Effect of chronic haloperidol treatment on synaptic protein mRNAs in the rat brain

Exercise prevents downregulation of hippocampal presynaptic proteins following olanzapine-elicited metabolic dysregulation in rats: Distinct roles of inhibitory and excitatory terminals

Schizophrenia patients treated with olanzapine, or other second-generation antipsychotics, frequently develop metabolic side-effects, such as glucose intolerance and increased adiposity. We previously observed that modeling these adverse effects in rodents also resulted in hippocampal shrinkage. Here, we investigated the impact of olanzapine treatment, and the beneficial influence of routine exercise, on the neurosecretion machinery of the hippocampus. Immunodensities and interactions of three soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins (syntaxin-1, synaptosome-associated protein of 25kDa (SNAP-25) and vesicle-associated membrane protein (VAMP)), synaptotagmin and complexins-1/2 were quantified in the hippocampus of sedentary and exercising rats exposed over 9weeks to vehicle (n=28) or olanzapine (10mg/kg/day, n=28). In addition, brain sections from subgroups of sedentary animals (n=8) were co-immunolabeled with antibodies against vesicular GABA (VGAT) and glutamate (VGLUT1) transporters, along with syntaxin-1, and examined by confocal microscopy to detect selective olanzapine effects within inhibitory or excitatory terminals. Following olanzapine treatment, sedentary, but not exercising rats showed downregulated (33-50%) hippocampal densities of SNARE proteins and synaptotagmin, without altering complexin levels. Strikingly, these effects had no consequences on the amount of SNARE protein-protein interactions. Lower immunodensity of presynaptic proteins was associated with reduced CA1 volume and glucose intolerance. Syntaxin-1 depletion appeared more prominent in VGAT-positive terminals within the dentate gyrus, and in non-VGAT/VGLUT1-overlapping areas of CA3. The present findings suggest that chronic exposure to olanzapine may alter hippocampal connectivity, especially in inhibitory terminals within the dentate gyrus, and along the mossy fibers of CA3. Together with previous studies, we propose that exercise-based therapies might be beneficial for patients being treated with olanzapine.

Differential effects of antipsychotics on hippocampal presynaptic protein expressions and recognition memory in a schizophrenia model in mice

We compared the effects of subchronic clozapine and haloperidol administration on the expression of SNAP-25 and synaptophysin in an animal model of schizophrenia based on the glutamatergic hypothesis. Mice were first treated with a non-competitive NMDA antagonist MK-801 (0.3 mg/kg/day) or saline for 5 days, and then clozapine (5 mg/kg/day), haloperidol (1 mg/kg/day) or saline was administered for two weeks. The locomotion test, as a behavioral model of the positive symptoms of schizophrenia, was applied after MK-801/saline administration on day 6 for acute effects and after antipsychotic/saline administration on day 19 for enduring effects on mice activity. Memory function was assessed by the Novel Object Recognition (NOR) test, one day after the last day of antipsychotic/saline administration (day 20). Western Blotting technique was used to determine SNAP-25 and synaptophysin expressions in the hippocampus and frontal cortex. Both antipsychotics reversed the enhanced locomotion effects of MK-801. MK-801 and haloperidol decreased recognition memory performance. On the other hand, clozapine did not compromise memory. It also did not reverse the negative effects of MK-801 on memory performance. MK-801 did not change SNAP-25 and synaptophysin expressions in the hippocampus and frontal cortex. Clozapine increased hippocampal SNAP-25, decreased hippocampal synaptophysin expression, whereas frontal SNAP-25 and synaptophysin expressions remained unchanged. Haloperidol had no effects on levels of SNAP-25 and synaptophysin in the frontal cortex and hippocampus. These findings support the idea that the differential effects of clozapine might be related to its plastic effects and synaptic reorganization of the hippocampus.

Use of biotinylated ubiquitin for analysis of rat brain mitochondrial proteome and interactome

Applicability of in vitro biotinylated ubiquitin for evaluation of endogenous ubiquitin conjugation and analysis of ubiquitin-associated protein-protein interactions has been investigated. Incubation of rat brain mitochondria with biotinylated ubiquitin followed by affinity chromatography on avidin-agarose, intensive washing, tryptic digestion of proteins bound to the affinity sorbent and their mass spectrometry analysis resulted in reliable identification of 50 proteins belonging to mitochondrial and extramitochondrial compartments. Since all these proteins were bound to avidin-agarose only after preincubation of the mitochondrial fraction with biotinylated ubiquitin, they could therefore be referred to as specifically bound proteins. A search for specific ubiquitination signature masses revealed several extramitochondrial and intramitochondrial ubiquitinated proteins representing about 20% of total number of proteins bound to avidin-agarose. The interactome analysis suggests that the identified non-ubiquitinated proteins obviously form tight complexes either with ubiquitinated proteins or with their partners and/or mitochondrial membrane components. Results of the present study demonstrate that the use of biotinylated ubiquitin may be considered as the method of choice for in vitro evaluation of endogenous ubiquitin-conjugating machinery in particular subcellular organelles and changes in ubiquitin/organelle associated interactomes. This may be useful for evaluation of changes in interactomes induced by protein ubiquitination under norm and various brain pathologies.

Altered neuronal markers following treatment with mood stabilizer and antipsychotic drugs indicate an increased likelihood of neurotransmitter release

Objective

Given the ability of mood stabilizers and antipsychotics to promote cell proliferation, we wanted to determine the effects of these drugs on neuronal markers previously reported to be altered in subjects with psychiatric disorders.

Methods

Male Sprauge-Dawley rats were treated with vehicle (ethanol), lithium (25.5 mg per day), haloperidol (0.1 mg/kg), olanzapine (1.0 mg/kg) or a combination of lithium and either of the antipsychotic drugs for 28 days. Levels of cortical synaptic (synaptosomal associated protein-25, synaptophysin, vesicle associated protein and syntaxin) and structural (neural cell adhesion molecule and alpha-synuclein) proteins were determined in each treatment group using Western blots.

Results

Compared to the vehicle treated group; animals treated with haloperidol had greater levels of synaptosomal associated protein-25 (p<0.01) and neural cell adhesion molecule (p<0.05), those treated with olanzapine had greater levels of synaptophysin (p<0.01) and syntaxin (p<0.01). Treatment with lithium alone did not affect the levels of any of the proteins. Combining lithium and haloperidol resulted in greater levels of synaptophysin (p<0.01), synaptosomal associated protein-25 (p<0.01) and neural cell adhesion molecule (p<0.01). The combination of lithium and olanzapine produced greater levels of synaptophysin (p<0.01) and alpha-synuclein (p<0.05).

Conclusion

Lithium alone had no effect on the neuronal markers. However, haloperidol and olanzapine affected different presynaptic markers. Combining lithium with olanzapine additionally increased alpha-synuclein. These drug effects need to be taken into account by future studies examining presynaptic and neuronal markers in tissue from subjects with psychiatric disorders.

Associations of SNAP-25 polymorphisms with cognitive dysfunctions in Caucasian patients with schizophrenia during a brief trail of treatment with atypical antipsychotics

The synaptosomal-associated protein of 25 kDa (SNAP-25) is part of the soluble N-ethylmaleimide-sensitive fusion protein (NSF) attachment receptor (SNARE), which mediates synaptic neurotransmission. In earlier studies a possible involvement of this protein in schizophrenia has been shown. As neurocognitive impairment is a core feature in the pathology of schizophrenia and considered to be a putative endophenotype according to genetic studies we investigated the influences of different SNAP-25 polymorphisms on neuropsychological test results before and during treatment with atypical antipsychotics. A total of 104 schizophrenic patients treated with atypical antipsychotics were genotyped for three different polymorphisms of the SNAP-25 gene (MnlI, TaiI and DdeI in the 3'-UTR). Cognitive function was assessed at baseline, week 4 or 6 and week 8 or 12. Results of individual neuropsychological tests were assigned to six cognitive domains (reaction time and quality; executive function; working, verbal and visual memory) and a general cognitive index. The MnlI and TaiI polymorphisms showed no associations to deficits on neuropsychological test results. In contrast, we observed a significant relation between the DdeI polymorphism of the SNAP-25 gene and cognitive dysfunctions. Homozygote T/T allele carriers of the DdeI polymorphism showed significant better neuropsychological test results in cognitive domains verbal memory and executive functions than those with the combined T/C and C/C genotypes (P < 0.01) at all three time points, but no differences in response to treatment with atypical antipsychotics. Additionally, TT carriers exhibited significantly better results in a general cognitive index (P < 0.05). As we observed an association between the DdeI polymorphism of the SNAP-25 gene and cognitive dysfunctions of schizophrenic patients our finding suggests that the SNAP-25 gene could play a role in the pathophysiology of neurocognitive dysfunctions in schizophrenia but is not predictive for treatment response with atypical antipsychotics.

Dopamine acting through D2 receptors modulates the expression of PSA-NCAM, a molecule related to neuronal structural plasticity, in the medial prefrontal cortex of adult rats

A "neuroplastic" hypothesis proposes that changes in neuronal structural plasticity may underlie the aetiology of depression and the action of antidepressants. The medial prefrontal cortex (mPFC) is affected by this disorder and shows an intense expression of the polysialylated form of the neural cell adhesion molecule (PSA-NCAM), a plasticity-associated molecule, which is expressed mainly in interneurons. The monoamines serotonin, dopamine and noradrenaline are the principal targets of antidepressant action. Pharmacological manipulation of serotonin levels regulates synaptophysin and PSA-NCAM expression in the adult mPFC. However, the involvement of structural plasticity on the antidepressant effects of dopamine has not been well explored yet. Using immunohistochemistry, we have studied the relationship between dopaminergic fibers and PSA-NCAM expressing neurons in the mPFC and the expression of D2 receptors. In order to evaluate the effects of dopamine in neuronal structural plasticity and on inhibitory neurotransmission, we have analyzed the expression of synaptophysin, PSA-NCAM and GAD67 in the mPFC after cortical dopamine depletion with 6-OHDA and after chronic treatments with the D2 receptor antagonist haloperidol or the D2 receptor agonist PPHT. Many dopaminergic fibers were observed in close apposition to PSA-NCAM expressing neurons and 76% of these cells co-expressed D2 receptor. Both haloperidol treatment and 6-OHDA injection reduced significantly PSA-NCAM, synaptophysin and GAD67 expression in the mPFC. Conversely, PPHT treatment increased the expression of these molecules. Our results give support to the "neuroplastic" hypothesis of depression, suggesting that dopamine acting on D2 receptors may modulate neuronal structural plasticity and inhibitory neurotransmission through changes in PSA-NCAM expression.

GLT-1 down-regulation induced by clozapine in rat frontal cortex is associated with synaptophysin up-regulation

In rat frontal cortex, extracellular levels of glutamate are raised by the anti-psychotic drug clozapine. We have recently shown that a significant reduction in the levels of the glutamate transporter GLT-1 may be one of the mechanisms responsible for this elevation. Here we studied whether GLT-1 down-regulation induced by chronic clozapine treatment is associated with changes in the expression of synaptophysin, synaptosome-associated protein of 25 kDa (SNAP-25) and vesicular glutamate transporter 1 (VGLUT1), three major presynaptic proteins involved in neurotransmitter release. Quantitative high-resolution confocal microscopy studies in vivo showed that GLT-1 down-regulation is closely associated with a significant increase in synaptophysin, but not SNAP-25 and VGLUT1, expression. This was confirmed in vitro studies, and in western blotting studies of synaptophysin, SNAP-25 and VGLUT1. In addition, our results show that, following clozapine treatment, synaptophysin expression increases in the very cortical regions in which GLT-1 expression is down-regulated. These findings suggest that part of the effects of clozapine may be exerted via an action on the presynaptic machinery involved in neurotransmitter release.

Differential expression of striatal synaptotagmin mRNA isoforms in hemiparkinsonian rats

Synaptotagmins (Syts) constitute a multi-gene family of 15 putative membrane trafficking proteins. The expression of some of the Syts in the brain might be dopaminergically controlled and thus affected by dopamine depletion in Parkinson's disease. We used hemiparkinsonian rats to investigate the effects of chronic striatal dopamine depletion and the acute effects of antiparkinsonic drug L-DOPA or D1 agonist (+/-)-6-chloro-7,8-dihydroxy-3-allyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrobromide (SKF82958) on the levels of striatal Syt I, II, IV, VI, VII, X, XI mRNA isoforms. On the 6-hydroxydopamine (6-OHDA)-lesioned side we observed a nearly total loss of tyrosine hydroxylase (TH), synaptotagmin I, Syt IV, Syt VII and Syt XI mRNA levels in the substantia nigra compacta (SNc). In dopamine-depleted striatum we also found a significant down-regulation Syt II and up-regulation of Syt X mRNA levels that could not be reversed by the acute treatment either with L-DOPA or SKF82958. By contrast, these two drugs induced an increase of Syt IV and Syt VII mRNA levels. A time-course study revealed the highest levels of Syt IV and VII mRNAs to occur at two hours and 12 hours after the treatment with SKF82958, respectively. D1 antagonist (+/-)-7-chloro-8-hydroxy-3-methyl-1-phenyl-2,3,4,5-tetrahydro-1H-3-benzazepine hydrochloride (SCH23390) but not D2 antagonist haloperidol prevented the L-DOPA-driven increase of Syt IV and VII mRNAs. These results imply that synaptic plasticity in response to chronic striatal dopamine depletion involves a complex pattern of changes in striatal Syt mRNA expression. The L-DOPA treatment does not reverse the changes in Syt II and Syt X gene expression, but recruits additional, D1 receptor-mediated changes in Syt IV and Syt VII gene expression. Whether these D1 receptor-mediated changes play a role in the alterations of synaptic transmission that results in the unwanted side effects of chronic L-DOPA treatment in Parkinson's disease remains to be determined.

The SNAP-25 gene may be associated with clinical response and weight gain in antipsychotic treatment of schizophrenia

The synaptosomal-associated protein of 25 kDa (SNAP-25) is an essential component of the core complex that mediates presynaptic vesicle trafficking. Thus, SNAP-25 is directly involved in the release of neurotransmitters. Quantitative alterations of SNAP-25 expression have been reported in brain regions and cerebrospinal fluid (CSF) of schizophrenics and in haloperidol treated rats. This observed altered expression may be influenced by genetic variants of SNAP-25. We hypothesized that polymorphisms of the SNAP-25 gene (sites DdeI, MnlI and TaiI in the 3'UTR) are associated with antipsychotic drug response and induced weight gain. A sample of 59 patients with prior suboptimal response to antipsychotic treatment and diagnosed with DSM-IV schizophrenia or schizoaffective disorder was examined. Patients were administered clozapine, haloperidol, olanzapine or risperidone for up to 14 weeks. Clinical response was defined as the difference between the baseline and the endpoint total scores on the Positive and Negative Syndrome Scale (PANSS). Weight was assessed at baseline and at study endpoint. ANOVA revealed that the MnlI and TaiI polymorphisms were associated with response (F[2,53] = 4.57, p = 0.01 and F[2,52] = 3.53, p = 0.03) and with weight gain (F[2,52] = 4.28, p = 0.01 and F[2,51] = 3.38, p = 0.04). When covariates were included, the MnlI polymorphism remained significantly associated with changes of PANSS scores, but not with weight gain. The DdeI polymorphism was not associated with response or weight gain. These findings suggest that SNAP-25 gene variants affect clinical response in patients with prior poor response to antipsychotics. Weight changes do not seem to be associated with polymorphism of the SNAP-25 gene, however, replication in independent samples is warranted.

Multiple molecular and neuropharmacological effects of MDMA (Ecstasy)

3,4-Methylenedioxymethamphetamine (MDMA), commonly referred to as Ecstasy, is a widely abused, psychoactive recreational drug, which induces short- and long-term neuropsychiatric behaviors. This drug is neurotoxic to serotonergic neurons in vivo, and induces programmed cell death in cultured human serotonergic cells and rat neocortical neurons. Over the years it has been shown that MDMA alters the release of several neurotransmitters in the brain, it induces recompartmentation of intracellular serotonin and c-fos, and modifies the expression of a few genes. Recently, we observed changes in gene expression in mice treated with MDMA, and cloned and sequenced 11 cDNAs thus affected (4 correspond to known and 7 to unknown genes). The effect of MDMA on two of these genes, GABA transporter 1 and synaptotagmin IV was studied in detail. Characterization of the relationship between a given gene and certain physiological or behavioral effects of MDMA could shed light on the mechanism of the drug's action. However, establishing such a connection is difficult for several reasons, including that serotonergic neurons are not the only cells affected by MDMA. In this review, molecular and neurochemical events that occur in the brain following exposure to MDMA, and link between the observed molecular changes with known physiological effects of the drug are discussed. It is indicated that MDMA alters the expression of several proteins involved in GABA neurotransmission, thus having critical effect on thermoregulation and MDMA acute toxicity. This analysis should facilitate development of novel approaches to prevent deleterious effects, especially mortality induced by MDMA and other abused psychostimulants.

Antipsychotics increase microtubule-associated protein 2 mRNA but not spinophilin mRNA in rat hippocampus and cortex

Antipsychotic (neuroleptic) drugs induce structural alterations in synaptic terminals and changes in the expression of presynaptic protein genes. Whether there are also changes in corresponding postsynaptic (dendritic) markers has not been determined. We describe the effect of 14-day treatment with typical (haloperidol, chlorpromazine) or atypical (clozapine, olanzapine, risperidone) antipsychotics on the expression of two dendritic protein genes, microtubule-associated protein 2 (MAP2) and spinophilin, using in situ hybridization, in the rat hippocampus, retrosplenial, and occipitoparietal cortices. MAP2 mRNA was increased modestly in the dentate gyrus and retrosplenial cortex by chlorpromazine, risperidone, and olanzapine and in the occipitoparietal cortex by chlorpromazine, haloperidol, and risperidone. None of the antipsychotics affected spinophilin mRNA in any area. Overall, these results show a modulation of MAP2 gene expression, likely reflecting functional or structural changes in the dendritic tree in response to some typical and atypical antipsychotics. The lack of change in spinophilin mRNA suggests that dendritic spines are not affected selectively by the drugs. The data provide further evidence that antipsychotics regulate genes involved in synaptic structure and function. Such actions may underlie their long-term effects on neural plasticity in areas of the brain implicated in the pathology of schizophrenia.

Presynaptic proteins in the prefrontal cortex of patients with schizophrenia and rats with abnormal prefrontal development

Dysfunction of the prefrontal cortex in schizophrenia may be associated with abnormalities in synaptic structure and/or function and reflected in altered concentrations of proteins in presynaptic terminals and involved in synaptic plasticity (synaptobrevin/ vesicle-associated membrane protein (VAMP), synaptosomal-associated protein-25 (SNAP-25), syntaxin, synaptophysin and growth-associated protein-43 (GAP-43)). We examined the immunoreactivity of these synapse-associated proteins via quantitative immunoblotting in the prefrontal cortex of patients with schizophrenia (n=18) and in normal controls (n=23). We also tested the stability of these proteins across successive post-mortem intervals in rat brains (at 0, 3, 12, 24, 48, and 70 h). To investigate whether experimental manipulation of prefrontal cortical development in the rat alters prefrontal synaptic protein levels, we lesioned the ventral hippocampus of rats on postnatal day 7 and measured immunoreactivity of presynaptic proteins in the prefrontal cortex on postnatal day 70. VAMP immunoreactivity was lower in the schizophrenic patients by 22% (P<0.03). There were no differences in the immunoreactivity of any other proteins measured in schizophrenic patients as compared to the matched controls. Proteins were fairly stable up to 24 h and thereafter the abundance of most proteins examined was significantly reduced (falling to as low as 20% of baseline levels at 48-70 h). VAMP immunoreactivity was higher in the lesioned rats as compared to sham controls by 22% (P&<0.03). There were no significant differences between the lesioned rats and sham animals in any other presynaptic protein. These data suggest that apparently profound prefrontal cortical dysfunction in schizophrenia, as well as in an animal model of schizophrenia, may exist without gross changes in the abundance of many synaptic proteins but discrete changes in selected presynaptic molecules may be present.

Elevated cerebrospinal fluid SNAP-25 in schizophrenia

BACKGROUND

Research suggests an association between abnormal exocytosis and schizophrenia. We previously demonstrated increased synaptosomal associated protein, 25 kDa (SNAP-25), a member of the exocytotic mechanism, in the cerebrospinal fluid (CSF) of schizophrenia subjects. In this study, we explored SNAP-25 level and clinical variables in a new group of subjects.

METHODS

Twenty-five haloperidol-treated subjects with chronic schizophrenia and twenty-five healthy control subjects participated in the study. Subjects received haloperidol treatment for at least 3 months and then had a lumbar puncture (n = 19). Medication was replaced by placebo, and the lumbar puncture was repeated (n = 25) after 6 weeks or sooner if limited psychotic symptoms occurred. We measured the level of SNAP-25 in the CSF and symptoms with the Brief Psychiatric Rating Scale (BPRS).

RESULTS

In both haloperidol (p =.001) and placebo (p =.001) treatment conditions, SNAP-25 was elevated. There was no significant difference in SNAP-25 level between conditions. We identified significant positive correlations among SNAP-25 and the BPRS total score and psychosis and thinking disturbance subscales in subjects on haloperidol.

CONCLUSIONS

These observations confirm our previous report of elevated CSF SNAP-25 and suggest that synaptic pathology may be linked with the pathophysiology of schizophrenia.

SNAP-25 reduction in the hippocampus of patients with schizophrenia

In this study, the authors sought to replicate the findings of reduced synaptosomal associated protein 25 kDa (SNAP-25) immunoreactivity in the hippocampus of patients with schizophrenia. The authors also measured N-methyl-D-aspartate (NMDA) receptor 1 (NR1) receptor subunit to determine if glutamatergic synapses were involved with the loss of SNAP-25. We found 49% less SNAP-25 immunointensity in the schizophrenic group (n=7) compared to the control (n=8) or bipolar groups (n=4) (P=.004). There was no change in NMDA NR1 levels in the three groups. The authors confirm the previous report of less SNAP-25 immunoreactivity in the hippocampus using a different cohort of patients with schizophrenia. It also appears that NMDA NR1 was unchanged, indicating that the overall level of NMDA glutamatergic synapses in hippocampus is normal. These data add to evidence suggesting that in schizophrenia the molecular pathology of the hippocampus involves presynaptic components.

Elevated D3 dopamine receptor mRNA in dopaminergic and dopaminoceptive regions of the rat brain in response to morphine

As opiates increase dopamine transmission, we measured the effects of morphine on dopamine-related genes using a real-time optic PCR assay that reliably detects small differences in mRNA in discrete brain regions. Tissue from dopaminoceptive and dopaminergic brain regions was collected from rats injected twice daily for 7 days with saline or increasing doses of morphine. Tissues were assayed for D1, D2 and D3 dopamine receptor mRNAs (D1R, D2R and D3R), as well as for mRNAs for tyrosine hydroxylase (TH) and the dopamine transporter (DAT). The neuron-associated mRNAs for SNAP-25 and synaptophysin, as well as the glial-associated mRNA for S100-beta and three 'housekeeping' mRNAs, were also measured. As reported previously by others, there was no alteration in D1R mRNA and a 25% decrease in D2R mRNA in the caudate-putamen, 2 h after the final morphine injection. Importantly, in the same RNA extracts, D3R mRNA showed significant increases of 85% in the caudate-putamen and 165% in the ventral midbrain, including the substantia nigra and ventral tegmental area. There were no other significant morphine effects. Mapping of brain regions in saline control rats agreed with previous studies, including showing the presence of low abundance TH mRNA and the absence of DAT mRNA in the caudate-putamen. The finding that chronic, intermittent injections of morphine caused an increase in D3R mRNA extends our understanding of the ability of D3R agonists to reduce the effects of morphine.

Synaptotagmin I and IV are differentially regulated in the brain by the recreational drug 3,4-methylenedioxymethamphetamine (MDMA)

3,4-Methylenedioxymethamphetamine (MDMA or Ecstasy) is a widely abused drug. In brains of mice exposed to MDMA, we recently detected altered expression of several cDNAs and genes by using the differential display polymerase chain reaction (PCR) method. Expression of one such cDNA, which exhibited 98% sequence homology with the synaptic vesicle protein synaptotagmin IV, decreased 2 h after MDMA treatment. Herein, the effect of MDMA on expression of both synaptotagmin I and IV was studied in detail, since the two proteins are functionally interrelated. PCR analyses (semi-quantitative and real-time) confirmed that upon treatment with MDMA, expression of synaptotagmin IV decreased both in the midbrain and frontal cortex of mice. Decreases in the protein levels of synaptotagmin IV were confirmed by Western immunoblotting with anti-synaptotagmin IV antibodies. In contrast, the same exposure to MDMA increased expression of synaptotagmin I in the midbrain, a region rich in serotonergic neurons, but not in the frontal cortex. This differential expression was confirmed at the protein level with anti-synaptotagmin I antibodies. MDMA did not induce down- or up-regulation of synaptotagmin IV and I, respectively, in serotonin transporter knockout mice (-/-) that are not sensitive to MDMA. Therefore, psychoactive drugs, such as MDMA, appear to modulate expression of synaptic vesicle proteins, and possibly vesicle trafficking, in the brain.

Antipsychotic drugs and neuroplasticity: insights into the treatment and neurobiology of schizophrenia

This paper reviews the evidence that antipsychotic drugs induce neuroplasticity. We outline how the synaptic changes induced by the antipsychotic drug haloperidol may help our understanding of the mechanism of action of antipsychotic drugs in general, and how they may help to elucidate the neurobiology of schizophrenia. Studies have provided compelling evidence that haloperidol induces anatomical and molecular changes in the striatum. Anatomical changes have been documented at the level of regional brain volume, synapse morphology, and synapse number. At the molecular level, haloperidol has been shown to cause phosphorylation of proteins and to induce gene expression. The molecular responses to conventional antipsychotic drugs are predominantly observed in the striatum and nucleus accumbens, whereas atypical antipsychotic drugs have a subtler and more widespread impact. We conclude that the ability of antipsychotic drugs to induce anatomical and molecular changes in the brain may be relevant for their antipsychotic properties. The delayed therapeutic action of antipsychotic drugs, together with their promotion of neuroplasticity suggests that modification of synaptic connections by antipsychotic drugs is important for their mode of action. The concept of schizophrenia as a disorder of synaptic organization will benefit from a better understanding of the synaptic changes induced by antipsychotic drugs.

Acute and chronic haloperidol treatments increase parkin mRNA levels in the rat brain

Mutations in the parkin gene cause autosomal recessive juvenile parkinsonism. We examined the effects of acute and chronic treatment with haloperidol on parkin mRNA expression in the rat brain by reverse transcription-polymerase chain reaction. Acute haloperidol treatment (2 mg/kg) increased parkin mRNA levels in the striatum and nucleus accumbens but not in the medial prefrontal cortex and substantia nigra. Four-week-treatment with haloperidol decanoate (25 mg eq/kg) produced a significant increase in parkin mRNA levels in the striatum without affecting to those in the medial prefrontal cortex, nucleus accumbens and substantia nigra. These results suggest that Parkin may be involved in the haloperidol-induced synaptic plasticity, since Parkin regulates the turnover of the synaptic protein, CDCrel-1.

Antipsychotic treatment induces alterations in dendrite- and spine-associated proteins in dopamine-rich areas of the primate cerebral cortex

BACKGROUND

Mounting evidence indicates that long-term treatment with antipsychotic medications can alter the morphology and connectivity of cellular processes in the cerebral cortex. The cytoskeleton plays an essential role in the maintenance of cellular morphology and is subject to regulation by intracellular pathways associated with neurotransmitter receptors targeted by antipsychotic drugs.

METHODS

We have examined whether chronic treatment with the antipsychotic drug haloperidol interferes with phosphorylation state and tissue levels of a major dendritic cytoskeleton-stabilizing agent, microtubule-associated protein 2 (MAP2), as well as levels of the dendritic spine-associated protein spinophilin and the synaptic vesicle-associated protein synaptophysin in various regions of the cerebral cortex of rhesus monkeys.

RESULTS

Among the cortical areas examined, the prefrontal, orbital, cingulate, motor, and entorhinal cortices displayed significant decreases in levels of spinophilin, and with the exception of the motor cortex, each of these regions also exhibited increases in the phosphorylation of MAP2. No changes were observed in either spinophilin levels or MAP2 phosphorylation in the primary visual cortex. Also, no statistically significant changes were found in tissue levels of MAP2 or synaptophysin in any of the cortical regions examined.

CONCLUSIONS

Our findings demonstrate that long-term haloperidol exposure alters neuronal cytoskeleton- and spine-associated proteins, particularly in dopamine-rich regions of the primate cerebral cortex, many of which have been implicated in the psychopathology of schizophrenia. The ability of haloperidol to regulate cytoskeletal proteins should be considered in evaluating the mechanisms of both its palliative actions and its side effects.

Molecular characterization of schizophrenia viewed by microarray analysis of gene expression in prefrontal cortex

Microarray expression profiling of prefrontal cortex from matched pairs of schizophrenic and control subjects and hierarchical data analysis revealed that transcripts encoding proteins involved in the regulation of presynaptic function (PSYN) were decreased in all subjects with schizophrenia. Genes of the PSYN group showed a different combination of decreased expression across subjects. Over 250 other gene groups did not show altered expression. Selected PSYN microarray observations were verified by in situ hybridization. Two of the most consistently changed transcripts in the PSYN functional gene group, N-ethylmaleimide sensitive factor and synapsin II, were decreased in ten of ten and nine of ten subjects with schizophrenia, respectively. The combined data suggest that subjects with schizophrenia share a common abnormality in presynaptic function. We set forth a predictive, testable model.

Long-term treatment with haloperidol decreases the mRNA levels of complexin I, but not complexin II, in rat prefrontal cortex, nucleus accumbens and ventral tegmental area

The effect of long-term treatment with haloperidol on gene expression of the presynaptic protein complexins was investigated in the discrete brain regions of rats, using reverse transcription-polymerase chain reaction. Four-week-treatment with haloperidol decanoate (25 mg eq/kg) produced a significant decrease in the mRNA levels of complexin I in the medial prefrontal cortex, nucleus accumbens and ventral tegmental area, but not in the striatum and substantia nigra. No significant changes in complexin II mRNA levels were observed in any brain region examined here. The reduced expression of complexin I may be associated with the haloperidol-induced depolarization block of mesocorticolimbic dopamine neurons.

Expression of complexin I and II mRNAs and their regulation by antipsychotic drugs in the rat forebrain

Complexin (cx) I and II are homologous synaptic protein genes which are differentially expressed in mouse and human brain and differentially affected in schizophrenia. We characterized the distribution of cx I and II mRNAs in rat forebrain and examined whether their abundance, or the transcript of the synaptic marker synaptophysin, is affected by 14 days' administration of antipsychotic drugs (haloperidol, chlorpromazine, risperidone, olanzapine, or clozapine). Cx I mRNA predominated in medial habenula, medial septum-diagonal band complex, and thalamus, whereas cx II mRNA was more abundant in most other regions, including isocortex and hippocampus. Within the hippocampus, cx I mRNA was primarily expressed by interneurons and cx II mRNA by granule cells and pyramidal neurons. Localized cx II mRNA signal was seen in the dentate gyrus molecular layer, suggestive of its transport into granule cell dendrites. Antipsychotic treatment produced selective, modest effects on cx mRNA expression. Cx I mRNA was elevated by olanzapine in dorsolateral striatum and frontoparietal cortex, while the abundance of cx II mRNA relative to cx I mRNA was decreased in both areas by olanzapine and haloperidol. Chlorpromazine increased cx II mRNA in frontoparietal cortex and synaptophysin mRNA in dorsolateral striatum. In summary, the data have implications both for understanding the effects of antipsychotic medication on synaptic organization, and for synaptic protein expression studies in patients treated with the drugs.

The neuropathological effects of antipsychotic drugs

In addition to their neurochemical effects, antipsychotic (neuroleptic) drugs produce structural brain changes. This property is relevant not only for understanding the drugs' mode of action, but because it complicates morphological studies of schizophrenia. Here the histological neuropathological effects of antipsychotics are reviewed, together with brief mention of those produced by other treatments sometimes used in schizophrenia (electroconvulsive shock, lithium and antidepressants). Most data come from drug-treated rats, though there are also some human post-mortem studies with broadly congruent findings. The main alteration associated with antipsychotic medication concerns the ultrastructure and proportion of synaptic subpopulations in the caudate nucleus. In rats, synapses and dendrites in lamina VI of the prefrontal cortex are also affected. The changes are indicative of a drug-induced synaptic plasticity, although the underlying mechanisms are poorly understood. Similarly, it is unclear whether the neuropathological features relate primarily to the therapeutic action of antipsychotics or, more likely, to their predisposition to cause tardive dyskinesia and other motor side-effects. Clozapine seems to cause lesser and somewhat different alterations than do typical antipsychotics, albeit based on few data. There is no good evidence that antipsychotics cause neuronal loss or gliosis, nor that they promote neurofibrillary tangle formation or other features of Alzheimer's disease.

Effects of atypical antipsychotic drugs vs. haloperidol on expression of heat shock protein in the discrete brain regions of phencyclidine-treated rats

Haloperidol augmented a trend of an increase in the heat shock protein (hsp70) mRNA levels induced by phencyclidine (PCP) in rat medial prefrontal cortex, nucleus accumbens and striatum, while the atypical antipsychotic drugs such as clozapine, olanzapine and risperidone decreased it. When administered alone, clozapine, but not haloperidol, decreased hsp70 mRNA levels. Haloperidol and the atypical antipsychotic drugs may thus have differential effects on hsp70 expression in some brain regions of PCP-treated rats.