QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text (PDF) All Versions of this Article: mol.105.019828v1 69/4/1366    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Fumagalli, F. Articles by Riva, M. A. Search for Related Content PubMed PubMed Citation Articles by Fumagalli, F. Articles by Riva, M. A.

Long-Term Exposure to the Atypical Antipsychotic Olanzapine Differently Up-Regulates Extracellular Signal-Regulated Kinases 1 and 2 Phosphorylation in Subcellular Compartments of Rat Prefrontal Cortex

Center of Neuropharmacology, Department of Pharmacological Sciences University of Milan, Milan, Italy (F.F., G.R., M.A.R.); Istituto di Ricovero e Cura a Carattere Scientifico, San Giovanni di Dio-Fatebenefratelli, Brescia, Italy (A.F., G.R.); and Department of Experimental and Clinical Pharmacology, School of Medicine, University of Catania, Catania, Italy (M.S., F.D.)

Received October 12, 2005; accepted January 3, 2006

	Abstract

Top Abstract Materials and Methods Results Discussion References

 
Antipsychotics are the drugs of choice for the treatment of schizophrenia. Besides blocking monoamine receptors, these molecules affect intracellular signaling mechanisms, resulting in long-term synaptic alterations. Western blot analysis was used to investigate the effect of long-term administration (14 days) with the typical antipsychotic haloperidol and the atypical olanzapine on the expression and phosphorylation state of extracellular signal-related kinases (ERKs) 1 and 2 (ERK1/2), proteins involved in the regulation of multiple intracellular signaling cascades. A single injection of both drugs produced an overall decrease in ERK1/2 phosphorylation in different subcellular compartments. Conversely, long-term treatment with olanzapine, but not haloperidol, increased ERK1/2 phosphorylation in the prefrontal cortex in a compartment-specific and time-dependent fashion. In fact, ERK1/2 phosphorylation was elevated in the nuclear and cytosolic fractions 2 h after the last drug administration, whereas it was enhanced only in the membrane fraction when the animals were killed 24 h after the last injection. This effect might be the result of an activation of the mitogen-activated protein kinase pathway, because the phosphorylation of extracellular signal-regulated kinase kinase 1/2 was also increased by long-term olanzapine administration. Our data demonstrate that long-term exposure to olanzapine dynamically regulates ERK1/2 phosphorylation in different subcellular compartments, revealing a novel mechanism of action for this atypical agent and pointing to temporally separated locations of signaling events mediated by these kinases after long-term olanzapine administration.

It has been shown that patients with schizophrenia have altered brain expression and/or phosphorylation of -catenin and AKT-glycogen synthase kinase-3 (Cotter et al., 1998; Kozlovsky et al., 2000; Beasley et al., 2001; Emamian et al., 2004). The relevance of these pathways to schizophrenia is corroborated by the evidence that antipsychotics increase levels and/or the activation state of these proteins in the brain of experimental animals (Emamian et al., 2004; Kang et al., 2004; Alimohamad et al., 2005) regardless of the therapeutic class. In addition, antipsychotics regulate cAMP-dependent protein kinase-mediated signaling in different rat cerebral regions (Turalba et al., 2004).

Recent data have shown that the MAP kinase pathway might also be modulated by short-term administration of antipsychotics (Pozzi et al., 2003; Valjent et al., 2004; Browning et al., 2005). Mitogen-activated protein kinase and extracellular signal-regulated kinase (ERK) represent a critical crossroad of multiple signaling cascades involved in the regulation of different cellular processes spanning from cell proliferation, differentiation, and survival (Schaeffer and Weber, 1999; Colucci-D'Amato et al., 2003; Sweatt, 2004) to synaptic plasticity and cognition (Valjent et al., 2001; Adams and Sweatt, 2002; Thomas and Huganir, 2004).

Because these proteins operate as multifunctional signaling integrators involved in the regulation of gene transcription (Sweatt, 2004), we investigated whether long-term administration of antipsychotics could alter their expression and phosphorylation state in the prefrontal cortex, a region that contributes most to the cognitive impairments observed in patients with schizophrenia (Weinberger et al., 2001).

Our results show that long-term treatment with the atypical antipsychotic olanzapine has specific modulatory effects on ERK1/2 phosphorylation that might account for the improvements in cognitive symptoms of schizophrenia produced by the drug.

	Materials and Methods

Top Abstract Materials and Methods Results Discussion References

 
Materials. General reagents were purchased from Sigma-Aldrich (Milano, Italy), and molecular biology reagents were obtained from Ambion (Austin, TX), New England Biolabs (Beverly, MA) and Promega (Milan, Italy). Olanzapine was obtained from Eli Lilly (Sesto Fiorentino, Italy); haloperidol was purchased from Sigma-Aldrich.

Animal Treatment and Drug Paradigms. Male Sprague-Dawley rats (Charles River, Calco, Italy) weighing 225 to 250 g were used throughout the experiments. Animals were housed for 2 weeks before any treatment and were maintained under a 12-h light/dark cycle with food and water available ad libitum.

For the short-term treatment, animals received a single injection only of either vehicle (saline), haloperidol (1 mg/kg), or olanzapine (2 mg/kg) and were killed by decapitation 30 min or 2 h later. For the long-term treatment, rats were injected daily with the drugs for 14 days and were killed 2 or 24 h after the last drug injection. Vehicle, haloperidol, and olanzapine were administered by subcutaneous injection. Although appropriate drug dosing in rats is controversial, in our experiments, drug doses were chosen in accordance with published protocols (Schotte et al., 1996; Bubser and Deutch, 2002; Kapur et al., 2003). All animal handling and experimental procedures were performed in accordance with the EC guidelines (EC Council Directive 86/609 1987) and with the Italian legislation on animal experimentation (Decreto Legislativo 116/92).

Preparation of Protein Extracts. Prefrontal cortex (approximately weight, 8 mg) was dissected from 2-mm slices (prefrontal cortex defined as Cg1, Cg3, and IL subregions, corresponding to the plates 6-9 of the atlas of Paxinos and Watson, 1996), immediately frozen on dry ice, and stored at -80°C. Different subcellular fractions were prepared as described previously (Maragnoli et al., 2004). Tissues were homogenized in a glass-glass potter in cold 0.32 M sucrose containing 1 mM HEPES solution, 0.1 mM EGTA, and 0.1 mM phenylmethylsulfonyl fluoride, pH 7.4, in presence of a complete set of protease inhibitors and a phosphatase inhibitor cocktail. The homogenized tissue was centrifuged at 5000g for 10 min. The resulting pellet (P1), corresponding to the nuclear fraction, was resuspended in a buffer (20 mM HEPES, 0.1 mM dithiothreitol, and 0.1 mM EGTA) with protease and phosphatase inhibitors; the supernatant (S1) was centrifuged at 9000g for 15 min to obtain a clarified fraction of cytosolic proteins (S2), and the pellet, corresponding to the membrane fraction (P2), was resuspended in the same buffer used for P1. Total protein content was measured in the P1, S2, and P2 fractions with the Bio-Rad Protein Assay (Bio-Rad, Milano, Italy).

Western Blot Analysis. ERK1/2 protein analysis was performed on P1, S2, and P2 fractions as described previously (Fumagalli et al., 2005). Total protein concentrations were adjusted to the same amount for all samples (10 µg per lane). All of the samples were run on an SDS-8% polyacrylamide gel under reducing conditions, and proteins were then electrophoretically transferred onto nitrocellulose membranes (Bio-Rad). Blots were blocked with 10% nonfat dry milk and then incubated with primary antibody. The blots were first probed with antibodies against the phosphorylated forms of the protein and then stripped and reprobed with antibodies against total proteins of same type. ERK1 and ERK2 native forms were detected by evaluating the band density at 44 and 42 kDa, respectively, after probing with a polyclonal antibody (1:10,000, 2 h, room temperature) (Santa Cruz Biotechnology, Santa Cruz, CA). Membranes were incubated for 1 h at room temperature with a 1:10,000 dilution of peroxidase-conjugated anti-rabbit IgG (Sigma-Aldrich). ERK1 and ERK2 phosphorylated forms were detected by evaluating the band density at 44 and 42 kDa, respectively, after probing with a monoclonal antibody (1:10,000, 4°C, overnight) (Santa Cruz Biotechnology). Membranes were incubated for 1 h with a 1:10,000 dilution of peroxidase-conjugated anti-mouse IgG (Sigma-Aldrich).

MEK1/2 native form was detected by evaluating the band density at 45 kDa after probing with a polyclonal antibody (1:5000, 2 h, room temperature) (Cell Signaling Technology). Membranes were incubated for 1 h at room temperature with a 1:5000 dilution of peroxidase-conjugated anti-rabbit IgG (Cell Signaling Technology). MEK1/2 phosphorylated form was detected by evaluating the band density at 45 kDa after probing with a polyclonal antibody (1:1000, 4°C, overnight) (Cell Signaling Technology). Membranes were incubated for 1 h at room temperature with a 1:1000 dilution of peroxidase-conjugated anti-rabbit IgG (Cell Signaling Technology).

ERK1 and ERK2 phosphorylated immunocomplexes were visualized by chemiluminescence using the SuperSignal West Femto (Pierce Chemical, Rockford, IL), whereas MEK1/2 phosphorylated immunocomplexes were detected using the ECL Western Blotting kit (Amersham Life Science, Milano, Italy). ERK1, ERK2, and MEK1/2 native immunocomplexes were visualized by chemiluminescence using the ECL Western Blotting kit (Amersham Life Science) according to the manufacturer's instructions.

Results were standardized to a -actin control protein, which was detected by evaluating the band density at 43 kDa after probing with a polyclonal antibody with a 1:10,000 dilution (Sigma-Aldrich). Membranes were incubated for 1 h at room temperature with a 1:10,000 dilution of peroxidase-conjugated anti-mouse IgG (Sigma-Aldrich).

Statistical Analysis. Expression and phosphorylation state of ERK1/2 were measured using the Quantity One software from Bio-Rad. The mean value of the control group within a single experiment was set at 100, and the data of animals injected with olanzapine or haloperidol were expressed as "percentages" of saline-treated animals. The phosphorylation of ERK1/2 was expressed as a ratio between phosphorylated ERKs and total ERKs (pERKs/tERKs). The total levels of ERKs were normalized with -actin (ERKs/-actin). The same analysis was carried out for the expression and phosphorylation state of MEK1/2.

Statistical evaluation of the changes produced by antipsychotic treatment on the phosphorylation state or expression of targets proteins was performed using a one-way analysis of variance (ANOVA) followed by Scheffé's F test. Significance for all tests was assumed at p < 0.05.

	Results

Top Abstract Materials and Methods Results Discussion References

 
The major aim of the present study was to examine the subcellular expression and phosphorylation state of ERK1/2 in rat prefrontal cortex after treatment with the typical antipsychotic haloperidol and the atypical olanzapine. The purity of cellular compartment preparation was demonstrated previously (Fumagalli et al., 2005). Both ERK isoforms were revealed by Western blot analysis, with a more intense immunoreactivity for ERK2.

View larger version (27K): [in this window] [in a new window]   Fig. 1. Effect of short-term treatment with haloperidol or olanzapine on ERK1/2 in rat prefrontal cortex. The phosphorylation (a and c) and expression (b and d) of ERK1/2 were investigated in animals that received a single injection of haloperidol (1 mg/kg) or olanzapine (2 mg/kg) and that were killed 30 min (a and b) or 2 h (c and d) later. The mean value of the control group was set at 100, and the data of animals injected with haloperidol or olanzapine were expressed as percentages of saline-treated animals. Data are the mean ± S.E.M. from six to eight independent determinations. *, p < 0.05 versus saline-injected rats (one-way ANOVA with Scheffé's F test).

Although 30 min after administration of both drugs total levels of ERK1/2 were not changed (Fig. 1b), single injection of olanzapine increased total ERK1/2 levels in the nucleus, with a concomitant decrease of their levels in the cytosol 2 h later (Fig. 1d). Conversely, at this time point, the short-term administration of haloperidol did not produce any significant change of the levels for both ERK isoforms in any cellular compartments.

We then performed two different long-term treatments (14 days) with haloperidol and olanzapine that could be distinguished on the basis of the time of sacrifice from the last injection. We reasoned that these distinct experimental paradigms could allow us to dissect between mechanisms directly related to (2 h) and those independent from (24 h) the last drug administration.

Figure 2a shows a representative immunoblotting demonstrating the increased ERK1/2 phosphorylation 2 h after the last injection of a 2-week treatment with olanzapine in rat prefrontal cortex. Quantitative analysis demonstrated that long-term treatment with olanzapine significantly enhanced ERK1 (+59%, p < 0.01) and ERK2 (+35%, p < 0.01) phosphorylation in the nuclear fraction of this brain region (Fig. 2b), whereas in the cytosolic fraction, the increase was restricted to ERK2 (+25%, p < 0.05) (Fig. 2b). Conversely, long-term haloperidol treatment did not elicit any significant change of ERK1/2 phosphorylation in the nuclear or in the cytosolic fractions (Fig. 2b). Furthermore, at this time point, phosphorylation of ERK1/2 isoforms was not changed after long-term haloperidol or olanzapine in the membrane fraction (Fig. 2b). No changes were measured in the total levels of ERK isoforms with either drugs in the different subcellular fractions (Fig. 2c).

View larger version (25K): [in this window] [in a new window]   Fig. 2. Effect of long-term antipsychotic treatment on ERK1/2 expression and phosphorylation in rat prefrontal cortex as measured 2 h after the last drug injection. The figures are representative immunoblots of native (t-ERK) and phosphorylated (p-ERK) forms of ERK1 and ERK2 in the nuclear, cytosolic, and membrane fractions from prefrontal cortex of saline (S)-, haloperidol (H)-, or olanzapine (O)-treated rats (a). Quantitative analysis of the effects of long-term haloperidol or olanzapine treatment are shown in b (ERK1/2 phosphorylation) and c (ERK1/2 expression). Animals were treated for 14 consecutive days with haloperidol (1 mg/kg) or olanzapine (2 mg/kg, twice a day) and killed 2 h after the last injection. The mean value of the control group was set at 100, and the data of animals injected with haloperidol or olanzapine were expressed as percentages of saline-treated animals. Data are the mean ± S.E.M. from eight independent determinations. *, p < 0.05, and **, p < 0.01 versus saline-injected rats (one-way ANOVA with Scheffé's F test).

View larger version (25K): [in this window] [in a new window]   Fig. 3. Effect of long-term antipsychotic treatment on ERK1/2 expression and activity in rat prefrontal cortex as measured 24 h after the last drug injection. The figures are representative immunoblots of native (t-ERK) and phosphorylated (p-ERK) forms of ERK1 and ERK2 in the nuclear, cytosolic, and membrane fractions from prefrontal cortex of saline (S)-, haloperidol (H)-, or olanzapine (O)-treated rats (a). Quantitative analysis of the effects of long-term haloperidol or olanzapine treatment are shown in b (ERK1/2 phosphorylation) and c (ERK1/2 expression). Animals were treated for 14 consecutive days with haloperidol (1 mg/kg) or olanzapine (2 mg/kg, twice a day) and were killed 24 h after the last injection. The mean value of the control group was set at 100, and the data of animals injected with haloperidol or olanzapine were expressed as percentages of saline-treated animals. Data are the mean ± S.E.M. from eight independent determinations. *, p < 0.05 versus saline-injected rats (one-way ANOVA with Scheffé's F test).

View larger version (16K): [in this window] [in a new window]   Fig. 4. Effect of long-term antipsychotic treatment on MEK1/2 expression and activity in rat prefrontal cortex 2 and 24 h after the last drug injection. a, the figures are representative immunoblots of native (t-MEK) and phosphorylated (p-MEK) forms of MEK1/2 in the cytosolic fraction from prefrontal cortex of saline (S)- or olanzapine (O)-treated rats. Quantitative analysis of the effects of long-term olanzapine treatment are shown in b (MEK1/2 phosphorylation) and c (MEK1/2 expression). Animals were treated for 14 consecutive days with olanzapine (2 mg/kg, twice a day) and were killed 2 or 24 h after the last injection. The mean value of the control group was set at 100, and the data of animals injected with olanzapine were expressed as percentages of saline-treated animals. Data are the mean ± S.E.M. from eight independent determinations. *, p < 0.05 versus saline-injected rats (one-way ANOVA with Scheffé's F test).

	Discussion

Top Abstract Materials and Methods Results Discussion References

 
Our results demonstrate that, in rat prefrontal cortex, ERK1/2 phosphorylation is selectively increased by longterm treatment with olanzapine, but not haloperidol, according to a finely tuned, compartment- and temporal-specific profile. The subcellular localization of such an effect is strictly correlated to the time of sacrifice from the last injection; in fact, such enhancement is specifically confined to the nuclear and cytosolic fraction 2 h after the last injection, but it is restricted to the membrane fraction when the animals are killed 24 h later.

A single injection of haloperidol or olanzapine produced an overall reduction of ERK1/2 phosphorylation in the nuclear and cytosolic compartments, an effect that might be the consequence of the blockade of dopaminergic and serotonergic receptors. In the case of olanzapine, however, whereas the antipsychotic directly reduces ERK1/2 phosphorylation 30 min after drug injection, the effect observed 2 h later may be the result of increased protein expression. Based on these data, we suggest that olanzapine might promote protein translocation from the cytosol to the nucleus 2 h after treatment, presumably in an attempt to counteract the decreased ERK1/2 phosphorylation.

The different effect of single versus repeated injections of olanzapine is suggestive of the possibility that long-term treatment with the atypical antipsychotic might determine adaptive mechanisms that lead to the up-regulation of ERK1/2 phosphorylation in selected cell compartments.

The specific, compartmentalized increase in ERK1/2 phosphorylation poses an interesting question regarding the role of ERKs in the different subcellular fractions with respect to the mechanism of action of antipsychotic drugs. Evidence exists that activated ERK1/2 play distinct roles in the nucleus [in which they activate transcription factors or immediate early genes such as Elk-1 or c-fos (Sgambato et al., 1998a,b)], in the cytoplasm [in which they seem to be implicated in the regulation of cytoplasmic proteins involved in synaptic rearrangements such as MAP2 (Bhat et al., 1998) or Cdk5 (Veeranna et al., 2000)], or in the membrane fraction [in which, postsynaptically, they participate in the regulation of plasticity and learning (Komiyama et al., 2002) while presynaptically are involved in regulating neurotransmitter release (Schenk et al., 2005)]. To this regard, Harding and associates (2005) recently demonstrated that a different threshold of activation exists for ERK1/2 in different subcellular compartments that might explain the temporal redistribution of the activated kinase after long-term olanzapine administration.

Olanzapine, similarly to other novel antipsychotics, has a complex pharmacodynamic profile, thus posing an important question as to how it enhances ERK1/2 phosphorylation in prefrontal cortex. Direct blockade of dopamine D2 receptors is not likely to contribute to ERK1/2 changes, because haloperidol, a preferential antagonist of these receptors, is devoid of any effect. Although we cannot exclude a role for a specific receptor subtype, it could be hypothesized that the activation of ERKs in prefrontal cortex might represent the consequence of complex events involving direct receptor antagonism and enhancement of neurotransmitter release produced by olanzapine. In fact, it has been shown that olanzapine increases dopamine and norepinephrine release in rat prefrontal cortex (Bymaster et al., 1999), an effect that may contribute to the increase in ERK1/2 phosphorylation (Zhong and Minneman, 1999; Runyan and Dash, 2004). In addition, atypical drugs enhance glutamate transmission, thus facilitating N-methyl-D-aspartate responses in pyramidal cells of medial prefrontal cortex (Heresco-Levy, 2003; Ninan et al., 2003).

Increased ERK1/2 phosphorylation may be the result of a direct activation of the MAP kinase pathway, or it might depend on indirect modulation by other pathways involved in the phosphorylation of these proteins. Based on our data, we propose that increased phosphorylation of MEK1/2, the kinase upstream of ERK1/2, is responsible of the up-regulation of ERK1/2 phosphorylation. However, we cannot rule out the possibility that other mechanisms participate in such enhancement. Among the intracellular cascades relevant for the action of olanzapine, the pathway of cAMP-dependent protein kinase can increase ERK1/2 phosphorylation (Yao et al., 1998; York et al., 1998; Grewal et al., 1999; Robertson et al., 1999). Alternatively, enhanced phosphorylation of ERK1/2 after long-term olanzapine treatment might also result from the inhibition of protein phosphatases. Indeed, long-term administration of atypical antipsychotics down-regulates the expression of serine-threonine phosphatases, the enzymatic system responsible for ERK1/2 dephosphorylation (MacDonald et al., 2005).

Postmortem studies in patients with schizophrenia (Kyosseva et al., 1999) and preclinical investigations in animal models of the disease using glutamate N-methyl-D-aspartate receptor antagonists (Kyosseva et al., 2001; Ahn et al., 2005) have shown dysregulation of the ERK pathway, suggesting that it may represent a target for therapeutic interventions. In support of these molecular observations, clinical studies have demonstrated that patients with schizophrenia display abnormalities in prefrontal information processing (Weinberger et al., 2001), which could contribute to the cognitive impairments associated with the disease. Clinical data indicate that olanzapine and in general second-generation anti-psychotics successfully improve specific cognitive domains in patients with schizophrenia, whereas haloperidol and classic neuroleptics are not effective (Purdon et al., 2000; Woodward et al., 2005). Given that the ERK pathway modulates cognition in the prefrontal cortex (Runyan and Dash, 2004), our data raise the possibility that olanzapine might improve cognitive processes via the up-regulation of ERK1/2 phosphorylation in the prefrontal cortex.

To sum up, our results indicate ERK as a dynamic target of antipsychotic administration, unraveling a previously unappreciated degree of subcellular regulation promoted by olanzapine. Although the findings need to be confirmed and extended to other antipsychotic drugs, these results could explain, at least in part, the ability of atypical antipsychotics in alleviating some of the schizophrenic negative symptoms and improving cognitive dysfunctions.

The potential implication of increased ERK1/2 phosphorylation after long-term antipsychotic administration might extend from schizophrenia to other psychiatric conditions. To this end olanzapine, but not haloperidol, delays or prevents relapse during long-term maintenance therapy of bipolar disorder (McCormack and Wiseman, 2004; Bowden, 2005). It should be emphasized that lithium and valproate, which are widely used for the treatment of bipolar disorder, increase ERK1/2 phosphorylation in rat prefrontal cortex after longterm administration (Einat et al., 2003), pointing to enhanced function of ERK pathway in this brain structure as a common event of the long-term therapeutic action of psychotropic drugs.

	Acknowledgements

 
We thank Eli-Lilly (Italy) for the generous gift of olanzapine.

	Footnotes

 
This project was supported by the Italian Ministry of University and Research (Fondo per gli Investimenti della Ricerca di Base 2001, to G.R.), the Ministry of Health (Ricerca finalizzata 2003, to M.A.R.), and the University of Milan (FIRST 2003-2004, to G.R. and M.A.R.).

ABBREVIATIONS: ERK1/2, extracellular signal-regulated kinase 1/2; MEK1/2, extracellular signal-regulated kinase kinase 1/2; MAP, mitogen-activated protein; ANOVA, analysis of variance.

Address correspondence to: Dr. M. A. Riva, Center of Neuropharmacology, Department of Pharmacological Sciences, Via Balzaretti 9, 20133 Milan, Italy. E-mail: m.riva{at}unimi.it

	References

Top Abstract Materials and Methods Results Discussion References

 
Adams JP and Sweatt JD (2002) Molecular psychology: roles for the ERK MAP kinase cascade in memory. Annu Rev Pharmacol Toxicol 42: 135-163.[CrossRef][Medline]

Ahn YM, Seo MS, Kim SH, Kim Y, Juhnn YS, and Kim YS (2005) The effects of MK-801 on the phosphorylation of Ser338-c-Raf-MEK-ERK pathway in the rat frontal cortex. Int J Neuropsychopharmacol, in press.

Alimohamad H, Rajakumar N, Seah YH, and Rushlow W (2005) Antipsychotics alter the protein expression levels of beta-catenin and GSK-3 in the rat medial prefrontal cortex and striatum. Biol Psychiatry 57: 533-542.[CrossRef][Medline]

Beasley C, Cotter D, Khan N, Pollard C, Sheppard P, Varndell I, Lovestone S, Anderton B, and Everall I (2001) Glycogen synthase kinase-3beta immunoreactivity is reduced in the prefrontal cortex in schizophrenia. Neurosci Lett 302: 117-120.[CrossRef][Medline]

Bhat RV, Engber TM, Finn JP, Koury EJ, Contreras PC, Miller MS, Dionne CA, and Walton KM (1998) Region-specific targets of p42/p44 MAPK signaling in rat brain. J Neurochem 70: 558-571.[Medline]

Bowden CL (2005) Treatment options for bipolar depression. J Clin Psychiatry 66 (Suppl 1): 3-6.

Browning JL, Patel T, Brandt PC, Young KA, Holcomb LA, and Hicks PB (2005) Clozapine and the mitogen-activated protein kinase signal transduction pathway: implications for antipsychotic actions. Biol Psychiatry 57: 617-623.[CrossRef][Medline]

Bubser M and Deutch AY (2002) Differential effects of typical and atypical antipsychotic drugs on striosome and matrix compartments of the striatum. Eur J Neurosci 15: 713-720.[Medline]

Bymaster F, Perry KW, Nelson DL, Wong DT, Rasmussen K, Moore NA, and Calligaro DO (1999) Olanzapine: a basic science update. Br J Psychiatry Suppl 37: 36-40.

Colucci-D'Amato L, Perrone-Capano C, and di Porzio U (2003) Chronic activation of ERK and neurodegenerative diseases. Bioessays 5: 1085-1095.

Cotter D, Kerwin R, al Sarraji S, Brion JP, Chadwich A, Lovestone S, Anderton B, and Everall I (1998) Abnormalities of Wnt signaling in schizophrenia—evidence for neurodevelopmental abnormality. Neuroreport 9: 1379-1383.[Medline]

Einat H, Yuan P, Gould TD, Li J, Du J, Zhang L, Manji HK, and Chen G (2003) The role of the extracellular signal-regulated kinase signaling pathway in mood modulation. J Neurosci 23: 7311-7316.[Abstract/Free Full Text]

Emamian ES, Hall D, Birnbaum MJ, Karayiorgou M, and Gogos JA (2004) Convergent evidence for impaired AKT1-GSK3beta signaling in schizophrenia. Nat Genet 36: 131-137.[CrossRef][Medline]

Fumagalli F, Molteni R, Calabrese F, Frasca A, Racagni G, and Riva MA (2005) Chronic fluoxetine administration inhibits extracellular signal-regulated kinase 1/2 phosphorylation in rat brain. J Neurochem 93: 1551-1560.[CrossRef][Medline]

Grewal SS, York RD, and Stork PJ (1999) Extracellular-signal-regulated kinase signalling in neurons. Curr Opin Neurobiol 9: 544-553.[CrossRef][Medline]

Harding A, Tian T, Westbury E, Frische E, and Hancock JF (2005) Subcellular localization determines MAP kinase signal output. Curr Biol 15: 869-873.[CrossRef][Medline]

Heresco-Levy U (2003) Glutamatergic neurotransmission modulation and the mechanisms of antipsychotic atypicality. Prog Neuropsychopharmacol Biol Psychiatry 27: 1113-1123.[CrossRef][Medline]

Kang UG, Seo MS, Roh MS, Kim Y, Yoon SC, and Kim YS (2004) The effects of clozapine on the GSK-3-mediated signaling pathway. FEBS Lett 560: 115-119.[CrossRef][Medline]

Kapur S, VanderSpek SC, Brownlee BA, and Nobrega JN (2003) Antipsychotic dosing in preclinical models is often unrepresentative of the clinical condition: a suggested solution based on in vivo occupancy. J Pharmacol Exp Ther 305: 625-631.[Abstract/Free Full Text]

Keefe RS, Seidman LJ, Christensen BK, Hamer RM, Sharma T, Sitskoorn MM, Rock SL, Woolson S, Tohen M, Tollefson GD, et al. (2006) Long-term neurocognitive effects of olanzapine or low-dose haloperidol in first-episode psychosis. Biol Psychiatry 59: 97-105.[CrossRef][Medline]

Komiyama NH, Watabe AM, Carlisle HJ, Porter K, Charlesworth P, Monti J, Strathdee DJ, O'Carroll CM, Martin SJ, Morris RG, et al. (2002) SynGAP regulates ERK/MAPK signaling, synaptic plasticity and learning in the complex with postsynaptic density 95 and NMDA receptor. J Neurosci 22: 9721-9732.[Abstract/Free Full Text]

Kozlovsky N, Belmaker RH, and Agam G (2000) Low GSK-3beta immunoreactivity in postmortem frontal cortex of schizophrenic patients. Am J Psychiatry 157: 831-833.[Abstract/Free Full Text]

Kyosseva SV, Elbein AD, Griffin WS, Mrak RE, Lyon M, and Karson CN (1999) Mitogen-activated protein kinases in schizophrenia. Biol Psychiatry 46: 689-696.[CrossRef][Medline]

Kyosseva SV, Owens SM, Elbein AD, and Karson CN (2001) Differential and region-specific activation of mitogen-activated protein kinases following chronic administration of phencyclidine in rat brain. Neuropsychopharmacology 24: 267-277.[CrossRef][Medline]

MacDonald ML, Eaton ME, Dudman JT, and Konradi C (2005) Antipsychotic drugs elevate mRNA levels of presynaptic proteins in the frontal cortex of the rat. Biol Psychiatry 57: 1041-1051.[CrossRef][Medline]

Maragnoli ME, Fumagalli F, Gennarelli M, Racagni G, and Riva MA (2004) Fluoxetine and olanzapine have synergistic effects in the modulation of fibroblast growth factor 2 expression within the rat brain. Biol Psychiatry 55: 1095-1102.[CrossRef][Medline]

McCormack PL and Wiseman LR (2004) Olanzapine: a review of its use in the management of bipolar I disorder. Drugs 64: 2709-2726.[Medline]

Meltzer HY (1991) The mechanism of action of novel antipsychotic drugs. Schizophr Bull 17: 263-287.[Abstract/Free Full Text]

Ninan I, Jardemark KE, and Wang RY (2003) Differential effects of atypical and typical antipsychotic drugs on N-methyl-D-aspartate- and electrically evoked responses in the pyramidal cells of the rat medial prefrontal cortex. Synapse 48: 66-79.[CrossRef][Medline]

Paxinos G and Watson C (1996) The Rat Brain in Stereotaxic Coordinates. Academic Press, New York.

Pozzi L, Hakansson K, Usiello A, Borgkvist A, Lindskog M, Greengard P, and Fisone G (2003) Opposite regulation by typical and atypical anti-psychotics of ERK1/2, CREB and Elk-1 phosphorylation in mouse dorsal striatum. J Neurochem 86: 451-459.[CrossRef][Medline]

Purdon SE, Jones BD, Stip E, Labelle A, Addington D, David SR, Breier A, and Tollefson GD (2000) Neuropsychological change in early phase schizophrenia during 12 months of treatment with olanzapine. The Canadian Collaborative Group for research in schizophrenia. Arch Gen Psychiatry 57: 249-258.[Abstract/Free Full Text]

Robertson ED, English JD, Adams JP, Selcher JC, Kondratick C, and Sweatt JD (1999) The mitogen-activated protein kinase cascade couples PKA and PKC to cAMP response element binding protein phosphorylation in area CA1 of hippocampus. J Neurosci 19: 4337-4348.[Abstract/Free Full Text]

Runyan JD and Dash PK (2004) Intra-medial prefrontal administration of SCH-23390 attenuates ERK phosphorylation and long-term memory for trace fear conditioning in rats. Neurobiol Learn Mem 82: 65-70.[CrossRef][Medline]

Schaeffer HJ and Weber MJ (1999) Mitogen-activated protein kinases: specific messages from ubiquitous messengers. Mol Cell Biol 19: 2435-2444.[Free Full Text]

Schenk U, Menna E, Kim T, Passafaro M, Chang S, De Camilli P, and Matteoli M (2005) A novel pathway for presynaptic mitogen-activated kinase activation via AMPA receptors. J Neurosci 25: 1654-1663.[Abstract/Free Full Text]

Schotte A, Janssen PF, Gommeren W, Luyten WH, Van Gompel P, De Lesage AS, Loore K, and Leysen JE (1996) Risperidone compared with new and reference antipsychotic drugs: in vitro and in vivo receptor binding. Psychopharmacology (Berl) 124: 57-73.[CrossRef][Medline]

Sgambato V, Pages C, Rogard M, Besson MJ, and Caboche J (1998a) Extracellular signal-regulated kinase (ERK) controls immediate early gene induction on corticostriatal stimulation. J Neurosci 18: 8814-8825.[Abstract/Free Full Text]

Sgambato V, Vanhoutte P, Pages C, Rogard M, Hipskind R, Besson MJ, and Caboche J (1998b) In vivo expression and regulation of Elk-1, a target of the extracellular-regulated kinase signaling pathway, in the adult rat brain. J Neurosci 18: 214-226.[Abstract/Free Full Text]

Sweatt JD (2004) Mitogen-activated protein kinases in synaptic plasticity and memory. Curr Opin Neurobiol 14: 311-317.[CrossRef][Medline]

Thomas GM and Huganir RL (2004) MAPK cascade signalling and synaptic plasticity. Nat Rev Neurosci 5: 173-183.[CrossRef][Medline]

Turalba AV, Leite-Morris KA, and Kaplan GB (2004) Antipsychotics regulate cyclic AMP-dependent protein kinase and phosphorylated cyclic AMP response element-binding protein in striatal and cortical brain regions in mice. Neurosci Lett 357: 53-57.[Medline]

Valjent E, Caboche J, and Vanhoutte P (2001) Mitogen-activated protein kinase/extracellular signal-regulated kinase induced gene regulation in brain: a molecular substrate for learning and memory? Mol Neurobiol 23: 83-99.[CrossRef][Medline]

Valjent E, Pages C, Herve D, Girault JA, and Caboche J (2004) Addictive and non-addictive drugs induce distinct and specific patterns of ERK activation in mouse brain. Eur J Neurosci 19: 1826-3186.[CrossRef][Medline]

Veeranna, Shetty KT, Takahashi M, Grant P, and Pant HC (2000) Cdk5 and MAPK are associated with complexes of cytoskeletal proteins in rat brain. Brain Res Mol Brain Res 76: 229-236.[Medline]

Weinberger DR, Egan MF, Bertolino A, Callicott JH, Mattay VS, Lipska BK, Berman KF, and Goldberg TE (2001) Prefrontal neurons and the genetics of schizophrenia. Biol Psychiatry 50: 825-844.[CrossRef][Medline]

Woodward ND, Purdon SE, Meltzer HY, and Zald DH (2005) A meta-analysis of neuropsychological change to clozapine, olanzapine, quetiapine and risperidone in schizophrenia. Int J Neuropsychopharmacol 8: 457-472.[CrossRef][Medline]

Yao H, York RD, Misra-Press A, Carr DW, and Stork PJ (1998) The cyclic adenosine monophosphate-dependent protein kinase (PKA) is required for the sustained activation of mitogen-activated kinases and gene expression by nerve growth factor. J Biol Chem 273: 8240-82477.[Abstract/Free Full Text]

York RD, Yao H, Dillon T, Ellig CL, Eckert SP, McCleskey EW, and Stork PJ (1998) Rap1 mediates sustained MAP kinase activation induced by nerve growth factor. Nature (Lond) 392: 622-626.[CrossRef][Medline]

Zhong H and Minneman KP (1999) Differential activation of mitogen-activated protein kinase pathways in PC12 cells by closely related alpha1-adrenergic receptor subtypes. J Neurochem 72: 2388-2396.[CrossRef][Medline]

This article has been cited by other articles:

				F. Fumagalli, A. Frasca, G. Racagni, and M. A. Riva Dynamic Regulation of Glutamatergic Postsynaptic Activity in Rat Prefrontal Cortex by Repeated Administration of Antipsychotic Drugs Mol. Pharmacol., May 1, 2008; 73(5): 1484 - 1490. [Abstract] [Full Text] [PDF]

				M. R. Ahmed, V. V. Gurevich, K. N. Dalby, J. L. Benovic, and E. V. Gurevich Haloperidol and Clozapine Differentially Affect the Expression of Arrestins, Receptor Kinases, and Extracellular Signal-Regulated Kinase Activation J. Pharmacol. Exp. Ther., April 1, 2008; 325(1): 276 - 283. [Abstract] [Full Text] [PDF]

				R. K. Singh, J. Shi, B. W. Zemaitaitis, and N. A. Muma Olanzapine Increases RGS7 Protein Expression via Stimulation of the Janus Tyrosine Kinase-Signal Transducer and Activator of Transcription Signaling Cascade J. Pharmacol. Exp. Ther., July 1, 2007; 322(1): 133 - 140. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) All Versions of this Article: mol.105.019828v1 69/4/1366    most recent Submit a response Alert me when this article is cited Alert me when eLetters are posted Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Fumagalli, F. Articles by Riva, M. A. Search for Related Content PubMed PubMed Citation Articles by Fumagalli, F. Articles by Riva, M. A.