Differential effects of typical and atypical antipsychotics on nerve growth factor and choline acetyltransferase expression in the cortex and nucleus basalis of rats

Canonical and Non-Canonical Antipsychotics' Dopamine-Related Mechanisms of Present and Next Generation Molecules: A Systematic Review on Translational Highlights for Treatment Response and Treatment-Resistant Schizophrenia

Schizophrenia is a severe psychiatric illness affecting almost 25 million people worldwide and is conceptualized as a disorder of synaptic plasticity and brain connectivity. Antipsychotics are the primary pharmacological treatment after more than sixty years after their introduction in therapy. Two findings hold true for all presently available antipsychotics. First, all antipsychotics occupy the dopamine D2 receptor (D2R) as an antagonist or partial agonist, even if with different affinity; second, D2R occupancy is the necessary and probably the sufficient mechanism for antipsychotic effect despite the complexity of antipsychotics' receptor profile. D2R occupancy is followed by coincident or divergent intracellular mechanisms, implying the contribution of cAMP regulation, β-arrestin recruitment, and phospholipase A activation, to quote some of the mechanisms considered canonical. However, in recent years, novel mechanisms related to dopamine function beyond or together with D2R occupancy have emerged. Among these potentially non-canonical mechanisms, the role of Na²⁺ channels at the dopamine at the presynaptic site, dopamine transporter (DAT) involvement as the main regulator of dopamine concentration at synaptic clefts, and the putative role of antipsychotics as chaperones for intracellular D2R sequestration, should be included. These mechanisms expand the fundamental role of dopamine in schizophrenia therapy and may have relevance to considering putatively new strategies for treatment-resistant schizophrenia (TRS), an extremely severe condition epidemiologically relevant and affecting almost 30% of schizophrenia patients. Here, we performed a critical evaluation of the role of antipsychotics in synaptic plasticity, focusing on their canonical and non-canonical mechanisms of action relevant to the treatment of schizophrenia and their subsequent implication for the pathophysiology and potential therapy of TRS.

Clozapine's multiple cellular mechanisms: What do we know after more than fifty years? A systematic review and critical assessment of translational mechanisms relevant for innovative strategies in treatment-resistant schizophrenia

Almost fifty years after its first introduction into clinical care, clozapine remains the only evidence-based pharmacological option for treatment-resistant schizophrenia (TRS), which affects approximately 30% of patients with schizophrenia. Despite the long-time experience with clozapine, the specific mechanism of action (MOA) responsible for its superior efficacy among antipsychotics is still elusive, both at the receptor and intracellular signaling level. This systematic review is aimed at critically assessing the role and specific relevance of clozapine's multimodal actions, dissecting those mechanisms that under a translational perspective could shed light on molecular targets worth to be considered for further innovative antipsychotic development. In vivo and in vitro preclinical findings, supported by innovative techniques and methods, together with pharmacogenomic and in vivo functional studies, point to multiple and possibly overlapping MOAs. To better explore this crucial issue, the specific affinity for 5-HT₂R, D1R, α_2c, and muscarinic receptors, the relatively low occupancy at dopamine D2R, the interaction with receptor dimers, as well as the potential confounder effects resulting in biased ligand action, and lastly, the role of the moiety responsible for lipophilic and alkaline features of clozapine are highlighted. Finally, the role of transcription and protein changes at the synaptic level, and the possibility that clozapine can directly impact synaptic architecture are addressed. Although clozapine's exact MOAs that contribute to its unique efficacy and some of its severe adverse effects have not been fully understood, relevant information can be gleaned from recent mechanistic understandings that may help design much needed additional therapeutic strategies for TRS.

Ribosomal Protein S6 Hypofunction in Postmortem Human Brain Links mTORC1-Dependent Signaling and Schizophrenia

The mechanistic target of rapamycin (also known as mammalian target of rapamycin) (mTOR)-dependent signaling pathway plays an important role in protein synthesis, cell growth, and proliferation, and has been linked to the development of the central nervous system. Recent studies suggest that mTOR signaling pathway dysfunction could be involved in the etiopathogenesis of schizophrenia. The main goal of this study was to evaluate the status of mTOR signaling pathway in postmortem prefrontal cortex (PFC) samples of subjects with schizophrenia. For this purpose, we quantified the protein expression and phosphorylation status of the mTOR downstream effector ribosomal protein S6 as well as other pathway interactors such as Akt and GSK3β. Furthermore, we quantified the status of these proteins in the brain cortex of rats chronically treated with the antipsychotics haloperidol, clozapine, or risperidone. We found a striking decrease in the expression of total S6 and in its active phosphorylated form phospho-S6 (Ser235/236) in the brain of subjects with schizophrenia compared to matched controls. The chronic treatment with the antipsychotics haloperidol and clozapine affected both the expression of GSK3β and the activation of Akt [phospho-Akt (Ser473)] in rat brain cortex, while no changes were observed in S6 and phospho-S6 (Ser235/236) protein expression with any antipsychotic treatment. These findings provide further evidence for the involvement of the mTOR-dependent signaling pathway in schizophrenia and suggest that a hypofunctional S6 may have a role in the etiopathogenesis of this disorder.

Ribosomal Protein S6 Hypofunction in Postmortem Human Brain Links mTORC1-Dependent Signaling and Schizophrenia

The mechanistic target of rapamycin (also known as mammalian target of rapamycin) (mTOR)-dependent signaling pathway plays an important role in protein synthesis, cell growth, and proliferation, and has been linked to the development of the central nervous system. Recent studies suggest that mTOR signaling pathway dysfunction could be involved in the etiopathogenesis of schizophrenia. The main goal of this study was to evaluate the status of mTOR signaling pathway in postmortem prefrontal cortex (PFC) samples of subjects with schizophrenia. For this purpose, we quantified the protein expression and phosphorylation status of the mTOR downstream effector ribosomal protein S6 as well as other pathway interactors such as Akt and GSK3β. Furthermore, we quantified the status of these proteins in the brain cortex of rats chronically treated with the antipsychotics haloperidol, clozapine, or risperidone. We found a striking decrease in the expression of total S6 and in its active phosphorylated form phospho-S6 (Ser235/236) in the brain of subjects with schizophrenia compared to matched controls. The chronic treatment with the antipsychotics haloperidol and clozapine affected both the expression of GSK3β and the activation of Akt [phospho-Akt (Ser473)] in rat brain cortex, while no changes were observed in S6 and phospho-S6 (Ser235/236) protein expression with any antipsychotic treatment. These findings provide further evidence for the involvement of the mTOR-dependent signaling pathway in schizophrenia and suggest that a hypofunctional S6 may have a role in the etiopathogenesis of this disorder.

Nerve Growth Factor Serum Levels Are Associated With Regional Gray Matter Volume Differences in Schizophrenia Patients

Numerous neuroimaging studies have revealed structural brain abnormalities in schizophrenia patients. There is emerging evidence that dysfunctional nerve growth factor (NGF) signaling may contribute to structural brain alterations found in these patients. In this pilot study, we investigated whether there was a correlation between NGF serum levels and gray matter volume (GMV) in schizophrenia patients. Further, we investigated whether there was an overlap between the correlative findings and cross-sectional GMV differences between schizophrenia patients (n = 18) and healthy controls (n = 19). Serum NGF was significantly correlated to GMV in the left prefrontal lobe, the left midcingulate cortex, and the brainstem in schizophrenia patients. However, we did not find any correlations of NGF serum levels with GMV in healthy controls. Schizophrenia patients showed smaller GMV than healthy controls in brain regions located in the bilateral limbic system, bilateral parietal lobe, bilateral insula, bilateral primary auditory cortex, left frontal lobe, and bilateral occipital regions. In a conjunction analysis, GMV in the left midcingulate cortex (MCC) appears negatively correlated to NGF serum levels in the group of schizophrenia patients and also to be reduced compared to healthy controls. These results suggest an increased vulnerability of schizophrenia patients to changes in NGF levels compared to healthy controls and support a role for NGF signaling in the pathophysiology of schizophrenia. As our pilot study is exploratory in nature, further studies enrolling larger sample sizes will be needed to further corroborate our findings and to investigate the influence of additional covariates.

Effects of the antipsychotics haloperidol, clozapine, and aripiprazole on the dendritic spine

Three types of antipsychotics, typical (e.g. haloperidol), atypical (e.g. clozapine), and dopamine partial agonist (e.g. aripiprazole), are administered for treatment of schizophrenia. These antipsychotics have different efficacy and side-effect profiles. We investigated whether aripiprazole, clozapine, and haloperidol differentially regulate the dendritic spine through the AKT-GSK-3 beta cascade. Dissociated cortical neurons from Sprague-Dawley rats were prepared and cultured for 28 days. Aripiprazole, clozapine, or haloperidol was administered to the rat cortical neurons. The levels of PSD95 protein and AKT-GSK-3 beta cascade-related proteins were investigated by Western blot. The number of spines and PSD95 puncta were investigated by immunofluorescence cell staining. Aripiprazole (1 µM or 10 µM) and clozapine (1 µM) increased the levels of PSD95 protein, the number of spines, phosphorylated Akt Thr308 and Ser473, and phosphorylated GSK-3 beta Ser9. On the other hand, haloperidol (1 µM or 10 µM) or an inappropriate concentration of clozapine (10 µM) decreased them. A GSK inhibitor also increased the levels of PSD-95 protein and caused the same morphology. Aripiprazole, clozapine, and haloperidol differentially regulate the dendritic spine, and this effect may occur through the AKT-GSK-3 beta cascade. Selection and appropriate dose of these antipsychotics may be important for the protection of dendritic spines in patients with schizophrenia.

Possible biomarkers modulating haloperidol efficacy and/or tolerability

Haloperidol (HP) is widely used in the treatment of several forms of psychosis. Despite of its efficacy, HP use is a cause of concern for the elevated risk of adverse drug reactions. adverse drug reactions risk and HP efficacy greatly vary across subjects, indicating the involvement of several factors in HP mechanism of action. The use of biomarkers that could monitor or even predict HP treatment impact would be of extreme importance. We reviewed the elements that could potentially be used as peripheral biomarkers of HP effectiveness. Although a validated biomarker still does not exist, we underlined the several potential findings (e.g., about cytokines, HP metabolites and genotypic biomarkers) which could pave the way for future research on HP biomarkers.

The endocannabinoid system and NGF are involved in the mechanism of action of resveratrol: a multi-target nutraceutical with therapeutic potential in neuropsychiatric disorders

RATIONALE

Resveratrol is a polyphenolic compound with antioxidant, anti-inflammatory, and neuroprotective effects. It has also shown antidepressant-like effects in the behavioral studies; however, its mechanism(s) of action merit further evaluation.

OBJECTIVES

The interaction between the nerve growth factor (NGF) and endocannabinoid system (eCBs) and their contribution to the antidepressant or emotional activity prompted us to evaluate their implications in the mechanism of action of resveratrol.

METHODS

After single and 4-week intraperitoneal (i.p.) once-daily injections of resveratrol (40, 80, and 100 mg/kg), amitriptyline (2.5, 5, and 10 mg/kg), or clonazepam (10, 20, and 40 mg/kg) into male Wistar rats, eCB and NGF contents were quantified in the brain regions implicated in the modulation of emotions by isotope-dilution liquid chromatography/mass spectrometry and Bio-Rad protein assay, respectively. In the case of any significant alteration of brain eCB or NGF level, the effect of pre-treatment with cannabinoid CB1 or CB2 receptor antagonist (AM251 or SR144528) was investigated.

RESULTS

Four-week treatment with resveratrol or amitriptyline resulted in a significant and sustained enhancement of NGF and eCB contents in dose-dependent and brain region-specific manner. Neither acute nor 4-week treatment with clonazepam affected brain eCB or NGF contents. Pre-treatment with AM251 (3 mg/kg), but not SR144528, prevented the enhancement of NGF protein levels. AM251 exhibited no effect by itself.

CONCLUSIONS

Resveratrol like the classical antidepressant, amitriptyline, affects brain NGF and eCB signaling under the regulatory drive of CB1 receptors.

The Effect of Antipsychotic Treatment on Cortical Gray Matter Changes in Schizophrenia: Does the Class Matter? A Meta-analysis and Meta-regression of Longitudinal Magnetic Resonance Imaging Studies

BACKGROUND

Deficits in cortical gray matter (GM) have been found in patients with schizophrenia, with evidence of progression over time. The aim of this study was to determine the role of potential moderators of such changes, in particular of the amount and type of antipsychotic medication intake.

METHODS

Longitudinal magnetic resonance imaging studies comparing changes in the volume of cortical GM over time between patients with schizophrenia and healthy control subjects published between January 1, 1983, and March 31, 2014, were analyzed. Hedges' g was calculated for each study and volume changes from baseline to follow-up were analyzed. Meta-regression statistics were applied to investigate the role of potential moderators of the effect sizes.

RESULTS

Eighteen studies involving 1155 patients with schizophrenia and 911 healthy control subjects were included. Over time, patients with schizophrenia showed a significantly higher loss of total cortical GM volume. This was related to cumulative antipsychotic intake during the interval between scans in the whole study sample. Subgroup meta-analyses of studies on patients treated with second-generation antipsychotics and first-generation antipsychotics revealed a different and contrasting moderating role of medication intake on cortical GM changes: more progressive GM loss correlated with higher mean daily antipsychotic intake in patients treated with at least one first-generation antipsychotic and less progressive GM loss with higher mean daily antipsychotic intake in patients treated only with second-generation antipsychotics.

CONCLUSIONS

These findings add useful information to the controversial debate on the brain structural effects of antipsychotic medication and may have both clinical relevance and theoretical implications.

Brain Structural Effects of Antipsychotic Treatment in Schizophrenia: A Systematic Review

The findings about the progressive brain changes in schizophrenia are controversial, and the potential confounding effect of antipsychotics on brain structure is still under debate. The goal of the current article was to review the existing longitudinal neuroimaging studies addressing the impact of antipsychotic drug treatment on brain changes in schizophrenia. A comprehensive search of PubMed was performed using combinations of key terms distributed into four blocks: "MRI", "longitudinal", "schizophrenia" and "antipsychotic". Studies were considered to be eligible for the review if they were original articles. Studies that examined only changes in brain density were excluded. A total of 41 MRI studies were identified and reviewed. Longitudinal MRI studies did not provide a consistent notion of the effects of antipsychotic treatment on the pattern of brain changes over time in schizophrenia. Overall, most of the included articles did not find a linear relationship between the degree of exposure and progressive brain changes. Further short- and longterm studies are warranted to a better understanding of the influence of antipsychotics in brain structural changes in schizophrenia and also to verify whether first and second generation antipsychotics may differentially affect brain morphometry.

Implication of NGF and endocannabinoid signaling in the mechanism of action of sesamol: a multi-target natural compound with therapeutic potential

RATIONALE

Sesamol, a natural compound with anti-inflammatory, antioxidant and neuroprotective properties, has shown promising antidepressant-like effects. However, its molecular target(s) have not been well defined, which merits further investigation.

OBJECTIVES

Based on the interaction between the neurotrophin and endocannabinoid (eCB) systems and their contribution to emotional reactivity and antidepressant action, we aimed to investigate the involvement of nerve growth factor (NGF) and eCB signalling in the mechanism of action of sesamol.

METHODS

Following acute and 4-week intraperitoneal (i.p.) administration of sesamol (40, 80 and 100 mg/kg), the classical antidepressant amitriptyline (2.5, 5 and 10 mg/kg) or the benzodiazepine flurazepam (5, 10 and 20 mg/kg), brain regional levels of NGF and eCB contents were quantified in rats by Bio-Rad protein assay and isotope-dilution liquid chromatography/mass spectrometry, respectively. In the case of any significant change, the cannabinoid CB1 and CB2 receptor antagonists (AM251 and SR144528) were administered i.p. 30 min prior to the injection of sesamol, amitriptyline or flurazepam.

RESULTS

Following the chronic treatment, sesamol, similar to amitriptyline, resulted in the sustained elevation of NGF and eCB contents in dose-dependent and brain region-specific fashion. Neither acute nor chronic treatment with flurazepam altered brain NGF or eCB contents. Pretreatment with 3 mg/kg AM251, but not SR144528, prevented the elevation of NGF protein levels. AM251 exerted no effect by itself.

CONCLUSIONS

Sesamol, similar to amitriptyline, is able to affect brain NGF and eCB signalling under the regulatory drive of the CB1 receptors.

Involvement of the neurotrophin and cannabinoid systems in the mechanisms of action of neurokinin receptor antagonists

The anxiolytic- and antidepressant-like effects of the neurokinin (NK) receptor antagonists have been shown in behavioral studies. According to the involvement of neurotrophin signaling in the mechanisms of action of psychotropic agents, we aimed to investigate whether the selective NK(1), NK(2), or NK(3) receptor antagonists (GR-205171, SR48968, and SR142801, respectively) affect nerve growth factor (NGF) contents in the brain regions involved in the modulation of emotions. To gain a mechanistical insight into the process by which the NK antagonists regulate brain NGF levels, we evaluated the role of the cannabinoid system which is linked to depression and/or antidepressant effects and appears to interact with neurotrophin signaling. According to the results, single injection of the NK receptor antagonists (3, 5, and 10mg/kg, i.p.) into gerbils did not alter NGF or endocannabinoid (eCB) levels quantified by Bio-Rad protein assay and isotope-dilution liquid chromatography/mass spectrometry, respectively. Three-week administration of 10mg/kg NK antagonists significantly elevated both NGF and eCB levels in brain-region specific fashion. Pre-application of the CB(1) receptor neutral antagonist AM4113 (5.6mg/kg) prevented the elevation of NGF or eCB induced by the NK antagonists. AM4113 showed no effect by itself. We conclude that the cannabinoid system is implicated in the mechanisms of action of NK receptor antagonists including the upregulation of brain NGF levels.

The cannabinergic system is implicated in the upregulation of central NGF protein by psychotropic drugs

RATIONALE

Studies on the regulation of nerve growth factor (NGF) levels by psychotropics are limited in scope and the mechanism(s) remain elusive which merit further elucidation.

OBJECTIVES

We aimed to perform a more comprehensive investigation on the possible effects of pharmacologically heterogeneous groups of psychotropic drugs on NGF contents in the brain regions involved in the modulation of emotions. As a mechanistic approach, we looked at the role of the cannabinergic system which is linked to depression and/or antidepressant effect and appears to interact with neurotrophin signaling.

METHODS

Following psychotropic treatment, NGF or endocannabinoid (eCB) contents were quantified by Bio-Rad protein assay and isotope-dilution liquid chromatography/mass spectrometry, respectively. In case of any significant change, the effects of pretreatment with the CB(1) receptor neutral antagonist AM4113 were investigated.

RESULTS

Single injection of nortriptyline, isocarboxazid, citalopram, diazepam, risperidone (2.5, 5, and 10 mg/kg, each), and fluphenazine (0.25, 0.5, and 1 mg/kg) into rats did not alter NGF or eCB contents. Following 4-week treatment, all drugs except diazepam elevated NGF or eCB levels in dose-dependent and brain region-specific fashion. Pretreatment with the highest dose of AM4113 (5.6 mg/kg) prevented psychotropic-induced NGF or eCB elevation. AM4113 had no effect by itself.

CONCLUSIONS

The cannabinergic system is implicated in the mechanisms of action of certain psychotropic drugs including the upregulation of brain NGF levels. This provides a better understanding of the pathophysiological mechanisms underlying neuropsychiatric disorders, leading to novel drug design.

Differential effects of antipsychotic and antidepressant drugs on neurogenic regions in rats

Increased neurogenesis in the hippocampus and subventricular zone (SVZ) of the brain of animals has been demonstrated following administration of several psychotropic medications. Such changes are thought to regenerate tissues and contribute to the beneficial effects of the medications. This study sought to determine if another neurogenic tissue, the peripheral olfactory epithelium (OE), might also exhibit changes after treatment with psychotropic medications. Young adult male rats were treated with risperidone and paliperidone, atypical antipsychotic medications; fluoxetine, a selective serotonin reuptake inhibitor (SSRI) antidepressant; and diluent control for 28days via drinking water. Bromodeoxyuridine (BrdU) was injected to label dividing cells and positive cells were quantified in the OE, cortical SVZ, and dentate gyrus (DG) of the hippocampus. In the first of two studies, paliperidone and risperidone treatment (at 1mg/kg/day) resulted in increased numbers over controls of BrdU positive cells in the OE. In the second study, examining OE, SVZ and DG in the same animal, paliperidone, but not risperidone or fluoxetine (0.6 mg/kg/day) resulted in increased cells in the OE and posterior SVZ. However, fluoxetine, but not paliperidone or risperidone treatment increased BrdU positive cells in the DG. These results show that psychotropic drug-induced cell proliferation occurs in the OE and parallels changes in the SVZ but not DG. Thus, the peripheral OE can serve as a proxy for certain psychotropic drug-induced actions on SVZ brain cell proliferation. This olfactory model can be employed in human research as a method to explore the neurogenesis effects of various pharmacologic treatments of neuropsychiatric disorders.

Antipsychotic drugs: comparison in animal models of efficacy, neurotransmitter regulation, and neuroprotection

Various lines of evidence indicate the presence of progressive pathophysiological processes occurring within the brains of patients with schizophrenia. By modulating chemical neurotransmission, antipsychotic drugs may influence a variety of functions regulating neuronal resilience and viability and have the potential for neuroprotection. This article reviews the current literature describing preclinical and clinical studies that evaluate the efficacy of antipsychotic drugs, their mechanism of action and the potential of first- and second-generation antipsychotic drugs to exert effects on cellular processes that may be neuroprotective in schizophrenia. The evidence to date suggests that although all antipsychotic drugs have the ability to reduce psychotic symptoms via D(2) receptor antagonism, some antipsychotics may differ in other pharmacological properties and their capacities to mitigate and possibly reverse cellular processes that may underlie the pathophysiology of schizophrenia.

Effect of antipsychotic drugs on brain morphometry. A randomized controlled one-year follow-up study of haloperidol, risperidone and olanzapine

BACKGROUND

The effect of antipsychotic drugs on brain morphology is under debate. Here we investigate the effects of risperidone, olanzapine and low doses of haloperidol on cortical and subcortical morphometry in first episode drug naïve patients with non-affective psychosis.

METHODS

Morphological variables were measured in three treatment groups (haloperidol=18; risperidone=16; olanzapine=18) and in healthy subjects (N=38) at baseline and after one year. The relationship between brain morphometric changes and changes in clinical scores was also assessed.

RESULTS

At one year, the three antipsychotics had had an equal effect on the gray matter cortical structure, overall and lobes (all p's>0.121.). A significant time-by-group interaction was found in lateral ventricle volume (F2,47=5.65; p=0.006). Post-hoc comparisons revealed a significant increase in lateral ventricles in patients treated with risperidone (p=0.009). Patients exposed to atypicals (olanzapine and risperidone) exhibited a decrease in caudate nucleus volume (p=0.001). In general, brain changes did not account in any significant manner for clinical changes over time in any treatment group.

CONCLUSIONS

We conclude that low doses of haloperidol, risperidone and olanzapine seem to have an equal effect on the gray matter cortical structure after 1 year of treatment. In contrast to typical antipsychotics, atypicals have differential effects on lateral ventricle and caudate nucleus volumes.

Erythropoietin prevents haloperidol treatment-induced neuronal apoptosis through regulation of BDNF

Functional alterations in the neurotrophin, brain-derived neurotrophic factor (BDNF) have recently been implicated in the pathophysiology of schizophrenia. Furthermore, animal studies have indicated that several antipsychotic drugs have time-dependent (and differential) effects on BDNF levels in the brain. For example, our previous studies in rats indicated that chronic treatment with the conventional antipsychotic, haloperidol, was associated with decreases in BDNF (and other neurotrophins) in the brain as well as deficits in cognitive function (an especially important consideration for the therapeutics of schizophrenia). Additional studies indicate that haloperidol has other deleterious effects on the brain (eg increased apoptosis). Despite such limitations, haloperidol remains one of the more commonly prescribed antipsychotic agents worldwide due to its efficacy for the positive symptoms of schizophrenia and its low cost. Interestingly, the hematopoietic hormone, erythropoietin, in its recombinant human form rhEPO has been reported to increase the expression of BDNF in neuronal tissues and to have neuroprotective effects. Such observations provided the impetus for us to investigate in the present study whether co-treatment of rhEPO with haloperidol could sustain the normal levels of BDNF in vivo in rats and in vitro in cortical neuronal cultures and further, whether BDNF could prevent haloperidol-induced apoptosis through the regulation of key apoptotic/antiapoptotic markers. The results indicated that rhEPO prevented the haloperidol-induced reduction in BDNF in both in vivo and in vitro experimental conditions. The sustained levels of BDNF in rats with rhEPO prevented the haloperidol-induced increase in caspase-3 (p<0.05) and decrease in Bcl-xl (p<0.01) protein levels. Similarly, in vitro experiments showed that rhEPO prevented (p<0.001) the haloperidol-induced neuronal cell death as well as the decrease in Bcl-xl levels (p<0.01). These findings may have significant implications for the development of neuroprotective strategies to improve clinical outcomes when antipsychotic drugs are used chronically.

Brain-derived neurotropic factor/TrkB signaling in the pathogenesis and novel pharmacotherapy of schizophrenia

The role of neurotropins, predominantly brain-derived neurotropic factor (BDNF), has been implicated in the pathophysiology as well as treatment outcome of schizophrenia. Both human and rodent studies indicate that the beneficial effects of antipsychotic drugs are mediated, at least in part, through BDNF and its receptor, TrkB. This review will discuss the available data on the levels of BDNF and TrkB in subjects with schizophrenia and in animals with and without conventional antipsychotics. The data concerning the impact of the antipsychotic drugs on BDNF/TrkB signaling will also be discussed. More importantly, this review will provide future perspective on BDNF/TrkB signaling as a novel molecular target to correct the pathogenesis and improve the long-term clinical outcome by treatments with conventional and adjunctive drugs.

Long-term antipsychotic treatments and crossover studies in rats: differential effects of typical and atypical agents on the expression of antioxidant enzymes and membrane lipid peroxidation in rat brain

Short-term (<45 days) treatment studies in rats have reported increased oxidative stress and oxidative (i.e., oxygen free radical-mediated) neural cell injury with typical antipsychotics such as haloperidol, but not with the atypicals such as clozapine, olanzapine or risperidone. However, now these and several other atypical antipsychotics that differ in their neurotransmitter receptor affinity profiles are being used for a long-term treatment of schizophrenia. Therefore, understanding of their long-term treatment effects on the expression of antioxidant enzymes and oxidative neural cell injury in rats may be important to explain the possible differential mechanisms underlying their long-term clinical and side effects profiles. The effect of 90 and 180 day exposure to haloperidol (HAL, 2mg/kg/day), a representative typical antipsychotic was compared to exposure to chlorpromazine (CPZ, 10mg/kg/day), ziprasidone (ZIP, 12mg/kg/day), risperidone (RISP, 2.5mg/kg/day), clozapine (CLOZ, 20mg/kg/day) or olanzapine (OLZ, 10mg/kg/day) on the expression of antioxidant defense enzymes and levels of lipid peroxidation in the rat brain. The drug-induced effects on various antioxidant defense enzymes; manganese-superoxide dismutase (MnSOD), copper-zinc superoxide dismutase (CuZnSOD) and catalase (CAT) were assessed by determination of their enzymatic activity and protein content. Immunohistochemical analysis was also carried out to assess the cellular levels of MnSOD and CuZnSOD and cellular morphology. The oxidative membrane damage was assessed by determination of levels of the lipid peroxidation product, hydroxyalkanals (HAEs) in the rat brain. Both 90 and 180 days of HAL treatment very significantly decreased the levels of MnSOD (50%) and CuZnSOD (80%) and increased the levels of HAEs compared to vehicle treatment. Smaller reduction was found in CAT (25%) and no change in the glutathione peroxidase (GSHPx). The levels of enzymatic activity correlated generally well with the levels of enzyme protein indicating that the changes were in the expression of net protein. Though atypical antipsychotics like ZIP, RISP and OLZ did not show any change in the HAEs levels up to 90 days, further treatment up to 180 days resulted in significantly increased levels of HAEs in CPZ, ZIP and RISP, but not in OLZ treated rats. Post-treatment with several atypical antipsychotics (OLZ=CLOZ>RISP) for 90 days after 90 day of HAL treatment significantly restored the HAL-induced loss in MnSOD and CuZnSOD activities and increase in lipid peroxidation products as well as cellular morphology. These data may be very helpful in planning long-term use as well as switch over of these antipsychotics for the management of schizophrenia.

The case for long-acting antipsychotic agents in the post-CATIE era

OBJECTIVE

Long-acting antipsychotic agents were developed to promote treatment compliance in patients requiring maintenance treatment for schizophrenia.

METHOD

An analysis of the impact of non-compliance on treatment outcomes in schizophrenia and the advantages and disadvantages of long-acting antipsychotics.

RESULTS

Partial or total non-compliance with oral antipsychotics remains widespread and is associated with significant increases in the risk of relapse, rehospitalization, progressive brain tissue loss and further functional deterioration. Long-acting agents have the potential to address issues of all-cause discontinuation and poor compliance. The development of the first long-acting atypical antipsychotic, which appears to be effective and well tolerated, should further improve the long-term management of schizophrenia.

CONCLUSION

Long-acting agents represent a valuable tool for the management of schizophrenia and merit wider use, especially in light of emerging literature regarding the neuroprotective advantages of atypical antipsychotics over conventional agents in terms of regenerating brain tissue during maintenance therapy.

The effects of adulthood olanzapine treatment on cognitive performance and neurotrophic factor content in male and female rats neonatally treated with quinpirole

Male and female Sprague-Dawley rats were administered quinpirole (1 mg/kg, i.p.) or saline once daily from postnatal day (P)1 to P21. This drug treatment has been shown to produce long-term priming of the D2 receptor. Beginning on P62, rats were administered the atypical antipsychotic olanzapine (2.5 mg/kg) or saline twice daily (i.p.) for 28 days. One day after olanzapine treatment ceased, rats were tested on the place and match-to-place versions of the Morris water maze (MWM) for seven consecutive days. Dopamine D2 receptor priming was verified through a yawning behavioural test, a D2 receptor-mediated event, before olanzapine was administered as well as after olanzapine treatment and behavioural testing were complete. Results showed that neonatal quinpirole treatment induced D2 priming that was eliminated by olanzapine treatment. On the MWM place version, D2-primed rats demonstrated a significant impairment that was eliminated by olanzapine treatment, but olanzapine treatment to animals neonatally treated with saline produced a significant deficit on the place version of the MWM. There were no significant deficits on the match-to-place version. Brain tissue analyses revealed that neonatal quinpirole treatment produced a significant decrease in hippocampal NGF, BDNF and ChAT that was eliminated by olanzapine treatment. Neonatal quinpirole treatment produced a significant decrease in BDNF and ChAT in the frontal cortex that was unaffected by olanzapine treatment. These results show that olanzapine eliminates D2 receptor priming and cognitive impairment and also alleviates decreases in neurotrophins and acetylcholinergic markers produced by D2 priming in the hippocampus.

Differential effects of haloperidol and olanzapine on levels of vascular endothelial growth factor and angiogenesis in rat hippocampus

Compared to first-generation antipsychotics (FGAs) such as haloperidol, second-generation antipsychotics (SGAs) such as olanzapine are found superior to improve cognitive performance and reduce negative symptoms with no extrapyramidal symptoms (EPS). These clinical effects of SGAs have been reported to be associated with the most replicated phenomenon, favorable changes in brain regional blood flow and volume. The changes in brain regional blood flow are shown to parallel changes in angiogenesis, which is primarily mediated by vascular endothelial growth factor (VEGF) through its receptor, Flk-1, on endothelial cells. Therefore, we studied the differential effects of time-dependent treatment (14 and 45 days) with haloperidol and olanzapine (2 and 10 mg/kg/day, respectively, in drinking water) on hippocampal levels of VEGF, its receptor Flk-1, and angiogenesis in adult rat. The levels of VEGF were determined by both Western blot analysis and ELISA, and Flk-1 levels were determined by Western blot analysis. Immunohistochemical analysis of rat endothelial cell antigen-1 (RECA-1) and laminin were used to evaluate the changes in angiogenesis. After 14 days of treatment with both haloperidol and olanzapine, the levels of VEGF and angiogenesis were significantly increased (p<0.001 vs vehicle for both), but 45 days of treatment with haloperidol reduced their levels back to levels in vehicle-treated rats. However, olanzapine treatment further increased VEGF levels (p<0.05 vs levels after 14 days of treatment). Changes in the levels of Flk-1 paralleled the changes in VEGF levels. Thus, the data indicate that haloperidol and olanzapine have distinct time-dependent patterns of regulation of VEGF and angiogenesis. These changes probably provide a new molecular mechanism to better explain their differential effects on the patterns of regional blood flow and associated changes in regional volume/neuroplasticity and psychopathology.

Differential effects of haloperidol and olanzapine on the expression of erythropoietin and its receptor in rat hippocampus and striatum

Compared with first-generation antipsychotics (FGAs), second-generation antipsychotics (SGAs) seem to be neuroprotective and trigger neuroplasticity. Because neuroplasticity is regulated by a variety of neurotrophic factors we studied differential effects of haloperidol (HAL, a FGA) and olanzapine (OLZ, a SGA) on temporal expression of erythropoietin (EPO), a potent neuroprotective factor and its receptor (EPOr) in rat brain. Rats (8-10/group) were treated with HAL or OLZ for 14 days (HAL-14 or OLZ-14) or 45 days (HAL-45 or OLZ-45). Animals were killed by decapitation or by perfusion to collect brains for immunoblotting and immunohistochemical analysis respectively. In hippocampus, the levels of both EPO and EPOr were significantly increased in HAL-14 (p < 0.001) and OLZ-14 (p < 0.001) groups. Their levels decreased in HAL-45 compared with levels in HAL-14 (EPO, p < 0.001; EPOr, p < 0.05), whereas the levels were further increased (EPO, p < 0.05) in OLZ-45 compared with OLZ-14. In striatum, the levels of both EPO and EPOr were unchanged in HAL-14 and EPO levels significantly decreased in HAL-45 (p < 0.05), whereas their levels were significantly increased in OLZ-14 and OLZ-45 compared with the vehicle-treated control (p < 0.001). Both EPO and EPOr were primarily expressed by neurons and endothelial cells. These data suggest that SGAs such as OLZ may have neuroprotective effects through expression of EPO that may be clinically relevant for long-term safe and beneficial management of psychotic patients.

Neuroprotective agents in schizophrenia and affective disorders

With the exception of dementia, the use of neuroprotective agents in psychiatric disorders is not yet well established. However, recent data from brain imaging studies and clinical trials support the view that neurodegenerative mechanisms may play a role in the pathophysiology of schizophrenia and affective disorders. Further evidence for the use of neuroprotective agents can be drawn from the findings that second-generation antipsychotics, mood stabilizers and antidepressants have been shown to have neuroprotective effects in vitro and in vivo. Neuroprotective agents as add-on therapies (e.g., modafinil, erythropoietin, glycine, D-serine, memantine and celecoxib) are currently being evaluated in schizophrenia and related disorders. This paper reviews the current options for neuroprotective treatment approaches focusing on schizophrenia and affective disorders.

Neurochemical effects of olanzapine in first-hospitalization manic adolescents: a proton magnetic resonance spectroscopy study

We used proton magnetic resonance spectroscopy (1H MRS) to compare the in vivo effects of olanzapine on prefrontal N-acetyl-aspartate (NAA) levels in treatment remitters and nonremitters. Secondary aims of this study were to identify neurochemical predictors of successful olanzapine treatment and other neurochemical effects of olanzapine. In all, 20 adolescents admitted for their first hospitalization for bipolar disorder, type I, manic or mixed and 10 demographically matched healthy subjects were recruited. Manic adolescents were treated with olanzapine monotherapy and scanned at three time points (N = 19). Medial and left and right lateral ventral prefrontal NAA, choline, creatine/phosphocreatine, myo-inositol, and glutamate/glutamine were measured at baseline, prior to receiving medication, and on days 7 and 28 of treatment. Healthy subjects did not receive medication but underwent 1H MRS scans at the same time points to assess for normal variability in metabolites over time. Although there was no overall increase in NAA in manic adolescents following 28 days of treatment with olanzapine, olanzapine remitters (N = 11, 58%) exhibited a greater increase in medial ventral prefrontal NAA compared with nonremitters (N = 8, 42%, p = 0.006). Specifically, from baseline to end point, NAA levels decreased in nonremitters (p = 0.03) and increased in remitters (p = 0.05). Manic adolescents treated with olanzapine had an increase from baseline to day 7 in medial (p = 0.002) and right lateral (p = 0.02) ventral prefrontal choline. Baseline medial ventral prefrontal choline was greater in olanzapine remitters than in nonremitters (p = 0.001). Successful treatment of mania with olanzapine may lead to increased ventral prefrontal neuronal viability and/or function as compared to unsuccessful treatment with olanzapine. Additionally, olanzapine-induced increases in choline may lead to alteration of abnormalities in cell membrane metabolism or second messenger pathways that are thought to be involved in the pathophysiology of bipolar disorder.

Time-Dependent Effects of Haloperidol and Ziprasidone on Nerve Growth Factor, Cholinergic Neurons, and Spatial Learning in Rats

In this rodent study, we evaluated the effects of different time periods (7, 14, 45, and 90 days) of oral treatment with haloperidol (HAL; 2.0 mg/kg/day) or ziprasidone (ZIP; 12.0 mg/kg/day) on nerve growth factor (NGF) and choline acetyltransferase (ChAT) levels in the hippocampus, and we subsequently assessed water maze task performance, prepulse inhibition (PPI) of the auditory gating response, and several NGF-related proteins and cholinergic markers after 90 days of treatment. Seven and 14 days of treatment with either HAL or ZIP resulted in a notable increase in NGF and ChAT immunoreactivity in the dentate gyrus (DG), CA1, and CA3 areas of the hippocampus. After 45 days, NGF and ChAT immunoreactivity had abated to control levels in ZIP-treated animals, but it was markedly reduced in HAL-treated subjects. After 90 days of treatment, NGF and ChAT levels were substantially lower than controls in both antipsychotic groups. Furthermore, after 90 days of treatment and a drug-free washout period, water maze performance (but not PPI) was impaired in both antipsychotic groups, although the decrement was greater in the HAL group. Several NGF-related and cholinergic proteins were diminished in the brains of subjects treated with either neuroleptic as well. These data support the premise that, although ZIP (given chronically) seems somewhat superior to HAL due to less pronounced behavioral effects and a more delayed appearance of neurochemical deficits, both antipsychotics produce time-dependent deleterious effects on NGF, cholinergic markers (i.e., important neurobiological substrates of memory), and cognitive function.

Differential effects of long-term treatment with typical and atypical antipsychotics on NGF and BDNF levels in rat striatum and hippocampus

The results of mostly short-term treatment studies in human patients and animals suggest that second-generation antipsychotics (SGAs) such as risperidone (RISP) and olanzapine (OLZ) compared to first-generation antipsychotics (FGAs) such as haloperidol (HAL) and chlorpromazine (CPZ) have neuroprotective effects. The animal studies indicate that these effects are probably mediated through increased expression of neurotrophic factors such as nerve growth factor (NGF) and brain derived neurotrophic factor (BDNF). However, since antipsychotics are commonly used for very long-term treatment periods, particularly in schizophrenic patients, it is important to measure the effects of chronic administration of antipsychotic drugs on the aforementioned growth factors. This study determined the effects of 90- and 180-day treatments with two FGAs, HAL and CPZ, and two SGAs, RISP and OLZ, on the levels of NGF and BDNF protein in hippocampus and striatum of rat. Furthermore, since a preliminary study showed that 90-day treatment of HAL caused significant reductions in the expression of both NGF and BDNF the HAL-treated animals were then switched to SGAs for the next 90 days to assess the potential for restoration of trophic factor levels. After the 90-day treatment, NGF levels in the hippocampus were reduced by 60-70% with HAL or CPZ, and by only 25-30% with RISP or OLZ compared to levels with vehicle only. After the 180-day treatment, NGF levels were further reduced with HAL, RISP, and OLZ, but not with CPZ. The magnitude of the NGF decreases in the striatum was larger (70-90%) with all the antipsychotics compared to the hippocampus. However, the pattern of BDNF changes in the hippocampus differed significantly from the striatum after 90- or 180-day treatment with the antipsychotics. In hippocampus, compared to controls, BDNF levels remained unchanged with OLZ both after 90 and 180 days of treatment. Whereas, larger decreases in BDNF levels were observed with HAL or CPZ and intermediate decreases were observed with RISP after 90 days of treatment that continued to decline up to 180 days. Furthermore, switching HAL animals after 90 days of treatment to either RISP or OLZ for the next 90 days significantly restored levels of both NGF and BDNF in both the brain regions. These data indicate that SGAs compared to FGAs induce less deleterious effects on neurotrophic factor levels in the brain and may also offer ability to reverse the more pronounced negative effects of FGAs as well. These data may have significant clinical implications for long-term antipsychotic selection as well as the common practice of antipsychotic switchover.