Perospirone, a Novel Antipsychotic Agent, Hyperpolarizes Rat Dorsal Raphe Neurons via 5-HT1A Receptor

Synthesis, characterization, HSA/DNA interactions and antitumor activity of new [Ru(η6-p-cymene)Cl2(L)] complexes

Three new ruthenium(II) complexes were synthesized from different substituted isothiazole ligands 5-(methylamino)-3-pyrrolidine-1-ylisothiazole-4-carbonitrile (1), 5-(methylamino)-3-(4-methylpiperazine-1-yl)isothiazole-4-carbonitrile (2) and 5-(methylamino)-3-morpholine-4-ylisothiazole-4-carbonitrile (3): [Ru(η⁶-p-cymene)Cl₂(L1)]·H₂O (4), [Ru(η⁶-p-cymene)Cl₂(L2)] (5) and [Ru(η⁶-p-cymene)Cl₂(L3)] (6). All complexes were characterized by IR, UV-Vis, NMR spectroscopy, and elemental analysis. The molecular structures of all ligands and complexes 4 and 6 were determined by an X-ray. The results of the interactions of CT-DNA (calf thymus deoxyribonucleic acid) and HSA (human serum albumin) with ruthenium (II) complexes reveal that complex 4 binds well to CT-DNA and HSA. Kinetic and thermodynamic parameters for the reaction between complex and HSA confirmed the associative mode of interaction. The results of Quantum mechanics (QM) modelling and docking experiments toward DNA dodecamer and HSA support the strongest binding of the complex 4 to DNA major groove, as well as its binding to IIa domain of HSA with the lowest ΔG energy, which agrees with the solution studies. The modified GOLD docking results are indicative for Ru(p-cymene)LCl··(HSA··GLU292) binding and GOLD/MOPAC(QM) docking/modelling of DNA/Ligand (Ru(II)-N(7)dG7) covalent binding. The cytotoxic activity of compounds was evaluated by MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assay. Neither of the tested compounds shows activity against a healthy MRC-5 cell line while the MCF-7 cell line is the most sensitive to all. Compounds 3, 4 and 5 were about two times more active than cisplatin, while the antiproliferative activity of 6 was almost the same as with cisplatin. Flow cytometry analysis showed the apoptotic death of the cells with a cell cycle arrest in the subG1 phase.

Antagonist and partial agonist at the dopamine D2 receptors in drug-naïve and non-drug-naïve schizophrenia: a randomized, controlled trial

Few data are available on the efficacy and safety of antipsychotics with different dopamine D2 receptor (D2-R)-binding properties in drug-naïve and non-drug-naïve schizophrenia. Thus, we aimed to assess whether antipsychotic medication history influences efficacy and tolerability in schizophrenia, based on a randomized controlled study of antipsychotics with mechanisms involving either full antagonism or partial agonism of D2-R. Patients with schizophrenia were recruited and given perospirone or aripiprazole in a 12-week, flexible-dose, open-label, randomized controlled study. Data were analyzed after dividing the patients into antipsychotic-naïve and antipsychotic-treated group according to antipsychotic medication histories. Efficacy and safety were evaluated using the Positive and Negative Syndrome Scale (PANSS), the Drug-Induced Extrapyramidal Symptoms Scale, and the Barnes Akathisia Rating Scale. In patients receiving perospirone, the antipsychotic-naïve group (n = 22) showed greater symptom improvement than that shown by the antipsychotic-treated group (n = 29), as assessed by efficacy evaluation scales such as the PANSS total, positive, and excited component score (p = .006, p < .001, p = .003, respectively). In patients receiving aripiprazole, however, there was no significant difference in efficacy between the antipsychotic-naïve (n = 18) and antipsychotic-treated (n = 31) groups. No significant intra-group or inter-group difference was noted with respect to any of the tolerability-related parameters assessed. The present study data support the hypothesis that antipsychotic medication history may influence efficacy in patients who receive a D2-R full antagonist but not a D2-R partial agonist.

Epigenetic regulation of resistance to emotional stress: possible involvement of 5-HT1A receptor-mediated histone acetylation

The ability to resist stress is an important defensive function of a living body. Thus, elucidation of the mechanisms by which the brain resists stress could help to pave the way for new therapeutic strategies for stress-related psychiatric disorders including depression. The present review focuses on the roles of brain 5-HT1A receptor-mediated epigenetic mechanisms in the development of resistance to emotional stress. Behavioral pharmacological studies have demonstrated that treatment with a 5-HT1A receptor agonist 24 h before testing suppressed the decrease in emotional behaviors induced by acute restraint stress. Studies with DNA microarray technology have revealed that histone deacetylase genes were decreased in the hippocampus of mice that had been pretreated with a 5-HT1A receptor agonist 24 h beforehand. This preliminary finding was supported by data that hippocampal acetylated histone H3 was increased in mice that had developed emotional resistance to acute restraint stress by 5-HT1A receptor agonist. Furthermore, the histone deacetylase inhibitor trichostatin A also protected against the emotional changes induced by acute restraint stress, accompanied by the induction of histone H3 acetylation. These findings suggest that epigenetic mechanisms that are functionally coupled with 5-HT1A receptors may play a key role in the development of resistance to emotional stress.

Long-term Efficacy and Tolerability of Perospirone for Young Help-seeking People at Clinical High Risk: a Preliminary Open Trial

OBJECTIVE

Interest in the "at-risk mental state" (ARMS) for psychosis has increased because early intervention is expected to delay or prevent the onset of schizophrenia. However, the optimum intervention strategy remains controversial, especially with regard to antipsychotics. Although administration of antipsychotic medications is often associated with adverse effects and raises ethical considerations, recent studies have shown that some novel antipsychotics are safer and more tolerable for young people than conventional antipsychotics. We investigated whether administration of perospirone, a combined serotonin (5-HT)/dopamine antagonist and 5-HT1A receptor agonist, could alleviate prodromal symptoms and be well tolerated by clinical high risk patients.

METHODS

The participants were outpatients seeking help. The Structured Interview for Prodromal Symptoms was performed in patients identified as being at clinical high risk. The Scale of Prodromal Symptoms (SOPS) was also completed and changes of subjective experience were assessed with the Subjective Well-being under Neuroleptics, short version. The incidence of akathisia was recorded by using the Barnes Akathisia Scale. Subjects were monitored for 26 weeks after starting medication.

RESULTS

SOPS scores improved significantly after 26 weeks of perospirone therapy, while BAS scores did not show deterioration. No serious adverse events occurred during the study.

CONCLUSION

This trial suggests that perospirone therapy provides a clinical benefit for clinical high risk subjects without causing serious adverse events. Although further placebo-controlled studies are needed for confirmation, perospirone might be one of optimum treatments for individuals at imminent risk of psychosis.

5-HT(1A) receptor: an old target as a new attractive tool in drug discovery from central nervous system to cancer

The serotonin receptor subtype 5-HT(1A) was one of the first serotonin receptor subtypes pharmacologically characterized. This receptor subtype has long been object of intense research and is implicated in the pathogenesis and treatment of anxiety and depressive disorders. In recent years, new chemical entities targeting the 5-HT(1A) receptor (alone or in combination with other molecular targets) have been proposed for novel therapeutic uses in neuroprotection, cognitive impairment, Parkinson's disease, pain treatment, malignant carcinoid syndrome, and prostate cancer. This Perspective compares existing data on expression and signaling activity of the 5-HT(1A) receptor to a ligand with an intrinsic agonist or antagonist profile. Our purpose is also to make a complete overview, useful for underlining the features needed to select a specific pharmacological profile rather than another one. This aspect could be really interesting to consider and justify the 5-HT(1A) receptor as a new attractive target for drug discovery.

A 12-week randomized, open-label study of perospirone versus aripiprazole in the treatment of Japanese schizophrenia patients

OBJECT

To evaluate the efficacy and safety of aripiprazole and perospirone in Japanese patients with schizophrenia.

METHODS

In this 12-week, randomized, flexible-dose, open-label study, patients diagnosed with schizophrenia were randomized to receive aripiprazole (3-30 mg/day, n=49) or perospirone (8-48 mg/day, n=51). Efficacy and safety were evaluated using the Positive and Negative Syndrome Scale (PANSS), the Clinical Global Impression-Severity Scale (CGI-S), the Drug-Induced Extrapyramidal Symptoms Scale (DIEPSS) and the Barnes Akathisia Rating Scale (BAS) before treatment and every 4 weeks after the initiation of treatment.

RESULTS

Fifty-eight patients completed this study (aripiprazole, n=31; perospirone, n=27). No significant differences in gender, episode, age, schizophrenia type, weight, previous treatment and PANSS score were observed between the two groups at baseline. Both groups showed significant improvements during the study, with reductions in the total PANSS scores (Repeated measure analysis of variance, both p<0.0001). There were no significant differences in the PANSS change scores, CGI-S change scores, DIEPSS total score, BAS total score or over time between groups. The most common adverse event was insomnia in both groups.

CONCLUSIONS

In Japanese schizophrenia patients, aripiprazole and perospirone showed equal efficacy, tolerability and patient compliance. Both drugs showed good efficacy for treating schizophrenia. This paper is the first randomized study to evaluate the comparative efficacy and safety of aripiprazole and perospirone in the treatment of patients with schizophrenia.

Atypical antipsychotics: trends in analysis and sample preparation of various biological samples

Atypical antipsychotics are increasingly popular and increasingly prescribed. In some countries, they can even be obtained over-the-counter, without a prescription, making their abuse quite easy. Although atypical antipsychotics are thought to be safer than typical antipsychotics, they still have severe side effects. Intoxications are not rare and some of them have a fatal outcome. Drug interactions involving atypical antipsychotics complicate patient management in clinical settings and the determination of the cause of death in fatalities. In view of the above, analytical strategies that can efficiently isolate atypical antipsychotics from a variety of biological samples and quantify them accurately, sensitively and reliably, are of utmost importance both for the clinical, as well as for the forensic toxicologist. In this review, we will present and discuss novel analytical strategies that have been developed from 2004 to the present day for the determination of atypical antipsychotics in various biological samples.

Comparative pharmacology of antipsychotics possessing combined dopamine D2 and serotonin 5-HT1A receptor properties

RATIONALE

There is increasing interest in antipsychotics intended to manage positive symptoms via D(2) receptor blockade and improve negative symptoms and cognitive deficits via 5-HT(1A) activation. Such a strategy reduces side-effects such as the extrapyramidal syndrome (EPS), weight gain, and autonomic disturbance liability.

OBJECTIVE

This study aims to review pharmacological literature on compounds interacting at both 5-HT(1A) and D(2) receptors (as well as at other receptors), including aripiprazole, perospirone, ziprasidone, bifeprunox, lurasidone and cariprazine, PF-217830, adoprazine, SSR181507, and F15063.

METHODS

We examine data on in vitro binding and agonism and in vivo tests related to (1) positive symptoms (e.g., psychostimulant-induced hyperactivity or prepulse inhibition deficit), (2) negative symptoms (e.g., phencyclidine-induced social interaction deficits and cortical dopamine release), and (3) cognitive deficits (e.g., phencyclidine or scopolamine-induced memory deficits). EPS liability is assessed by measuring catalepsy and neuroendocrine impact by determining plasma prolactin, glucose, and corticosterone levels.

RESULTS

Compounds possessing "balanced" 5-HT(1A) receptor agonism and D(2) antagonism (or weak partial agonism) and, in some cases, combined with other beneficial properties, such as 5-HT(2A) receptor antagonism, are efficacious in a broad range of rodent pharmacological models yet have a lower propensity to elicit EPS or metabolic dysfunction.

CONCLUSIONS

Recent compounds exhibiting combined 5-HT(1A)/D(2) properties may be effective in treating a broader range of symptoms of schizophrenia and be better tolerated than existing antipsychotics. Nevertheless, further investigations are necessary to evaluate recent compounds, notably in view of their differing levels of 5-HT(1A) affinity and efficacy, which can markedly influence activity and side-effect profiles.

Pharmacokinetics and metabolism update for some recent antipsychotics

INTRODUCTION

The search for drugs that reduce psychotic symptoms, with minimal adverse effects, has led to the development of new agents that act somewhat differently from their older antipsychotic counterparts. These agents, which include aripiprazole, lurasidone and perospirone, act by targeting both D₂ and 5-HT(1A) receptors, in addition to other characteristic receptors.

AREAS COVERED

This article covers the pharmacokinetics and metabolism of aripiprazole, perospirone, lurasidone and cariprazine. The review also describes the effects of physiological and pathological variables on these drugs as well as potential drug interactions. The author provides the reader with knowledge of the fundamental pharmacokinetic characteristics and metabolic pathways of these new antipsychotics, emphasizing the clinically important common features and differences compared to other older agents.

EXPERT OPINION

Aripiprazole, perospirone, lurasidone and cariprazine share some of the pharmacokinetic characteristics of older, lipophilic antipsychotics and, like these, each has some distinct pharmacokinetic features that are clinically beneficial and some that are not. We await the results of future practical effectiveness trials of these new antipsychotics and their follow-on derivatives to learn more about their benefit/risk profile compared with established antipsychotics. It is hoped that some of these newer antipsychotics will not only increase the range of pharmacotherapeutic options, but decisively improve the expectations of psychotherapy for schizophrenia.

Genetic polymorphisms in dopamine- and serotonin-related genes and treatment responses to risperidone and perospirone

We investigated the possible association between genetic polymorphisms in the dopamine receptor and serotonin transporter genes and the responses of schizophrenic patients treated with either risperidone or perospirone. The subjects comprised 27 patients with schizophrenia who were clinically evaluated both before and after treatment. The genotyping of the polymorphisms of the dopamine D2 receptor gene (DRD2) (rs1801028 and rs6277), the dopamine D4 receptor gene (DRD4) (120-bp tandem repeats and rs1800955), and serotonin transporter gene (5HTT)(variable number of tandem repeats; VNTR) were performed using the real-time polymerase chain reaction and sequencing. In DRD2 and 5HTT-VNTR, there were no significant correlations between clinical response and polymorphism in the case of risperidone, and for perospirone treatment it was impossible to analyze the clinical evaluation due to the absence of genotype information. On the other hand, in DRD4 there were significant correlations in the two-factor interaction effect on the Positive and Negative Syndrome Scale (PANSS) between the two drugs [120-bp tandem repeat, p=0.003; rs1800955, p=0.043]. Although the small sample represents a serious limitation, these results suggest that variants in DRD4 are a predictor of whether treatment will be more effective with risperidone or with perospirone in individual patients.

Randomized clinical comparison of perospirone and risperidone in patients with schizophrenia: Kansai Psychiatric Multicenter Study

AIM

Perospirone is classified as a second-generation antipsychotic agent for the treatment of schizophrenia. Perospirone binds with high affinity to serotonin 5-HT2A receptors and dopamine D2 receptors. There are no reports of clinical comparisons of perospirone and risperidone in multicenter studies. To clarify the clinical traits of perospirone in the treatment of schizophrenia, the clinical efficacies and side-effects of perospirone and risperidone were compared in a randomized clinical multicenter trial.

METHODS

Sixty-six schizophrenia patients were enrolled in the trial. The Positive and Negative Syndrome Scale (PANSS) total, positive, negative and general symptoms scores and Drug-Induced Extra-Pyramidal Symptoms Scale (DIEPSS) scores were investigated at 0, 4, 8 and 12 weeks.

RESULTS

Significant reductions in the PANSS total and subscale scores were observed in both the perospirone and risperidone groups, with no significant between-group differences at 4 and 12 weeks. Risperidone improved the total scores and overall psychopathologic symptom total scores more effectively than perospirone at week 8. There were no significant differences in the DIEPSS scores at 0, 4, 8 and 12 weeks between the perospirone and risperidone groups. The numbers of patients who dropped out did not differ between the perospirone and risperidone groups.

CONCLUSIONS

Perospirone was as effective as risperidone against positive and negative symptoms in patients with schizophrenia. Both antipsychotic agents were equally well-tolerated.

Augmentation of antidepressants with perospirone for treatment-resistant major depressive disorder

We examined the efficacy and tolerability of perospirone, a dopamine D2 and 5-HT2A receptor antagonist and a partial 5-HT1A receptor agonist, in the augmentation of antidepressant treatment of partially responding and nonresponding patients with major depressive disorder. Twelve patients with major depressive disorder and an incomplete or no response to different kinds of antidepressants (selective serotonin reuptake inhibitor, milnacipran, or sulpride) monotherapy or polytherapy for 8 weeks or more were treated with perospirone augmentation in an eight-week, open-label study. Data were gathered from July 2006 to March 2008. The mean duration of antidepressant pharmacotherapy at baseline was 28 weeks. At baseline, the mean (+/-SD) of the MADRS scores was 35.8+/-10.1. The mean (+/-SD) initial dose of perospirone was 7.0+/-2.9 mg/day and the final dose was 11.7+/-6.6 mg/day. Significant reductions in MADRS scores were observed at weeks 2, 4, 6 and 8. Although two of the twelve subjects who completed the protocol achieved remission by the study endpoint, five of the twelve patients were responders (i.e., >50% improvement in the MADRS score). Sleepiness and tremor were observed in six patients and one patient, respectively, resulting in a reduction of perospirone dose due to these side effects. The discontinuation rate after 8 weeks of treatment was zero. These findings suggest that perospirone may be an effective augmentation strategy for improving therapeutic response in patients with treatment-resistant major depressive disorder when administered in combination with standard antidepressant therapy. Based on this clinical evidence, a double-blind, placebo-controlled trial is warranted.

Phencyclidine-induced cognitive deficits in mice are improved by subsequent subchronic administration of the antipsychotic drug perospirone: role of serotonin 5-HT1A receptors

Accumulating evidence suggests that the serotonin 5-HT(1A) receptor may play a role in the pathophysiology of schizophrenia. The present study was undertaken to examine the effects of perospirone, an atypical antipsychotic drug with 5-HT(1A) receptor agonism, on cognitive deficits in mice after repeated administration of the NMDA receptor antagonist phencyclidine (PCP). Subsequent subchronic (14 days) administration of perospirone (1.0, 3.0, or 10 mg/kg) significantly attenuated PCP (10 mg/kg)-induced cognitive deficits in mice, in a dose-dependent manner. The effects of perospirone (10 mg/kg) were significantly antagonized by co-administration of the selective 5-HT(1A) receptor antagonist WAY100635 (1.0 mg/kg). Furthermore, hypothermia by the 5-HT(1A) receptor agonist 8-OH DPAT (0.25 mg/kg) was significantly attenuated in mice treated with PCP. Moreover, a receptor binding assay using [(3)H]WAY100635 revealed that levels of 5-HT(1A) receptors in the hippocampus, but not in the frontal cortex, of PCP-treated mice were significantly lower than those of saline-treated mice. These findings suggest that repeated PCP administration alters 5-HT(1A) receptor function in the mouse brain, and that subsequent subchronic administration of perospirone ameliorates PCP-induced cognitive deficits via 5-HT(1A) receptors. Therefore, perospirone could be a potential therapy for the cognitive deficits observed in schizophrenic patients.

A pharmaco-EEG study on antipsychotic drugs in healthy volunteers

RATIONALE

Both psychotropic drugs and mental disorders have typical signatures in quantitative electroencephalography (EEG). Previous studies found that some psychotropic drugs had EEG effects opposite to the EEG effects of the mental disorders treated with these drugs (key-lock principle).

OBJECTIVES

We performed a placebo-controlled pharmaco-EEG study on two conventional antipsychotics (chlorpromazine and haloperidol) and four atypical antipsychotics (olanzapine, perospirone, quetiapine, and risperidone) in healthy volunteers. We investigated differences between conventional and atypical drug effects and whether the drug effects were compatible with the key-lock principle.

METHODS

Fourteen subjects underwent seven EEG recording sessions, one for each drug (dosage equivalent of 1 mg haloperidol). In a time-domain analysis, we quantified the EEG by identifying clusters of transiently stable EEG topographies (microstates). Frequency-domain analysis used absolute power across electrodes and the location of the center of gravity (centroid) of the spatial distribution of power in different frequency bands.

RESULTS

Perospirone increased duration of a microstate class typically shortened in schizophrenics. Haloperidol increased mean microstate duration of all classes, increased alpha 1 and beta 1 power, and tended to shift the beta 1 centroid posterior. Quetiapine decreased alpha 1 power and shifted the centroid anterior in both alpha bands. Olanzapine shifted the centroid anterior in alpha 2 and beta 1.

CONCLUSIONS

The increased microstate duration under perospirone and haloperidol was opposite to effects previously reported in schizophrenic patients, suggesting a key-lock mechanism. The opposite centroid changes induced by olanzapine and quetiapine compared to haloperidol might characterize the difference between conventional and atypical antipsychotics.

Discovery of 3-hydroxy-4-carboxyalkylamidino-5-arylamino-isothiazoles as potent MEK1 inhibitors

3-Hydroxy-4-carboxyalkylamidino-5-arylamino-isothiazoles were discovered as potent in vitro MEK1 inhibitors.

Role of 5-HT(1A) receptors in the modulation of stress-induced lactate metabolism in the medial prefrontal cortex and basolateral amygdala

RATIONALE

Lactate has been shown to play a significant role in energy metabolism and reflect neural activity in the brain.

OBJECTIVES

Using in vivo microdialysis technique, we measured extracellular lactate concentrations in the medial prefrontal cortex (mPFC) and the basolateral amygdaloid (BLA) nucleus of rats under electric foot shock stress. Moreover, to examine the role of serotonin (5-HT)(1A) receptors in brain energy metabolism in response to stressors, we attempted to determine whether the stress-induced changes of extracellular lactate levels in the mPFC and BLA are attenuated by tandospirone, a partial agonist at 5-HT(1A) receptors, or perospirone, a novel atypical antipsychotic with a 5-HT(1A) receptor partial agonist and 5-HT(2A)/dopamine-D(2) antagonist property.

RESULTS

Foot shock stress led to an increase in extracellular lactate concentrations both in the mPFC and BLA. Tandospirone (2 mg/kg) attenuated the foot shock stress-induced increase of extracellular lactate concentrations in both of the brain regions, which was blocked by pretreatment with WAY-100635, a selective 5-HT(1A) antagonist. On the other hand, perospirone (0.3 mg/kg) attenuated the increment of extracellular lactate concentrations in the mPFC and BLA, which was unaltered by pretreatment with WAY-100635.

CONCLUSIONS

These results indicate that the foot shock stress-induced increase in lactate metabolism is partly regulated by 5-HT(1A) receptors both in cortical and limbic regions.

NMR study on cis-N-[4-[4-(1,2-benzisozole-3-yl)-1-piperazinyl] butyl]cyclohexane-1,2-dicarboximide monohydrochloride dihydrate

Cis-N-[4-[4-(1,2-benzisozole-3-yl)-1-piperazinyl]butyl]cyclohexane-1,2-dicarboximide monohydrochloride dihydrate was studied spectroscopically. Complete NMR assignments were made using DEPT, H-H COSY, as well as HMQC and HMBC heteronuclear correlation techniques. The hydrochloride salt was found at delta > 10. The dihydrate was present in the region delta 3-4 in DMSO-d6 solvent. Asymmetry carbon C3 brought chemical-shift-nonequivalent of cis-cyclohexanyl group, splitting four systems H1, H1', H2 and H2'. Diamagnetic anisotropy of benzisozolyl group results in three troops peaks of piperazinyl group.

A benzisothiazole derivative and antipsychotic agent, perospirone, for augmentation of selective serotonin reuptake inhibitors (SSRIs) in refractory obsessive-compulsive disorder (OCD): two patient case series

Even though selective serotonin reuptake inhibitors (SSRIs) are the mainstay of pharamacological treatment for obsessive-compulsive disorder (OCD), as many as 40% of patients do not have an adequate response to these medications. For such SSRI-refractory patients, the augmentation of SSRIs with new-generation antipsychotics that modulate both 5-HT and DA systems has recently been proven effective in controlled augmentation studies. The benzisothiazole derivative perospirone is a new serotonin 5-HT2 and dopamine D2 antagonist available in Japan for the treatment of schizophrenia. As its unique property, perospirone also exhibits 5-HT1A agonistic action. We present two SSRI-refractory OCD patients who showed little improvement with adequate trials of SSRI monotherapy, but exhibited significant improvement in their OCD symptoms after the addition of perospirone to ongoing SSRI treatment. The cases suggest that perospirone augmentation may be an effective and well-tolerated strategy for SSRI-refractory OCD patients. Controlled studies are required to further confirm the efficacy and tolerability of perospirone augmentation for treatment-resistant OCD.

Novel antipsychotics in schizophrenia

Several atypical antipsychotics have become available for the treatment of schizophrenia that are at least as effective as conventional treatment and with fewer extrapyramidal side effects. Their presumed mechanisms of therapeutic action vary and are no longer limited to dopamine D2 receptor antagonism. Numerous novel drugs are in development, with a variety of receptor affinities and other supposed therapeutic effects. This article will review current developments in drug discovery alongside contemporary evidence for potential substrates and mechanisms of antipsychotic action. Despite many promising developments there is no ideal antipsychotic to date. Progress in drug treatment for schizophrenia is confronted by several areas of difficulty which, barring serendipity, must be resolved before real advances can be anticipated.

Role of C-terminal region in the functional regulation of rat serotonin transporter (SERT)

Previously, we revealed that the state of the actin cytoskeleton affects the uptake activity of the serotonin transporter (SERT). Recently, it was reported that the C-terminus of SERT interacts with MacMARCKS, a substrate of PKC that can bind to the actin cytoskeleton. To elucidate the importance of the C-terminal region in the regulation of SERT activity and the interaction with the actin cytoskeleton, we examined whether the overexpression of the C-terminus affects the transport activity of SERT. To this end, we overexpressed a GFP-fused 30-amino acid construct of the SERT C-terminus (GFP-SERT-CT) in HEK293 cells stably expressing FLAG-tagged SERT (FL-SERT-HEK293 cells). The SERT uptake activity and transporter current were attenuated in GFP-SERT-CT-expressing FL-SERT-HEK293 cells, as compared with GFP-expressing FL-SERT-HEK293 cells. Eadie-Hofstee analysis revealed that GFP-SERT-CT overexpression attenuated the SERT uptake activity by reducing the Vmax, but not changing the Km, which was consistent with the results of experiments on the cell-surface expression of SET using biotinylation/immunoblot analysis. Immunocytochemical analysis demonstrated that GFP-SERT-CT was co-localized with FLAG-SERT and cortical actin at the plasma membrane. In addition, the SERT C-terminus did not affect dopamine transporter activity. These findings showed the significance of the C-terminal region to the functional regulation of SERT, suggesting that GFP-SERT-CT acts as a molecular decoy to disrupt the interaction between SERT and the actin cytoskeleton.

Perospirone, a Novel Antipsychotic Drug, Inhibits Marble-Burying Behavior via 5-HT1A Receptor in Mice: Implications for Obsessive-Compulsive Disorder

Perospirone is a novel atypical antipsychotic drug with dopamine (DA) D(2)- and serotonin (5-hydroxytryptamine, 5-HT) 5-HT(2A)-receptor antagonist, and 5-HT(1A)-receptor agonist properties. In the present study, we examined the effect of perospirone on marble-burying behavior, which has been considered an animal model of obsessive-compulsive disorder (OCD), compared with the effects of other antipsychotics such as haloperidol and risperidone. Perospirone at a dose of 10 mg/kg (p.o.) inhibited marble-burying behavior without affecting the locomotor activity in mice. On the other hand, haloperidol (0.1 mg/kg, i.p.) and risperidone (1 mg/kg, p.o.) showed significant suppression of locomotor activity at the dose that inhibited marble-burying behavior. Furthermore, the inhibition of marble-burying behavior by perospirone was antagonized by WAY100135 (10 mg/kg, i.p.), a selective 5-HT(1A)-receptor antagonist. WAY100135 at the same dose also antagonized the inhibition of marble-burying behavior by 8-OH-DPAT (3 mg/kg, i.p.), a selective 5-HT(1A)-receptor agonist. These findings suggest that perospirone may exhibit anti-OCD activity in clinical use and that 5-HT(1A)-receptor agonistic activity may be involved in the inhibition of marble-burying behavior by perospirone.

Effects of serotonin–dopamine antagonists on prepulse inhibition and neurotransmitter contents in the rat cortex

Perospirone is a serotonin-dopamine antagonist (SDA) recently developed in Japan as an atypical antipsychotic to be used in the treatment of schizophrenia. The amines and amino acids in the cortex are assumed to play an important role in the cognitive dysfunction of schizophrenia. To investigate the acute effect of perospirone on cognition, we compared perospirone to risperidone and haloperidol by assessing their influence on prepulse inhibition (PPI). Moreover, we studied the effects of these drugs on amine and amino acid contents in the rat cortex. Perospirone had a significant influence: PPI, dopamine turnover and glycine contents increased statistically and serotonin decreased statistically in comparison to control levels. Our results suggest that, of the three antipsychotic drugs, only perospirone promotes cognition, and this ability is associated with increase in dopamine turnover, reduction in serotonin turnover and increase in glycine contents.