Effect of atypical antipsychotics on phencyclidine-induced expression of arc in rat brain

Serotonergic and Adrenergic Neuroreceptor Manipulation Ameliorates Core Symptoms of ADHD through Modulating Dopaminergic Receptors in Spontaneously Hypertensive Rats

The core symptoms of attention deficit hyperactivity disorder (ADHD) are due to the hypofunction of the brain's adrenergic (NE) and dopamine (DA) systems. Drugs that enhance DA and NE neurotransmission in the brain by blocking their transporters or receptors are the current therapeutic strategies. Of late, the emerging results point out the serotonergic (5-HT) system, which indirectly modulates the DA activity in reducing the core symptoms of ADHD. On this basis, second-generation antipsychotics, which utilize 5-HT receptors, were prescribed to children with ADHD. However, it is not clear how serotonergic receptors modulate the DA activity to minimize the symptoms of ADHD. The present study investigates the efficacy of serotonergic and alpha-2 adrenergic receptor manipulation in tackling the core symptoms of ADHD and how it affects the DA neuroreceptors in the brain regions involved in ADHD. Fifteen-day-old male spontaneously hypertensive rats (SHRs) received 5-HT1A agonist (ipsapirone) or 5-HT2A antagonist (MDL 100907) (i.p.) or alpha-2 agonist (GFC) from postnatal days 15 to 42 along with age-matched Wistar Kyoto rats (WKY) (n = 8 in each group). ADHD-like behaviors were assessed using a battery of behavioral tests during postnatal days 44 to 65. After the behavioral tests, rat brains were processed to estimate the density of 5-HT1A, 5-HT2A, DA-D1, and DA-D2 neuroreceptors in the prefrontal cortex, the striatum, and the substantia nigra. All three neuroreceptor manipulations were able to minimize the core symptoms of ADHD in SHRs. The positive effect was mainly associated with the upregulation of 5-HT2A receptors in all three areas investigated, while 5-HT1A was in the prefrontal cortex and the substantia nigra. Further, the DA-D1 receptor expression was downregulated by all three neuroreceptor manipulations except for alpha-2 adrenergic receptor agonists in the striatum and 5-HT2A antagonists in the substantia nigra. The DA-D2 expression was upregulated in the striatum while downregulated in the prefrontal cortex and the substantia nigra. In this animal model study, the 5-HT1A agonist or 5-HT2A antagonist monotherapies were able to curtail the ADHD symptoms by differential expression of DA receptors in different regions of the brain.

Dysregulated Signaling at Postsynaptic Density: A Systematic Review and Translational Appraisal for the Pathophysiology, Clinics, and Antipsychotics' Treatment of Schizophrenia

Emerging evidence from genomics, post-mortem, and preclinical studies point to a potential dysregulation of molecular signaling at postsynaptic density (PSD) in schizophrenia pathophysiology. The PSD that identifies the archetypal asymmetric synapse is a structure of approximately 300 nm in diameter, localized behind the neuronal membrane in the glutamatergic synapse, and constituted by more than 1000 proteins, including receptors, adaptors, kinases, and scaffold proteins. Furthermore, using FASS (fluorescence-activated synaptosome sorting) techniques, glutamatergic synaptosomes were isolated at around 70 nm, where the receptors anchored to the PSD proteins can diffuse laterally along the PSD and were stabilized by scaffold proteins in nanodomains of 50-80 nm at a distance of 20-40 nm creating "nanocolumns" within the synaptic button. In this context, PSD was envisioned as a multimodal hub integrating multiple signaling-related intracellular functions. Dysfunctions of glutamate signaling have been postulated in schizophrenia, starting from the glutamate receptor's interaction with scaffolding proteins involved in the N-methyl-D-aspartate receptor (NMDAR). Despite the emerging role of PSD proteins in behavioral disorders, there is currently no systematic review that integrates preclinical and clinical findings addressing dysregulated PSD signaling and translational implications for antipsychotic treatment in the aberrant postsynaptic function context. Here we reviewed a critical appraisal of the role of dysregulated PSD proteins signaling in the pathophysiology of schizophrenia, discussing how antipsychotics may affect PSD structures and synaptic plasticity in brain regions relevant to psychosis.

Towards Novel Treatments for Schizophrenia: Molecular and Behavioural Signatures of the Psychotropic Agent SEP-363856

Schizophrenia is a complex psychopathology whose treatment is still challenging. Given the limitations of existing antipsychotics, there is urgent need for novel drugs with fewer side effects. SEP-363856 (SEP-856) is a novel psychotropic agent currently under phase III clinical investigation for schizophrenia treatment. In this study, we investigated the ability of an acute oral SEP-856 administration to modulate the functional activity of specific brain regions at basal levels and under glutamatergic or dopaminergic-perturbed conditions in adult rats. We found that immediate-early genes (IEGs) expression was strongly upregulated in the prefrontal cortex and, to a less extent, in the ventral hippocampus, suggesting an activation of these regions. Furthermore, SEP-856 was effective in preventing the hyperactivity induced by an acute injection of phencyclidine (PCP), but not of d-amphetamine (AMPH). The compound effectively normalized the PCP-induced increase in IEGs expression in the PFC at all doses tested, whereas only the highest dose determined the major modulations on AMPH-induced changes. Lastly, SEP-856 acute administration corrected the cognitive deficits produced by subchronic PCP administration. Taken together, our data provide further insights on SEP-856, suggesting that modulation of the PFC may represent an important mechanism for the functional and behavioural activity of this novel compound.

Effect of pharmacological manipulations on Arc function

Activity-regulated cytoskeleton-associated protein (Arc) is a brain-enriched immediate early gene that regulates important mechanisms implicated in learning and memory. Arc levels are controlled through a balance of induction and degradation in an activity-dependent manner. Arc further undergoes multiple post-translational modifications that regulate its stability, localization and function. Recent studies demonstrate that these features of Arc can be pharmacologically manipulated. In this review, we discuss some of these compounds, with an emphasis on drugs of abuse and psychotropic drugs. We also discuss inflammatory states that regulate Arc.

Immediate-Early Genes Modulation by Antipsychotics: Translational Implications for a Putative Gateway to Drug-Induced Long-Term Brain Changes

An increasing amount of research aims at recognizing the molecular mechanisms involved in long-lasting brain architectural changes induced by antipsychotic treatments. Although both structural and functional modifications have been identified following acute antipsychotic administration in humans, currently there is scarce knowledge on the enduring consequences of these acute changes. New insights in immediate-early genes (IEGs) modulation following acute or chronic antipsychotic administration may help to fill the gap between primary molecular response and putative long-term changes. Moreover, a critical appraisal of the spatial and temporal patterns of IEGs expression may shed light on the functional "signature" of antipsychotics, such as the propensity to induce motor side effects, the potential neurobiological mechanisms underlying the differences between antipsychotics beyond D2 dopamine receptor affinity, as well as the relevant effects of brain region-specificity in their mechanisms of action. The interest for brain IEGs modulation after antipsychotic treatments has been revitalized by breakthrough findings such as the role of early genes in schizophrenia pathophysiology, the involvement of IEGs in epigenetic mechanisms relevant for cognition, and in neuronal mapping by means of IEGs expression profiling. Here we critically review the evidence on the differential modulation of IEGs by antipsychotics, highlighting the association between IEGs expression and neuroplasticity changes in brain regions impacted by antipsychotics, trying to elucidate the molecular mechanisms underpinning the effects of this class of drugs on psychotic, cognitive and behavioral symptoms.

Chronic administration of haloperidol and clozapine induces differential effects on the expression of Arc and c-Fos in rat brain

The modulation of genes implicated in synaptic plasticity following administration of antipsychotic drugs has been instrumental in understanding their possible mode of action. Arc (Arg 3.1) is one such gene closely associated with changes in synaptic plasticity. In this study we have investigated the changes in expression of Arc protein following acute and chronic administration of a typical antipsychotic (haloperidol) and an atypical antipsychotic (clozapine) by means of immunohistochemistry compared to the prototypic gene marker c-Fos. In dorsal striatum haloperidol (1 mg/kg) significantly increased Arc expression following both acute and chronic (21 day) administration with evidence of modulation in induction after repeated dosing. No significant changes were observed following either acute or chronic administration of clozapine (20 mg/kg). In the nucleus accumbens shell both clozapine and haloperidol induced Arc expression following acute administration, again with evidence of modulation after chronic dosing. The pattern of induction of Arc expression following haloperidol and clozapine in both dorsal and ventral striatum was similar to that for c-Fos. In medial prefrontal and cingulate cortex, Arc expression was significantly decreased by clozapine but not haloperidol without any indication of modulation following chronic dosing, whereas no significant changes in c-Fos expression were observed with either drug. Since synaptic modulation mediated by Arc is associated with down-regulation of the AMPA glutamate receptor, this study suggests a mechanism whereby enhanced glutamate receptor efficacy in medial cortical areas may be a component of antipsychotic drug action.

The dopaminergic stabilizers pridopidine and ordopidine enhance cortico-striatal Arc gene expression

The dopaminergic stabilizers pridopidine [4-(3-(methylsulfonyl)phenyl)-1-propylpiperidine] and ordopidine [1-ethyl-4-(2-fluoro-3-(methylsulfonyl)phenyl)piperidine] inhibit psychostimulant-induced hyperactivity, and stimulate behaviour in states of hypoactivity. While both compounds act as dopamine D2 receptor antagonists in vitro, albeit with low affinity, their specific state-dependent behavioural effect profile is not shared by D2 receptor antagonists in general. To further understand the neuropharmacological effects of pridopidine and ordopidine, and how they differ from other dopaminergic compounds in vivo, we assessed the expression of activity-regulated cytoskeleton-associated protein/activity-regulated gene 3.1 (Arc), an immediate early gene marker associated with synaptic activation, in the frontal cortex and striatum. Furthermore, monoamine neurochemistry and locomotor activity were assessed. The effects of pridopidine and ordopidine were compared to reference dopamine D1 and D2 receptor agonists and antagonists, as well as the partial dopamine D2 agonist aripiprazole. Pridopidine and ordopidine induced significant increases in cortical Arc expression, reaching 2.2- and 1.7-fold levels relative to control, respectively. In contrast, none of the reference dopamine D1 and D2 compounds tested increased cortical Arc expression. In the striatum, significant increases in Arc expression were seen with both pridopidine and ordopidine as well as the dopamine D2 receptor antagonists, remoxipride and haloperidol. Interestingly, striatal Arc expression correlated strongly and positively with striatal 3,4-dihydroxyphenylacetic acid, suggesting that antagonism of dopamine D2 receptors increases Arc expression in the striatum. In conclusion, the concurrent increase in cortical and striatal Arc expression induced by pridopidine and ordopidine appears unique for the dopaminergic stabilizers, as it was not shared by the reference compounds tested. The increase in cortical Arc expression is hypothesized to reflect enhanced N-methyl-D-aspartic acid receptor-mediated signalling in the frontal cortex, which could contribute to the state-dependent locomotor effects of pridopidine and ordopidine.

Antipsychotic drug effects in schizophrenia: a review of longitudinal FMRI investigations and neural interpretations

The evidence that antipsychotics improve brain function and reduce symptoms in schizophrenia is unmistakable, but how antipsychotics change brain function is poorly understood, especially within neuronal systems. In this review, we investigated the hypothesized normalization of the functional magnetic resonance imaging (fMRI) blood oxygen level dependent signal in the context of antipsychotic treatment. First, we conducted a systematic PubMed search to identify eight fMRI investigations that met the following inclusion criteria: case-control, longitudinal design; pre- and post-treatment contrasts with a healthy comparison group; and antipsychotic-free or antipsychotic-naive patients with schizophrenia at the start of the investigation. We hypothesized that aberrant activation patterns or connectivity between patients with schizophrenia and healthy comparisons at the first imaging assessment would no longer be apparent or "normalize" at the second imaging assessment. The included studies differed by analysis method and fMRI task but demonstrated normalization of fMRI activation or connectivity during the treatment interval. Second, we reviewed putative mechanisms from animal studies that support normalization of the BOLD signal in schizophrenia. We provided several neuronal-based interpretations of these changes of the BOLD signal that may be attributable to long-term antipsychotic administration.

Haloperidol induces higher Homer1a expression than risperidone, olanzapine and sulpiride in striatal sub-regions

Homer1a and Yotiao are two post-synaptic density proteins at the crossroad of dopamine-glutamate neurotransmission. Homer1a has been implicated in the pathophysiology of schizophrenia and is differentially induced by typical and atypical antipsychotics, perhaps according to their dopaminergic profile. Yotiao has been involved in glutamate and dopamine post-synaptic signalling. Here, we seek to determine whether Homer1a and Yotiao might be implicated in post-synaptic response to antipsychotics with affinity to different dopamine D(2) receptors: haloperidol (0.8mg kg(-1)), risperidone (3mg kg(-1)), olanzapine (2.5mg kg(-1)) and (-)-sulpiride (50mg kg(-1)). Homer1a expression was significantly induced by haloperidol compared to vehicle and to atypical antipsychotics in almost all striatal sub-regions. Atypical antipsychotics induced the gene in the lateral putamen and in the core of the accumbens only. All antipsychotics, with the exclusion of sulpiride, elicited a dorsolateral-to-ventromedial distribution pattern of Homer1a expression. No significant induction was detected for Yotiao. These results suggest that the quantitative and topographical pattern of Homer1a expression may putatively be related to antipsychotics affinity and/or occupancy at dopamine D(2) receptors.

An Evaluation of Phencyclidine (PCP) Psychosis: A Retrospective Analysis at a State Facility

It has been reported in the literature that phencyclidine (PCP) psychosis recovery may take up to 4-6 weeks. This retrospective review sought to determine whether patients with a new onset of PCP psychosis have a longer hospitalization than those patients with new onset functional psychosis. The PCP arm (N = 20) was found to have a significantly shorter hospitalization than those with a new onset functional psychosis (N = 20)-mean 4.8 days (range 1-9) versus 13.6 days (range 3-41), p < .05. In addition, patients with psychosis related to PCP use were treated more aggressively with conventional antipsychotics than patients with a new onset functional psychosis at this facility.

Effects of repeated treatment of phencyclidine on cognition and gene expression in C57BL/6 mice

A number of studies indicate that glutamatergic N-methyl-D-aspartate (NMDA) neurotransmission is disturbed in schizophrenia partly based on the findings that NMDA receptor antagonists such as phencyclidine (PCP) can reproduce a schizophrenia-like syndrome in both humans and rodents. This study investigated whether repeated administration of low doses of PCP can induce cognitive dysfunctions in mice at doses which produce no sensorimotor disturbances. In addition, the effects on cognition were related to the expression of two genes, Arc and spinophilin, which have been related to neuronal plasticity and learning. Adult male C57Bl/6J mice received daily s.c. doses of PCP (0.5-2.0 mg/kg) or saline for 7 d. Testing was performed 24 h after the last day of treatment. Only the 2.0 mg/kg PCP dose produced a consistent impairment in spatial learning and working memory performed in the water-maze task without any apparent sensorimotor deficits. Importantly, the 2.0 mg/kg PCP dose produced no impairment in a non-spatial learning paradigm in the water-maze task. PCP treatment altered Arc mRNA levels in the hippocampus and retrosplenial agranular cortex while leaving the striatum and prefrontal cortex unaffected. The mRNA expression of spinophilin was down-regulated in striatum by repeated PCP treatment. These results demonstrate that repeated treatment with low doses of PCP in mice can produce specific cognitive deficits which are associated with alterations in gene expression in brain regions that appear to play a role in the pathophysiology of schizophrenia. These results suggest that the low-dose PCP model may have significant potential in characterizing the behavioural and molecular mechanisms underlying cognitive deficits seen in schizophrenia patients.

Antipsychotic drugs modulate Arc expression in the rat brain

We found that, in the striatum, acute injections of the first generation antipsychotic (FGA) haloperidol or the second generation antipsychotic (SGA) olanzapine enhanced Arc mRNA levels, however such induction persisted for at least 2 h in haloperidol-treated rats whereas it waned as early as 1 h after olanzapine injection. Conversely, repeated injections led to a persistent decrease of striatal Arc gene expression, regardless of the agent examined. In the frontal cortex, acute injection of both antipsychotics caused a reduction of Arc mRNA levels which persisted for at least 2 h. Following repeated treatment, olanzapine reduced Arc mRNA levels 2 h, but not 24 h, post-treatment whereas haloperidol was ineffective. Of note, the SGA quetiapine regulated the Arc gene expression similarly to olanzapine. Given the particular nature of Arc, our findings show its fine tuning following antipsychotic administration to be highly dependent on the length of the treatment and on the brain region investigated and suggest that antipsychotic drugs affect this marker of neuronal activity differently.

Differential expression of IEG mRNA in rat brain following acute treatment with clozapine or haloperidol: a semi-quantitative RT-PCR study

Antipsychotic drugs have been shown to modulate immediate early gene (IEG) expression in rat brain regions that are associated with schizophrenia, which may be directly linked to their immediate therapeutic benefit. In this study, we analysed the expression profile of a series of IEGs (c-fos, c-jun, fra-1, Krox-20, Krox-24, arc, sgk-1, BDNF and NARP) in six rat brain regions (prefrontal cortex, hippocampus, striatum, nucleus accumbens, thalamus and cerebellum). Rats (n=5) were administered either clozapine (20 mg/kg i.p.), haloperidol (1 mg/kg i.p.) or the appropriate vehicle with pre-treatment times of 1, 6 and 24 h. IEG expression was analysed in these regions by Taqman RT-PCR. The spatial and temporal profile of IEG induction following antipsychotic drug treatment correlates with regions associated with the efficacy and side effect profile of each drug. In particular, sgk-1 expression levels after antipsychotic drug treatment may have predictive value when investigating the profile of a novel antipsychotic drug.

Comparison between intraperitoneal and subcutaneous phencyclidine administration in Sprague-Dawley rats: a locomotor activity and gene induction study

In a putative model of acute phencyclidine (PCP)-induced psychosis we evaluated effects of the drug on locomotor activity (LMA) and immediate early gene (IEG) induction in the rat using two routes of drug administration, intraperitoneal (i.p.) and subcutaneous (s.c.). Adult male rats received saline or PCP (1.0-5.0 mg/kg) either i.p or s.c. and were assessed for LMA for 60 min. At the end of the LMA testing animals were culled and blood and brain samples were collected for PCP concentration analysis. Separate cohorts of animals received 5.0 mg/kg PCP (i.p. or s.c.) and were used to investigate (1) the pharmacokinetics of PCP or (2) induction of IEG (Arc, c-fos, BDNF, junB, Krox-20, sgk-1, NURR1, fra-2, Krox-24, and egr-3) mRNA expression in the prefrontal cortex (PFC). Administration of PCP resulted in locomotor hyperactivity which was more robust and longer-lasting in animals dosed s.c. compared to i.p.-treated-animals. Differences in hyperlocomotion were paralleled by higher concentrations of PCP in the blood and in the brain of s.c.-treated animals compared to i.p.-treated animals. The differences in the concentration of PCP between the two routes of administration were detected 30 min after dosing and persisted for up to 4 h. Administration of PCP via the s.c. route resulted in induction of more IEGs and consistently larger magnitudes of induction than that via the i.p. route. Therefore, we have outlined the dosing conditions to induce rapid and robust effect of acute PCP on behaviour, gene induction, and pharmacokinetic profile, to allow investigation of this as a potential animal model of acute psychosis.

Clozapine, SCH 23390 and alpha-flupenthixol but not haloperidol attenuate acute phencyclidine-induced disruption of conditional discrimination performance

RATIONALE

Forebrain dopamine (DA) manipulation has recently been shown to selectively disrupt a conditional discrimination task whose design parameters approximate tasks repeatedly shown to be impaired in schizophrenia.

OBJECTIVE

To investigate the reversal potential of the D(1)/D(2) receptor antagonist alpha-flupenthixol, the selective D(1) antagonist SCH 23390, the typical antipsychotic haloperidol and the atypical antipsychotic clozapine on acute phencyclidine (PCP)-induced disruption of a conditional discrimination task dependent on the ability to use task-setting cues that inform goal-directed performance.

MATERIALS AND METHODS

Rats learned a conditional discrimination task where reinforcement was contingent on an appropriate lever press during a specific auditory stimulus.

RESULTS

PCP disrupted task performance at 1.5 mg/kg, attenuated correct lever pressing at 2.5 mg/kg and abolished overall responding at 5 mg/kg (experiment 1). Pavlovian-instrumental transfer task results (experiment 2) showed that 1.5 and 2.5 mg/kg PCP had no disruptive effects on basic sensory, motor or motivational processes; however, such deficits were evident in 5-mg/kg-treated animals. PCP (1.5 mg/kg) disruption of conditional discrimination was attenuated by acute pretreatment with clozapine, SCH 23390 and alpha-flupenthixol; however, pretreatment with haloperidol did not attenuate task disruption.

CONCLUSION

The predictive validity of the conditional discrimination model is enhanced as the selective task disruption by the preeminent psychotomimetic PCP is reversed by clozapine (known to ameliorate cognitive deficits in schizophrenia) and the role of DA D(1) receptors as mediators of tasks that require conditional relationships is discussed.

Morphine activates Arc expression in the mouse striatum and in mouse neuroblastoma Neuro2A MOR1A cells expressing mu-opioid receptors

Activity-regulated cytoskeleton-associated protein (Arc) is an effector immediate early gene product implicated in long-term potentiation and other forms of neuroplasticity. Earlier studies demonstrated Arc induction in discrete brain regions by several psychoactive substances, including drugs of abuse. In the present experiments, the influence of morphine on Arc expression was assessed by quantitative reverse transcription real-time PCR and Western blotting in vivo in the mouse striatum/nucleus accumbens and, in vitro, in the mouse Neuro2A MOR1A cell line, expressing mu-opioid receptor. An acute administration of morphine produced a marked increase in Arc mRNA and protein level in the mouse striatum/nucleus accumbens complex. After prolonged opiate treatment, tolerance to the stimulatory effect of morphine on Arc expression developed. No changes in the striatal Arc mRNA levels were observed during spontaneous or opioid antagonist-precipitated morphine withdrawal. In Neuro2A MOR1A cells, acute, but not prolonged, morphine treatment elevated Arc mRNA level by activation of mu-opioid receptor. This was accompanied by a corresponding increase in Arc protein level. Inhibition experiments revealed that morphine induced Arc expression in Neuro2A MOR1A cells via intracellular signaling pathways involving mitogen-activated protein (MAP) kinases and protein kinase C. These results lend further support to the notion that stimulation of opioid receptors may exert an activating influence on some intracellular pathways and leads to induction of immediate early genes. They also demonstrate that Arc is induced in the brain in vivo after morphine administration and thus may play a role in neuroadaptations produced by the drug.

Microarray analysis of differentially expressed genes in rat frontal cortex under chronic risperidone treatment

Long-term administration of antipsychotic drugs can induce differential expression of a variety of genes in the brain, which may underscore the molecular mechanism of the clinical efficacy and/or side effects of antipsychotic drugs. We used cDNA microarray analysis to screen differentially expressed genes in rat frontal cortex under 4 weeks' treatment of risperidone (1 mg/kg). Using real-time quantitative PCR, we were able to verify eight genes, whose expression were significantly upregulated in rat frontal cortex under chronic risperidone treatment when compared with control animals. These genes include receptor for activated protein kinase C, amida, cathepsin D, calpain 2, calcium-independent receptor for alpha-latrotoxin, monoamine oxidase B, polyubiquitin, and kinesin light chain. In view of the physiological function of these genes, the results of our study suggest that chronic risperidone treatment may affect the neurotransmission, synaptic plasticity, and proteolysis of brain cells. This study also demonstrates that cDNA microarray analysis is useful for uncovering genes that are regulated by chronic antipsychotic drugs treatment, which may help bring new insight into the molecular mechanism of antipsychotic drugs.

Comparative analysis of acute and chronic administration of haloperidol and clozapine using [3H] 2-deoxyglucose metabolic mapping

In an effort to compare and contrast the mechanisms of action of typical and atypical antipsychotic drugs, [3H] 2-deoxyglucose metabolic mapping was employed following acute and chronic administration of haloperidol (1 mg/kg i.p. acute and 0.5 mg/kg i.p. chronic) and clozapine (20 mg/kg i.p., both acute and chronic). Optical density ratios (ODR) were measured in 62 brain structures. An overall decrease in ODR was observed in many of the regions analyzed. Acute haloperidol elicited significant decreases, particularly in the thalamus and hippocampus. Acute clozapine decreased glucose uptake in the caudate putamen, hippocampus, central gray, locus coreleus, and the thalamus. In both chronically treated haloperidol and clozapine animals, significant decreases in ODR were seen in the thalamus and hippocampal areas most dramatically, with other changes in the superior colliculus, retrospenial cortex, and the cerebellum. Clozapine caused significant effects in 32 nuclei acutely and only 19 nuclei chronically. Haloperidol caused significant effects in 23 nuclei acutely and 15 nuclei chronically. The pattern of change induced by haloperidol and clozapine were remarkably similar when considering their pharmacology is somewhat different. Both antipsychotics elicited fewer significant changes upon chronic administration.

cDNA microarray analysis of gene expression in anxious PVG and SD rats after cat-freezing test

To identify genes involved in the development of anxiety or fear, we analyzed the gene expression profiles of the cortex of anxious hooded PVG and Sprague-Dawley (SD) rats after exposure to the cat-freezing test apparatus. These two rat strains showed a marked difference in the extent of anxious behavior on the cat-freezing test; the hooded PVG rats showed highly anxious behavior while a low anxiety state was observed in SD rats. A cDNA microarray consisting of 5,931 genes was employed to investigate the global mRNA expression profiles of anxiety-related genes. According to the assumption that an abundance ratio of > or =1.5 is indicative of a change in gene expression, we detected 16 upregulated and 38 downregulated genes in PVG hooded and SD rats. Some of these genes have not yet been associated with anxiety (e.g. FGF), while other genes were recently found to be expressed in an anxious state (e.g., rat nerve growth factor-induced gene, NGFI-A). Our study also focused on the expression of some neurotransmitter receptors that have already been proven to be relevant to anxiety or fear, e.g., gamma-aminobutyric acid (GABA), cholecystokinin (CCK) and 5-HT(3) receptors. To further confirm the microarray data, the mRNA expressions of three genes: rat activity-regulated cytoskeleton-associated gene (Arc), rat NGFI-A gene and rat 5-HT(3) receptor (5-HT(3)R) mRNA, were studied by reverse transcription-polymerase chain reaction (RT-PCR). The results of RT-PCR were basically consistent with those from cDNA microarray. Our study therefore demonstrated that the microarray technique is an efficient tool for analyzing global expression profiles of anxiety-related genes, which may also provide further insight into the molecular mechanisms underlying the states of anxiety and fear.

Effects of the adenosine A(1) receptor agonist N(6)-cyclopentyladenosine on phencyclidine-induced behavior and expression of the immediate-early genes in the discrete brain regions of rats

Because of the possible interaction between adenosine receptors and dopaminergic functions, the compound acting on the specific adenosine receptor subtype may be a candidate for novel antipsychotic drugs. To elucidate the antipsychotic potential of the selective adenosine A(1) receptor agonist N(6)-cyclopentyladenosine (CPA), we examined herein the effects of CPA on phencyclidine (PCP)-induced behavior and expression of the immediate-early genes (IEGs), arc, c-fos and jun B, in the discrete brain regions of rats. PCP (7.5 mg/kg, s.c.) increased locomotor activity and head weaving in rats and this effect was significantly attenuated by pretreatment with CPA (0.5 mg/kg, s.c.). PCP increased the mRNA levels of c-fos and jun B in the medial prefrontal cortex, nucleus accumbens and posterior cingulate cortex, while leaving the striatum and hippocampus unaffected. CPA pretreatment significantly attenuated the PCP-induced increase in c-fos mRNA levels in the medial prefrontal cortex and nucleus accumbens. CPA also significantly attenuated the PCP-induced arc expression in the medial prefrontal cortex and posterior cingulate cortex. When administered alone, CPA decreased the mRNA levels of all IEGs examined in the nucleus accumbens, but not in other brain regions. Based on the ability of CPA to inhibit PCP-induced hyperlocomotion and its interaction with neural systems in the medial prefrontal cortex, posterior cingulate cortex and nucleus accumbens, the present results provide further evidence for a significant antipsychotic effect of the adenosine A(1) receptor agonist.

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.