Effect of adjunctive treatment with serotonin-1A agonist tandospirone on memory functions in schizophrenia

Prevention of MK-801-induced amnestic effect with combined activation of 5-HT1A and muscarinic receptors in mice

BACKGROUND

Muscarinic or 5-HT1A receptors are crucial in learning and memory processes, and their expression is evident in the brain areas involved in cognition. The administration of the activators of these receptors prevents the development of cognitive dysfunctions in animal models of schizophrenia induced by MK-801 (N-methyl-d-aspartate receptor antagonist) administration. GABAergic dysfunction is considered as one of the most important causes of MK-801-induced spatial learning deficits.

METHODS

Novel object recognition (NOR) and Morris water maze (MWM) tests were used to study the anti-amnestic effect of the biased 5-HT1A receptor agonist (F15599) alone or in combinations with VU0357017 (M1 receptor allosteric agonist), VU0152100 (M4 receptor positive allosteric modulator), and VU0238429 (M5 receptor positive allosteric modulator) on MK-801-induced dysfunctions. The compounds were administered for 5 consecutive days. Animals tested with the MWM underwent 5-day training. Western blotting was used to study the expressions of 5-HT1A receptors and the level of GAD65 in the frontal cortices (FCs) and hippocampi of the animals.

RESULTS

F15599 prevented the amnestic effect induced by MK-801 in the MWM at a dose of 0.1 mg/kg. The co-administration of the compound with muscarinic receptors activators had no synergistic effect. The additive effect of the combinations was evident in the prevention of declarative memory dysfunctions investigated in NOR. The administration of MK-801 impaired 5-HT1A expression in the hippocampi and decreased GAD65 levels in both the FCs and hippocampi. The administration of muscarinic ligands prevented these MK-801-induced deficits only in the hippocampi of MWM-trained animals. No effects of the compounds were observed in untrained mice.

CONCLUSION

Our results indicate that F15599 prevents schizophrenia-related spatial learning deficits in the MWM; however, the activity of the compound is not intensified with muscarinic receptors activators. In contrast, the combined administration of the ligands is effective in the NOR model of declarative memory. The muscarinic receptors activators reversed MK-801-induced 5-HT1A and GAD65 dysfunctions in the hippocampi of MWM-trained mice, but not in untrained mice.

Neonatal hypoxia impairs serotonin release and cognitive functions in adult mice

Children who experienced moderate perinatal asphyxia (MPA) are at risk of developing long lasting subtle cognitive and behavioral deficits, including learning disabilities and emotional problems. The prefrontal cortex (PFC) regulates cognitive flexibility and emotional behavior. Neurons that release serotonin (5-HT) project to the PFC, and compounds modulating 5-HT activity influence emotion and cognition. Whether 5-HT dysregulations contribute to MPA-induced cognitive problems is unknown. We established a MPA mouse model, which displays recognition and spatial memory impairments and dysfunctional cognitive flexibility. We found that 5-HT expression levels, quantified by immunohistochemistry, and 5-HT release, quantified by in vivo microdialysis in awake mice, are reduced in PFC of adult MPA mice. MPA mice also show impaired body temperature regulation following injection of the 5-HT1A receptor agonist 8-OH-DPAT, suggesting the presence of deficits in 5-HT auto-receptor function on raphe neurons. Finally, chronic treatment of adult MPA mice with fluoxetine, an inhibitor of 5-HT reuptake transporter, or the 5-HT1A receptor agonist tandospirone rescues cognitive flexibility and memory impairments. All together, these data demonstrate that the development of 5-HT system function is vulnerable to moderate perinatal asphyxia. 5-HT hypofunction might in turn contribute to long-term cognitive impairment in adulthood, indicating a potential target for pharmacological therapies.

Augmentation therapy with tandospirone citrate in vascular depression patients with mild cognitive impairment: A prospective randomized clinical trial

Cognitive impairment is a prominent clinical manifestation of vascular depression (VaDep). The current study aimed to assess the efficacy of tandospirone citrate in VaDep cases with mild cognitive impairment (VaDep-MCI) as well as the role of plasma monoamine neurotransmitters during the treatment. In this single-blind, randomized controlled study, 116 participants were randomly assigned to the tandospirone (tandospirone citrate-escitalopram) and control (escitalopram) groups. The primary endpoints were changes in cognitive test scores from baseline to Week 8, including the Rey Auditory Verbal Learning Test (RAVLT), Semantic Verbal Fluency (SVF) test, Trail Making Test (TMT), Digital Span Test (DST) and Clock Drawing Test (CDT) scores. Generalized estimating equation models were used to examine repeated measures. The results showed that compared with the changes in the control group from baseline to Week 8, the tandospirone group showed more significant changes in SVF score at Weeks 4 (p < 0.05) and 8 (p < 0.001), and TMT (B-A) score at Week 8 (p < 0.05). RAVLT, DST and DCT scores were relatively stable in both groups during the study period. Moreover, mediation analysis showed that these results were not mediated by the alleviation of depression symptoms. Partial Spearman correlation analysis showed that only plasma 5-hydroxytryptamine (5-HT) was positively correlated with Hamilton Depression Rating Scale score after Bonferroni correction (r = 0.347, p < 0.001). Augmentation therapy with tandospirone citrate improved the executive and language functions of VaDep-MCI patients. Additionally, plasma 5-HT levels may serve as a potential biomarker of VaDep severity. These findings may provide clinical insights into the treatment of vascular depression.

5-HT1A Receptor Agonist Treatment Partially Ameliorates Rett Syndrome Phenotypes in mecp2-Null Mice by Rescuing Impairment of Neuron Transmission and the CREB/BDNF Signaling Pathway

Rett syndrome (RTT) is an X-linked neurodevelopmental disorder caused by mutations in the gene that encodes methyl CpG-binding protein 2 (MECP2) and is characterized by the loss of acquired motor and language skills, stereotypic movements, respiratory abnormalities and autistic features. There has been no effective treatment for this disorder until now. In this study, we used a Mecp2-null (KO) mouse model of RTT to investigate whether repeated intraperitoneal treatment with the 5-HT1A receptor agonist tandospirone could improve the RTT phenotype. The results showed that administration of tandospirone significantly extended the lifespan of Mecp2-KO mice and obviously ameliorated RTT phenotypes, including general condition, hindlimb clasping, gait, tremor and breathing in Mecp2-KO mice. Tandospirone treatment significantly improved the impairment in GABAergic, glutaminergic, dopaminergic and serotoninergic neurotransmission in the brainstem of Mecp2-KO mice. Decreased dopaminergic neurotransmission in the cerebellum of Mecp2-KO mice was also significantly increased by tandospirone treatment. Moreover, RNA-sequencing analysis found that tandospirone modulates the RTT phenotype, partially through the CREB1/BDNF signaling pathway in Mecp2-KO mice. These findings provide a new option for clinical treatment.

Beneficial effects of atypical antipsychotics on object recognition deficits after adolescent toluene exposure in mice: involvement of 5-HT1A receptors

Background: Inhalant (e.g. toluene) misuse by adolescents has been linked to psychosis and persistent cognitive deficits. Identifying effective strategies to improve cognitive deficits following chronic toluene misuse is critical. 5-HT_1A receptor has been proposed as a target for the treatment of cognitive deficits.Objectives: We compared the effects of antipsychotics on recognition deficits after adolescent toluene exposure in mice and elucidated the role of 5-HT_1A receptors in the cognition-improving effects of antipsychotics.Methods: Male NMRI mice (n = 279) received one injection per day of either toluene (750 mg/kg) or corn oil at postnatal days 35-39 and 42-46. Thereafter, the acute and subchronic effects of haloperidol, aripiprazole, or clozapine on toluene-induced recognition deficits were evaluated by novel object recognition test.Results: Acute administration of aripiprazole (p < .05) and clozapine (p < .01), but not haloperidol, significantly attenuated the toluene-induced recognition deficits. Pretreatment with 5-HT_1A receptor antagonist WAY -100,635 (p < .05) blocked their beneficial effects. Moreover, 5-HT_1A receptor agonist buspirone (p < .01) ameliorated the toluene-induced recognition deficits, which was reversed by WAY -100,635 (p < .001). Finally, after repeated treatment with clozapine, aripiprazole, and buspirone daily for 14 days, the impaired object recognition in toluene-exposed mice was significantly improved (p < .05) and the beneficial effects lasted for at least 2 weeks (p < .05).Conclusions: The results indicate that clozapine and aripiprazole, which display 5-HT_1A agonist properties, restored cognitive deficits in mice induced by adolescent toluene exposure. These findings suggest that these antipsychotics should be further explored as a potential treatment option for cognitive deficits in patients with psychosis associated with toluene exposure.

Cognitive Deficit in Schizophrenia: From Etiology to Novel Treatments

Schizophrenia is a major mental illness characterized by positive and negative symptoms, and by cognitive deficit. Although cognitive impairment is disabling for patients, it has been largely neglected in the treatment of schizophrenia. There are several reasons for this lack of treatments for cognitive deficit, but the complexity of its etiology-in which neuroanatomic, biochemical and genetic factors concur-has contributed to the lack of effective treatments. In the last few years, there have been several attempts to develop novel drugs for the treatment of cognitive impairment in schizophrenia. Despite these efforts, little progress has been made. The latest findings point to the importance of developing personalized treatments for schizophrenia which enhance neuroplasticity, and of combining pharmacological treatments with non-pharmacological measures.

A functional HTR1A polymorphism, rs6295, predicts short-term response to lurasidone: confirmation with meta-analysis of other antipsychotic drugs

Stimulation of the serotonin (5-HT)1A receptor (HTR1A) has been shown to contribute to the mechanism of action of some atypical antipsychotic drugs (APDs), including clozapine and lurasidone. A meta-analysis of rs6295, a functional polymorphism located at the promoter region of HTR1A, showed association with clinical response in schizophrenic patients treated with atypical APD. We have now tested whether other SNPs related to rs6295 predict response to lurasidone. We first evaluated whether rs358532 and rs6449693, tag SNPs for rs6295, predicted response to lurasidone, using data from two clinical trials of acutely psychotic schizophrenia patients with European (EUR, n = 171) or African (AFR, n = 131) ancestry; we then determined if those findings could be replicated in a third trial of lurasidone of similar design. Weekly changes (up to 6 weeks) in the Positive and Negative Syndrome Scale (PANSS) Total score and its five subscales were used to assess response. In EUR, a significant association, or trends for association, were observed for PANSS Total (p = 0.035), positive (p = 0.039), negative (p = 0.004), and disorganization (p = 0.0087) subscales, at week 1-6. There was a trend for replication with PANNS Total (p = 0.036) in the third trial. No significant association was observed in AFR or the placebo group. Meta-analysis of five studies, including the three with lurasidone, showed that rs6295 was associated with improvement in positive (p = 0.023) and negative (p ≤ 0.0001) symptoms in EUR patients with schizophrenia. This is the first study to show a significant association between functional HTR1A polymorphisms and treatment response to lurasidone. The meta-analysis provides additional evidence that rs6295 could be a race-dependent biomarker for predicting treatment response to APDs in schizophrenic patients with European Ancestry.

Role of tandospirone, a 5-HT1A receptor partial agonist, in the treatment of central nervous system disorders and the underlying mechanisms

5-hydroxytryptamine (5-HT, serotonin) is an important neurotransmitter in the modulation of the cognitive, behavioral and psychological functions in animals and humans. Among the fourteen subtypes of 5-HT receptor, 5-HT1A receptor has been extensively studied. Tandospirone, an azapirone derivative with strong and selective agonist effect on 5-HT1A receptor, has been used for the treatment of anxiety disorders especially generalized anxiety disorder for decades. Recently, tandospirone showed the efficacy in relieving the syndromes of social anxiety disorder and post-traumatic stress disorder as well as in potentiating the effect of antidepressants in the treatment of depression in both preclinical and clinical studies. More impressively, the beneficial effect of tandospirone has been revealed on improvement of motor dysfunction of Parkinson's disease and cognitive deficits of schizophrenia either in monotherapy or in combination with other drugs. This review discusses the superiority of tandospirone in the treatment of the disorders and associated mechanisms in central nervous system from the literature.

HTR1A Gene Polymorphisms and 5-HT1A Receptor Partial Agonist Antipsychotics Efficacy in Schizophrenia

Individual differences in serotonin 1A (5-HT1A) receptor may result in variable response to antipsychotics with 5-HT1A receptor partial agonism. We investigated the relationship between 5-HT1A receptor gene (HTR1A) single nucleotide polymorphisms (SNPs) and efficacy of antipsychotics with 5-HT1A receptor partial agonism in Japanese patients with schizophrenia. Perospirone or aripiprazole was administered to 100 patients with schizophrenia in a randomized controlled study. Candidate SNPs were rs6295 (which affects HTR1A expression and function), rs1364043, rs878567, and rs10042486. Efficacy at week 12 of treatment was evaluated using the Positive and Negative Syndrome Scale (PANSS) 5-factor subscales (excitement/hostility, depression/anxiety, cognition, positive, and negative). Rs1364043 T allele was correlated with the percent change in the PANSS 5-factor negative score (P < 0.01). Haplotype analysis showed that the rs10042486-rs6295-rs1364043 T-C-G haplotype was correlated with worse negative score improvement (haplotype frequency, 0.675; P = 0.014), and the relatively rare T-G-T haplotype correlated with better efficacy (haplotype frequency, 0.05; P = 0.031). This is the first study to show that rs10042486-rs6295-rs1364043 HTR1A variants may be correlated with the improvement of the PANSS 5-factor negative score during treatment with 5-HT1A partial agonist antipsychotics. Studies with larger sample sizes and in different ethnic groups are warranted.

Verbal memory

Verbal memory is impaired in neurological and psychiatric conditions and provides one of the main targets of intervention. Specifically, this cognitive domain has been shown to provide a major determinant of outcome in schizophrenia and mood disorders. Therefore, verbal memory disturbances should be focused in the development of novel pharmacological and psychosocial therapeutics. Effective integration between preclinical and clinical studies should provide a key to the pursuit of drugs enhancing verbal memory.

Alterations of 5-HT1A receptor-induced G-protein functional activation and relationship to memory deficits in patients with pharmacoresistant temporal lobe epilepsy

The 5-hydroxytryptamine-1A (5-HT1A) receptors are known to be involved in the inhibition of seizures in epilepsy. Moreover, studies propose a role for the 5-HT1A receptor in memory function; it is believed that the higher density of this receptor in the hippocampus plays an important role in its regulation. Positron emission tomography (PET) studies in patients with mesial temporal lobe epilepsy (mTLE) have demonstrated that a decrease in 5-HT1A receptor binding in temporal regions may play a role in memory impairment. The evidences lead us to speculate whether this decrease in receptor binding is associated with a reduced receptor number or if the functionality of the 5-HT1A receptor-induced G-protein activation and/or the second messenger cascade is modified. The purpose of the present study is to determine 5-HT1A receptor-induced G-protein functional activation by 8-OH-DPAT-stimulated [(35)S]GTPγS binding assay in hippocampal tissue of surgical patients with mTLE. We correlate functional activity with epilepsy history and neuropsychological assessment of memory. We found that maximum functional activation stimulation values (Emax) of [(35)S]GTPγS binding were significantly increased in mTLE group when compared to autopsy samples. Furthermore, significant correlations were found: (1) positive coefficients between the Emax with the age of patient and frequency of seizures; (2) negative coefficients between the Emax and working memory, immediate recall and delayed recall memory tasks. Our data suggest that the epileptic hippocampus of patients with mTLE presents an increase in 5-HT1A receptor-induced G-protein functional activation, and that this altered activity is related to age and seizure frequency, as well as to memory consolidation deficit.

Tandospirone, a 5-HT1A partial agonist, ameliorates aberrant lactate production in the prefrontal cortex of rats exposed to blockade of N-methy-D-aspartate receptors; Toward the therapeutics of cognitive impairment of schizophrenia

Rationale: Augmentation therapy with serotonin-1A (5-HT_1A) receptor partial agonists has been suggested to improve cognitive impairment in patients with schizophrenia. Decreased activity of prefrontal cortex may provide a basis for cognitive deficits of the disease. Lactate plays a significant role in the supply of energy to the brain, and glutamatergic neurotransmission contributes to lactate production.

Objectives and methods: The purposes of this study were to examine the effect of repeated administration (once a daily for 4 days) of tandospirone (0.05 or 5 mg/kg) on brain energy metabolism, as represented by extracellular lactate concentration (eLAC) in the medial prefrontal cortex (mPFC) of a rat model of schizophrenia.

Results: Four-day treatment with MK-801, an NMDA-R antagonist, prolonged eLAC elevation induced by foot-shock stress (FS). Co-administration with the high-dose tandospirone suppressed prolonged FS-induced eLAC elevation in rats receiving MK-801, whereas tandospirone by itself did not affected eLAC increment.

Conclusions: These results suggest that stimulation of 5-HT_1A receptors ameliorates abnormalities of energy metabolism in the mPFC due to blockade of NMDA receptors. These findings provide a possible mechanism, based on brain energy metabolism, by which 5-HT_1A agonism improve cognitive impairment of schizophrenia and related disorders.

Possible dose-side effect relationship of antipsychotic drugs: relevance to cognitive function in schizophrenia

Management of adverse events is a major concern of clinicians who use antipsychotic drugs. The incidence of motor side effects is dose dependent. Atypical antipsychotic drugs are less likely to induce neurologic side effects compared with typical (conventional) antipsychotics, such as haloperidol. Some recent, large-scale studies have shown that the incidence of metabolic side effects often associated with atypical agents does not differ among typical and atypical antipsychotics. Cognitive function, such as verbal learning memory, working memory, executive function, verbal fluency and attention/information processing, is the most influential determinant of outcome in patients with schizophrenia. Atypical antipsychotic drugs have been shown to be more efficacious in treating cognitive disturbances of schizophrenia compared with typical antipsychotic drugs. Serotonin (5-hydroxytryptamine [5-HT]) receptor subtypes, such as the 5-HT1A receptor, are considered to mediate the ability of antipsychotic drugs to enhance cognition. On the other hand, treatment with some atypical agents, such as risperidone, may deteriorate working memory in some people with early-stage schizophrenia. The paradoxical side effects of these antipsychotic drugs in terms of cognition may be attributable to dose, duration of treatment and type of cognitive domain. Further research will add to the worldwide endeavor to develop more effective psychotropic drugs accompanied with minimal side effects, for the improvement of cognition, adherence and long-term outcome in patients with schizophrenia or other major psychiatric illnesses.

Translating the N-methyl-D-aspartate receptor antagonist model of schizophrenia to treatments for cognitive impairment in schizophrenia

The N-methyl-D-aspartate receptor (NMDAR) antagonists, phencyclidine (PCP), dizocilpine (MK-801), or ketamine, given subchronically (sc) to rodents and primates, produce prolonged deficits in cognitive function, including novel object recognition (NOR), an analog of human declarative memory, one of the cognitive domains impaired in schizophrenia. Atypical antipsychotic drugs (AAPDs) have been reported to improve declarative memory in some patients with schizophrenia, as well as to ameliorate and prevent the NOR deficit in rodents following scNMDAR antagonist treatment. While the efficacy of AAPDs to improve cognitive impairment in schizophrenia (CIS) is limited, at best, and controversial, single doses of all currently available AAPDs so far tested transiently restore NOR in rodents following scNMDAR antagonist treatment. Typical antipsychotic drugs (APDs), e.g. haloperidol and perphenazine, are ineffective in this rodent model, and may be less effective as treatments of some domains of CIS. Serotonergic mechanisms, including, but not limited to serotonin (5-HT)2A and 5-HT7 antagonism, 5-HT(1A), and GABA(A) agonism, contribute to the efficacy of the AAPDs in the scNMDAR antagonist rodent models, which are relevant to the loss of GABA interneuron/hyperglutamate hypothesis of the etiology of CIS. The ability of sub-effective doses of the atypical APDs to ameliorate NOR in the scNMDAR-treated rodents can be restored by the addition of a sub-effective dose of the 5-HT(1A) partial agonist, tandospirone, or the 5-HT7 antagonist, SB269970. The mGluR2/3 agonist, LY379268, which itself is unable to restore NOR in the scNMDAR-treated rodents, can also restore NOR when given with lurasidone, an AAPD. Enhancing cortical and hippocampal dopamine and acetylcholine efflux, or both, may contribute to the restoration of NOR by the atypical APDs. Importantly, co-administration of lurasidone, tandospirone, or SB269970, with PCP, to rodents, at doses 5-10 fold greater than those acutely effective to restore NOR following scNMDAR treatment, prevents the effect of scPCP to produce an enduring deficit in NOR. This difference in dosage may be relevant to utilizing AAPDs to prevent the onset of CIS in individuals at high risk for developing schizophrenia. The scNMDAR paradigm may be useful for identifying possible means to treat and prevent CIS.

The role of serotonin in cognitive function: evidence from recent studies and implications for understanding depression

BACKGROUND

Symptoms of cognitive impairment such as poor concentration, memory loss and difficulty with decision making are prevalent in patients with depression, but currently are not specific targets for treatment. However, patients can continue to demonstrate cognitive impairments even when apparently clinically recovered. Drugs that potentiate serotonin (5-HT) function, such as selective serotonin reuptake inhibitors (SSRIs), are the mainstay of treatment for depression. Nevertheless, our understanding of the effects of SSRIs and other conventional antidepressant therapy on cognitive function in healthy humans and depressed patients remains limited.

OBJECTIVE

The purpose of this article is to provide a concise overview for clinicians on the impact of pharmacological manipulation of 5-HT on cognitive function in healthy humans with additional reference to animal models where human data are lacking, particularly regarding specific 5-HT receptor subtype modulation.

FINDINGS

The most consistent observation following manipulation of serotonin levels in humans is that low extracellular 5-HT levels are associated with impaired memory consolidation. Preclinical data show that agonism and antagonism at specific 5-HT receptors can exert effects in animal models of cognition.

CONCLUSIONS

Larger, consistently designed studies are needed to understand the roles of 5-HT in cognition in healthy and depressed individuals. Efforts to target specific 5-HT receptors to improve cognitive outcomes are warranted.

Blonanserin reverses the phencyclidine (PCP)-induced impairment in novel object recognition (NOR) in rats: role of indirect 5-HT(1A) partial agonism

Blonanserin is an atypical antipsychotic drug (APD) which, compared to other atypical APDs, is a relatively selective serotonin (5-HT)2A and dopamine D2 antagonist. Comparing blonanserin with more broadly acting atypical APDs could be useful to test the contributions of actions at other monoamine receptors, e.g. 5-HT1A receptors, to the reversal of PCP-induced novel object recognition (NOR) deficit. In this study, we tested the effect of blonanserin alone, and in combination with 5-HT1A agents, on NOR deficit induced by subchronic treatment with the N-methyl-D-aspartate (NMDA) receptor antagonist, phencyclidine (PCP; 2 mg/kg), b.i.d., for 7 days. Blonanserin, 1mg/kg, but not 0.3mg/kg, improved the PCP-induced NOR deficit. However, at 1mg/kg, object exploration was diminished. Co-administration of sub-effective doses of blonanserin (0.3 mg/kg) and the 5-HT1A partial agonist, tandospirone (0.2 mg/kg), significantly reversed the NOR deficit without diminishing activity during the acquisition or retention periods. The combination of WAY100635 (0.6 mg/kg), a 5-HT1A antagonist, and blonanserin (1 mg/kg), also diminished object exploration which prevented assessment of the effect of this combination on NOR. WAY100635 (0.6 mg/kg) blocked the ameliorating effect of risperidone (0.1 mg/kg), another atypical APD with low affinity for 5-HT1A receptors, but did not impair exploration. These results suggest that blonansein and risperidone, atypical APDs which lack a direct action on 5-HT1A receptors require 5-HT1A receptor stimulation to reverse the subchronic PCP-induced NOR deficit and provide a support for clinical trial of blonanserin in combination with tandospirone to ameliorate cognitive impairment in schizophrenia and to have fewer side effects.

Prevention of the phencyclidine-induced impairment in novel object recognition in female rats by co-administration of lurasidone or tandospirone, a 5-HT(1A) partial agonist

Hypoglutamatergic function may contribute to cognitive impairment in schizophrenia (CIS). Subchronic treatment with the N-methyl-D-aspartate receptor antagonist, phencyclidine (PCP), induces enduring deficits in novel object recognition (NOR) in rodents. Acute treatment with atypical antipsychotic drugs (APDs), which are serotonin (5-HT)(2A)/dopamine D(2) antagonists, but not typical APDs, eg, haloperidol, reverses the PCP-induced NOR deficit in rats. We have tested the ability of lurasidone, an atypical APD with potent 5-HT(1A) partial agonist properties, tandospirone, a selective 5-HT(1A) partial agonist, haloperidol, a D(2) antagonist, and pimavanserin, a 5-HT(2A) inverse agonist, to prevent the development of the PCP-induced NOR deficit. Rats were administered lurasidone (0.1 or 1 mg/kg), tandospirone (5 mg/kg), pimavanserin (3 mg/kg), or haloperidol (1 mg/kg) b.i.d. 30 min before PCP (2 mg/kg, b.i.d.) for 7 days (day1-7), followed by a 7-day washout (day 8-14). Subchronic treatment with PCP induced an enduring NOR deficit. Lurasidone (1 mg/kg) but not 0.1 mg/kg, which is effective to acutely reverse the deficit due to subchronic PCP, or tandospirone, but not pimavanserin or haloperidol, significantly prevented the PCP-induced NOR deficit on day 15. The ability of lurasidone co-treatment to prevent the PCP-induced NOR deficit was enduring and still present at day 22. The preventive effect of lurasidone was blocked by WAY100635, a selective 5-HT(1A) antagonists, further evidence for the importance of 5-HT(1A) receptor stimulation in the NOR deficit produced by subchronic PCP. Further study is needed to determine whether these results concerning mechanism and dosage can be the basis for prevention of the development of CIS in at risk populations.

The role of 5-HT1A receptors in phencyclidine (PCP)-induced novel object recognition (NOR) deficit in rats

RATIONALE

Atypical antipsychotic drugs (APDs), many of which are direct or indirect serotonin (5-HT)(1A) agonists, and tandospirone, a 5-HT(1A) partial agonist, have been reported to improve cognition in schizophrenia.

OBJECTIVES AND METHODS

We tested the effect of 5-HT(1A) agonism, alone, and in combination with other psychotropic agents, including the atypical APD, lurasidone, in reversing the deficit in novel object recognition (NOR) induced by subchronic treatment with the non-competitive NMDA receptor antagonist, phencyclidine (PCP) (2 mg/kg, b.i.d., for 7 days).

RESULTS

Subchronic treatment with PCP induced a persistent NOR deficit. Lurasidone (0.1 mg/kg), a potent 5-HT(1A) partial agonist, 5-HT(2A) antagonist, and weaker D(2) antagonist, tandospirone (0.6 mg/kg), and the selective post-synaptic 5-HT(1A) agonist, F15599 (0.16 mg/kg), ameliorated the subchronic PCP-induced-NOR deficit. The 5-HT(1A) antagonist, WAY100635 (0.6 mg/kg), blocked the ameliorating effects of tandospirone and lurasidone. The combination of sub-effective doses of tandospirone (0.2 mg/kg) and lurasidone (0.03 mg/kg) also reversed the PCP-induced NOR-deficit. Buspirone, a less potent partial 5-HT(1A) agonist than tandospirone, was less effective. Co-administration of tandospirone (0.2 mg/kg) and pimavanserin (3 mg/kg), a relatively selective 5-HT(2A) receptor inverse agonist, did not reverse the effect of sub-chronic PCP on NOR. The D(2) antagonist, haloperidol, blocked the ameliorating effect of tandospirone on the PCP-induced deficit in NOR.

CONCLUSIONS

These results indicate that 5-HT(1A) agonism is adequate to ameliorate the PCP-induced impairment in NOR and suggest further study of utilizing the combination of a 5-HT(1A) agonist and an atypical APD to ameliorate some types of cognitive impairment in schizophrenia.

Effect of transient blockade of N-methyl-D-aspartate receptors at neonatal stage on stress-induced lactate metabolism in the medial prefrontal cortex of adult rats: role of 5-HT1A receptor agonism

Decreased activity of the medial prefrontal cortex (mPFC) has been considered a basis for core symptoms of schizophrenia, an illness associated with a neurodevelopmental origin. Evidence from preclinical and clinical studies indicates that serotonin (5-HT)1A receptors play a crucial role in the energy metabolism of the mPFC. This study was undertaken to determine (1) if transient blockade of N-methyl-D-aspartate receptors during the neonatal stage inhibit energy demands in response to stress, as measured by extracellular lactate concentrations, in the mPFC at the young adult stage, and (2) if tandospirone, a 5-HT1A partial agonist, reverses the effect of the neonatal insult on energy metabolism. Male pups received MK-801 (0.20 mg/kg) on postnatal days (PDs) 7-10. On PD 63, footshock stress-induced lactate levels were measured using in vivo microdialysis technique. Tandospirone (0.1, 1.0, and 5.0 mg/kg) was administered once daily for 14 days before the measurement of lactate levels. Neonatal MK-801 treatment suppressed footshock stress-induced lactate production in the mPFC, but not caudate-putamen, whereas basal lactate levels were not significantly changed in either brain region. The MK-801-induced suppression of footshock stress-induced lactate production in the mPFC was attenuated by tandospirone at 1.0mg/kg/day, but not 0.1 or 5.0 mg/kg/day, which is an effect antagonized by coadministration of WAY-100635, a selective 5-HT1A antagonist. These results suggest a role for impaired lactate metabolism in some of the core symptoms of schizophrenia, for example, negative symptoms and cognitive deficits. The implications for the ability of 5-HT1A agonism to ameliorate impaired lactate production in the mPFC of this animal model are discussed.

Quetiapine and Buspirone Both Elevate Cortical Levels of Noradrenaline and Dopamine In vivo, but Do Not have Synergistic Effects

Decreased cognitive ability is a significant problem in schizophrenia, and it has been proposed that augmentation of antipsychotics with 5HT(1A) receptor agonists may improve cognitive performance. Clinical studies have been mixed but there have been no studies specifically examining the effects of combining the atypical antipsychotic quetiapine with the 5HT(1A) receptor partial agonist, buspirone on monoamine release. This is of interest given previous evidence that monoamine release can alter cognition in schizophrenia. In the present study we measured in vivo levels of monoamines in the frontal cortex of Sprague Dawley rats and examined if buspirone (2.5 mg/kg i.p.), altered monoamine release both when given alone and when combined with quetiapine (10 mg/kg i.p.). We found that serotonin levels were not altered by either drug, either alone or in combination. In contrast, both buspirone and quetiapine monotherapy significantly increased release of noradrenaline (112 and 160% respectively) and dopamine (169 and 191% respectively) compared to controls. However, there were no additional increases in in vivo monoamine release when the combination of these drugs were given. One possible explanation for these negative findings could be that the intrinsic 5HT(1A) agonist activity of quetiapine on its own is of such significance that it is not further enhanced by buspirone. These findings do not support clinical studies combining buspirone and quetiapine, if these were to be used on the basis of enhanced monoamine neurotransmission. These findings may also have implications for the atypical antipsychotic drugs in development which combine dopamine D(2) antagonism with 5HT(1A) partial agonism.

Serotonergic mechanisms as targets for existing and novel antipsychotics

A variety of serotonin (5-HT) receptors, especially 5-HT(2A), 5-HT(1A), 5-HT(6), 5-HT(7), and 5-HT(2C), have been postulated to contribute to the mechanism of action of atypical antipsychotic drugs (APDs), i.e., APDs which cause fewer extrapyramidal side effects (EPS) at clinically optimal doses, in contrast with typical APDs, which are more likely to cause EPS. This advantage, rarely disputed, has made such drugs the preferred treatment for schizophrenia and other indications for APDs. These 5-HT receptors are still of interest as components of novel multireceptor or stand-alone APDs, and potentially to remediate cognitive deficits in schizophrenia. Almost all currently available atypical APDs are 5-HT(2A) receptor inverse agonists, as well as dopamine (DA) D(2) receptor antagonists or partial agonists. Amisulpride, an exceptional atypical APD, has 5-HT(7) antagonism to complement its DA D(2/3) antagonism. Some atypical APDs are also 5-HT(1A) partial agonists, 5-HT(6), or 5-HT(7) antagonists, or some combination of the above. 5-HT(2C) antagonism has been found to contribute to the metabolic side effects of some atypical APDs, whereas 5-HT(2C) agonists have potential as stand-alone APDs and/or cognitive enhancers. This review will provide an update of current preclinical and clinical evidence for the role of these five 5-HT receptors in the actions of current APDs and for the development of novel psychotropic drugs.

Measurement of the serotonin 1A receptor availability in patients with schizophrenia during treatment with the antipsychotic medication ziprasidone

The aim of this study was to compare 5-HT(1A) availability in vivo in individuals with schizophrenia before and during treatment with the atypical antipsychotic ziprasidone. Six individuals with schizophrenia underwent two PET scans with [(11)C]WAY 100635; the first while medication-free (baseline) and the second while taking the atypical antipsychotic ziprasidone (on-medication). Regional volumes of distribution (V(T), mL g(-1)) were derived using a two-tissue compartment kinetic model. Outcome measures included binding potential relative to the plasma (BP(P), mL g(-1)) and the binding potential relative to the nonspecific distribution volume (BP(ND), unitless). No significant differences were observed in regional BP(P) or BP(ND) with ziprasidone treatment. A significant correlation was noted between BP(P) measured in the orbitofrontal cortex during the on-medication condition and degree of improvement in negative symptoms with treatment (r = 0.96, p = 0.004). Consistent with the published literature of changes in 5-HT(1A) binding during treatment with 5-HT(1A) receptor agonists, this study did not detect a significant reduction in 5-HT(1A) binding with ziprasidone. The finding of a relationship between 5-HT(1A) binding and the degree of improvement in negative symptoms provides further support for the role of the 5-HT(1A) receptor in the pathophysiology and treatment of this symptom domain.

LORETA analysis of three-dimensional distribution of δ band activity in schizophrenia: relation to negative symptoms

We sought to determine if altered electroencephalography (EEG) activities, such as delta band activity, in specific brain regions are associated with psychotic symptoms. Data were obtained from 17 neuroleptic-naive patients with schizophrenia and age- and sex-matched 17 healthy control subjects. Low Resolution Brain Electromagnetic Tomography (LORETA) was used to generate current source density images of delta, theta, alpha, and beta activities. Localization of the difference in EEG activity between the two groups was assessed by voxel-by-voxel non-paired t-test of the LORETA images. Spearman's correlation coefficient was obtained to relate LORETA values of EEG current density in brain regions showing a significant between-group difference and psychopathology scores. Delta band activity, represented by LORETA current density, was greater for patients in the following areas; the left inferior temporal gyrus, right middle frontal gyrus, right superior frontal gyrus, right inferior frontal gyrus, and right parahippocampal gyrus. LORETA values for delta band activity in the above five brain regions were negatively correlated with negative, but not positive symptoms. The results of this study suggest the role for electrophysiological changes in some of the brain regions, e.g. prefrontal cortex, in the manifestation of negative symptoms.

The role of serotonin in the NMDA receptor antagonist models of psychosis and cognitive impairment

OBJECTIVE

To review the evidence that agents which preferentially affect serotonin (5-HT) attenuate the ability of N-methyl-D-aspartate (NMDA) receptor non-competitive antagonists (NMDA-RA), e.g., phencyclidine (PCP), dizocilpine (MK-801), and ketamine, to stimulate locomotor activity (LA), and to impair novel object recognition (NOR).

RATIONALE

NMDA-RA-induced increased LA and impairment of NOR are widely used models of the pathophysiology of schizophrenia, the mechanism of action of antipsychotic drugs (APDs), and the identification of novel treatments. Serotonin (5-HT) plays an important role in attenuating these effects of NMDA-RA.

RESULTS

Selective 5-HT(2A) inverse agonists, e.g., M100907 and ACP-103, and atypical APDs, which are more potent 5-HT(2A) than D(2) antagonists, e.g., clozapine and lurasidone, are more effective than selective D(2) receptor antagonists to attenuate NMDA-RA-induced increased LA. 5-HT(2A) inverse agonists alone are not effective to improve NMDA-RA-impaired NOR, but augment the effects of atypical, but not typical APDs, to improve NOR. The 5-HT(1A) receptor partial agonist tandospirone alone and the 5-HT(1A) agonist effects of atypical APDs may substitute for, or contribute to, the effects of D(2) and 5-HT(2A) receptor antagonism to reverse the NMDA-RA impairment in NOR. 5-HT(6) and 5-HT(7) receptor antagonists may also attenuate these NMDA-RA-induced behaviors. 5-HT(2C) receptor inverse agonist, but not neutral antagonists, block NOR in naïve rats and the effects of atypical APDs to restore NOR in PCP-treated rats, suggesting the importance of the constitutive activity of 5-HT(2C) receptors in NOR.

CONCLUSIONS

Multiple 5-HT receptors contribute to effective treatments to reverse adverse effects of NMDA-RA which model psychosis and cognitive impairment.

Effect of tandospirone, a serotonin-1A receptor partial agonist, on information processing and locomotion in dizocilpine-treated rats

RATIONALE

Augmentation therapy with serotonin-1A receptor (5-HT1A) partial agonists has been suggested to ameliorate psychotic symptoms in patients with schizophrenia.

OBJECTIVE AND METHODS

The objective of the present study was to examine the effect of repeated administration of tandospirone (0.05 and 5 mg/kg) on locomotor activity in a novel environment and on sensorimotor gating in rats treated with the N-methyl-D-aspartate receptor antagonist MK-801, which has been used in animal models of schizophrenia. Furthermore, we sought to determine whether the effect of tandospirone on these behavioural measures is blocked by WAY 100635 (0.3 mg/kg), a 5-HT1A receptor antagonist, and whether there is an interaction between haloperidol (0.1 mg/kg; a dopamine-D2 receptor antagonist) and tandospirone.

RESULTS

Tandospirone at 5 mg/kg, but not 0.05 mg/kg, decreased locomotor activity in saline or MK-801-treated rats, which were not affected by co-treatment with WAY 100635. Haloperidol decreased locomotion both in saline and MK-801-treated animals, and this effect was not evident in the latter group receiving the higher dose of tandospirone. Tandospirone (5 mg/kg)-induced disruption of sensorimotor gating in saline or MK-801-treated animals was reversed by WAY-100635, but not by haloperidol.

CONCLUSIONS

These findings suggest that behavioural changes induced by tandospirone are not fully blocked by 5-HT1A antagonists and that tandospirone (5 mg/kg) potentiates the effect of MK-801. Overall, these findings point to an interaction between NMDA and 5-HT(1A) receptors. Part of the effect of tandospirone on locomotor activity may be mediated by the actions of its active metabolites on other neurotransmitter systems.

Serotonin-1A receptor gene polymorphism and the ability of antipsychotic drugs to improve attention in schizophrenia

INTRODUCTION

The purpose of this study was to determine if the functional single nucleotide polymorphisms of rs6259 C(-1019)G in the promoter region, which regulates serotonin 5-HT(1A) receptor transcription, affects the ability of antipsychotic drugs to improve attention in patients with schizophrenia.

METHODS

Subjects were neuroleptic-free and meeting DSM-IV-TR criteria for schizophrenia. Psychopathology and attention were evaluated with the Scale for the Assessment of Positive Symptoms (SAPS) and the Scale for the Assessment of Negative Symptoms (SANS) at baseline and 3 months after treatment with atypical antipsychotic drugs (AAPDs). DNA was extracted from peripheral blood following standard procedures. Genotyping was performed with HS-Taq assay (LaboPass).

RESULTS

Data were available from 30 subjects (male/female=19/11), in which 17 had the CC genotype, three had the GG genotype, and 10 were heterozygous. The 3-month treatment with AAPDs was associated with significant improvements in positive and negative symptoms, but not attention as measured by SANS-Attention subscale in the entire subject group. There were no significant differences in the degree of improvements of SAPS and SANS scores between the CC genotype group and the (C/G plus G/G) combined group. On the other hand, improvement of attention was significantly greater for the former group compared to the latter group (P<0.016), suggesting a detrimental influence of the G-allele.

CONCLUSION

These results provide additional support to the role of 5-HT(1A) receptors in some of the cognitive disturbances of schizophrenia. Further studies with a larger number of subjects are warranted.

The effects of antipsychotic drugs administration on 5-HT1A receptor expression in the limbic system of the rat brain

Increasing evidence suggests that 5-HT1A receptors are involved in the pathophysiology and treatment of schizophrenia. This paper investigated 5-HT1A receptor mRNA expression and binding density in female rats treated with aripiprazole (2.25 mg/kg/day), olanzapine (1.5 mg/kg/day), haloperidol (0.3 mg/kg/day) or vehicle (control) orally three times/day for 1 or 12 weeks. Animals were sacrificed 48 h after the last administration. Aripiprazole significantly increased 5-HT1A receptor binding density by 33% in the CA1 region of the hippocampus and by 21% in the medial posterodorsal nuclei of posterior amygdala (MeP) compared to the control group after 1 week of treatment. Olanzapine significantly decreased 5-HT1A receptor binding density by 17-22% in Layers I-IV of the cingulate cortex after 1 week of treatment. Neither of these antipsychotic drugs affected 5-HT1A receptor binding density after 12 weeks drug treatment. As expected, haloperidol treatment did not have any significant effect on 5-HT1A binding density after 1 or 12 weeks of treatment. 5-HT1A receptor mRNA expression was not altered by antipsychotic treatment in any brain region. The results indicate that aripiprazole and olanzapine have differential effects on 5-HT1A receptor expression, which may contribute to their distinct profiles in improving negative symptoms and cognitive deficits in schizophrenia. Aripiprazole and olanzapine may produce adaptation and desensitization of 5-HT1A receptor expression after long term treatment.

Treatment of cognitive dysfunction in chronic schizophrenia by augmentation of atypical antipsychotics with buspirone, a partial 5-HT(1A) receptor agonist

OBJECTIVES

To assess effects of a semi-acute administration of buspirone in comparison to a placebo on cognitive function and negative symptoms in patients with schizophrenia and schizoaffective disorder.

METHODS

In a 6-week, double-blind, placebo-controlled, independent groups study 18 subjects (14 males, four females) received in random order either placebo or buspirone (15-30 mg/day). A neuropsychological assessment using the Hopkins verbal learning test (HVLT) simple reaction time (SRT), choice reaction time (CRT), n-back spatial working memory task and the stroop colour and word test was performed at baseline and final visit. Symptom rating scales were administered at testing weeks 0, 2, 4 and 6.

RESULTS

Repeated measures ANOVA was used to examine changes in performance on tests over time. There were no statistically significant differences between placebo and buspirone treatments on either cognitive function measures or symptom ratings.

CONCLUSION

Semi-acute adjunct treatment with buspirone may be too short to be clinically efficacious in patients with schizophrenia. Intrinsic activation of 5-HT(1A) receptors by atypical antipsychotics may hinder the ability of buspirone to further improve cognitive functions. Buspirone did not affect clinical outcomes for this chronically ill group of patients being treated with atypical antipsychotic drugs.

Serotonin1A receptors in the pathophysiology of schizophrenia: development of novel cognition-enhancing therapeutics

Serotonin (5-HT) receptors have been suggested to play key roles in psychosis, cognition, and mood via influence on neurotransmitters, synaptic integrity, and neural plasticity. Specifically, genetic evidence indicates that 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptor single-nucleotide polymorphisms (SNPs) are related to psychotic symptoms, cognitive disturbances, and treatment response in schizophrenia. Data from animal research suggest the role of 5-HT in cognition via its influence on dopaminergic, cholinergic, glutamatergic, and GABAergic function. This article provides up-to-date findings on the role of 5-HT receptors in endophenotypic variations in schizophrenia and the development of newer cognition-enhancing medications, based on basic science and clinical evidence. Imaging genetics studies on associations of polymorphisms of several 5-HT receptor subtypes with brain structure, function, and metabolism suggest a role for the prefrontal cortex and the parahippocampal gyrus in cognitive impairments of schizophrenia. Data from animal experiments to determine the effect of agonists/antagonists at 5-HT(1A), 5-HT(2A), and 5-HT(2C) receptors on behavioral performance in animal models of schizophrenia based on the glutamatergic hypothesis provide useful information. For this purpose, standard as well as novel cognitive tasks provide a measure of memory/information processing and social interaction. In order to scrutinize mixed evidence for the ability of 5-HT(1A) agonists/antagonists to improve cognition, behavioral data in various paradigms from transgenic mice overexpressing 5-HT(1A) receptors provide valuable insights. Clinical trials reporting the advantage of 5-HT(1A) partial agonists add to efforts to shape pharmacologic perspectives concerning cognitive enhancement in schizophrenia by developing novel compounds acting on 5-HT receptors. Overall, these lines of evidence from translational research will facilitate the development of newer pharmacologic strategies for the treatment of cognitive disturbances of schizophrenia.

5-HT1A gene variants and psychiatric disorders: a review of current literature and selection of SNPs for future studies

5-HT1A receptors are key components of the serotonin system, acting both pre- and post- synaptically in different brain areas. There is a growing amount of evidence showing the importance of 5-HT1A in different psychiatric disorders, from mood to anxiety disorders, moving through suicidal behaviour and psychotic disorders. Findings in the literature are not consistent with any definite 5-HT1A influence in psychiatric disorders. 5-HT1A gene variants have been reported to play some role in mood disorders, anxiety disorders and psychotic disorders. Again, the literature findings are not unequivocal. Concerning response to treatment, the C(-1019)G variant seems to be of primary interest in antidepressant response: C allele carriers generally show a better response to treatment, especially in Caucasian samples. Together with the C(-1019)G (rs6295) variant, the Ile28Val (rs1799921), Arg219Leu (rs1800044) and Gly22Ser (rs1799920) variants have been investigated in possible associations with psychiatric disorders, also with no definitive results. This lack of consistency can be also due to an incomplete gene investigation. To make progress on this point, a list of validated single nucleotide polymorphisms (SNPs) covering the whole gene is proposed for further investigations.

Effect of MK-801 on gene expressions in the amygdala of rats

Rodents treated with N-methyl-D-aspartate (NMDA) antagonists have been thought to be an animal model of schizophrenia. In this study, we examined gene expression in the amygdala of rats chronically treated with MK-801, as well as behavioral changes, such as social behavior, in these animals. The social interaction test, a measure of social behavior, and locomotor activity was performed in male Wistar rats injected with MK-801 (0.13 mg/kg i.p.) or saline for 14 days. Changes in mRNA levels were analyzed using a GeneChip microarray system. Real-time quantitative PCR (RT-qPCR) assay was subsequently conducted to confirm the results of the microarray analysis. MK-801 decreased social interaction and increased locomotor activity in rats, consistent with previous reports. We found 23 downregulated genes and 16 upregulated genes, with the gene encoding arginine-vasopressin (AVP) being most downregulated, and that for transthyretin (Ttr) most upregulated. mRNA levels, quantified by RT-qPCR assay, were altered for genes related to neuropeptides (AVP, Sstr2), the arachidonic cascade (Ptgds), myelination (Mobp, Enpp2), neurotrophic factors (Igfbp2), and hormonal milieu (Ttr). Downregulation of the AVP gene in the amygdala of MK-801-treated rats may provide a basis for the ability of AVP-analogues to ameliorate the behavioral disturbances caused by blockade of the NMDA receptor. The results of this study provide an insight into the neural substrates responsible for the generation of psychotic symptoms.

Wechsler Memory Scale Revised Edition: neural correlates of the visual paired associates subtest adapted for fMRI

Memory deficits in neurological and psychiatric patients are evaluated by neuropsychological tests such as the Wechsler Memory Scale Revised Edition (WMS-R). Neuropsychological data from patients with circumscribed lesions point to single elements of the underlying neural network but fail to identify its whole extent. We report the fMRI adaptation of a subtest of the WMS-R, the Visual Paired Associates. Fifteen healthy, right-handed male volunteers were studied using a 1.5T MRI scanner. The encoding of the combination between a shape and a colour, the assessment of the retrieval of this combination immediately after encoding took place, and the underlying network employed during retrieval a second time after approximately 25 min were investigated. The results show a fronto-parieto-occipital network with left frontal accentuation for encoding and a fronto-parieto-occipital network for immediate and delayed retrieval. Noteworthy is the specific role of the thalamus. During immediate retrieval, the thalamus showed significant bilateral activation; during delayed retrieval, there was no significant activation. The thalami are part of an extended hippocampal-diencephalic system which is critical for efficient encoding and normal retrieval of new episodic information. We describe the probability of thalamocortical connections during retrieval based on the Thalamus Connectivity Atlas. The cerebellum showed significant activation in all conditions; its part in higher cognitive functions such as memory was thereby confirmed.

Effect of buspirone, a serotonin1A partial agonist, on cognitive function in schizophrenia: a randomized, double-blind, placebo-controlled study

In previous studies, we demonstrated that tandospirone, a serotonin-5-HT1A partial agonist, added to ongoing treatment with small to moderate doses of typical antipsychotic drugs, improved executive function and verbal learning and memory. However, tandospirone is not available in most countries, and atypical antipsychotic drugs (AAPDs) have largely replaced typical antipsychotic drugs as the primary treatment for schizophrenia. Therefore, the goal of this randomly assigned placebo-controlled double-blind study was to determine if the addition of buspirone, a widely available 5-HT1A partial agonist, would enhance cognitive function, in subjects with schizophrenia treated with AAPDs. Seventy-three patients with schizophrenia, who had been treated with an AAPD for at least three months, were randomly assigned to receive either buspirone, 30 mg/day, or matching placebo. All other medications remained unchanged. Attention, verbal fluency, verbal learning and memory, verbal working memory, and executive function, as well as psychopathology, were assessed at baseline, and 6 weeks, and 3 and 6 months after baseline. A significant Time x Group interaction effect was noted on the Digit Symbol Substitution Test, a measure of attention/speeded motor performance, due to better performance of the buspirone group compared to the placebo group at 3 months. No significant interaction effects were noted for other domains of cognition. Scores on the Brief Psychiatric Rating Scale (Total, Positive) were improved during treatment with buspirone but not placebo, but the effects did not reach statistical significance. The results of this study showed a possible benefit of buspirone augmentation of AAPDs to enhance attention. However, we did not replicate the results of the previous study with tandospirone, which may be due to the differences between tandospirone and buspirone, between typical antipsychotics and AAPDs, or a combination of the above. Further study to determine the usefulness of 5-HT1A agonist treatment in schizophrenia is indicated.

5-HT1A receptor agonist properties of antipsychotics determined by [35S]GTPgammaS binding in rat hippocampal membranes

1. 5-Hydroxytryptamine 1A (5-HT1A) receptors have attracted increasing attention as a promising target for antipsychotic therapy. Although many atypical antipsychotic drugs, including the prototype clozapine, have been reported to be partial agonists at 5-HT1A receptors, these results are often fragmental and derived mainly from experiments that used cultured cells. 2. In the present study, [35S]guanosine 5'-O-(3-thiotriphosphate) ([35S]GTPgammaS) binding assay in rat hippocampal membranes was applied to a series of antipsychotic drugs, especially atypical antipsychotics. 3. Most, but not all, of atypical antipsychotic drugs and the classical antipsychotic drug nemonapride behaved as partial agonists at 5-HT1A receptors with varied potencies and relative efficacies. The most potent compound was perospirone with a mean EC50 of 27 nmol/L, followed by aripiprazole (45 nmol/L) > ziprasidone (480 nmol/L) > nemonapride (790 nmol/L) > clozapine (3900 nmol/L) > quetiapine (26,000 nmol/L). The maximal percentage increases over the basal binding (%Emax) for these antipsychotic drugs were 30-50%, with the exception of perospirone (approximately 15%), whereas 5-HT stimulated the binding to a mean %Emax of 105%. 4. Increasing concentrations of the selective and neutral 5-HT1A antagonist WAY100635 shifted the concentration-response curve of nemonapride-stimulated [35S]GTPgammaS binding to the right and in parallel. 5. The relative efficacy or intrinsic activity of a compound was affected differently by the differing concentrations of guanosine diphosphate (GDP) in the assay buffer, which should be taken into consideration when determining the relative efficacies of these antipsychotics as 5-HT1A receptor agonists. 6. These results provide important information concerning the relevance of 5-HT1A receptor partial agonist properties in the treatment for schizophrenic patients with most, if not all, of atypical antipsychotic drugs.

In vivo actions of aripiprazole on serotonergic and dopaminergic systems in rodent brain

RATIONALE

Aripiprazole is an atypical antipsychotic drug with high in vitro affinity for 5-HT(1A), 5-HT(2A) and dopamine (DA) D2 receptors. However, its in vivo actions in the brain are still poorly characterized.

OBJECTIVE

The aim was to study the in vivo actions of aripiprazole in the rat and mouse brain.

METHODS

Brain microdialysis and single-unit extracellular recordings were performed.

RESULTS

The systemic administration of aripiprazole reduced 5-HT output in the medial prefrontal cortex (mPFC) and dorsal raphe nucleus of the rat. Aripiprazole also reduced extracellular 5-HT in the mPFC of wild-type (WT) but not of 5-HT(1A) (-/-) knockout (KO) mice. Aripiprazole reversed the elevation in extracellular 5-HT output produced by the local application of the 5-HT(2A/2C) receptor agonist DOI in mPFC. Aripiprazole also increased the DA output in mPFC of WT but not of 5-HT(1A) KO mice, as observed for atypical antipsychotic drugs, in contrast to haloperidol. Contrary to haloperidol, which increases the firing rate of DA neurons in the ventral tegmental area (VTA), aripiprazole induced a very moderate reduction in dopaminergic activity. Haloperidol fully reversed the inhibition in dopaminergic firing rate induced by apomorphine, whereas aripiprazole evoked a partial reversal that was significantly different from that evoked by haloperidol and from the spontaneous reversal of dopaminergic activity in rats treated with apomorphine.

CONCLUSIONS

These results indicate that aripiprazole modulates the in vivo 5-HT and DA release in mPFC through the activation of 5-HT(1A) receptors. Moreover, aripiprazole behaves as a partial agonist at DA D2 autoreceptors in vivo, an action which clearly distinguishes it from haloperidol.

F15063, a compound with D2/D3 antagonist, 5-HT 1A agonist and D4 partial agonist properties. II. Activity in models of positive symptoms of schizophrenia

BACKGROUND AND PURPOSE

F15063 is a high affinity D(2)/D(3) antagonist, D(4) partial agonist, and high efficacy 5-HT(1A) agonist, with little affinity (40-fold lower than for D(2) receptors) at other central targets. Here, the profile of F15063 was evaluated in models of positive symptoms of schizophrenia and motor side-effects.

EXPERIMENTAL APPROACH

Rodent behavioural tests were based on reversal of hyperactivity induced by psychostimulants and on measures of induction of catalepsy and 'serotonin syndrome'.

KEY RESULTS

F15063 potently (ED(50)s: 0.23 to 1.10 mg kg(-1) i.p.) reversed methylphenidate-induced stereotyped behaviors, blocked d-amphetamine and ketamine hyperlocomotion, attenuated apomorphine-induced prepulse inhibition (PPI) deficits, and was active in the conditioned avoidance test. In mice, it reversed apomorphine-induced climbing (ED(50)=0.30 mg kg(-1) i.p.). F15063, owing to its 5-HT(1A) agonism, did not produce (ED(50)>40 mg kg(-1) i.p.) catalepsy in rats and mice, a behavior predictive of occurrence of extra-pyramidal syndrome (EPS) in man. This absence of cataleptogenic activity was maintained upon sub-chronic treatment of rats for 5 days at 40 mg kg(-1) p.o. Furthermore, F15063 did not induce the 'serotonin syndrome' in rats (flat body posture and forepaw treading: ED(50) >32 mg kg(-1) i.p.).

CONCLUSIONS AND IMPLICATIONS

F15063 conformed to the profile of an atypical antipsychotic, with potent actions in models of hyperdopaminergic activity but without inducing catalepsy. These data suggest that F15063 may display potent antipsychotic actions with low EPS liability. This profile is complemented by a favourable profile in rodent models of negative symptoms and cognitive deficits of schizophrenia (companion paper).

The effect of perospirone on auditory P300 in schizophrenia: a preliminary study

The present study was performed to determine the effect of perospirone, a novel antipsychotic drug with D(2)/5-HT(2A) antagonist and partial 5-HT(1A) agonist properties, on auditory P300 in eight patients with chronic schizophrenia. Switching to an equivalent dose of perospirone from prior antipsychotic medication was associated with a significant improvement in the negative symptoms of the positive and negative syndrome scale (PANSS). The change in P300 amplitude following a switch to perospirone correlated significantly with the improvement of general psychopathology symptoms, as well as with the change in scores on items of delusions, hallucinatory behavior, emotional withdrawal, depression, poor attention, and disturbance of volition. These results suggest that clinical improvement in response to perospirone in some patients may, at least in part, be mediated through cognitive change indexed by P300 in chronic schizophrenia.

Perospirone in the treatment of schizophrenia: effect on verbal memory organization

The present study was performed to determine if perospirone, a novel antipsychotic drug with D2/5-HT2A antagonist and partial 5-HT1A agonist properties, would improve memory organization in twelve patients with chronic schizophrenia. Switching to equivalent dose of perospirone from prior antipsychotic medication was associated with a significant improvement in indices of verbal memory organization of the Auditory Verbal Learning Test. Negative symptoms and extrapyramidal side effects were also ameliorated after switching to perospirone. The distinct cognitive enhancement profile of perospirone may be attributable to its partial 5-HT1A agonist action.

Differential profile of antipsychotics at serotonin 5-HT1A and dopamine D2S receptors coupled to extracellular signal-regulated kinase

The effects of antipsychotics targeting dopamine D2 and serotonin 5-HT1A receptors were compared with conventional antipsychotics on phosphorylation of Extracellular signal-Regulated Kinase 1/2 (ERK 1/2) in CHO cell lines stably expressing either the human serotonin 5-HT1A or human dopamine D2S receptor. All antipsychotics except haloperidol and olanzapine exhibited agonist properties at serotonin 5-HT1A receptors. Emax values (% effect of 10 microM 5-HT) were: bifeprunox (74), SSR181507 (73), SLV313 (72), aripiprazole (60), ziprasidone (56), clozapine (33). At dopamine D2S receptors, partial agonist activity (% effect of 10 microM dopamine) was observed for bifeprunox (76), SSR181507 (66) and aripiprazole (59). Other antipsychotics attenuated dopamine-induced ERK phosphorylation, with pK(B) values of : SLV313 (8.5), haloperidol (8.1), olanzapine (7.8), ziprasidone (7.7), and clozapine (6.4). Amongst the dopamine D2/serotonin 5-HT1A receptor compounds, aripiprazole acts as a partial dopamine D2S and serotonin 5-HT1A receptor agonist. SSR181507 and bifeprunox possess a profile of action similar to each other, efficaciously stimulating both serotonin 5-HT1A and dopamine D2S receptors. In contrast, SLV313, also an efficacious serotonin 5-HT1A receptor agonist, acted as a high potency dopamine D2 receptor antagonist. Thus, antipsychotics display varying efficacies at serotonin 5-HT1A and dopamine D2S receptors which may play a major role in their differential functional profiles in blocking the diverse symptoms of schizophrenia.

Effects of novel antipsychotics with mixed D(2) antagonist/5-HT(1A) agonist properties on PCP-induced social interaction deficits in the rat

Considerable interest has arisen in identifying antipsychotic agents with improved efficacy against negative symptoms, such as social withdrawal. In rats, a social interaction deficit can be induced by the NMDA antagonist phencyclidine (PCP). Here, we examined the effects of antipsychotics, reported to exert dual 5-HT(1A)/D(2) actions, on PCP-induced social interaction deficits. Drugs were administered daily for 3 days in combination with either vehicle or PCP (2.5mg/kg, SC) and social interaction was measured on the last day of drug treatment. Pairs of unfamiliar rats receiving the same treatment were placed in a large open field for 10 min and the number of social behaviors were scored. The results indicate that: (1) PCP significantly reduced social interaction by over 50% compared with vehicle-treated controls; (2) haloperidol (0.0025-0.16 mg/kg, SC) and clozapine (0.04-10mg/kg, IP) did not reverse PCP-induced social interaction deficits; (3) the substituted benzamide remoxipride reversed PCP-induced deficits at 0.63 and 2.5mg/kg (4) the 5-HT(1A) agonist 8-OH-DPAT was inactive (at 0.01-0.63 mg/kg, SC); (5) among compounds reported to exert dual 5-HT(1A)/D(2) actions, SSR181507 (at 0.16 mg/kg, SC) and aripiprazole (at 0.04 and 0.16 mg/kg, IP), but not ziprasidone (0.04-2.5mg/kg, IP), SLV313 (0.0025-0.16 mg/kg, SC) or bifeprunox (0.01-0.63 mg/kg, IP), significantly reversed PCP-induced social interaction deficits; and (6) the 5-HT(1A) receptor antagonist WAY100635 blocked the effects of SSR181507 and aripiprazole. These findings indicate that the balance of activity at 5-HT(1A) and D(2) receptors profoundly influences the activity of antipsychotics in this model of social withdrawal, and their potential benefit on at least some of the negative symptoms of schizophrenia.

SSR181507, a dopamine D(2) receptor antagonist and 5-HT(1A) receptor agonist. I: Neurochemical and electrophysiological profile

SSR181507 ((3-exo)-8-benzoyl-N-[[(2S)7-chloro-2,3-dihydro-1,4-benzodioxin-1-yl]methyl]-8-azabicyclo[3.2.1]octane-3-methanamine monohydrochloride) is a novel tropanemethanamine benzodioxane derivative that possesses high and selective affinities for D2-like and 5-HT(1A) receptors (K(I)=0.8, 0.2, and 0.2 nM for human D(2), D(3), and 5-HT(1A), respectively). In vivo, SSR181507 inhibited [(3)H]raclopride binding to D(2) receptors in the rat (ID(50)=0.9 and 1 mg/kg, i.p. in limbic system and striatum, respectively). It displayed D(2) antagonist and 5-HT(1A) agonist properties in the same concentration range in vitro (IC(50)=5.3 nM and EC(50)=2.3 nM, respectively, in the GTPgammaS model) and in the same dose range in vivo (ED(50)=1.6 and 0.7 mg/kg, i.p. on striatal DA and 5-HT synthesis, respectively, and 0.03-0.3 mg/kg, i.v. on dorsal raphe nucleus firing rate). It selectively enhanced Fos immunoreactivity in mesocorticolimbic areas as compared to the striatum. This regional selectivity was confirmed in electrophysiological studies where SSR181507, given acutely (0.1-3 mg/kg, i.p.) or chronically (3 mg/kg, i.p., o.d., 22 days), increased or decreased, respectively, the number of spontaneous active DA cells in the ventral tegmental area, but not in the substantia nigra. Moreover, SSR181507 increased both basal and phasic DA efflux (as assessed by microdialysis and electrochemistry) in the medial prefrontal cortex and nucleus accumbens, but not in the striatum. This study shows that the combination of D(2) receptor antagonism and 5-HT(1A) agonism, in the same dose range, confers on SSR181507 a unique neurochemical and electrophysiological profile and suggests the potential of this compound for the treatment of the main dimensions of schizophrenia.

SSR181507, a dopamine D2 receptor antagonist and 5-HT1A receptor agonist. II: Behavioral profile predictive of an atypical antipsychotic activity

SSR181507 ((3-exo)-8-benzoyl-N-(((2S)7-chloro-2,3-dihydro-1,4-benzodioxin-1-yl)methyl)-8-azabicyclo(3.2.1)octane-3-methanamine monohydrochloride) is a novel tropanemethanamine benzodioxane that displays antagonist activity at dopamine D(2) receptors and agonist activity at 5-HT(1A) receptors. SSR181507 antagonized apomorphine-induced climbing in mice and stereotypies in rats (ED(50) of 2 and 3.4 mg/kg i.p., respectively) and blocked D-amphetamine-induced hyperlocomotion in rats at lower doses (0.3-1 mg/kg i.p.). At 1-10 mg/kg, it was found to disrupt active avoidance in mice. SSR181507 did not induce catalepsy in rats (MED>60 mg/kg i.p.) and antagonized (3-10 mg/kg i.p.) haloperidol-induced catalepsy. SSR181507 was also active in two models sensitive to antidepressant/anxiolytic drugs: in a guinea-pig pup/mother separation test, it decreased (1-3 mg/kg i.p.) the time spent vocalizing during the separation episode, and in a lithium-induced taste aversion procedure in rats, it partially reversed (3 mg/kg i.p.) the decrease of intake of a saccharin solution. Furthermore, SSR181507 increased (3 mg/kg i.p.) the latency time to paradoxical sleep in rats, an effect commonly observed with antidepressants. Coadministration of the selective 5-HT(1A) blocker SL88.0338 produced catalepsy and antagonized the effects of SSR181507 in the depression/anxiety tests, confirming the view that activation of 5-HT(1A) receptors confers an atypical profile on SSR181507, and is responsible for its antidepressant/anxiolytic properties. Finally, SSR181507 (1-3 mg/kg) did not affect memory performance in a Morris water maze task in rats. The pharmacological profile of SSR181507 suggests that it should control the symptoms of schizophrenia, in the absence of extrapyramidal signs and cognitive deficits, with the additional benefit of antidepressant/anxiolytic activities.

Semantic structure in schizophrenia as assessed by the category fluency test: effect of verbal intelligence and age of onset

It has been reported that long-term memory function, including the semantic structure of category, is impaired in patients with schizophrenia. The present study was performed to determine: (1) whether the deficit in semantic structure in schizophrenia is independent of cultural backgrounds, and (2) the effect of age of onset and verbal intelligence on the degradation of semantic structure in these patients. Fifty-seven Japanese patients with schizophrenia and 33 normal control subjects entered the study. The semantic structure was derived by Multidimensional Scaling (MDS) analysis based on data from the ANIMAL category fluency test. The semantic structure was compared between: (1) schizophrenic patients as a whole vs. normal control subjects; (2) earlier onset (age of onset <20 years) vs. later-onset groups of patients; and (3) high Vocabulary score (score of the Vocabulary subtest from the WAIS-R>7) vs. low Vocabulary score patient groups. Normal control subjects demonstrated the domestic/size dimension in semantic structure, while no such dimension was obtained in patients with schizophrenia. The subgroup comparisons revealed that the later onset or the high Vocabulary score group maintained a relatively intact semantic structure compared with the earlier onset or the low Vocabulary score group, respectively. These findings suggest that the deficit in semantic structure in patients with schizophrenia is commonly observed irrespective of cultural backgrounds, and that age of onset and the level of verbal intelligence are closely related to severity of degradation of the semantic structure in schizophrenia.

5-HT(1A) receptor dysfunction in female patients with schizophrenia

BACKGROUND

Serotonin (5-HT)(1A) receptors are of interest in the pathophysiology of schizophrenia (SCH) and the mechanism of action of atypical antipsychotic drugs. To test the hypothesis that 5-HT(1A) receptor responsivity is significantly different in patients with SCH compared to normal control subjects, the neuroendocrine study was performed using ipsapirone (IPS), a 5-HT(1A) partial agonist, as a probe.

METHODS

Ipsapirone 0.5 mg/kg, p.o. or placebo were administered, in random order, to patients with SCH (n = 43; 32 male) and normal controls (n = 33; 21 male). Blood samples for plasma cortisol and body temperature were obtained from 30 min before to 180 min after administration of IPS or placebo.

RESULTS

Female normal control subjects had markedly greater increases in plasma cortisol following IPS than did male control subjects. The placebo response-corrected plasma cortisol response to IPS was significantly blunted in female SCH compared to female normal control subjects (p =.0001). The IPS-stimulated plasma cortisol response in male SCH did not differ from that of male normal control subjects or female SCH. There were no significant differences in the IPS-induced hypothermia in men and women or between patients with SCH and normal control subjects. Behavioral responses to IPS, including nausea, dizziness, irritability, and feeling less well, did not differ between groups.

CONCLUSIONS

These results suggest that the post-synaptic 5-HT(1A) receptor mediated endocrine response is diminished in female SCH compared to female normal control subjects, possibly secondary to an abnormality in intracellular signal transduction mechanism.

The effect of tandospirone, a serotonin(1A) agonist, on memory function in schizophrenia

BACKGROUND

The purpose of this study was to test the hypothesis that the addition of tandospirone, a 5-HT(1A) partial agonist, to ongoing treatment with typical antipsychotic drugs, would improve memory function in patients with schizophrenia.

METHODS

Eleven outpatients (male/female = 7/4) with schizophrenia who had been on stable doses of haloperidol and biperiden were given tandospirone, 30 mg/day, for 4 weeks. The Wechsler Memory Scale-Revised (WMS-R) was administered at baseline and 4 weeks after the addition of tandospirone. The Brief Psychiatric Rating Scale (BPRS; Total, Positive, and Negative subscale scores) and the Simpson-Angus Scale for Extrapyramidal Symptoms (SAS) were also completed on the two occasions. To exclude the possibility of a practice effect on the WMS-R test, 11 age-matched patients with schizophrenia (M/F = 7/4) were tested at baseline and after a 4-week interval.

RESULTS

Repeated measures analysis of variance revealed a significant time by group (patients with or without tandospirone) effect for the Verbal-, but not the Visual Memory composite scores of the WMS-R test; no significant change was observed in patients without tandospirone, whereas improvement in the Verbal Memory score was noted in patients receiving tandospirone. Moreover, there was improvement in the Inclusion score, an index of memory organization as measured by the Logical Memory subtest of WMS-R, only in patients with tandospirone. Scores on the BPRS and SAS were improved during treatment with tandospirone, but the effects did not reach statistical significance.

CONCLUSIONS

The results suggest that adjunctive treatment with 5-HT(1A) agonists may improve some types of memory function in schizophrenia.