so that positivelabeled cells were selected only if they reached a defined threshold above background, then the integrated optical density (IOD = immunoreactive area average optical density) values of PrL and Cg1 plus M2 were measured and designated as optical density (OD). Optical density value of hippocampal subregions and background were measured by placing several adjacent circular cursors with a diameter of 100 μm along the pyramidal cell layer of CA1 (8 cursors) and CA3 (12 cursors), the granule cell layer of DG (8 cursors), and corpus callosum (CC, 8 cursors). Optical density values of corpus callosum were designated as background. The differences of value between the target and background were calculated and designated as OD. All results were normalized by taking the value of the vehicle group as 100%.

2.4. Western Blot

After sacrificing animals, the brains were rapidly removed and dissected to obtain the prefrontal cortex and hippocampus [33]. Tissue from individual rats was immediately homogenized on ice in ice-cold lysis buffer (137 mM NaCl, 20 mM Tris–HCl (pH 8.0), 1% NP-40, 10% glycerol, 1 mM PMSF, 10 mg/mL aprotinin, 1 mg/mL leupeptin, and 0.5 mM sodium vanadate), sonicated, and centrifuged. The supernatants were stored at until assayed.

Samples containing 20  g of protein were resolved by 7.5% (for detection of ErbB4 receptor) or 10% (for NRG1 isoforms) SDS–PAGE gels. Immunoblotting was conducted with NRG1 - (sc-347, 1  :  1000) or ErbB4- (sc-283, 1  :  1000) specific antibodies (all from Santa Cruz Biotechnology Inc.). We stripped and reprobed bolts with rabbit antiactin polyclonal antibody (Santa Cruz Biotechnology Inc.). The immunoreactive signals of NRG1 and ErbB4 were quantified by densitometry and the values were corrected based on their corresponding actin levels. All results were normalized by taking the value of the vehicle group as 100%.

2.5. Antibody Specificity

The specificity of antibodies was examined by Western blot as previously described [32]. The signal of the 65 kDa NRG1 isoform was reduced and labeling of the other NRG1 isoforms and ErbB4 isoforms was eliminated by preabsorption with corresponding antigen peptides (Santa Cruz Biotechnology Inc.). Antibodies against actin generated one main band.

2.6. Statistical Analysis

All data were expressed as the means S.E.M. Statistical differences between groups were determined by independent samples -test. Differences of were considered to be significant.

3. Results

3.1. Changes of NRG1 and ErbB4 Protein Expressions in the Prefrontal Cortex

Protein samples extracted from rat prefrontal cortex were analyzed by Western blot. Quantitative data showed that expressions of all five NRG1 isoforms were significantly elevated with relative levels (% of vehicle treated controls) of 220 5 for 35 kDa isoform, 245 22 for 65 kDa isoform, 255 23 for 80 kDa isoform, 266 10 for 85 kDa isoform, and 224 18 for 95 kDa isoform, respectively, while all three isoforms of ErbB4 were also significantly upregulated with relative levels (% of vehicle treated controls) of 190 26 for 60 kDa isoform, 164 5 for 120 kDa isoform, and 199 12 for 185 kDa isoform, respectively (Figures 1(a)1(d)).

fig1
Figure 1: Expression of NRG1 and ErbB4 proteins in the rat prefrontal cortex. (a) Representative Western blots of NRG1 protein isoforms. (b) Quantitative analysis of NRG1 immunoblots. (c) Representative Western blots of ErbB4 proteins isoforms. (d) Quantitative analysis of ErbB4 immunoblots. The data were normalized by taking the value of vehicle group as 100% and expressed as means S.E.M. ( = 5). . (e) Representative section of ErbB4 immunohistochemistry in the PrL region of prefrontal cortex from vehicle group. (f) Representative section of ErbB4 immunohistochemistry in the PrL region of prefrontal cortex from MK-801-treated group. (g) Representative section of ErbB4 immunohistochemistry in the Cg1 and M2 region of prefrontal cortex from vehicle group. (h) Representative section of ErbB4 immunohistochemistry in the Cg1 and M2 region of prefrontal cortex from MK-801-treated group. Arrows indicate ErbB4-expressing neurons in the prefrontal cortex. Scale bar for (e)–(h): 50  m.

Immunohistochemistry was applied to localize and quantitate NRG1 and ErbB4 immunoreactivity in different subregions of prefrontal cortex (Figures 1(e)1(h) and Table 1). Quantification of immunoreactive intensity showed slight increases of NRG1 expression in the two cortex subregions of prelimbic cortex (PrL) and the cingulate cortex area 1 plus secondary motor cortex (Cg1 and M2), but did not reach statistic significance. However, the immunoreactivity of ErbB4 was significantly increased in the PrL region, while no significant difference was observed in Cg1 and M2 region. From the DAB-stained morphology of immunopositive cells, it is noticed that they are mainly neuron-like cells [32].

tab1
Table 1: Immunoreactivity of NRG1 and ErbB4 in the rat prefrontal cortex and hippocampal subregions.
3.2. Changes of NRG1 and ErbB4 Protein Expressions in the Hippocampus

Western blot analysis revealed that expressions of three NRG1 isoforms were significantly elevated with relative levels (% of vehicle treated controls) of 169 7 for 35 kDa isoform, 159 17 for 65 kDa isoform, and 134 12 for 95 kDa isoform, respectively; while all three isoforms of ErbB4 were also significantly upregulated with relative levels (% of vehicle treated controls) of 330 28 for 60 kDa isoform, 221 15 for 120 kDa isoform, and 235 26 for 185 kDa isoform, respectively (Figures 2(a)2(d)).

fig2
Figure 2: Expression of NRG1 and ErbB4 proteins in the rat hippocampus. (a) Representative Western blots of NRG1 protein isoforms. (b) Quantitative analysis of NRG1 immunoblots. (c) Representative Western blots of ErbB4 protein isoforms. (d) Quantitative analysis of ErbB4 immunoblots. The data were normalized by taking the value of vehicle group as 100% and expressed as means S.E.M. ( = 5). . (e) Representative section of NRG1 immunohistochemistry in the hippocampal CA1 region from vehicle group. (f) Representative section of NRG1 immunohistochemistry in the hippocampal CA1 region from MK-801-treated group. (g) Representative section of NRG1 immunohistochemistry in the hippocampal CA3 region from vehicle group. (h) Representative section of NRG1 immunohistochemistry in the hippocampal CA3 region from MK-801-treated group. (i) Representative section of NRG1 immunohistochemistry in the hippocampal DG region from vehicle group. (j) Representative section of NRG1 immunohistochemistry in the hippocampal DG region from MK-801-treated group. Arrows indicate NRG1-expressing neurons in the hippocampus. Scale bar for (e)–(j): 50  m.

Consistent with Western blot results, immunostaining analysis revealed significant increases of NRG1 immunoreactivity in the pyramidal cell layer of CA1 and CA3 and in the granule cell layer of the dentate gyrus (Figures 2(e)2(j) and Table 1). Similar to the results for NRG1 , MK-801 increased expression of ErbB4 receptor in the CA1 subregion, while there were no significant differences that can be detected in CA3 and the dentate gyrus. From the DAB-stained morphology of immunopositive cells, it ia noticed that they are mainly neuron-like cells [32].

4. Discussion

Our major findings from this study were that in this schizophrenia animal model induced by chronic MK-801 administration, Western blot results showed significantly increased protein levels of NRG1 in the rat prefrontal cortex, while immunohistochemistry analysis observed the increase of NRG1 immunoreactivity in the PrL and the Cg1 and M2 regions, but it did not reach statistic significance. This discrepancy results between Western blot and immuohistochemistry may be due to the different sensitivity of these two assessments and small sample size. Additionally, in this study, we found that protein level of ErbB4 is upregulated in the rat prefrontal cortex by Western blot, while the immunoreactivity of ErbB4 only increased in the PrL region. Furthermore, protein levels of both NRG1 and ErbB4 were increased in rat hippocampus, but the increased immunoreactivities of the two proteins were located in different subregions. Significantly increased NRG1 immuoreactivity can be seen in the pyramidal cell layer of CA1 and CA3 and in the granule cell layer of the dentate gyrus, while ErbB4 was only significantly increased in CA1 subregion. There might be important role and mechanisms beyond the distinguishable expression patterns of NRG1 and ErbB4 in this schizophrenia model which need further investigations.

Our findings are consistent with the clinical observations of dysregulated expression of NRG1 and ErbB4 in postmortem brain of schizophrenia patients [20, 21]. Interestingly, our previous study found that changes of NRG1 and ErbB4 protein levels can be induced by chronic administration of antipsychotic drugs in normal rat prefrontal cortex and hippocampus [32], indicating that regulations of NRG1 and ErbB4 proteins may be associated with pathophysiological cascades and therapeutic outcomes of schizophrenia.

Although the roles and mechanisms of the increased NRG1 and ErbB4 in this rat schizophrenia model and correlation to the schizophrenia pathophysiology are incompletely understood from this study, the potential roles and mechanisms might be speculated. Our data showed that repeated blockade of NMDA receptor increased the expression of NRG1 and ErbB4, suggesting that changes of both NRG1 and ErbB4 expressions are associated with NMDA receptor function in this rat model for schizophrenia. Perhaps this is due to the fact that ErbB4 colocalizes with NMDA receptors at postsynaptic sites through interaction with PDZ domain-containing proteins, presuming that there is cross-talk between NMDA receptor and NRG1-ErbB4 signaling [20, 34, 35].

We are aware that there are several limitations in this short study. We did not study the time course of NRG1 and ErbB4 expression and correlation to the late behavioral deficits, which need to be performed in the future. Since we only tested this rat schizophrenia animal model, we need to know whether increased expression of NRG1 and ErbB4 in other schizophrenia animal models is a common pathological phenomenon of schizophrenia. Except the protein expression changes, we also need to know the function changes of NRG1-ErbB4 signaling, in terms of better understanding their roles and mechanisms. The cellular sources and subcellular distributions of both NRG1 and ErbB4 need to be carefully defined with double staining techniques. Lastly, genetic alteration and pharmacological approaches for manipulating NRG1 and ErbB4 expressions can be applied to further investigate their pathological importance and therapeutic potentials in schizophrenia.

5. Conclusion

In summary, our present study indicates that protein levels of NRG1 and ErbB4 in the prefrontal cortex and hippocampus are increased in this rat model of schizophrenia induced by repeated MK-801 administration. These findings suggest that altered expressions of NRG1 and ErbB4 might attribute to the schizophrenia. Further study of the role and mechanism of NRG1 and ErbB4 may lead to better understanding of the pathophysiology of schizophrenia.

Acknowledgment

This work was supported by National Natural Scientific Foundation of China (Grant no.: 30770775 and 30800361).

References

  1. P. J. Harrison and M. J. Owen, “Genes for schizophrenia? Recent findings and their pathophysiological implications,” The Lancet, vol. 361, no. 9355, pp. 417–419, 2003. View at Publisher · View at Google Scholar · View at Scopus
  2. P. J. Harrison and D. R. Weinberger, “Schizophrenia genes, gene expression, and neuropathology: on the matter of their convergence,” Molecular Psychiatry, vol. 10, no. 1, pp. 40–68, 2005. View at Publisher · View at Google Scholar · View at Scopus
  3. A. J. Law, J. E. Kleinman, D. R. Weinberger, and C. S. Weickert, “Disease-associated intronic variants in the ErbB4 gene are related to altered ErbB4 splice-variant expression in the brain in schizophrenia,” Human Molecular Genetics, vol. 16, no. 2, pp. 129–141, 2007. View at Publisher · View at Google Scholar · View at Scopus
  4. N. Norton, V. Moskvina, D. W. Morris et al., “Evidence that interaction between neuregulin 1 and its receptor erbB4 increases susceptibility to schizophrenia,” American Journal of Medical Genetics Part B, vol. 141B, no. 1, pp. 96–101, 2006. View at Publisher · View at Google Scholar · View at Scopus
  5. G. Silberberg, A. Darvasi, R. Pinkas-Kramarski, and R. Navon, “The involvement of ErbB4 with schizophrenia: association and expression studies,” American Journal of Medical Genetics Part B, vol. 141B, no. 2, pp. 142–148, 2006. View at Publisher · View at Google Scholar · View at Scopus
  6. R. Gerlai, P. Pisacane, and S. Erickson, “Heregulin, but not ErbB2 or ErbB3, heterozygous mutant mice exhibit hyperactivity in multiple behavioral tasks,” Behavioural Brain Research, vol. 109, no. 2, pp. 219–227, 2000. View at Publisher · View at Google Scholar · View at Scopus
  7. M. S. Golub, S. L. Germann, and K. C. K. Lloyd, “Behavioral characteristics of a nervous system-specific erbB4 knock-out mouse,” Behavioural Brain Research, vol. 153, no. 1, pp. 159–170, 2004. View at Publisher · View at Google Scholar · View at Scopus
  8. H. Stefansson, E. Sigurdsson, V. Steinthorsdottir et al., “Neuregulin 1 and susceptibility to schizophrenia,” American Journal of Human Genetics, vol. 71, no. 4, pp. 877–892, 2002. View at Google Scholar · View at Scopus
  9. G. D. Fischbach and K. M. Rosen, “ARIA: a neuromuscular junction neuregulin,” Annual Review of Neuroscience, vol. 20, pp. 429–458, 1997. View at Publisher · View at Google Scholar · View at Scopus
  10. A. Buonanno and G. D. Fischbach, “Neuregulin and ErbB receptor signaling pathways in the nervous system,” Current Opinion in Neurobiology, vol. 11, no. 3, pp. 287–296, 2001. View at Publisher · View at Google Scholar · View at Scopus
  11. L. Mei and W.-C. Xiong, “Neuregulin 1 in neural development, synaptic plasticity and schizophrenia,” Nature Reviews Neuroscience, vol. 9, no. 6, pp. 437–452, 2008. View at Publisher · View at Google Scholar · View at Scopus
  12. G. Carpenter, “ErbB-4: mechanism of action and biology,” Experimental Cell Research, vol. 284, no. 1, pp. 66–77, 2003. View at Publisher · View at Google Scholar · View at Scopus
  13. G. Lemke, “Glial control of neuronal development,” Annual Review of Neuroscience, vol. 24, pp. 87–105, 2001. View at Publisher · View at Google Scholar · View at Scopus
  14. A. N. Garratt, S. Britsch, and C. Birchmeier, “Neuregulin, a factor with many functions in the life of a Schwann cell,” BioEssays, vol. 22, no. 11, pp. 987–996, 2000. View at Publisher · View at Google Scholar · View at Scopus
  15. G. V. Michailov, M. W. Sereda, B. G. Brinkmann et al., “Axonal neuregulin-1 regulates myelin sheath thickness,” Science, vol. 304, no. 5671, pp. 700–703, 2004. View at Publisher · View at Google Scholar · View at Scopus
  16. K.-A. Nave and J. L. Salzer, “Axonal regulation of myelination by neuregulin 1,” Current Opinion in Neurobiology, vol. 16, no. 5, pp. 492–500, 2006. View at Publisher · View at Google Scholar · View at Scopus
  17. C. Taveggia, G. Zanazzi, A. Petrylak et al., “Neuregulin-1 type III determines the ensheathment fate of axons,” Neuron, vol. 47, no. 5, pp. 681–694, 2005. View at Publisher · View at Google Scholar · View at Scopus
  18. S. E. Arnold, K. Talbot, and C.-G. Hahn, “Neurodevelopment, neuroplasticity, and new genes for schizophrenia,” Progress in Brain Research, vol. 147, pp. 319–345, 2004. View at Publisher · View at Google Scholar · View at Scopus
  19. R. M. Esper, M. S. Pankonin, and J. A. Loeb, “Neuregulins: versatile growth and differentiation factors in nervous system development and human disease,” Brain Research Reviews, vol. 51, no. 2, pp. 161–175, 2006. View at Publisher · View at Google Scholar · View at Scopus
  20. C.-G. Hahn, H.-Y. Wang, D.-S. Cho et al., “Altered neuregulin 1-erbB4 signaling contributes to NMDA receptor hypofunction in schizophrenia,” Nature Medicine, vol. 12, no. 7, pp. 824–828, 2006. View at Publisher · View at Google Scholar · View at Scopus
  21. V. Z. Chong, M. Thompson, S. Beltaifa, M. J. Webster, A. J. Law, and C. S. Weickert, “Elevated neuregulin-1 and ErbB4 protein in the prefrontal cortex of schizophrenic patients,” Schizophrenia Research, vol. 100, no. 1–3, pp. 270–280, 2008. View at Publisher · View at Google Scholar · View at Scopus
  22. D. Rujescu, A. Bender, M. Keck et al., “A pharmacological model for psychosis based on N-methyl-D-aspartate receptor hypofunction: molecular, cellular, functional and behavioral abnormalities,” Biological Psychiatry, vol. 59, no. 8, pp. 721–729, 2006. View at Publisher · View at Google Scholar · View at Scopus
  23. D. Kondziella, E. Brenner, E. M. Eyjolfsson, K. R. Markinhuhta, M. L. Carlsson, and U. Sonnewald, “Glial-neuronal interactions are impaired in the schizophrenia model of repeated MK801 exposure,” Neuropsychopharmacology, vol. 31, no. 9, pp. 1880–1887, 2006. View at Publisher · View at Google Scholar · View at Scopus
  24. J. W. Olney and N. B. Farber, “Glutamate receptor dysfunction and schizophrenia,” Archives of General Psychiatry, vol. 52, no. 12, pp. 998–1007, 1995. View at Google Scholar · View at Scopus
  25. J. D. Jentsch and R. H. Roth, “The neuropsychopharmacology of phencyclidine: from NMDA receptor hypofunction to the dopamine hypothesis of schizophrenia,” Neuropsychopharmacology, vol. 20, no. 3, pp. 201–225, 1999. View at Publisher · View at Google Scholar · View at Scopus
  26. G. E. Duncan, S. Miyamoto, J. N. Leipzig, and J. A. Lieberman, “Comparison of brain metabolic activity patterns induced by ketamine, MK- 801 and amphetamine in rats: support for NMDA receptor involvement in responses to subanesthetic dose of ketamine,” Brain Research, vol. 843, no. 1-2, pp. 171–183, 1999. View at Publisher · View at Google Scholar · View at Scopus
  27. D. R. Weinberger, M. S. Aloia, T. E. Goldberg, and K. F. Berman, “The frontal lobes and schizophrenia,” Journal of Neuropsychiatry and Clinical Neurosciences, vol. 6, no. 4, pp. 419–427, 1994. View at Google Scholar
  28. B. Elvevag and T. E. Goldberg, “Cognitive impairment in schizophrenia is the core of the disorder,” Critical Reviews in Neurobiology, vol. 14, no. 1, pp. 1–21, 2000. View at Google Scholar · View at Scopus
  29. D. P. Eisenberg and K. F. Berman, “Executive function, neural circuitry, and genetic mechanisms in schizophrenia,” Neuropsychopharmacology, vol. 35, no. 1, pp. 258–277, 2010. View at Publisher · View at Google Scholar · View at Scopus
  30. M. S. Seo, S. H. Kim, Y. M. Ahn et al., “The effects of repeated administrations of MK-801 on ERK and GSK-3ß signalling pathways in the rat frontal cortex,” International Journal of Neuropsychopharmacology, vol. 10, no. 3, pp. 359–368, 2007. View at Publisher · View at Google Scholar · View at Scopus
  31. G. Paxinos and C. Watson, The Rat Brain in Stereotaxic Coordinate, Academic Press, San Diego, Calif, USA, 2005.
  32. X.-D. Wang, Y.-A. Su, C.-M. Guo, Y. Yang, and T.-M. Si, “Chronic antipsychotic drug administration alters the expression of neuregulin 1β, ErbB2, ErbB3, and ErbB4 in the rat prefrontal cortex and hippocampus,” International Journal of Neuropsychopharmacology, vol. 11, no. 4, pp. 553–561, 2008. View at Publisher · View at Google Scholar · View at Scopus
  33. D. A. Gearhart, M.-L. Middlemore, and A. V. Terry, “ELISA methods to measure cholinergic markers and nerve growth factor receptors in cortex, hippocampus, prefrontal cortex, and basal forebrain from rat brain,” Journal of Neuroscience Methods, vol. 150, no. 2, pp. 159–173, 2006. View at Publisher · View at Google Scholar · View at Scopus
  34. R. A. G. Garcia, K. Vasudevan, and A. Buonanno, “The neuregulin receptor ErbB-4 interacts with PDZ-containing proteins at neuronal synapses,” Proceedings of the National Academy of Sciences of the United States of America, vol. 97, no. 7, pp. 3596–3601, 2000. View at Publisher · View at Google Scholar · View at Scopus
  35. Y. Z. Huang, S. Won, D. W. Ali et al., “Regulation of neuregulin signaling by PSD-95 interacting with ErbB4 at CNS synapses,” Neuron, vol. 26, no. 2, pp. 443–455, 2000. View at Google Scholar · View at Scopus