Synergistic dopamine increase in the rat prefrontal cortex with the combination of quetiapine and fluvoxamine

Dose-Dependent Biphasic Action of Quetiapine on AMPK Signalling via 5-HT7 Receptor: Exploring Pathophysiology of Clinical and Adverse Effects of Quetiapine

Recent pharmacological studies indicated that the modulation of tripartite-synaptic transmission plays important roles in the pathophysiology of schizophrenia, mood disorders and adverse reactions. Therefore, to explore the mechanisms underlying the clinical and adverse reactions to atypical antipsychotics, the present study determined the effects of the sub-chronic administration of quetiapine (QTP: 3~30 μM) on the protein expression of 5-HT7 receptor (5-HT7R), connexin43 (Cx43), cAMP level and intracellular signalling, Akt, Erk and adenosine monophosphate-activated protein kinase (AMPK) in cultured astrocytes and the rat hypothalamus, using ultra-high-pressure liquid chromatography with mass spectrometry and capillary immunoblotting systems. QTP biphasically increased physiological ripple-burst evoked astroglial D-serine release in a concentration-dependent manner, peaking at 10 μM. QTP enhanced the astroglial signalling of Erk concentration-dependently, whereas both Akt and AMPK signalling’s were biphasically enhanced by QTP, peaking at 10 μM and 3 μM, respectively. QTP downregulated astroglial 5-HT7R in the plasma membrane concentration-dependently. Protein expression of Cx43 in astroglial cytosol and intracellular cAMP levels were decreased and increased by QTP also biphasically, peaking at 3 μM. The dose-dependent effects of QTP on the protein expression of 5-HT7R and Cx43, AMPK signalling and intracellular cAMP levels in the hypothalamus were similar to those in astrocytes. These results suggest several complicated pharmacological features of QTP. A therapeutically relevant concentration/dose of QTP activates Akt, Erk and AMPK signalling, whereas a higher concentration/dose of QTP suppresses AMPK signalling via its low-affinity 5-HT7R inverse agonistic action. Therefore, 5-HT7R inverse agonistic action probably plays important roles in the prevention of a part of adverse reactions of QTP, such as weight gain and metabolic complications.

Monoaminergic Multilocus Genetic Variants Interact with Stressful Life Events in Predicting Changes in Adolescent Anxiety Symptoms: A One-year Longitudinal Study

Research suggests that genetic variants linked to monoaminergic neurotransmitter function moderate the association between stress and anxiety symptoms, but examining gene-environment (G × E) interactions with individual genes limits power. As one of polygenetic approaches, the multilocus genetic profile score is derived theoretically from combining the effects of multiple candidate genes based on the "biological plausibility". Using this approach, the current study examined the interaction between monoaminergic multilocus genetic variants and stressful life events on the changes in adolescent anxiety symptoms across a one-year timespan. In a Chinese Han adolescent sample which was derived from three vocational high schools (N = 587; T1: M_age = 16.47 ± 1.53 years; 50.8%, girls), the monoaminergic multilocus genetic profile score was calculated using 5-HTR2C rs6318, TPH2 rs4570625 and DRD2 rs1800497 polymorphisms. Results showed that this monoaminergic multilocus genetic profile score interacted with stressful life events in predicting changes in anxiety symptoms. Consistent with the G×E hypothesis of differential susceptibility, adolescents with more monoaminergic plasticity alleles not only suffered more from high levels of stressful life events, which increased the risk for anxiety symptoms, but also benefited more from low levels of stressful life events, which decreased the risk for anxiety symptoms. There were no significant G × E interactions when individual polymorphisms were examined in isolation. The results highlight the importance of examining aggregated influences of multiple genes in G × E interactions underlying the longitudinal development of adolescent anxiety symptoms.

Serotonin/dopamine interaction: Electrophysiological and neurochemical evidence

The interaction between serotonin (5-HT) and dopamine (DA) in the central nervous system (CNS) plays an important role in the adaptive properties of living animals to their environment. These are two modulatory, divergent systems shaping and regulating in a widespread manner the activity of neurobiological networks and their interaction. The concept of one interaction linking these two systems is rather elusive when looking at the mechanisms triggered by these two systems across the CNS. The great variety of their interacting mechanisms is in part due to the diversity of their neuronal origin, the density of their fibers in a given CNS region, the distinct expression of their numerous receptors in the CNS, the heterogeneity of their intracellular signaling pathway that depend on the cellular type expressing their receptors, and the state of activity of neurobiological networks, conditioning the outcome of their mutual influences. Thus, originally conceptualized as inhibition of 5-HT on DA neuron activity and DA neurotransmission, this interaction is nowadays considered as a multifaceted, mutual influence of these two systems in the regulation of CNS functions. These new ways of understanding this interaction are of utmost importance to envision the consequences of their dysfunctions underlined in several CNS diseases. It is also essential to conceive the mechanism of action of psychotropic drugs directly acting on their function including antipsychotic, antidepressant, antiparkinsonian, and drug of abuse together with the development of therapeutic strategies of Alzheimer's diseases, epilepsy, obsessional compulsive disorders. The 5-HT/DA interaction has a long history from the serendipitous discovery of antidepressants and antipsychotics to the future, rationalized treatments of CNS disorders.

The preclinical discovery and development of quetiapine for the treatment of mania and depression

INTRODUCTION

Bipolar disorder is a chronic disabling condition characterized by alternating manic and depressive episodes. Bipolar disorder has been associated with functional impairment, poor quality of life, morbidity and mortality. Despite its significant clinical, social and economic burden, treatment options for bipolar disorder are still limited. Several clinical trials have shown efficacy of the atypical antipsychotic quetiapine (QTP) in the treatment of this condition. However, the mechanisms underlying the antidepressant and anti-manic effects of QTP remain poorly understood. Areas covered: The article provides the emerging evidence from pre-clinical studies regarding the antidepressant and anti-manic mechanisms of action of QTP. In combination with its primary active metabolite norquetiapine, QTP modulates several neurotransmitter systems, including serotonin, dopamine, noradrenaline and histamine. QTP also seems to influence mediators of the immune system. Expert opinion: Pre-clinical studies have provided valuable information on the potential antidepressant mechanisms of action of QTP, but pre-clinical studies on QTP's anti-manic effects are still scarce. A major problem refers to the lack of valid experimental models for bipolar disorder. Additionally, immune and genetic based studies are largely descriptive. The role of the QTP metabolite norquetiapine in modulating non-neurotransmitter systems also needs to be further addressed.

Serotonergic modulation of the activity of mesencephalic dopaminergic systems: Therapeutic implications

Since their discovery in the mammalian brain, it has been apparent that serotonin (5-HT) and dopamine (DA) interactions play a key role in normal and abnormal behavior. Therefore, disclosure of this interaction could reveal important insights into the pathogenesis of various neuropsychiatric diseases including schizophrenia, depression and drug addiction or neurological conditions such as Parkinson's disease and Tourette's syndrome. Unfortunately, this interaction remains difficult to study for many reasons, including the rich and widespread innervations of 5-HT and DA in the brain, the plethora of 5-HT receptors and the release of co-transmitters by 5-HT and DA neurons. The purpose of this review is to present electrophysiological and biochemical data showing that endogenous 5-HT and pharmacological 5-HT ligands modify the mesencephalic DA systems' activity. 5-HT receptors may control DA neuron activity in a state-dependent and region-dependent manner. 5-HT controls the activity of DA neurons in a phasic and excitatory manner, except for the control exerted by 5-HT_2C receptors which appears to also be tonically and/or constitutively inhibitory. The functional interaction between the two monoamines will also be discussed in view of the mechanism of action of antidepressants, antipsychotics, anti-Parkinsonians and drugs of abuse.

Prazosin addition to fluvoxamine: A preclinical study and open clinical trial in OCD

The efficacy of selective serotonin reuptake inhibitors (SRIs) in psychiatric disorders may be "augmented" through the addition of atypical antipsychotic drugs. A synergistic increase in dopamine (DA) release in the prefrontal cortex has been suggested to underlie this augmentation effect, though the mechanism of action is not clear yet. We used in vivo microdialysis in rats to study DA release following the administration of combinations of fluvoxamine (10 mg/kg) and quetiapine (10 mg/kg) with various monoamine-related drugs. The results confirmed that the selective 5-HT1A antagonist WAY-100635 (0.05 mg/kg) partially blocked the fluvoxamine-quetiapine synergistic effect (maximum DA increase dropped from 325% to 214%). A novel finding is that the α1-adrenergic blocker prazosin (1 mg/kg), combined with fluvoxamine, partially mimicked the effect of augmentation (maximum DA increase 205%; area-under-the-curve 163%). As this suggested that prazosin augmentation might be tested in a clinical study, we performed an open clinical trial of prazosin 20 mg addition to SRI in therapy-resistant patients with obsessive-compulsive disorder applying for neurosurgery. A small, non-significant reduction in Yale Brown Obsessive Compulsive Scale (Y-BOCS) scores was observed in 10 patients and one patient was classified as a responder with a reduction in Y-BOCS scores of more than 25%. We suggest that future clinical studies augmenting SRIs with an α1-adrenergic blocker in less treatment resistant cases should be considered. The clinical trial "Prazosin in combination with a serotonin reuptake inhibitor for patients with Obsessive Compulsive disorder: an open label study" was registered at 24/05/2011 under trial number ISRCTN61562706: http://www.controlled-trials.com/ISRCTN61562706.

Intracellular pathways of antipsychotic combined therapies: implication for psychiatric disorders treatment

Dysfunctions in the interplay among multiple neurotransmitter systems have been implicated in the wide range of behavioral, emotional and cognitive symptoms displayed by major psychiatric disorders, such as schizophrenia, bipolar disorder or major depression. The complex clinical presentation of these pathologies often needs the use of multiple pharmacological treatments, in particular (1) when monotherapy provides insufficient improvement of the core symptoms; (2) when there are concurrent additional symptoms requiring more than one class of medication and (3) in order to improve tolerability, by using two compounds below their individual dose thresholds to limit side effects. To date, the choice of drug combinations is based on empirical paradigm guided by clinical response. Nonetheless, several preclinical studies have demonstrated that drugs commonly used to treat psychiatric disorders may impact common intracellular target molecules (e.g. Akt/GSK-3 pathway, MAP kinases pathway, postsynaptic density proteins). These findings support the hypothesis that convergence at crucial steps of transductional pathways could be responsible for synergistic effects obtained in clinical practice by the co-administration of those apparently heterogeneous pharmacological compounds. Here we review the most recent evidence on the molecular crossroads in antipsychotic combined therapies with antidepressants, mood stabilizers, and benzodiazepines, as well as with antipsychotics. We first discuss clinical clues and efficacy of such combinations. Then we focus on the pharmacodynamics and on the intracellular pathways underpinning the synergistic, or concurrent, effects of each therapeutic add-on strategy, as well as we also critically appraise how pharmacological research may provide new insights on the putative molecular mechanisms underlying major psychiatric disorders.

Deep brain stimulation of the accumbens increases dopamine, serotonin, and noradrenaline in the prefrontal cortex

Deep brain stimulation (DBS) of the nucleus accumbens (NAc) is effective in treatment-refractory obsessive-compulsive disorder and major depressive disorder. However, little is known about the neurobiological mechanisms underlying the rapid and effective changes of DBS. One of the hypotheses is that DBS modulates activity of monoamine neurotransmitters. In this study, we evaluated the effects of DBS in the NAc core on the extracellular concentration of monoaminergic neurotransmitters in the medial (mPFC) and orbital prefrontal cortex (OFC). Freely moving rats were bilaterally stimulated in the NAc core for 2 h while dopamine, serotonin, and noradrenaline were measured using in vivo microdialysis in the mPFC and the OFC. We report rapid increases in the release of dopamine and serotonin to a maximum of 177% and 127% in the mPFC and an increase up to 171% and 166% for dopamine and noradrenaline in the OFC after onset of stimulation in the NAc core. These results provide further evidence for the distal effects of DBS and corroborate previous clinical and pre-clinical findings of altered neuronal activity in prefrontal areas.

Catechol-O-methyltranferase gene expression is associated with response to citalopram in obsessive-compulsive disorder

OBJECTIVE

To determine whether polymorphisms of the dopamine D(2) receptor (DRD2) and catechol-O-methyl-transferase (COMT) receptor genes affect the efficacy of quetiapine addition to citalopram in patients with OCD.

METHODS

Sixty-four drug-free or drug-naïve patients meeting DSM-IV criteria for OCD were randomized to 10 weeks double-blind treatment with citalopram (60 mg/day) with quetiapine (300 -450 mg/day) or with placebo. The change from baseline to endpoint on the total Yale-Brown Obsessive-Compulsive Scale (Y-BOCS) and the response to treatment were the primary outcome measures. Response was defined as a 25% decrease in Y-BOCS score. Responders and nonresponders were stratified according to DRD2 TaqI A and COMT Val(158)Met genotypes.

RESULTS

No significant differences in genotype distribution or allele frequencies of the COMT or DRD2 receptor were found between responders and nonresponders to citalopram with quetiapine. However, nearly half of responders to citalopram with placebo carried the Met/Met (48%) genotype of the COMT polymorphism compared to none of the nonresponders (χ(2) = 10.06, df = 2, P = 0.007).

CONCLUSIONS

The Met allele load of the COMT receptor gene was associated with response to 10 weeks of treatment with citalopram in drug-free or drug-naïve OCD patients.

5-HT2 ligands in the treatment of anxiety and depression

INTRODUCTION

One third of depressed patients do not respond adequately to conventional antidepressants including the selective serotonin reuptake inhibitors (SSRIs). Therefore, multi-target drugs or augmentation strategies have been developed for the management of SSRIs-resistant patients. In this context, the 5-HT(2) receptor subtypes represent promising targets but their precise roles have yet to be determined.

AREAS COVERED

The aim of this review is to shed some light on the preclinical evidence supporting the use of 5-HT(2A) and/or 5-HT(2C) receptor antagonists such as antipsychotics, as potential effective adjuncts in SSRIs-resistant depression. This review synthesizes the current literature about the behavioral, electrophysiological and neurochemical effects of 5-HT(2) receptors ligands on the monoaminergic systems but also on adult hippocampal neurogenesis.

EXPERT OPINION

Although studies support the hypothesis that the inactivation of 5-HT(2A) and/or 5-HT(2C) receptors might be of interest to reinforce different facets of the therapeutic activity of SSRIs, this pharmacological strategy remains debatable notably because of the lack of chronic data in relevant animal models. Conversely, emerging evidence suggests that the activation of 5-HT(2B) receptor is required for antidepressant-like activity, opening the way to new therapeutic approaches. However, the potential risks related to the enhancement of monoaminergic neurotransmissions could represent a major concern.

Quetiapine ameliorates stress-induced cognitive inflexibility in rats

The antidepressant action of quetiapine has been demonstrated in clinical and preclinical studies. Nevertheless, little is known about its effectiveness in the treatment of frontal-like cognitive disturbances that may be associated with stress-related disorder. Therefore, the aim of the present study was to investigate whether quetiapine would prevent and/or reverse stress-induced cognitive impairments in a rat model of prefrontal cortex (PFC)-dependent attentional set-shifting task (ASST). Because quetiapine augmentation to selective serotonin reuptake inhibitors (SSRIs) has recently been proven to be beneficial in neuropsychiatric disorders, a separate experiment was designed to assess the impact of combined administration of inactive doses of quetiapine and escitalopram on ASST performance in rats. According to our previous studies, 1 h daily exposure to restraint stress for 7 days significantly and specifically impaired extra-dimensional (ED) set-shifting ability of rats. Quetiapine (2.5 mg/kg, PO) given to rats prior to the restraint sessions completely prevented this stress-induced cognitive inflexibility. Similar effect was demonstrated after pretreatment with the α1-adrenoceptor antagonist, prazosin (1 mg/kg, IP). Moreover, acute administration of quetiapine before the test reversed set-shifting deficits in stressed rats (0.63, 1.25 and 2.5 mg/kg, PO) and improved ED performance of cognitively unimpaired control animals (1.25 and 2.5 mg/kg, PO). Finally, the combined administration of inactive doses of quetiapine (0.63 and 0.3 mg/kg in control and stressed rats, respectively) and escitalopram (0.3 mg/kg, IP) facilitated set-shifting performance in either control or stressed rats. In conclusion, quetiapine administration either prevented or reversed stress-induced cognitive inflexibility in rats. In addition to promoting of set-shifting by itself, quetiapine also enhanced the procognitive efficacy of escitalopram. The potential contribution of the antagonism at α1-adrenoceptors to the mechanisms underlying the protective action of quetiapine requires further evaluation. These findings may have therapeutic implications for the treatment of frontal-like disturbances, particularly cognitive inflexibility, in stress-related psychiatric disorders. This article is part of a Special Issue entitled 'Cognitive Enhancers'.

Acute treatment with fluvoxamine elevates rat brain serotonin synthesis in some terminal regions: an autoradiographic study

INTRODUCTION

A considerable body of evidence indicates the involvement of the neurotransmitter serotonin (5-HT) in the pathogenesis and treatment of depression.

METHODS

The acute effect of fluvoxamine, on 5-HT synthesis rates was investigated in rat brain regions, using α-(14)C-methyl-L-tryptophan as a tracer. Fluvoxamine (25 mg/kg) and saline (control) were injected intraperitoneally, one hour before the injection of the tracer (30 μCi).

RESULTS

There was no significant effect of fluvoxamine on plasma free tryptophan. After Benjamini-Hochberg False Discovery Rate correction, a significant decrease in the 5-HT synthesis rate in the fluvoxamine treated rats, was found in the raphe magnus (-32%), but not in the median (-14%) and dorsal (-3%) raphe nuclei. In the regions with serotonergic axon terminals, significant increases in synthesis rates were observed in the dorsal (+41%) and ventral (+43%) hippocampus, visual (+38%), auditory (+65%) and parietal (+37%) cortex, and the substantia nigra pars compacta (+56%). There were no significant changes in the 5-HT synthesis rates in the median (+11%) and lateral (+24%) part of the caudate-putamen, nucleus accumbens (+5%), VTA (+16%) or frontal cortex (+ 6%).

CONCLUSIONS

The data show that the acute administration of fluvoxamine affects 5-HT synthesis rates in a regionally specific pattern, with a general elevation of the synthesis in the terminal regions and a reduction in some cell body structures. The reasons for the regional specific effect of fluvoxamine on 5-HT synthesis are unclear, but may be mediated by the presynaptic serotonergic autoreceptors.

Effects of quetiapine and sertindole on subchronic ketamine-induced deficits in attentional set-shifting in rats

RATIONALE

Prefrontal cortical dysfunctions, including an impaired ability to shift perceptual attentional set, are core features of schizophrenia. Nevertheless, the effectiveness of second-generation antipsychotic drugs in treating specific prefrontal dysfunctions remains equivocal.

OBJECTIVES

To model schizophrenia-like cognitive inflexibility in rats, we evaluated the effects of repeated administration of ketamine, the noncompetitive antagonist of the N-methyl-D: -aspartate receptor, after a washout period of 14 days in the attentional set-shifting task (ASST). Next, we investigated whether the atypical antipsychotics quetiapine and sertindole would alleviate the ketamine-induced set-shifting impairment.

METHODS

Ketamine (30 mg/kg) was administered intraperitoneally to rats once daily for 5 or 10 consecutive days to assess its efficacy in producing cognitive impairment. The ASST was performed 14 days following the final drug administration. Quetiapine (0.63, 1.25 or 2.5 mg/kg) or sertindole (2.5 mg/kg) was administered per os 120 min before testing.

RESULTS

The results of the present study demonstrate that ketamine treatment for 10 but not 5 days significantly and specifically impaired rats' performance in the extra-dimensional shift (EDs) stage of the ASST. This cognitive inflexibility was reversed by acute administration of sertindole or quetiapine. Quetiapine also promoted set-shifting in cognitively unimpaired control animals.

CONCLUSION

The data presented here show that subchronic administration of ketamine induces cognitive inflexibility after a washout period. This cognitive deficit likely reflects clinically relevant aspects of cognitive dysfunction encountered in schizophrenic patients. The beneficial effects of quetiapine on set-shifting may have therapeutic implications for the treatment of schizophrenia and other disorders associated with frontal-dependent cognitive impairments.

Behavioral pattern analysis and dopamine release in quinpirole-induced repetitive behavior in rats

Obsessive-compulsive disorder (OCD) is a chronic and disabling psychiatric disease with a lifetime prevalence of 2-3%. People with OCD suffer from intrusive, unwanted and recurrent thoughts (obsessions) and/or repetitive ritualistic behaviors (compulsions). The aim of this study is to quantify the dimensions of ritualistic 'compulsive-like' behavior in quinpirole-induced behavior in rats by using T-pattern behavioral analysis. In addition, we investigated whether the behavioral effects elicited by quinpirole sensitization remained after 2 weeks of cessation of treatment. Finally, to study the neurobiological underpinnings of this 'compulsive-like' behavior, we investigated the effect of quinpirole treatment on the extracellular dopamine levels in the nucleus accumbens. Once established, 'compulsive-like' behavior is dependent upon quinpirole administration, as this behavior rapidly normalized after cessation of treatment. After a single dose of quinpirole the dopamine level decreased more in saline pre-treated animals as compared with animals given quinpirole treatment continuously. Furthermore, T-pattern analysis revealed that quinpirole-induced behavior consists, unlike OCD rituals, of a smaller behavioral repertoire. As seen in patients with OCD, quinpirole-treated animals performed these behaviors with a high rate of repetition. These findings suggest that quinpirole-induced behavior mimics only part of the compulsive behavior as shown in OCD patients.

Translational approaches to obsessive-compulsive disorder: from animal models to clinical treatment

Obsessive-compulsive disorder (OCD) is characterized by obsessions (intrusive thoughts) and compulsions (repetitive ritualistic behaviours) leading to functional impairment. Accumulating evidence links these conditions with underlying dysregulation of fronto-striatal circuitry and monoamine systems. These abnormalities represent key targets for existing and novel treatment interventions. However, the brain bases of these conditions and treatment mechanisms are still not fully elucidated. Animal models simulating the behavioural and clinical manifestations of the disorder show great potential for augmenting our understanding of the pathophysiology and treatment of OCD. This paper provides an overview of what is known about OCD from several perspectives. We begin by describing the clinical features of OCD and the criteria used to assess the validity of animal models of symptomatology; namely, face validity (phenomenological similarity between inducing conditions and specific symptoms of the human phenomenon), predictive validity (similarity in response to treatment) and construct validity (similarity in underlying physiological or psychological mechanisms). We then survey animal models of OC spectrum conditions within this framework, focusing on (i) ethological models; (ii) genetic and pharmacological models; and (iii) neurobehavioural models. We also discuss their advantages and shortcomings in relation to their capacity to identify potentially efficacious new compounds. It is of interest that there has been rather little evidence of 'false alarms' for therapeutic drug effects in OCD models which actually fail in the clinic. While it is more difficult to model obsessive cognition than compulsive behaviour in experimental animals, it is feasible to infer cognitive inflexibility in certain animal paradigms. Finally, key future neurobiological and treatment research areas are highlighted.

The acute and chronic effects of combined antipsychotic-mood stabilizing treatment on the expression of cortical and striatal postsynaptic density genes

The detection of changes in postsynaptic gene expression after the administration of mood stabilizers, alone or in combination with antipsychotics, and antidepressants in animal models of drug treatment, may represent a valuable strategy to explore the molecular targets of the mainstay treatments for bipolar disorder. In this study we investigated, in both acute and chronic paradigms, the expression of specific postsynaptic density genes (Homer1a, Homer1b/c, and PSD95) and genes putatively implicated in mood stabilizers mechanism of action (GSK3b, ERK) after administration of first (haloperidol) or second generation antipsychotics (quetiapine 30 mg/kg), alone or in combination with valproate. Moreover, we compared the effects of an antidepressant agent widely used in bipolar depression (citalopram) with a low dose of quetiapine (15 mg/kg), which has been demonstrated to display antidepressant action in bipolar depression. In striatal regions, Homer1a expression was strongly induced by haloperidol compared to all the other treatments. Haloperidol plus valproate also markedly induced Homer1a, but to a significant lesser extent than haloperidol alone. Also in the chronic paradigm haloperidol, but not haloperidol plus valproate, induced Homer1a expression in all the subregions of the caudate-putamen and in the nucleus accumbens core. The high dose of quetiapine significantly induced Homer1a in anterior cingulated, premotor and motor subregions of the cortex, and the extent of induction was significantly higher as compared to the lower dose. Oppositely, Homer1a expression was decreased in the cortex by citalopram acute administration. ERK gene was upregulated in cortex and striatum by the acute treatment with valproate and with the combination of haloperidol or quetiapine plus valproate, whereas no significant differences were noticed in GSK3b expression among treatments. PSD95 showed a significant upregulation by acute citalopram and by haloperidol plus valproate in both cortical and subcortical regions. Haloperidol and quetiapine 30 mg/kg, oppositely, significantly reduced the expression of the gene in the cortex. In conclusion, these results suggest that the combined treatment with a typical or an atypical antipsychotic plus valproate may induce differential modulation of postsynaptic genes expression when compared to the effects of these drugs individually administered.

Role of serotonin in central dopamine dysfunction

The interaction between serotonin (5-HT) and dopamine (DA)-containing neurons in the brain is a research topic that has raised the interest of many scientists working in the field of neuroscience since the first demonstration of the presence of monoamine-containing neurons in the mid 1960. The bulk of neuroanatomical data available clearly indicate that DA-containing neurons in the brain receive a prominent innervation from serotonin (5-hydroxytryptamine, 5-HT) originating in the raphe nuclei of the brainstem. Compelling electrophysiological and neurochemical data show that 5-HT can exert complex effects on the activity of midbrain DA neurons mediated by its various receptor subtypes. The main control seems to be inhibitory, this effect being more marked in the mesocorticolimbic DA system as compared to the DA nigrostriatal system. In spite of a direct effect of 5-HT by its receptors located on DA cells, 5-HT can modulate their activity indirectly, modifying gamma-aminobutyric (GABA)-ergic and glutamatergic input to the ventral tegmental area (VTA) and substantia nigra pars compacta (SNc). Although 5-HT/DA interaction in the brain has been extensively studied, much work remains to be done to clarify this issue. The recent development of subtype-selective ligands for 5-HT receptors will not only allow a detailed understanding of this interaction but also will lead to the development of new treatment strategies, appropriate for those neuropsychiatric disorders in which an alteration of the 5-HT/DA balance is supposed.

Effects of quetiapine on monoamine, GABA, and glutamate release in rat prefrontal cortex

INTRODUCTION

The atypical antipsychotic drug, quetiapine (QTP), is effective in schizophrenia and mood disorders, but induces seizures compared to typical antipsychotics.

METHODS

To explore the mechanisms of action of QTP, we determined its effects on extracellular levels of norepinephrine, dopamine, serotonin, gamma-aminobutyric acid (GABA), and glutamate in the medial prefrontal cortex (mPFC) using microdialysis, and neuronal firing in the ventral tegmental area (VTA), locus coeruleus (LC), dorsal raphe nucleus (DRN), and mediodorsal thalamic nucleus (MTN) by telemetry in freely moving rats.

RESULTS

QTP (10 and 30 mg/kg, i.p.) activated neuronal firing in the VTA, LC, and MTN without affecting that in the DRN. QTP increased extracellular levels of norepinephrine, dopamine, and glutamate without affecting serotonin or GABA levels in the mPFC. The stimulatory effects of QTP on norepinephrine and dopamine were mediated by positive alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/glutamatergic and negative GABA-mediated NMDA/glutamatergic regulation.

DISCUSSION

The dopaminergic terminal projecting from the VTA received inhibitory GABA-mediated NMDA/glutamatergic regulation, but not stimulatory AMPA/glutamatergic regulation. However, both dopaminergic and noradrenergic terminals from the LC received stimulatory AMPA/glutamatergic regulation from the MTN, but not inhibitory GABA-mediated NMDA/glutamatergic regulation. These findings correlating neuronal activities in nuclei with neurotransmitter release suggested that the effects of QTP on neurotransmission in the mPFC depend on activated neuronal projections located outside the mPFC. Furthermore, positive interaction between LC and MTN afferents are potentially important in the pharmacological mechanisms of neurotransmitter regulation by QTP and hint at mechanisms underlying the atypical profile of this drug for treatment of schizophrenia and as a mood stabilizer and proconvulsive agent.

Multifunctional pharmacotherapy: what can we learn from study of selective serotonin reuptake inhibitor augmentation of antipsychotics in negative-symptom schizophrenia?

Many patients suffering from major psychiatric disorders do not respond adequately to monotherapy and require additional drugs. To date, there are no objective guidelines for deciding which combination may be effective, and the choice is based on previous clinical experience and on trial and error. Even when combination drugs are effective, the biochemical mechanisms responsible for the value-added effect are unknown. Understanding the mechanism of such synergism may provide a rational basis for choosing drug combinations and for developing more effective drugs. In schizophrenia, negative symptoms respond poorly to antipsychotics, but may improve when these are augmented with selective serotonin reuptake inhibitors (SSRI). This augmenting effect cannot be explained by summating the pharmacological effects of the individual drugs. We proposed that the study of SSRI augmentation can serve as a window to understanding the biochemical mechanisms of clinically effective drug synergism. In a series of studies we identified unique biochemical effects of the combination, different from each individual drug, and proposed that some of these are involved in mediating the clinical effect. Here we review some of the findings and propose that the mechanism of action involves regionally selective modulation of the GABA system. The evidence indicates that the SSRI antidepressant-antipsychotic combination may be a useful paradigm for studying therapeutically effective synergistic drug interactions in schizophrenia. Although as yet limited in scope, the findings of definable molecular targets for synergistic SSRI-antipsychotic interaction provide new directions to inform future research and provide novel bio-molecular targets for drug development.

Quetiapine augmentation in depressed patients with partial response to antidepressants

OBJECTIVE

Clinical trials suggest between 30-50% of depressed patients have an inadequate outcome to antidepressant pharmacotherapy. Among the approaches to improve outcome has been augmentation with antipsychotic medications. We aim to investigate the efficacy and tolerability of augmentation with quetiapine in depressed patients with a partial response to antidepressants.

METHODS

Patients with a Major Depressive Disorder (DSMIV) who had partial/no response to a stable dose of an Selective Serotonin Reuptake Inhibitors (SSRI)/SNRI were recruited. All patients received add-on quetiapine (200-600 mg nocte) in a 6-week trial. Outcome measures (HAMD, MADRS) were assessed at screening, baseline, weeks 1, 2, 4 and 6. Extrapyramidal symptoms (EPSEs) were assessed at baseline, weeks 2, 4 and 6. A neuropsychological battery of tests was administered at baseline, weeks 3 and 6.

RESULTS

Nineteen patients entered the trial and 18 completed the trial per protocol. We report a rapid improvement in depression ratings over 6 weeks (p < 0.0005) and remission rates of 67% at week 1 and 94% at week 6. There was no evidence of EPSE and no worsening (and some improvement) of cognition.

CONCLUSION

This suggests clinical benefits of quetiapine augmentation of SSRI/SNRI antidepressants with no worsening, and possible improvements in cognition.

Role of serotonin in obsessive–compulsive disorder

Obsessive–compulsive disorder (OCD) is a psychiatric disorder consisting of obsessions and compulsions. Over the past two decades, it has been suggested that OCD might be related to the functioning of brain serotonin systems, mainly because of the antiobsessional efficacy of selective serotonin-reuptake inhibitors (SSRIs). Although the efficacy of SSRIs suggests a role of the serotonergic system in OCD, the exact function of serotonin is still unclear. Is the serotonergic system implicated in the pathophysiology of OCD, or is it implicated in the treatment effect in OCD? Do SSRIs compensate for a fundamental abnormality of the serotonergic system, or do SSRIs modulate an intact serotonergic system to compensate for another neurotransmitter mechanism? This review summarizes evidence supporting a role for the serotonin transporter and serotonin receptor subtypes in the pathophysiology and treatment of OCD.

Mechanistic model for the acute effect of fluvoxamine on 5-HT and 5-HIAA concentrations in rat frontal cortex

A mechanistic model is proposed to predict the time course of the concentrations of 5-HT and its metabolite 5-hydroxyindolacetic acid (5-HIAA) in rat frontal cortex following acute administration of SSRIs. In the model, SSRIs increase synaptic 5-HT concentrations by reversible blockade of the SERT in a direct concentration-dependent manner, while the 5-HT response is attenuated by negative feedback via 5-HT autoreceptors. In principle, the model allows for the description of oscillatory patterns in the time course of 5-HT and 5-HIAA concentrations in brain extracellular fluid. The model was applied in a pharmacokinetic-pharmacodynamic (PK/PD) investigation on the time course of the microdialysate 5-HT and 5-HIAA response in rat frontal cortex following a 30-min intravenous infusion of 3.7 and 7.3mg/kg fluvoxamine. Directly after administration of fluvoxamine, concentrations of 5-HT were increased to approximately 450-600% of baseline values while 5-HIAA concentrations were decreased. Thereafter 5-HT and 5-HIAA concentrations gradually returned to baseline values in 6-10h, respectively. The PK/PD analysis revealed that inhibition of 5-HT reuptake was directly related to the fluvoxamine concentration in plasma, with 50% inhibition of 5-HT reuptake occurring at a plasma concentration of 1.1ng/ml (EC50). The levels of 5-HT at which 50% of the inhibition of the 5-HT response was reached (IC50) amounted to 272% of baseline. The model was unable to capture the oscillatory patterns in the individual concentration time curves, which appeared to occur randomly. The proposed mechanistic model is the first step in modeling of complex neurotransmission processes. The model constitutes a useful basis for prediction of the time course of median 5-HT and 5-HIAA concentrations in the frontal cortex in behavioral pharmacology studies in vivo.

Differential effects of adjunctive methylphenidate and citalopram on extracellular levels of serotonin, noradrenaline and dopamine in the rat brain

Several clinical studies have suggested that the combined treatment with methylphenidate and citalopram may accelerate the onset of antidepressant action and induce an improvement even in treatment-refractory patients. In the present study, in vivo microdialysis was used to monitor the extracellular levels of serotonin, noradrenaline and dopamine in the prefrontal cortex, hippocampus, nucleus accumbens and striatum of the rat. Administration of methylphenidate (2.5 mg/kg s.c.) with citalopram (5 mg/kg i.p.) compared to methylphenidate alone caused a marked enhancement of dopamine levels in the prefrontal cortex, n. accumbens and hippocampus, but not in the striatum. Citalopram-induced increase in serotonin levels was strongly enhanced by adjunctive methylphenidate in the hippocampus, but attenuated in the cortex. These findings suggest that the proposed augmentation effects of adjuvant methylphenidate to citalopram are most likely associated with enhanced dopamine transmission in the corticolimbic areas, whereas serotonin and noradrenaline levels show differential and region specific responses.

Dopamine and serotonin metabolism in response to chronic administration of fluvoxamine and haloperidol combined treatment

Treating primary 'negative symptoms' of schizophrenia with a combination of a typical antipsychotic and a selective serotonin reuptake inhibitor, is more effective than with antipsychotic alone and is similar to the effect of the atypical antipsychotic, clozapine. The mechanism of this treatment combination is unknown and may involve changes in dopaminergic and serotonin systems. We studied dopamine and serotonin metabolism in different rat brain areas at 1.5 and 24 h after the last dosage of chronic treatment (30 days), with haloperidol plus fluvoxamine, each drug alone, and clozapine. Haloperidol-fluvoxamine combination, haloperidol, and clozapine treatments increased striatal and frontal cortex dopamine turnover and reduced striatal tyrosine hydroxylase activity at 1.5 h. At 24 h both dopamine turnover and tyrosine hydroxylase activity were reduced. Thus, in chronically treated animals, release of striatal dopamine increases following a drug pulse and returns to baseline by 24 h. Serotonin and 5-hydroxyindoleacetic acid concentrations were decreased at 1.5 h in haloperidol-fluvoxamine and clozapine groups and returned to normal levels by 24 h. A limited behavioral assessment showed that treatment with haloperidol plus fluvoxamine reduced motor activity compared to haloperidol, and increased sniffing compared to haloperidol, fluvoxamine and clozapine. These findings indicate that combining antipsychotic with SSRI results in specific changes in dopaminergic and serotonergic systems and in behavior. The possibility that these may be relevant to the mechanism underlying the clinical effectiveness of augmentation treatment warrant further study.

Effects of quetiapine on cognitive functioning in obsessive-compulsive disorder

In recent years, growing evidence supports the efficacy of antipsychotic addition to serotonin reuptake inhibitors in patients with treatment-refractory obsessive-compulsive disorder. This study is the first to investigate the effects of antipsychotic addition on cognitive functioning in obsessive-compulsive disorder patients. Cognitive functioning was evaluated at baseline and at endpoint of an 8-week double-blind, placebo-controlled quetiapine addition trial. Neurocognitive performance was compared between the placebo and quetiapine group and between responders and nonresponders. The neuropsychological test battery consisted of the national adult reading test, the Wisconsin Card Sorting Test, the Trail Making Test, verbal fluency, the Stroop Color Word Test, the California Verbal Learning Test, the Rey Complex Figure Task, the Continuous Performance Test, and the Digit Symbol Substitution. The results of this study suggest that quetiapine addition to serotonin reuptake inhibitors has no major effects on cognitive functioning in obsessive-compulsive disorder patients, apart from some evidence for a failure to maintain set on the Wisconsin Card Sorting Test. It is proposed that this failure may be caused by attention difficulties owing to somnolence.

Antipsychotic augmentation of serotonergic antidepressants in treatment-resistant obsessive-compulsive disorder: a meta-analysis of the randomized controlled trials

This study aimed to determine the effectiveness of antipsychotic augmentation of serotonergic antidepressants in the management of treatment-resistant obsessive compulsive disorder by carrying out a meta-analysis of all randomized controlled trials. Studies selected through a literature search conducted in March 2006. Ten trials comparing antipsychotic drugs versus placebo met inclusion criteria (haloperidol [n=1], risperidone [n=3], olanzapine [n=2], quetiapine [n=4]). A total of 157 patients were randomized to study drug and 148 were randomized to placebo. Response occurred more often among patients randomized to antipsychotic drugs. The weighted combined response rate ratio by random effects meta-analysis was 3.31 (95% CI 1.40-7.84). Significant between studies heterogeneity was partly explained by the definition of refractoriness, the type and dose of the drug used and the inclusion or exclusion of patients with tic disorders. The study supports the use of antipsychotic drugs as an augmentation strategy but more and larger trials are needed.

Quetiapine augmentation of selective serotonin reuptake inhibitors in treatment-resistant obsessive-compulsive disorder: a six-month follow-up case series

Obsessive-compulsive disorder (OCD) is a relatively common, often chronic and disabling disorder with high rates of partial and/or absent response to standard, recommended treatments, such as selective serotonin reuptake inhibitors (SSRIs) and psychotherapy. This article presents the cases of four patients suffering from OCD and comorbid mood or anxiety disorders, who were treated with SSRIs at adequate doses for at least 12 weeks, showing a partial response. Quetiapine treatment was added to SSRIs at a dose of 25 mg/day and titrated up to 200 mg/day. Patients were followed up for 6 months. After 12 weeks, all the patients were classified as "much improved" on the Clinical Global Impression-Improvement scale and showed a Yale-Brown Obsessive-Compulsive Scale score reduction > or =35%. After 6 months of follow-up, all the patients maintained the same level of improvement. Although quetiapine augmentation to SSRIs has shown mixed results in published controlled trials in the acute treatment (12 weeks) of patients with treatment-resistant OCD, this case series indicates that patients who benefit from this pharmacologic regimen in the acute phase tend to maintain such an improvement. Larger follow-up studies are warranted to confirm our findings.

Adjunctive quetiapine for serotonin reuptake inhibitor-resistant obsessive-compulsive disorder: a meta-analysis of randomized controlled treatment trials

Small studies have shown positive effects from adding a variety of antipsychotic agents in patients with obsessive-compulsive disorder who are unresponsive to treatment with serotonin reuptake inhibitors. The evidence, however, is contradictory. This paper reports a meta-analysis of existing double-blind randomized placebo-controlled studies looking at the addition of the second-generation antipsychotic quetiapine in such cases. Three studies fulfilled the inclusion criteria. Altogether 102 individuals were subjected to analysis using Review Manager (4.2.7). The results showed evidence of efficacy for adjunctive quetiapine (<400 mg/day) on the primary efficacy criterion, measured as changes from baseline in total Yale-Brown Obsessive Compulsive Scale scores (P=0.008), the clinical significance of which was limited by between-study heterogeneity. The mechanism underlying the effect may involve serotonin and/or dopamine neurotransmission.

Effects of divalproex and atypical antipsychotic drugs on dopamine and acetylcholine efflux in rat hippocampus and prefrontal cortex

Mood stabilizers (e.g., valproic acid) and antipsychotic drugs (APDs) are commonly co-administered in the treatment of bipolar disorder and schizophrenia. The basis for any synergism between these classes of drugs in either group of disorders has been little studied. Previous studies have shown that atypical APDs (e.g., clozapine) preferentially increases dopamine (DA) and acetylcholine (ACh) efflux in rat medial prefrontal cortex (mPFC) and hippocampus (HIP), both of which have been suggested to contribute to their ability to improve cognition in patients with schizophrenia. We have recently reported that the anticonvulsant mood stabilizers (AMS), valproic acid, carbamazepine, and zonisamide, but not lithium, also preferentially increase DA efflux in the rat mPFC, and that, at subthreshold doses, the AMS also augment the ability of the atypical APDs clozapine and risperidone to increase DA but not ACh efflux in the mPFC. The present study examined the ability of divalproex (DVX), which is chemically related to valproic acid, to enhance DA and ACh efflux in the HIP and to augment the effect of atypical APDs on ACh efflux in the HIP and mPFC. DVX, 500 mg/kg, significantly increased DA and ACh efflux in the HIP, and DA, but not ACh, efflux in the mPFC, whereas a lower dose of DVX, 50 mg/kg, had no effect on DA or ACh in either region. However, DVX, 50 mg/kg, combined with the atypical APDs olanzapine (1.0 mg/kg) or aripiprazole (0.3 mg/kg) significantly potentiated the effect of both APDs on DA, but not ACh efflux in the HIP and mPFC. Pretreatment of olanzapine or aripiprazole with the selective serotonin 5-HT(1A) antagonist, WAY100635 (1.0 mg/kg) partially but significantly blocked the effect of the combination of DVX, 50 mg/kg, and olanzapine or aripiprazole, on DA efflux in both the HIP and mPFC. WAY100635 did not affect the ability of the combination of olanzapine or aripiprazole and DVX to enhance ACh efflux in the HIP or mPFC. Subchronic administration of the combination of DVX, 50 mg/kg, and risperidone, produced significantly greater increases in DA and ACh efflux in the mPFC, but these increases were not significantly different from those following the acute administration of the combination of risperidone and DVX. These results provide further evidence that the AMS, DVX, augments the ability of atypical APDs to increase DA or ACh efflux in either the HIP or mPFC or both. The clinical significance of this potentiation for the beneficial clinical effects of this combination of agents and the differences between AMS in this regard warrants further study.

Multi-target strategies for the improved treatment of depressive states: Conceptual foundations and neuronal substrates, drug discovery and therapeutic application

Major depression is a debilitating and recurrent disorder with a substantial lifetime risk and a high social cost. Depressed patients generally display co-morbid symptoms, and depression frequently accompanies other serious disorders. Currently available drugs display limited efficacy and a pronounced delay to onset of action, and all provoke distressing side effects. Cloning of the human genome has fuelled expectations that symptomatic treatment may soon become more rapid and effective, and that depressive states may ultimately be "prevented" or "cured". In pursuing these objectives, in particular for genome-derived, non-monoaminergic targets, "specificity" of drug actions is often emphasized. That is, priority is afforded to agents that interact exclusively with a single site hypothesized as critically involved in the pathogenesis and/or control of depression. Certain highly selective drugs may prove effective, and they remain indispensable in the experimental (and clinical) evaluation of the significance of novel mechanisms. However, by analogy to other multifactorial disorders, "multi-target" agents may be better adapted to the improved treatment of depressive states. Support for this contention is garnered from a broad palette of observations, ranging from mechanisms of action of adjunctive drug combinations and electroconvulsive therapy to "network theory" analysis of the etiology and management of depressive states. The review also outlines opportunities to be exploited, and challenges to be addressed, in the discovery and characterization of drugs recognizing multiple targets. Finally, a diversity of multi-target strategies is proposed for the more efficacious and rapid control of core and co-morbid symptoms of depression, together with improved tolerance relative to currently available agents.

Augmentation by citalopram of risperidone-induced monoamine release in rat prefrontal cortex

RATIONALE

A typical antipsychotics (APDs), e.g. olanzapine and risperidone, have been reported to be effective adjunctive treatment for depression if selective serotonin (5-HT) reuptake inhibitors (SSRIs) alone are ineffective.

OBJECTIVES AND METHODS

We utilized microdialysis in awake, freely moving rats to study the effect of risperidone in combination with citalopram, an SSRI, on extracellular 5-HT, dopamine (DA), and norepinephrine (NE) efflux in rat medial prefrontal cortex (mPFC).

RESULTS

Risperidone (1.0 mg/kg, s.c.), given alone, significantly increased 5-HT, DA, and NE concentrations in the mPFC. Citalopram (10 mg/kg, s.c.), by itself, produced a significant increase in 5-HT levels only. The combination of risperidone and citalopram produced significantly greater increases in efflux of both DA and NE than risperidone alone. However, the effect of this combination on extracellular 5-HT concentrations was not significantly different than that of citalopram alone. The augmentation of DA and NE efflux induced by risperidone plus citalopram could be partially blocked by the selective 5-HT1A antagonist, WAY 100635 (0.2 mg/kg, s.c.).

CONCLUSIONS

The results suggest that the ability of atypical APDs to augment the therapeutic efficacy of SSRIs in major depression and treatment-resistant depression may be due, at least in part, to potentiation of SSRI-induced increases in cortical DA and NE. The contributions of 5-HT1A receptor stimulation and 5-HT2A and alpha2 adrenergic receptor antagonism to this augmentation are discussed.

Lack of Enhanced Effect of Antipsychotics Combined With Fluvoxamine on Acetylcholine Release in Rat Prefrontal Cortex

We have shown that coadministration of sulpiride and fluvoxamine preferentially increases the release of dopamine in the prefrontal cortex. To study the possible role of the cortical cholinergic system in this effect, we combined several other antipsychotic drugs with fluvoxamine and examined the effects on acetylcholine release in rat prefrontal cortex. Risperidone and clozapine significantly increased the release of acetylcholine but sulpiride did not, and fluvoxamine did not enhance the effects of the antipsychotics. These results further support the previous suggestion that the cortical dopamine system plays an important role in the effects of antipsychotic drugs administered in combination with fluvoxamine.