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

Pharmacokinetic/pharmacodynamic modeling of cortical dopamine concentrations after quetiapine lipid core nanocapsules administration to schizophrenia phenotyped rats

Schizophrenia (SCZ) response to pharmacological treatment is highly variable. Quetiapine (QTP) administered as QTP lipid core nanocapsules (QLNC) has been shown to modulate drug delivery to the brain of SCZ phenotyped rats (SPR). In the present study, we describe the brain concentration-effect relationship after administrations of QTP as a solution or QLNC to SPR and naïve animals. A semimechanistic pharmacokinetic (PK) model describing free QTP concentrations in the brain was linked to a pharmacodynamic (PD) model to correlate the drug kinetics to changes in dopamine (DA) medial prefrontal cortex extracellular concentrations determined by intracerebral microdialysis. Different structural models were investigated to fit DA concentrations after QTP dosing, and the final model describes the synthesis, release, and elimination of DA using a pool compartment. The results show that nanoparticles increase QTP brain concentrations and DA peak after drug dosing to SPR. To the best of our knowledge, this is the first study that combines microdialysis and PK/PD modeling in a neurodevelopmental model of SCZ to investigate how a nanocarrier can modulate drug PK and PD, contributing to the development of new treatment strategies for SCZ.

Maintenance Electroconvulsive Therapy in Catatonia: Clinical Profiles From a Case Series

OBJECTIVES

This study aims to conduct a descriptive analysis of the clinical features and treatment responses in 6 patients with catatonia who received maintenance electroconvulsive therapy (ECT).

METHODS

Our study included all patients who underwent maintenance ECT (mECT) at the Hospital Clínic de Barcelona between September 2020 and September 2022 following a catatonic episode.

RESULTS

The study cohort comprised 5 patients with schizophrenia and 1 patient with major depressive disorder. Among patients with schizophrenia, the first catatonic episode occurred several years after their initial paranoid psychotic episode, whereas the patient with depression experienced a rapid progression from the first depressive episode to catatonia. After acute ECT, 4 patients achieved complete symptomatic remission, 1 patient exhibited a partial response, and another maintained a severe catatonic state. Maintenance ECT was indicated because of the high risk of severe relapses. The mean frequency of mECT sessions was 9.83 (SD, 5.60) days. Notably, 66.67% of the patients were concurrently receiving clozapine as part of their pharmacological treatment. Among patients with schizophrenia, mECT sessions could not be extended beyond 7 to 10 days, whereas the depressed patient could space ECT sessions up to 21 days without experiencing a relapse.

CONCLUSIONS

Maintenance ECT proves to be a safe and well-tolerated strategy for preventing relapses in severe catatonic patients who have previously stabilized with acute ECT. Further research is needed to develop clinical guidelines that define optimal application strategies for mECT in catatonia.

Neurometabolic alterations in children and adolescents with functional neurological disorder

OBJECTIVES

In vivo magnetic resonance spectroscopy (MRS) was used to investigate neurometabolic homeostasis in children with functional neurological disorder (FND) in three regions of interest: supplementary motor area (SMA), anterior default mode network (aDMN), and posterior default mode network (dDMN). Metabolites assessed included N-acetyl aspartate (NAA), a marker of neuron function; myo-inositol (mI), a glial-cell marker; choline (Cho), a membrane marker; glutamate plus glutamine (Glx), a marker of excitatory neurotransmission; γ-aminobutyric acid (GABA), a marker of inhibitor neurotransmission; and creatine (Cr), an energy marker. The relationship between excitatory (glutamate and glutamine) and inhibitory (GABA) neurotransmitter (E/I) balance was also examined.

METHODS

MRS data were acquired for 32 children with mixed FND (25 girls, 7 boys, aged 10.00 to 16.08 years) and 41 healthy controls of similar age using both short echo point-resolved spectroscopy (PRESS) and Mescher-Garwood point-resolved spectroscopy (MEGAPRESS) sequences in the three regions of interest.

RESULTS

In the SMA, children with FND had lower NAA/Cr, mI/Cr (trend level), and GABA/Cr ratios. In the aDMN, no group differences in metabolite ratios were found. In the pDMN, children with FND had lower NAA/Cr and mI/Cr (trend level) ratios. While no group differences in E/I balance were found (FND vs. controls), E/I balance in the aDMN was lower in children with functional seizures-a subgroup within the FND group. Pearson correlations found that increased arousal (indexed by higher heart rate) was associated with lower mI/Cr in the SMA and pDMN.

CONCLUSIONS

Our findings of multiple differences in neurometabolites in children with FND suggest dysfunction on multiple levels of the biological system: the neuron (lower NAA), the glial cell (lower mI), and inhibitory neurotransmission (lower GABA), as well as dysfunction in energy regulation in the subgroup with functional seizures.

Treatment with the second-generation antipsychotic quetiapine is associated with increased subgenual ACC activation during reward processing in major depressive disorder

BACKGROUND

The second-generation antipsychotic (SGA) quetiapine is an essential option for antidepressant augmentation therapy in major depressive disorder (MDD), yet neurobiological mechanisms behind its antidepressant properties remain unclear. As SGAs interfere with activity in reward-related brain areas, including the anterior cingulate cortex (ACC) - a key brain region in antidepressant interventions, this study examined whether quetiapine treatment affects ACC activity during reward processing in MDD patients.

METHODS

Using the ACC as region of interest, an independent t-test comparing reward-related BOLD response of 51 quetiapine-taking and 51 antipsychotic-free MDD patients was conducted. Monetary reward outcome feedback was measured in a card-guessing paradigm using pseudorandom blocks. Participants were matched for age, sex, and depression severity and analyses were controlled for confounding variables, including total antidepressant medication load, illness chronicity and acute depression severity. Potential dosage effects were examined in a 3 × 1 ANOVA. Differences in ACC-related functional connectivity were assessed in psycho-physiological interaction (PPI) analyses.

RESULTS

Left subgenual ACC activity was significantly higher in the quetiapine group compared to antipsychotic-free participants and dependent on high-dose quetiapine intake. Results remained significant after controlling for confounding variables. The PPI analysis did not yield significant group differences in ACC-related functional connectivity.

LIMITATIONS

Causal interpretation is limited due to cross-sectional findings.

CONCLUSION

Elevated subgenual ACC activity to rewarding stimuli may represent a neurobiological marker and potential key interface of quetiapine's antidepressant effects in MDD. These results underline ACC activity during reward processing as an investigative avenue for future research and therapeutic interventions to improve MDD treatment outcomes.

Therapeutic Potential and Limitation of Serotonin Type 7 Receptor Modulation

Although a number of mood-stabilising atypical antipsychotics and antidepressants modulate serotonin type 7 receptor (5-HT7), the detailed contributions of 5-HT7 function to clinical efficacy and pathophysiology have not been fully understood. The mood-stabilising antipsychotic agent, lurasidone, and the serotonin partial agonist reuptake inhibitor, vortioxetine, exhibit higher binding affinity to 5-HT7 than other conventional antipsychotics and antidepressants. To date, the initially expected rapid onset of antidepressant effects-in comparison with conventional antidepressants or mood-stabilising antipsychotics-due to 5-HT7 inhibition has not been observed with lurasidone and vortioxetine; however, several clinical studies suggest that 5-HT7 inhibition likely contributes to quality of life of patients with schizophrenia and mood disorders via the improvement of cognition. Furthermore, recent preclinical studies reported that 5-HT7 inhibition might mitigate antipsychotic-induced weight gain and metabolic complication by blocking other monoamine receptors. Further preclinical studies for the development of 5-HT7 modulation against neurodevelopmental disorders and neurodegenerative diseases have been ongoing. To date, various findings from various preclinical studies indicate the possibility that 5-HT7 modifications can provide two independent strategies. The first is that 5-HT7 inhibition ameliorates the dysfunction of inter-neuronal transmission in mature networks. The other is that activation of 5-HT7 can improve transmission dysfunction due to microstructure abnormality in the neurotransmission network-which could be unaffected by conventional therapeutic agents-via modulating intracellular signalling during the neurodevelopmental stage or via loss of neural networks with aging. This review attempts to describe the current and novel clinical applications of 5-HT7 modulation based on preclinical findings.

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.

Pimavanserin augments the efficacy of atypical antipsychotic drugs in a mouse model of treatment-refractory negative symptoms of schizophrenia

Negative symptoms are a core, pervasive, and often treatment-refractory phenotype of schizophrenia, one which contributes to poor functional outcome, ability to work, pursue educational goals, and quality of life, as well as caretaker burden. Improvement of negative symptoms in some patients with schizophrenia has been reported with some atypical antipsychotic drugs [AAPDs], but improvement is absent in many patients and partial in others. Therefore, more effective treatments are needed, and better preclinical models of negative symptoms are needed to identify them. Sub-chronic [sc] treatment of rodents with phencyclidine [PCP], a noncompetitive N-methyl-d-aspartate [NMDAR] antagonist, produces deficits in social interactions [SI] that have been widely studied as a model of negative symptoms in schizophrenia. Acute restraint stress [ARS] also provides a model of treatment-refractory negative symptoms [TRS] to AAPDs. By themselves, in sc-PCP mice, the AAPDs, risperidone, olanzapine, and aripiprazole, but not the selective 5-HT_2AR inverse agonist, pimavanserin [PIM], rescued the SI deficit in sc-PCP mice, as did the combination of PIM with sub-effective doses of each of these AAPDs. These three AAPDs alone did not rescue SI deficit in sc-PCP+2h-ARS mice, indicating these mice were treatment refractory. However, co-administration of PIM with any of the AAPDs significantly restored SI in these mice. PIM may be an effective adjunctive therapy for treating negative symptoms of schizophrenia in some patients who have failed to respond to AAPDs, but further studies are needed.

Effects of an Atypical Antipsychotic, Zotepine, on Astroglial L-Glutamate Release through Hemichannels: Exploring the Mechanism of Mood-Stabilising Antipsychotic Actions and Antipsychotic-Induced Convulsion

Accumulating neuropsychopharmacological evidence has suggested that functional abnormalities of astroglial transmission and protein kinase B (Akt) contribute to the pathophysiology and/or pathomechanisms of several neuropsychiatric disorders, such as epilepsy, schizophrenia, affective disorders and antipsychotic-induced convulsions. Therefore, to explore the pathophysiology of mood-stabilising antipsychotics and the proconvulsive actions of atypical antipsychotics, the present study determined the effects of a mood-stabilising, atypical, antipsychotic agent, zotepine (ZTP), on astroglial L-glutamate release and the expression of connexin43 (Cx43) protein in cortical, primary, cultured astrocytes using ultra-high-pressure liquid chromatography and capillary immunoblotting systems. Both acute and subchronic administrations of therapeutically relevant concentrations of ZTP did not affect astroglial L-glutamate release or Cx43 expression in plasma membranes; however, chronic administration of a therapeutically relevant concentration of ZTP increased astroglial L-glutamate release and Cx43 expression in the plasma membrane. Subchronic administrations of a supratherapeutic concentration of ZTP enhanced astroglial L-glutamate release and Cx43 expression in the plasma membrane, whereas acute administration of a supratherapeutic concentration of ZTP enhanced astroglial L-glutamate release without affecting Cx43 expression. These stimulatory effects of ZTP on astroglial L-glutamate release through activated hemichannels and Cx43 trafficking to the astroglial plasma membrane were suppressed by the Akt inhibitor. These results suggest that ZTP enhances astroglial L-glutamate release in a concentration-dependent and time-dependent manner due to the enhanced function of astroglial hemichannels, probably via activation of Akt signalling. Therefore, the enhanced astroglial L-glutamatergic transmission induced by ZTP is, at least partially, involved in the mood-stabilising antipsychotic and proconvulsive actions of ZTP.

Reductions in midbrain GABAergic and dopamine neuron markers are linked in schizophrenia

Reductions in the GABAergic neurotransmitter system exist across multiple brain regions in schizophrenia and encompass both pre- and postsynaptic components. While reduced midbrain GABAergic inhibitory neurotransmission may contribute to the hyperdopaminergia thought to underpin psychosis in schizophrenia, molecular changes consistent with this have not been reported. We hypothesised that reduced GABA-related molecular markers would be found in the midbrain of people with schizophrenia and that these would correlate with dopaminergic molecular changes. We hypothesised that downregulation of inhibitory neuron markers would be exacerbated in schizophrenia cases with high levels of neuroinflammation. Eight GABAergic-related transcripts were measured with quantitative PCR, and glutamate decarboxylase (GAD) 65/67 and GABA_A alpha 3 (α3) (GABRA3) protein were measured with immunoblotting, in post-mortem midbrain (28/28 and 28/26 control/schizophrenia cases for mRNA and protein, respectively), and analysed by both diagnosis and inflammatory subgroups (as previously defined by higher levels of four pro-inflammatory cytokine transcripts). We found reductions (21 – 44%) in mRNA encoding both presynaptic and postsynaptic proteins, vesicular GABA transporter (VGAT), GAD1, and parvalbumin (PV) mRNAs and four alpha subunits (α1, α2, α3, α5) of the GABA_A receptor in people with schizophrenia compared to controls (p < 0.05). Gene expression of somatostatin (SST) was unchanged (p = 0.485). We confirmed the reduction in GAD at the protein level (34%, p < 0.05). When stratifying by inflammation, only GABRA3 mRNA exhibited more pronounced changes in high compared to low inflammatory subgroups in schizophrenia. GABRA3 protein was expressed by 98% of tyrosine hydroxylase-positive neurons and was 23% lower in schizophrenia, though this did not reach statistical significance (p > 0.05). Expression of transcripts for GABA_A receptor alpha subunits 2 and 3 (GABRA2, GABRA3) were positively correlated with tyrosine hydroxylase (TH) and dopamine transporter (DAT) transcripts in schizophrenia cases (GABRA2; r > 0.630, GABRA3; r > 0.762, all p < 0.001) but not controls (GABRA2; r < − 0.200, GABRA3; r < 0.310, all p > 0.05). Taken together, our results support a profound disruption to inhibitory neurotransmission in the substantia nigra regardless of inflammatory status, which provides a potential mechanism for disinhibition of nigrostriatal dopamine neurotransmission.

Chronic Administrations of Guanfacine on Mesocortical Catecholaminergic and Thalamocortical Glutamatergic Transmissions

It has been established that the selective α2A adrenoceptor agonist guanfacine reduces hyperactivity and improves cognitive impairment in patients with attention-deficit/hyperactivity disorder (ADHD). The major mechanisms of guanfacine are considered to involve the activation of the postsynaptic α2A adrenoceptor of glutamatergic pyramidal neurons in the frontal cortex, but the effects of chronic guanfacine administration on catecholaminergic and glutamatergic transmissions associated with the orbitofrontal cortex (OFC) are yet to be clarified. The actions of guanfacine on catecholaminergic transmission, the effects of acutely local and systemically chronic (for 7 days) administrations of guanfacine on catecholamine release in pathways from the locus coeruleus (LC) to OFC, the ventral tegmental area (VTA) and reticular thalamic-nucleus (RTN), from VTA to OFC, from RTN to the mediodorsal thalamic-nucleus (MDTN), and from MDTN to OFC were determined using multi-probe microdialysis with ultra-high performance liquid chromatography. Additionally, the effects of chronic guanfacine administration on the expression of the α2A adrenoceptor in the plasma membrane fraction of OFC, VTA and LC were examined using a capillary immunoblotting system. The acute local administration of therapeutically relevant concentrations of guanfacine into the LC decreased norepinephrine release in the OFC, VTA and RTN without affecting dopamine release in the OFC. Systemically, chronic administration of therapeutically relevant doses of guanfacine for 14 days increased the basal release of norepinephrine in the OFC, VTA, RTN, and dopamine release in the OFC via the downregulation of the α2A adrenoceptor in the LC, OFC and VTA. Furthermore, systemically, chronic guanfacine administration did not affect intrathalamic GABAergic transmission, but it phasically enhanced thalamocortical glutamatergic transmission. The present study demonstrated the dual actions of guanfacine on catecholaminergic transmission-acute attenuation of noradrenergic transmission and chronic enhancement of noradrenergic transmission and thalamocortical glutamatergic transmission. These dual actions of guanfacine probably contribute to the clinical effects of guanfacine against ADHD.

Current Limitations and Candidate Potential of 5-HT7 Receptor Antagonism in Psychiatric Pharmacotherapy

Several mood-stabilizing atypical antipsychotics and antidepressants weakly block serotonin (5-HT) receptor type-7 (5-HT7R); however, the contributions of 5-HT7R antagonism to clinical efficacy and pathophysiology are yet to be clarified. A novel mood-stabilizing antipsychotic agent, lurasidone exhibits predominant binding affinity to 5-HT7R when compared with other monoamine receptors. To date, we have failed to discover the superior clinical efficacy of lurasidone on schizophrenia, mood, or anxiety disorders when compared with conventional mood-stabilizing atypical antipsychotics; however, numerous preclinical findings have indicated the possible potential of 5-HT7R antagonism against several neuropsychiatric disorders, as well as the generation of novel therapeutic options that could not be expected with conventional atypical antipsychotics. Traditional experimental techniques, electrophysiology, and microdialysis have demonstrated that the effects of 5-HT receptor type-1A (5-HT1AR) and 5-HT7R on neurotransmission are in contrast, but the effect of 5-HT1AR is more predominant than that of 5-HT7R, resulting in an insufficient understanding of the 5-HT7R function in the field of psychopharmacology. Accumulating knowledge regarding the pharmacodynamic profiles of 5-HT7R suggests that 5-HT7R is one of the key players in the establishment and remodeling of neural development and cytoarchitecture during the early developmental stage to the mature brain, and dysfunction or modulation of 5-HT7R is linked to the pathogenesis/pathophysiology of neuropsychiatric and neurodevelopmental disorders. In this review, to explore candidate novel applications for the treatment of several neuropsychiatric disorders, including mood disorders, schizophrenia, and other cognitive disturbance disorders, we discuss perspectives of psychopharmacology regarding the effects of 5-HT7R antagonism on transmission and intracellular signaling systems, based on preclinical findings.

Candidate Strategies for Development of a Rapid-Acting Antidepressant Class That Does Not Result in Neuropsychiatric Adverse Effects: Prevention of Ketamine-Induced Neuropsychiatric Adverse Reactions

Non-competitive N-methyl-D-aspartate/glutamate receptor (NMDAR) antagonism has been considered to play important roles in the pathophysiology of schizophrenia. In spite of severe neuropsychiatric adverse effects, esketamine (racemic enantiomer of ketamine) has been approved for the treatment of conventional monoaminergic antidepressant-resistant depression. Furthermore, ketamine improves anhedonia, suicidal ideation and bipolar depression, for which conventional monoaminergic antidepressants are not fully effective. Therefore, ketamine has been accepted, with rigorous restrictions, in psychiatry as a new class of antidepressant. Notably, the dosage of ketamine for antidepressive action is comparable to the dose that can generate schizophrenia-like psychotic symptoms. Furthermore, the psychotropic effects of ketamine precede the antidepressant effects. The maintenance of the antidepressive efficacy of ketamine often requires repeated administration; however, repeated ketamine intake leads to abuse and is consistently associated with long-lasting memory-associated deficits. According to the dissociative anaesthetic feature of ketamine, it exerts broad acute influences on cognition/perception. To evaluate the therapeutic validation of ketamine across clinical contexts, including its advantages and disadvantages, psychiatry should systematically assess the safety and efficacy of either short- and long-term ketamine treatments, in terms of both acute and chronic outcomes. Here, we describe the clinical evidence of NMDAR antagonists, and then the temporal mechanisms of schizophrenia-like and antidepressant-like effects of the NMDAR antagonist, ketamine. The underlying pharmacological rodent studies will also be discussed.

A Working Hypothesis Regarding Identical Pathomechanisms between Clinical Efficacy and Adverse Reaction of Clozapine via the Activation of Connexin43

Clozapine (CLZ) is an approved antipsychotic agent for the medication of treatment-resistant schizophrenia but is also well known as one of the most toxic antipsychotics. Recently, the World Health Organization’s (WHO) global database (VigiBase) reported the relative lethality of severe adverse reactions of CLZ. Agranulocytosis is the most famous adverse CLZ reaction but is of lesser lethality compared with the other adverse drug reactions of CLZ. Unexpectedly, VigiBase indicated that the prevalence and relative lethality of pneumonia, cardiotoxicity, and seizures associated with CLZ were more serious than that of agranulocytosis. Therefore, haematological monitoring in CLZ patients monitoring system provided success in the prevention of lethal adverse events from CLZ-induced agranulocytosis. Hereafter, psychiatrists must amend the CLZ patients monitoring system to protect patients with treatment-resistant schizophrenia from severe adverse CLZ reactions, such as pneumonia, cardiotoxicity, and seizures, according to the clinical evidence and pathophysiology. In this review, we discuss the mechanisms of clinical efficacy and the adverse reactions of CLZ based on the accumulating pharmacodynamic findings of CLZ, including tripartite synaptic transmission, and we propose suggestions for amending the monitoring and medication of adverse CLZ reactions associated with pneumonia, cardiotoxicity, and seizures.

Semi-Mechanistic Pharmacokinetic Modeling of Lipid Core Nanocapsules: Understanding Quetiapine Plasma and Brain Disposition in a Neurodevelopmental Animal Model of Schizophrenia

This study investigated plasma and brain disposition of quetiapine lipid core nanocapsules (QLNC) in naive and schizophrenic (SCZ-like) rats and developed a semimechanistic model to describe changes in both compartments following administration of the drug in solution (FQ) or nanoencapsulated. QLNC (1 mg/ml) presented 166 ± 39 nm, low polydispersity, and high encapsulation (93.0% ± 1.4%). A model was built using experimental data from total and unbound plasma and unbound brain concentrations obtained by microdialysis after administration of single intravenous bolus dose of FQ or QLNC to naive and SCZ-like rats. A two-compartment model was identifiable both in blood and in brain with a bidirectional drug transport across the blood-brain barrier (CL_in and CL_out). SCZ-like rats' significant decrease in brain exposure with FQ (decrease in CL_in) was reverted by QLNC, showing that nanocarriers govern quetiapine tissue distribution. Model simulations allowed exploring the potential of LNC for brain delivery. SIGNIFICANCE STATEMENT: A population approach was used to simultaneously model total and unbound plasma and unbound brain quetiapine concentrations allowing for quantification of the rate and extent of the drug's brain distribution following administration of both free drug in solution or as nanoformulation to naive and SCZ-like rats. The model-based approach is useful to better understand the possibilities and limitations of this nanoformulation for drug delivering to the brain, opening the opportunity to use this approach to improve SCZ-treatment-limited response rates.

Interaction between Mesocortical and Mesothalamic Catecholaminergic Transmissions Associated with NMDA Receptor in the Locus Coeruleus

Noncompetitive N-methyl-D-aspartate/glutamate receptor (NMDAR) antagonists contribute to the pathophysiology of schizophrenia and mood disorders but improve monoaminergic antidepressant-resistant mood disorder and suicidal ideation. The mechanisms of the double-edged sword clinical action of NMDAR antagonists remained to be clarified. The present study determined the interaction between the NMDAR antagonist (MK801), α1 adrenoceptor antagonist (prazosin), and α2A adrenoceptor agonist (guanfacine) on mesocortical and mesothalamic catecholaminergic transmission, and thalamocortical glutamatergic transmission using multiprobe microdialysis. The inhibition of NMDAR in the locus coeruleus (LC) by local MK801 administration enhanced both the mesocortical noradrenergic and catecholaminergic coreleasing (norepinephrine and dopamine) transmissions. The mesothalamic noradrenergic transmission was also enhanced by local MK801 administration in the LC. These mesocortical and mesothalamic transmissions were activated by intra-LC disinhibition of transmission of γ-aminobutyric acid (GABA) via NMDAR inhibition. Contrastingly, activated mesothalamic noradrenergic transmission by MK801 enhanced intrathalamic GABAergic inhibition via the α1 adrenoceptor, resulting in the suppression of thalamocortical glutamatergic transmission. The thalamocortical glutamatergic terminal stimulated the presynaptically mesocortical catecholaminergic coreleasing terminal in the superficial cortical layers, but did not have contact with the mesocortical selective noradrenergic terminal (which projected terminals to deeper cortical layers). Furthermore, the α2A adrenoceptor suppressed the mesocortical and mesothalamic noradrenergic transmissions somatodendritically in the LC and presynaptically/somatodendritically in the reticular thalamic nucleus (RTN). These discrepancies between the noradrenergic and catecholaminergic transmissions in the mesocortical and mesothalamic pathways probably constitute the double-edged sword clinical action of noncompetitive NMDAR antagonists.

Pathogenesis and pathophysiology of autosomal dominant sleep-related hypermotor epilepsy with S284L-mutant α4 subunit of nicotinic ACh receptor

BACKGROUND AND PURPOSE

The mechanisms causing spontaneous epileptic seizures, including carbamazepine-resistant/zonisamide -sensitive seizures and comorbidity in autosomal dominant sleep-related hypermotor epilepsy (ADSHE) are unclear. This study investigated functional abnormalities in thalamocortical transmission in transgenic rats bearing rat S286L-mutant Chrna4 (S286L-TG) of α4 subunit of the nicotinic ACh receptor (nAChR) that corresponds to the human S284L-mutant CHRNA4.

EXPERIMENTAL APPROACH

Effects of carbamazepine and zonisamide on epileptic discharges of S286L-TG rat were measured using telemetry electrocorticogram. Transmission abnormalities of L-glutamate and GABA in thalamocortical pathway of S286L-TG rats were investigated using multiprobe microdialysis and ultra-high-performance liquid-chromatography.

KEY RESULTS

Epileptic discharges in S286L-TG rats were reduced by zonisamide but not by carbamazepine, similar to that of S284L-ADSHE patients. Carbamazepine unaffected functional abnormality in transmission of S286L-TG rats. However, zonisamide was able to compensate for the attenuated S286L-mutant nAChR induced GABA release in frontal-cortex, without affecting attenuated thalamocortical glutamatergic transmission. Excitatory effects of S286L-mutant nAChR on thalamocortical transmission were attenuated compared with those of wild-type nAChR. Loss-of-function of S286L-nAChR enhanced transmission in thalamocortical motor pathway by predominantly attenuating GABAergic transmission. However, it attenuated transmission in thalamocortical cognitive pathway by reducing inhibitory GABAergic and excitatory glutamatergic transmission.

CONCLUSION AND IMPLICATIONS

Our results suggest that functional abnormalities of S286L-nAChR are associated with intra-frontal and thalamocortical transmission, possibly contributing to the pathogenesis of ADSHE-seizure and comorbidity of S284L-ADSHE. Selective compensation of impaired GABAergic transmission by zonisamide (but not by carbamazepine) in frontal cortex may be involved, at least partially, in carbamazepine-resistant ADSHE-seizure of S284L-ADSHE patients.

Pathomechanism of nocturnal paroxysmal dystonia in autosomal dominant sleep-related hypermotor epilepsy with S284L-mutant α4 subunit of nicotinic ACh receptor

To study the pathomechanism and pathophysiology of nocturnal paroxysmal dystonia of autosomal dominant sleep-related hypermotor epilepsy (ADSHE), this study determined functional abnormalities in thalamic hyperdirect pathway from reticular thalamic nucleus (RTN), motor thalamic nuclei (MoTN), subthalamic nucleus (STN) to substantia nigra pars reticulata (SNr) of transgenic rats (S286L-TG) bearing S286 L missense mutation of rat Chrna4 gene, which corresponds to the S284 L mutation in the human CHRNA4 gene. The activation of α4β2-nAChR in the RTN increased GABA release in MoTN resulting in reduced glutamatergic transmission in thalamic hyperdirect pathway of wild-type. Contrary to wild-type, activation of S286L-mutant α4β2-nAChR (loss-of-function) in the RTN relatively enhanced glutamatergic transmission in thalamic hyperdirect pathway of S286L-TG via impaired GABAergic inhibition in intra-thalamic (RTN-MoTN) pathway. These functional abnormalities in glutamatergic transmission in hyperdirect pathway contribute to the pathomechanism of electrophysiologically negative nocturnal paroxysmal dystonia of S286L-TG. Therapeutic-relevant concentration of zonisamide (ZNS) inhibited the glutamatergic transmission in the hyperdirect pathway via activation of group II metabotropic glutamate receptor (II-mGluR) in MoTN and STN. The present results suggest that S286L-mutant α4β2-nAChR induces GABAergic disinhibition in intra-thalamic (RTN-MoTN) pathway and hyperactivation of glutamatergic transmission in thalamic hyperdirect pathway (MoTN-STN-SNr), possibly contributing to the pathomechanism of nocturnal paroxysmal dystonia of ADSHE patients with S284L mutant CHRNA4. Inhibition of glutamatergic transmission in thalamic hyperdirect pathway induced by ZNS via activation of II-mGluR may be involved, at least partially, in ZNS-sensitive nocturnal paroxysmal dystonia of ADSHE patients with S284L mutation.

Catatonia-Like Syndrome Treated With Low-Dose Ketamine

BACKGROUND

Ketamine's application in psychiatry have expanded, but it appears never to have been previously used to diagnose and treat patients with catatonia-like syndrome that occasionally present to emergency departments.

CASE REPORT

A 23-year-old male was observed to suddenly stop talking. His ED GCS was 8 and had normal vital signs. While verbally unresponsive, he refused to open his eyes, demonstrated waxy flexibility of his arms, but the balance of his physical, neurological, and laboratory exams were normal. Strongly suspecting a catatonic state, they needed to rapidly confirm that diagnosis or begin evaluating him for potentially life-threatening non-psychiatric illnesses. Lacking other diagnostic modalities, they administered low-dose ketamine boluses. Ketamine 25 mg (1 mL) was diluted in 9 mL NS (2.5 mg/mL). Based on similar protocols, 1 mL of the solution (0.03 mg/Kg) was given intravenously every few minutes. After 12.5 mg ketamine, he was conscious and verbal. Subsequent history confirmed a prior episode requiring an extensive, non-productive medical evaluation. Psychiatry later confirmed the diagnosis. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: Patients with catatonia-like states pose a difficult diagnostic and therapeutic dilemma. Multiple interventions have been used with varying success. Optimal interventions provide a rapid resolution (or demonstrate that a psychiatric cause is not likely), be safe, encompass few contraindications, and be familiar to the clinician. In our patient, subanesthetic doses of ketamine fulfilled these criteria and successfully resolved the condition. If shown effective in other cases, ketamine would be a valuable addition to our psychiatric armamentarium.

Quetiapine Abuse Fourteen Years Later: Where Are We Now? A Systematic Review

Background: Quetiapine, an atypical antipsychotic endowed with weak dopamine antagonist, potent 5-HT_2A-blocking, partial 5-HT_1A-agonist, anti-H₁ histamine, adrenolytic, and sigma₁ receptor agonist activities, since an original 2004 report is increasingly misused. Although some of its pharmacodynamics might explain some motives for voluptuary use, most of its actions are directed at setting-off those motives. Hence, it is possible that its popularity in special populations is due to the fact that the unpleasant or unwanted effects of addiction substances are somehow soothed by quetiapine. Currently, quetiapine is tested in substance use disorders, showing some promise, but it is likely to be misused in certain contexts. Objectives: To review the evidence for the use of quetiapine as addiction substance and investigate the characteristics of populations involved in such addiction. Methods: A systematic review of literature on various databases retrieved on September 7, 2018 87 records to comment. Results. We reviewed the evidence for quetiapine's addictive potential in the light of its pharmacodynamics properties and presented two cases of recreational quetiapine use, by a 35-year old male patient with past addictive behavior and by a 50-year-old woman with major depressive disorder and conversion disorder. We found quetiapine to be abused mainly by addict populations and people with law involvement. Conclusions/Importance: There is no reason to include quetiapine among regulated substances, but monitoring of its use in selected populations is warranted. Psychiatrists and physicians working in the penitentiary system should be aware of the addictive potential of quetiapine and adopt measures restricting its use.

Vortioxetine Subchronically Activates Serotonergic Transmission via Desensitization of Serotonin 5-HT1A Receptor with 5-HT3 Receptor Inhibition in Rats

Vortioxetine is a novel, multimodal antidepressant with unique targets, including the inhibition of the serotonin transporter (SET), of serotonin 5-HT₃ (5-HT3R), and of 5-HT₇ (5-HT7R) receptors and partial agonism to serotonin 5-HT_1A (5-HT1AR) receptors in humans. Vortioxetine has a lower affinity to 5-HT1AR and 5-HT7R in rats compared with humans, but several behavior studies have demonstrated its powerful antidepressant-like actions. In spite of these efforts, detailed effects of the subchronic administration of vortioxetine on serotonergic transmission remain to be clarified. This study examined the mechanisms underlying the clinical effects of vortioxetine by measuring the releases of 5-HT and GABA in the medial prefrontal cortex (mPFC) of freely moving rats compared with the selective SET inhibitor, escitalopram. Inhibition of 5-HT3R in the mPFC enhanced regional 5-HT release via GABAergic disinhibition. Activation of somatodendritic 5-HT1AR in the dorsal raphe nucleus (DRN) and presynaptic 5-HT1AR in the mPFC inhibited 5-HT release in the mPFC. Escitalopram subchronically activated mesocortical serotonergic transmission via desensitization of 5-HT1AR in the mPFC and DRN and of 5-HT3R in the mPFC; however, vortioxetine also subchronically activated mesocortical serotonergic transmission via desensitization of 5-HT1AR in the mPFC and DRN but not of 5-HT3R in the mPFC. These demonstrations, the desensitization of 5-HT1AR with the inhibition of 5-HT3R (without 5-HT3R desensitization), at least partially, contribute to the multimodal antidepressant action of vortioxetine in rats.

Pharmacological Discrimination of Effects of MK801 on Thalamocortical, Mesothalamic, and Mesocortical Transmissions

N-methyl-d-aspartate/glutamate receptor (NMDAR) is one of the major voltage-sensitive ligand-gated cation channel. Several noncompetitive NMDAR antagonists contribute to pathophysiology of schizophrenia and mood disorders; however, the effects of inhibition of NMDAR on several transmitter system have not been well clarified. Thus, this study determined the selective NMDAR antagonist, MK801 (dizocilpine), on thalamocortical, mesothalamic, and mesocortical transmissions associated with l-glutamate, GABA, serotonin, norepinephrine, and dopamine using multiprobe microdialysis. Perfusion with MK801 into the medial prefrontal cortex (mPFC) increased and decreased respective regional releases of monoamine and GABA without affecting l-glutamate. The mPFC MK801-induced monoamine release is generated by the regional GABAergic disinhibition. Perfusion with MK801 into the reticular thalamic nucleus (RTN) decreased GABA release in the mediodorsal thalamic nucleus (MDTN) but increased releases of l-glutamate and catecholamine without affecting serotonin in the mPFC. The RTN MK801-induced l-glutamate release in the mPFC was generated by GABAergic disinhibition in the MDTN, but RTN MK801-induced catecholamine release in the mPFC was generated by activation of α-amino-3-hydroxy-5-methyl-4-isoxazolepropionate/glutamate receptor (AMPAR) which received l-glutamate release from thalamocortical glutamatergic terminals in the mPFC. Perfusion with MK801 into the dorsal raphe nucleus (DRN) decreased GABA release in the DRN but selectively increased serotonin release in the MDTN and mPFC. These DRN MK801-induced serotonin releases in the both mPFC and MDTN were also generated by GABAergic disinhibition in the DRN. These results indicate that the GABAergic disinhibition induced by NMDAR inhibition plays important roles in the MK801-induced releases of l-glutamate and monoamine in thalamic nuclei and cortex.

Lurasidone Sub-Chronically Activates Serotonergic Transmission via Desensitization of 5-HT1A and 5-HT7 Receptors in Dorsal Raphe Nucleus

Lurasidone is an atypical mood-stabilizing antipsychotic agent with unique receptor-binding profile, including 5-HT7 receptor (5-HT7R) antagonism. Effects of 5-HT7R antagonism on transmitter systems of schizophrenia and mood disorders, however, have not been well clarified. Thus, this study examined the mechanisms underlying the clinical effects of lurasidone by measuring mesocortical serotonergic transmission. Following systemic and local administrations of lurasidone, MK801 and 5-HT receptor modulators, we determined releases of 5-HT in dorsal raphe nucleus (DRN), mediodorsal thalamic nucleus (MDTN) and medial prefrontal cortex (mPFC) and γ-aminobutyric acid (GABA) in DRN using multiprobe microdialysis with ultra-high-performance liquid chromatography (UHPLC). Serotonergic and GABAergic neurons in the DRN are predominantly regulated by inhibitory 5-HT1A receptor (5-HT1AR) and excitatory 5-HT7R, respectively. Lurasidone acutely generates GABAergic disinhibition by 5-HT7R antagonism, but concomitant its 5-HT1AR agonism prevents serotonergic hyperactivation induced by 5-HT7R inhibition. During treatments with 5-HT1AR antagonist in DRN, lurasidone dose-dependently increased 5-HT release in the DRN, MDTN and mPFC. Contrary, lurasidone chronically enhanced serotonergic transmission and GABAergic disinhibition in the DRN by desensitizing both 5-HT1AR and 5-HT7R. These effects of lurasidone acutely prevented MK801-evoked 5-HT release by GABAergic disinhibition via N-methyl-D-aspartate (NMDA)/glutamate receptor (NMDA-R)-mediated inhibition of 5-HT1AR function, but enhanced MK801-induced 5-HT release by desensitizing 5-HT1AR and 5-HT7R. These results indicate that acutely lurasidone fails to affect 5-HT release, but chronically enhances serotonergic transmission by desensitizing both 5-HT1AR and 5-HT7R. These unique properties of lurasidone ameliorate the dysfunctions of NMDA-R and augment antidepressive effects.

Lurasidone inhibits NMDA receptor antagonist-induced functional abnormality of thalamocortical glutamatergic transmission via 5-HT7 receptor blockade

BACKGROUND AND PURPOSE

Lurasidone is an atypical mood-stabilizing antipsychotic with a unique receptor-binding profile, including 5-HT₇ receptor antagonism; however, the detailed effects of 5-HT₇ receptor antagonism on various transmitter systems relevant to schizophrenia, particularly the thalamo-insular glutamatergic system and the underlying mechanisms, are yet to be clarified.

EXPERIMENTAL APPROACH

We examined the mechanisms underlying the clinical effects of lurasidone by measuring the release of l-glutamate, GABA, dopamine, and noradrenaline in the reticular thalamic nucleus (RTN), mediodorsal thalamic nucleus (MDTN) and insula of freely moving rats in response to systemic injection or local infusion of lurasidone or MK-801 using multiprobe microdialysis with ultra-HPLC.

KEY RESULTS

Systemic MK-801 (0.5 mg·kg^-1 ) administration increased insular release of l-glutamate, dopamine, and noradrenaline but decreased GABA release. Systemic lurasidone (1 mg·kg^-1 ) administration also increased insular release of l-glutamate, dopamine, and noradrenaline but without affecting GABA. Local lurasidone administration into the insula (3 μM) did not affect MK-801-induced insular release of l-glutamate or catecholamine, whereas local lurasidone administration into the MDTN (1 μM) inhibited MK-801-induced insular release of l-glutamate and catecholamine, similar to the 5-HT₇ receptor antagonist SB269970.

CONCLUSIONS AND IMPLICATIONS

The present results indicate that MK-801-induced insular l-glutamate release is generated by activation of thalamo-insular glutamatergic transmission via MDTN GABAergic disinhibition resulting from NMDA receptor inhibition in the MDTN and RTN. Lurasidone inhibited this MK-801-evoked insular l-glutamate release through inhibition of excitatory 5-HT₇ receptor in the MDTN. These effects on thalamo-insular glutamatergic transmission may contribute to the antipsychotic and mood-stabilizing actions of lurasidone.

Clozapine Normalizes a Glutamatergic Transmission Abnormality Induced by an Impaired NMDA Receptor in the Thalamocortical Pathway via the Activation of a Group III Metabotropic Glutamate Receptor

Pharmacological mechanisms of gold-standard antipsychotics against treatment-refractory schizophrenia, such as clozapine (CLZ), remain unclear. We aimed to explore the mechanisms of CLZ by investigating the effects of MK801 and CLZ on tripartite synaptic transmission in the thalamocortical glutamatergic pathway using multi-probe microdialysis and primary cultured astrocytes. l-glutamate release in the medial prefrontal cortex (mPFC) was unaffected by local MK801 administration into mPFC but was enhanced in the mediodorsal thalamic nucleus (MDTN) and reticular thalamic nucleus (RTN) via GABAergic disinhibition in the RTN–MDTN pathway. The local administration of therapeutically relevant concentrations of CLZ into mPFC and MDTN increased and did not affect mPFC l-glutamate release. The local administration of the therapeutically relevant concentration of CLZ into mPFC reduced MK801-induced mPFC l-glutamate release via presynaptic group III metabotropic glutamate receptor (III-mGluR) activation. However, toxic concentrations of CLZ activated l-glutamate release associated with hemichannels. This study demonstrated that RTN is a candidate generator region in which impaired N-methyl-d-aspartate (NMDA)/glutamate receptors likely produce thalamocortical hyperglutamatergic transmission. Additionally, we identified several mechanisms of CLZ relating to its superiority in treatment-resistant schizophrenia and its severe adverse effects: (1) the prevention of thalamocortical hyperglutamatergic transmission via activation of mPFC presynaptic III-mGluR and (2) activation of astroglial l-glutamate release associated with hemichannels. These actions may contribute to the unique clinical profile of CLZ.

Amantadine Combines Astroglial System Xc- Activation with Glutamate/NMDA Receptor Inhibition

A glutamate/NMDA receptor (NMDA-R) antagonist, amantadine (AMA) exhibits a broad spectrum of clinically important properties, including antiviral, antiparkinsonian, neuroprotective, neuro-reparative and cognitive-enhancing effects. However, both clinical and pre-clinical studies have demonstrated that noncompetitive NMDA-R antagonists induce severe schizophrenia-like cognitive deficits. Therefore, this study aims to clarify the clinical discrepancy between AMA and noncompetitive NMDA-R antagonists by comparing the effects of AMA with those of a noncompetitive NMDA-R antagonist, MK801, on rat tripartite glutamatergic synaptic transmission using microdialysis and primary cultured astrocytes. Microdialysis study demonstrated that the stimulatory effects of AMA on L-glutamate release differed from those of MK801 in the globus pallidus, entorhinal cortex and entopeduncular nucleus. The stimulatory effect of AMA on L-glutamate release was modulated by activation of cystine/glutamate antiporter (Sxc). Primary cultured astrocytes study demonstrated that AMA also enhanced glutathione synthesis via Sxc activation. Furthermore, carbon-monoxide induced damage of the astroglial glutathione synthesis system was repaired by AMA but not MK801. Additionally, glutamate/AMPA receptor (AMPA-R) antagonist, perampanel enhanced the protective effects of AMA. The findings of microdialysis and cultured astrocyte studies suggest that a combination of Sxc activation with inhibitions of ionotropic glutamate receptors contributes to neuroprotective, neuro-reparative and cognitive-enhancing activities that can mitigate several neuropsychiatric disorders.

Memantine protects thalamocortical hyper-glutamatergic transmission induced by NMDA receptor antagonism via activation of system xc<sup/>

Deficiencies in N-methyl-d-aspartate (NMDA)/glutamate receptor (NMDAR) signaling have been considered central to the cognitive impairments of schizophrenia; however, an NMDAR antagonist memantine (MEM) improves cognitive impairments of Alzheimer's disease and schizophrenia. These mechanisms of paradoxical clinical effects of NMDAR antagonists remain unclear. To explore the mechanisms by which MK801 and MEM affect thalamocortical transmission, we determined interactions between local administrations of MK801, MEM, system xc^- (Sxc), and metabotropic glutamate receptors (mGluRs) on extracellular glutamate and GABA levels in the mediodorsal thalamic nucleus (MDTN) and medial prefrontal cortex (mPFC) using dual-probe microdialysis with ultra-high-pressure liquid chromatography. Effects of MK801 and MEM on Sxc activity were also determined using primary cultured astrocytes. Sxc activity was enhanced by MEM, but was unaffected by MK801. MK801 enhanced thalamocortical glutamatergic transmission by GABAergic disinhibition in the MDTN. In the MDTN and the mPFC, MEM weakly increased glutamate release by activating Sxc, whereas MEM inhibited thalamocortical glutamatergic transmission. Paradoxical effects of MEM were induced following secondary activation of inhibitory II-mGluR and III-mGluR by exporting glutamate from astroglial Sxc. The present results suggest that the effects of therapeutically relevant concentrations of MEM on thalamocortical glutamatergic transmission are predominantly caused by activation of Sxc rather than inhibition of NMDAR. These demonstrations suggest that the combination between reduced NMDAR and activated Sxc contribute to the neuroprotective effects of MEM. Furthermore, activation of Sxc may compensate for the cognitive impairments that are induced by hyperactivation of thalamocortical glutamatergic transmission following activation of Sxc/II-mGluR in the MDTN and Sxc/II-mGluR/III-mGluR in the mPFC.

Effects of acute and sub-chronic administrations of guanfacine on catecholaminergic transmissions in the orbitofrontal cortex

The selective α2A adrenoceptor agonist guanfacine reduces hyperactivity and improves cognitive impairment in patients with attention-deficit/hyperactivity disorder (ADHD). The major mechanisms of guanfacine have been considered to involve activation of postsynaptic α2A adrenoceptor in frontal pyramidal neurons. However, the effects of chronic guanfacine administration on catecholaminergic transmissions associated with the orbitofrontal cortex (OFC) remain unclear. To explore the mechanisms of action of guanfacine on catecholaminergic transmission, the effects of its acute local or sub-chronic systemic administration on catecholamine release within pathways from locus coeruleus (LC) to OFC and reticular thalamic nucleus (RTN), from RTN to mediodorsal thalamic nucleus (MDTN), and from MDTN to OFC were determined using multi-probe microdialysis with ultra-high performance liquid chromatography. Acute OFC local administration of guanfacine did not affect catecholamine release in OFC. Acute LC local and sub-chronic systemic administrations of guanfacine reduced norepinephrine release in LC, OFC and RTN, and also reduced GABA release in MDTN, whereas AMPA-induced (perfusion with AMPA into NDTN) releases of l-glutamate, norepinephrine and dopamine in OFC were enhanced by sub-chronic systemic guanfacine administration. This study identified that catecholaminergic transmission is composed of three pathways: direct noradrenergic and co-releasing catecholaminergic LC-OFC pathways and intermediate LC-OFC (LC-RTN-MDTN-OFC) pathway. We demonstrated the dual actions of guanfacine on catecholaminergic transmission: attenuation of direct noradrenergic LC-OFC transmission at the resting stage and enhancement of direct co-releasing catecholaminergic LC-OFC transmission via GABAergic disinhibition in the intermediate LC-OFC pathway. These dual actions of guanfacine probably contribute to clinical actions of guanfacine against ADHD and its comorbid symptoms. This article is part of the Special Issue entitled 'Current status of the neurobiology of aggression and impulsivity'.

Chronic administration of quetiapine stimulates dorsal hippocampal proliferation and immature neurons of male rats, but does not reverse psychosocial stress-induced hyponeophagic behavior

Quetiapine, an atypical antipsychotic, has been used for the treatment of several neuropsychiatric disorders. However, the underlying mechanism of the broad therapeutic range of quetiapine remains unknown. We previously reported that several aversive conditions affect dorsal/ventral hippocampal neurogenesis differentially. This study was aimed to elucidate the positive effects of chronic treatment with quetiapine on regional differences in hippocampal proliferation and immature neurons and behavioral changes under psychosocial stress using the Resident-Intruder paradigm. Twenty-three male Sprague-Dawley rats were intraperitoneally administered a vehicle or quetiapine (10 mg/kg) once daily for 28 days. Two weeks after starting the injections, animals were exposed to intermittent social defeat (four times over two weeks). The behavioral effects of stress and quetiapine were evaluated by the Novelty-Suppressed Feeding (NSF) test. The stereological quantification of hippocampal neurogenesis was estimated using immunostaining with Ki-67 and doublecortin (DCX). Chronic quetiapine treatment stimulated the Ki-67- and DCX-positive cells in the dorsal hippocampus, but not in the ventral subregion. The stress-induced changes in neurogenesis and hyponeophagic behavior were not reversed by repeated administration of quetiapine. Future study with additional behavioral tests is needed to elucidate the functional significance of the quetiapine-induced increase in dorsal hippocampal neurogenesis.

Quetiapine Attenuates the Neuroinflammation and Executive Function Deficit in Streptozotocin-Induced Diabetic Mice

Diabetic patients are at increased risk for developing memory and cognitive deficit. Prior studies indicate that neuroinflammation might be one important underlying mechanism responsible for this deficit. Quetiapine (QTP) reportedly exerts a significant neuroprotective effect in animal and human studies. Here, we investigated whether QTP could prevent memory deterioration and cognitive impairment in a streptozotocin- (STZ-) induced diabetic mouse model. In this study, we found that STZ significantly compromised the behavioral performance of mice in a puzzle box test, but administering QTP effectively attenuated this behavioral deficit. Moreover, our results showed that QTP could significantly inhibit the activation of astrocytes and microglia in these diabetic mice and reduce the generation and release of two cytokines, tumor necrosis factor-α (TNF-α) and monocyte chemoattractant protein-1 (MCP-1). Meanwhile, QTP also prevented the protein loss of the synaptic protein synaptophysin (SYP) and myelin basic protein (MBP). Here, our results indicate that QTP could inhibit neuroinflammatory response from glial cells and block the injury of released cytokines to neurons and oligodendrocytes in diabetic mice (DM). These beneficial effects could protect diabetic mice from the memory and cognitive deficit. QTP may be a potential treatment compound to handle the memory and cognitive dysfunction in diabetic patients.

Cystine/Glutamate Antiporter and Aripiprazole Compensate NMDA Antagonist-Induced Dysfunction of Thalamocortical L-Glutamatergic Transmission

To explore pathophysiology of schizophrenia, this study analyzed the regulation mechanisms that are associated with cystine/glutamate antiporter (Sxc), group-II (II-mGluR), and group-III (III-mGluR) metabotropic glutamate-receptors in thalamo-cortical glutamatergic transmission of MK801-induced model using dual-probe microdialysis. L-glutamate release in medial pre-frontal cortex (mPFC) was increased by systemic- and local mediodorsal thalamic nucleus (MDTN) administrations of MK801, but was unaffected by local administration into mPFC. Perfusion into mPFC of activators of Sxc, II-mGluR, and III-mGluR, and into the MDTN of activators of Sxc, II-mGluR, and GABA_A receptor inhibited MK801-evoked L-glutamate release in mPFC. Perfusion of aripiprazole (APZ) into MDTN and mPFC also inhibited systemic MK801-evoked L-glutamate release in mPFC. Inhibition of II-mGluR in mPFC and MDTN blocked inhibitory effects of Sxc-activator and APZ on MK801-evoked L-glutamate release; however, their inhibitory effects were blocked by the inhibition of III-mGluR in mPFC but not in MDTN. These results indicate that reduced activation of the glutamate/NMDA receptor (NMDAR) in MDTN enhanced L-glutamate release in mPFC possibly through GABAergic disinhibition in MDTN. Furthermore, MDTN-mPFC glutamatergic transmission receives inhibitory regulation of Sxc/II-mGluR/III-mGluR functional complex in mPFC and Sxc/II-mGluR complex in MDTN. Established antipsychotic, APZ inhibits MK801-evoked L-glutamate release through the activation of Sxc/mGluRs functional complexes in both MDTN and mPFC.

5-HT1A parital agonism and 5-HT7 antagonism restore episodic memory in subchronic phencyclidine-treated mice: role of brain glutamate, dopamine, acetylcholine and GABA

RATIONALE

The effect of atypical antipsychotic drugs (AAPDs), e.g., lurasidone, to improve cognitive impairment associated with schizophrenia (CIAS), has been suggested to be due, in part, to enhancing release of dopamine (DA), acetylcholine (ACh), and glutamate (Glu) in cortex and hippocampus.

RESULTS

The present study found acute lurasidone reversed the cognitive deficit in novel object recognition (NOR) in subchronic (sc) phencyclidine (PCP)-treated mice, an animal model for CIAS. This effect of lurasidone was blocked by pretreatment with the 5-HT_1AR antagonist, WAY-100635, or the 5-HT₇R agonist, AS 19. Lurasidone significantly increased medial prefrontal cortex (mPFC) ACh, DA, and Glu efflux, all of which were blocked by WAY-100635, with similar effects in the dorsal striatum (dSTR), except for the absence of an effect on Glu increase. AS 19 inhibited Glu, but not DA efflux, in the dSTR. The selective 5-HT₇R antagonist, SB-26970, increased mPFC DA, 5-HT, Glu, and, importantly, also GABA efflux and striatal DA, NE, 5-HT, and Glu efflux, indicating tonic inhibition of the release of these neurotransmitters by 5-HT₇R stimulation. These results provide new evidence that GABA release in the mPFC is tonically inhibited by 5-HT₇R stimulation and suggest that a selective 5-HT₇R antagonist might be clinically useful to enhance cortical GABAergic release. All SB-269970 effects were blocked by AS 19 or WAY-100635, suggesting 5-HT_1AR agonism is necessary for the release of these neurotransmitters by SB-269970. Lurasidone increased ACh, DA, and NE but not Glu efflux in mPFC and dSTR DA and Glu efflux in 5-HT₇ KO mice.

CONCLUSION

We conclude that lurasidone-induced Glu efflux in mPFC requires 5-HT₇R antagonism while its effects on cortical ACh and DA efflux are mainly due to 5-HT_1AR stimulation.

Systematic review of catatonia treatment

OBJECTIVE

To investigate the evidence-based treatment of catatonia in adults. The secondary aim is to develop a treatment protocol.

MATERIALS AND METHODS

A systematic review of published treatment articles (case series, cohort or randomized controlled studies) which examined the effects of particular interventions for catatonia and/or catatonic symptoms in adult populations and used valid outcome measures was performed. The articles for this review were selected by searching the electronic databases of the Cochrane Library, MEDLINE, EMBASE and PSYCHINFO.

RESULTS

Thirty-one articles met the inclusion criteria. Lorazepam and electroconvulsive therapy (ECT) proved to be the most investigated treatment interventions. The response percentages in Western studies varied between 66% and 100% for studies with lorazepam, while in Asian and Indian studies, they were 0% and 100%. For ECT, the response percentages are 59%-100%. There does not seem to be evidence for the use of antipsychotics in catatonic patients without any underlying psychotic disorder.

CONCLUSION

Lorazepam and ECT are effective treatments for which clinical evidence is found in the literature. It is not possible to develop a treatment protocol because the evidence for catatonia management on the basis of the articles reviewed is limited. Stringent treatment studies on catatonia are warranted.

Evaluation of short interval cortical inhibition and intracortical facilitation from the dorsolateral prefrontal cortex in patients with schizophrenia

GABAergic and glutamatergic dysfunction in the dorsolateral prefrontal cortex (DLPFC) are thought to be the core pathophysiological mechanisms of schizophrenia. Recently, we have established a method to index these functions from the DLPFC using the paired transcranial magnetic stimulation (TMS) paradigms of short interval intracortical inhibition (SICI) and facilitation (ICF) combined with electroencephalography (EEG). In this study, we aimed to evaluate neurophysiological indicators related to GABA_A and glutamate receptor-mediated functions respectively from the DLPFC in patients with schizophrenia using these paradigms, compared to healthy controls. Given that these activities contribute to cognitive functions, the relationship between the TMS-evoked potential (TEP) modulations by SICI/ICF and cognitive/clinical measures were explored. Compared to controls, patients showed reduced inhibition in P60 (t₂₂ = −4.961, p < 0.0001) by SICI and reduced facilitation in P60 (t₂₂ = 5.174, p < 0.0001) and N100 (t₂₂ = 3.273, p = 0.003) by ICF. In patients, the modulation of P60 by SICI was correlated with the longest span of the Letter-Number Span Test (r = −0.775, p = 0.003), while the modulation of N100 by ICF was correlated with the total score of the Positive and Negative. Syndrome Scale (r = 0.817, p = 0.002). These findings may represent the pathophysiology, which may be associated with prefrontal GABA_A and glutamatergic dysfunctions, in the expression of symptoms of schizophrenia.

EEG-arousal regulation as predictor of treatment response in patients suffering from obsessive compulsive disorder

OBJECTIVES

Aim of this study was to analyze whether electroencephalogram (EEG)-based CNS-arousal markers differ for patients suffering from obsessive compulsive disorder (OCD) that either respond or do not respond to cognitive behavioral therapy (CBT), selective serotonin reuptake inhibitors (SSRIs) or their combination. Further the study aimed to identify specific response-predictors for the different therapy approaches.

METHODS

CNS-arousal from 51 unmedicated patients during fifteen-minute resting state was assessed using VIGALL (Vigilance Algorithm Leipzig). Clinical Global Impression (CGI) scores were used to assess response or non-response after three to six months following therapy (CBT, n=18; SSRI, n=11 or combination, n=22). Differences between Responders (R) and Non-Responders (NR) were identified using multivariate analysis of covariance (MANCOVA) models.

RESULTS

MANCOVA revealed that Responders spent significant less time at the highest CNS-arousal stage 0. Further, low amounts of the highest CNS-arousal stages were specifically predictive for a response to a combined treatment approach.

CONCLUSIONS

The fact that CNS-arousal markers allowed discrimination between Responders and Non-Responders and also between Responders of different treatment arms underlines a possible clinical value of EEG-based markers.

SIGNIFICANCE

These results encourage further research on EEG-arousal regulation for determining pathophysiological subgroups for treatment response.

RP5063, an atypical antipsychotic drug with a unique pharmacologic profile, improves declarative memory and psychosis in mouse models of schizophrenia

Various types of atypical antipsychotic drugs (AAPDs) modestly improve the cognitive impairment associated with schizophrenia (CIAS). RP5063 is an AAPD with a diverse and unique pharmacology, including partial agonism at dopamine (DA) D₂, D₃, D₄, serotonin (5-HT)_1A, and 5-HT_2A receptors (Rs), full agonism at α₄β₂ nicotinic acetylcholine (ACh)R (nAChR), and antagonism at 5-HT_2B, 5-HT₆, and 5-HT₇Rs. Most atypical APDs are 5-HT_2A inverse agonists. The efficacy of RP5063 in mouse models of psychosis and episodic memory were studied. RP5063 blocked acute phencyclidine (PCP)-as well as amphetamine-induced hyperactivity, indicating antipsychotic activity. Acute administration of RP5063 significantly reversed subchronic (sc)PCP-induced impairment in novel object recognition (NOR), a measure of episodic memory, but not reversal learning, a measure of executive function. Co-administration of a sub-effective dose (SED) of RP5063 with SEDs of a 5-HT₇R antagonist, a 5-HT_1BR antagonist, a 5-HT_2AR inverse agonist, or an α₄β₂ nAChR agonist, restored the ability of RP5063 to ameliorate the NOR deficit in scPCP mice. Pre-treatment with a 5-HT_1AR, a D₄R, antagonist, but not an α₄β₂ nAChR antagonist, blocked the ameliorating effect of RP5063. Further, co-administration of scRP5063 prior to each dose of PCP prevented the effect of PCP to produce a deficit in NOR for one week. RP5063, given to scPCP-treated mice for one week restored NOR for one week only. Acute administration of RP5063 significantly increased cortical DA efflux, which may be critical to some of its cognitive enhancing properties. These results indicate that RP5063, by itself, or as an adjunctive treatment has a multifaceted basis for improving some cognitive deficits associated with schizophrenia.

Effects of Antipsychotic Administration on Brain Glutamate in Schizophrenia: A Systematic Review of Longitudinal 1H-MRS Studies

Schizophrenia is associated with brain glutamate dysfunction, but it is currently unclear whether antipsychotic administration can reduce the extent of glutamatergic abnormality. We conducted a systematic review of proton magnetic resonance spectroscopy (¹H-MRS) studies examining the effects of antipsychotic treatment on brain glutamate levels in schizophrenia. The Medline database was searched to identify relevant articles published until December 2016. Inclusion required that studies examined longitudinal changes in brain glutamate metabolites in patients with schizophrenia before and after initiation of first antipsychotic treatment or a switch in antipsychotic treatment. The searches identified eight eligible articles, with baseline and follow-up measures in a total of 168 patients. The majority of articles reported a numerical reduction in brain glutamate metabolites with antipsychotic treatment, and the estimated overall mean reduction of 6.5% in Glx (the combined signal from glutamate and glutamine) across brain regions. Significant reductions in glutamate metabolites in at least one brain region were reported in four of the eight studies, and none of the studies reported a significant glutamatergic increase after antipsychotic administration. Relationships between the degree of change in glutamate and the degree of improvement in symptoms have been inconsistent but may provide limited evidence that antipsychotic response may be associated with lower glutamate levels before treatment and a greater extent of glutamatergic reduction during treatment. Further longitudinal, prospective studies of glutamate and antipsychotic response are required to confirm these findings.

Antipsychotic treatment modulates glutamate transport and NMDA receptor expression

Schizophrenia patients often suffer from treatment-resistant cognitive and negative symptoms, both of which are influenced by glutamate neurotransmission. Innovative therapeutic strategies such as agonists at metabotropic glutamate receptors or glycin reuptake inhibitors try to modulate the brain's glutamate network. Interactions of amino acids with monoamines have been described on several levels, and first- and second-generation antipsychotic agents (FGAs, SGAs) are known to exert modulatory effects on the glutamatergic system. This review summarizes the current knowledge on effects of FGAs and SGAs on glutamate transport and receptor expression derived from pharmacological studies. Such studies serve as a control for molecular findings in schizophrenia brain tissue and are clinically relevant. Moreover, they may validate animal models for psychosis, foster basic research on antipsychotic substances and finally lead to a better understanding of how monoaminergic and amino acid neurotransmissions are intertwined. In the light of these results, important differences dependent on antipsychotic substances, dosage and duration of treatment became obvious. While some post-mortem findings might be confounded with multifold drug effects, others are unlikely to be influenced by antipsychotic treatment and could represent important markers of schizophrenia pathophysiology. In similarity to the convergence of toxic and psychotomimetic effects of dopaminergic, serotonergic and anti-glutamatergic substances, the therapeutic mechanisms of SGAs might merge on a yet to be defined molecular level. In particular, serotonergic effects of SGAs, such as an agonism at 5HT1A receptors, represent important targets for further clinical research.

Astrocyte-dependent protective effect of quetiapine on GABAergic neuron is associated with the prevention of anxiety-like behaviors in aging mice after long-term treatment

Previous studies have demonstrated that quetiapine (QTP) may have neuroprotective properties; however, the underlying mechanisms have not been fully elucidated. In this study, we identified a novel mechanism by which QTP increased the synthesis of ATP in astrocytes and protected GABAergic neurons from aging-induced death. In 12-month-old mice, QTP significantly improved cell number of GABAegic neurons in the cortex and ameliorated anxiety-like behaviors compared to control group. Complimentary in vitro studies showed that QTP had no direct effect on the survival of aging GABAergic neurons in culture. Astrocyte-conditioned medium (ACM) pretreated with QTP (ACMQTP) for 24 h effectively protected GABAergic neurons against aging-induced spontaneous cell death. It was also found that QTP boosted the synthesis of ATP from cultured astrocytes after 24 h of treatment, which might be responsible for the protective effects on neurons. Consistent with the above findings, a Rhodamine 123 test showed that ACMQTP, not QTP itself, was able to prevent the decrease in mitochondrial membrane potential in the aging neurons. For the first time, our study has provided evidence that astrocytes may be the conduit through which QTP is able to exert its neuroprotective effects on GABAergic neurons. The neuroprotective properties of quetiapine (QTP) have not been fully understood. Here, we identify a novel mechanism by which QTP increases the synthesis of ATP in astrocytes and protects GABAergic neurons from aging-induced death in a primary cell culture model. In 12-month-old mice, QTP significantly improves cell number of GABAegic neurons and ameliorates anxiety-like behaviors. Our study indicates that astrocytes may be the conduit through which QTP exerts its neuroprotective effects on GABAergic neurons.

Role of concomitant inhibition of the norepinephrine transporter for the antipsychotic effect of quetiapine

Quetiapine alleviates both positive and negative symptoms as well as certain cognitive impairments in schizophrenia despite a low D2 receptor occupancy and may also be used as monotherapy in bipolar and major depressive disorder. The mechanisms underlying the broad clinical utility of quetiapine remain to be clarified, but may be related to the potent inhibition of the norepinephrine transporter (NET) by norquetiapine, the major metabolite of quetiapine in humans. Since norquetiapine is not formed in rodents we here investigated in rats whether NET-inhibition may, in principle, contribute to the clinical effectiveness of quetiapine and allow for its low D2 receptor occupancy, by combining quetiapine with the selective NET-inhibitor reboxetine. Antipsychotic-like activity was assessed using the conditioned avoidance response (CAR) test, dopamine output in the medial prefrontal cortex (mPFC) and the nucleus accumbens was measured using in vivo microdialysis, and NMDA receptor-mediated transmission was measured using intracellular electrophysiological recordings in pyramidal cells of the mPFC in vitro. Adjunct reboxetine potentiated the suppression of CAR by quetiapine. Moreover, concomitant administration of quetiapine and reboxetine resulted in a synergistic increase in cortical, but not accumbal, dopamine output. The combination of low, clinically relevant concentrations of quetiapine (60 nM) and reboxetine (20 nM) markedly facilitated cortical NMDA receptor-mediated transmission in contrast to either drug alone, an effect that could be inhibited by the D₁ receptor antagonist SCH23390. We conclude that concomitant NET-inhibition by norquetiapine may contribute to the overall antipsychotic effectiveness of quetiapine in spite of its relatively low level of D₂ occupancy.

Aripiprazole differentially regulates the expression of Gad67 and γ-aminobutyric acid transporters in rat brain

The molecular etiology of schizophrenia comprises abnormal neurotransmission of the amino acid GABA (γ-aminobutyric acid). Neuropathological studies convincingly revealed reduced expression of glutamic acid decarboxylase (Gad67) in GABAergic interneurons. Several antipsychotics influence the expression of GABAergic genes, but aripiprazole (APZ), a partial dopaminergic and serotonergic receptor agonist, has not been involved into these studies so far. We treated Sprague-Dawley rats for 4 weeks or 4 months with APZ suspended in drinking water and doses of 10 and 40 mg per kg body weight. Gene expression of Gad67, the vesicular GABA transporter Slc32a1 (solute carrier family, Vgat), the transmembrane transporters Slc6a1 (Gat1) and Slc6a11 (Gat3) was assessed by semiquantitative radioactive in situ hybridization. APZ treatment resulted in time- and dose-dependent effects with qualitative differences between brain regions. In the 10-mg group, Slc6a1 was strongly induced after 4 weeks in the hippocampus, amygdala, and cerebral cortex, followed by an induction of Gad67 in the same regions after 4 months, while frontocortical regions as well as basal ganglia showed dose-dependent reductions of Gad67 expression after 4 months. In several frontocortical and subcortical regions, we observed a decrease of Slc32a1 and an increase of Slc6a11 expression. In conclusion, APZ modulates gene expression of GABAergic marker genes involved into pathogenetic theories of schizophrenia. APZ only partially mirrors the effects of other antipsychotics with some important differences regarding brain regions. The findings might be explained by regulatory connections between serotonergic, GABAergic, and dopaminergic neurotransmission and should be validated in behavioral animal models of psychotic disorders.

Ethanol-induced alterations of amino acids measured by in vivo microdialysis in rats: a meta-analysis

PURPOSE

In recent years in vivo microdialysis has become an important method in research studies investigating the alterations of neurotransmitters in the extracellular fluid of the brain. Based on the major involvement of glutamate and γ-aminobutyric acid (GABA) in mediating a variety of alcohol effects in the mammalian brain, numerous microdialysis studies have focused on the dynamical behavior of these systems in response to alcohol.

METHODS

Here we performed multiple meta-analyses on published datasets from the rat brain: (i) we studied basal extracellular concentrations of glutamate and GABA in brain regions that belong to a neurocircuitry involved in neuropsychiatric diseases, especially in alcoholism (Noori et al., Addict Biol 17:827-864, 2012); (ii) we examined the effect of acute ethanol administration on glutamate and GABA levels within this network and (iii) we studied alcohol withdrawal-induced alterations in glutamate and GABA levels within this neurocircuitry.

RESULTS

For extraction of basal concentrations of these neurotransmitters, datasets of 6932 rats were analyzed and the absolute basal glutamate and GABA levels were estimated for 18 different brain sites. In response to different doses of acute ethanol administration, datasets of 529 rats were analyzed and a non-linear dose response (glutamate and GABA release) relationship was observed in several brain sites. Specifically, glutamate in the nucleus accumbens shows a decreasing logarithmic dose response curve. Finally, regression analysis of 11 published reports employing brain microdialysis experiments in 104 alcohol-dependent rats reveals very consistent augmented extracellular glutamate and GABA levels in various brain sites that correlate with the intensity of the withdrawal response were identified.

CONCLUSIONS

In summary, our results provide standardized basal values for future experimental and in silico studies on neurotransmitter release in the rat brain and may be helpful to understand the effect of ethanol on neurotransmitter release. Furthermore, this study illustrates the benefit of meta-analyses using the generalization of a wide range of preclinical data.

Is quetiapine suitable for treatment of acute schizophrenia with catatonic stupor? A case series of 39 patients

PURPOSE

We aimed to determine which antipsychotic is most effective for the treatment of acute schizophrenia with catatonic stupor.

PATIENTS AND METHODS

Data were obtained from the medical records of 450 patients with the diagnosis of schizophrenia, who had received acute psychiatric inpatient treatment between January 2008 and December 2010 at our hospital. Among them, 39 patients (8.7%) met the definition of catatonic stupor during hospitalization. The diagnoses of schizophrenia in all 39 patients were reconfirmed during the maintenance phase. We retrospectively reviewed the medical records of these 39 patients to investigate which antipsychotics were chosen for treatment during the period from admission to recovery from catatonia, at the time of discharge, and 12 and 30 months after discharge.

RESULTS

As compared to other antipsychotics, it was found out that use of quetiapine had better outcomes and hence was used more often. A total of 61.5% of patients were on quetiapine at the time of recovery from catatonia and 51.3% of patients were on quetiapine at the time of discharge as compared to only 17.9% of patients on quetiapine on admission. However, at 12 and 30 months after discharge, the rates had decreased to 38.4% and 25.6%. Similarly, of 29 patients who were not administered electroconvulsive therapy, quetiapine was used at significantly higher rates at the time of recovery from catatonia (48.3%) than at the time of admission (17.2%). All 39 patients had received an antipsychotic as the first-line treatment and some antipsychotics might have contributed to the development of catatonia.

CONCLUSION

This study suggests that quetiapine is a promising agent for the treatment of schizophrenia with catatonic stupor during the acute phase.

The vigilance regulation model of affective disorders and ADHD

According to the recently proposed vigilance model of affective disorders (vigilance in the sense of "brain arousal"), manic behaviour is partly interpreted as an autoregulatory attempt to stabilise vigilance by creating a stimulating environment, and the sensation avoidance and withdrawal in Major Depressive Disorder (MDD) is seen as an autoregulatory reaction to tonically increased vigilance. Indeed, using a newly developed EEG-based algorithm, hyperstable vigilance was found in MDD, and the contrary, with rapid drops to sleep stages, in mania. Furthermore, destabilising vigilance (e.g. by sleep deprivation) triggers (hypo)mania and improves depression, whereas stabilising vigilance, e.g. by prolonged sleep, improves mania. ADHD and mania have common symptoms, and the unstable vigilance might be a common pathophysiology. There is even evidence that psychostimulants might ameliorate both ADHD and mania. Hyperactivity of the noradrenergic system could explain both the high vigilance level in MDD and, as recently argued, anhedonia and behavioural inhibition. Interestingly, antidepressants and electroconvulsions decrease the firing rate of neurons in the noradrenergic locus coeruleus, whereas many antimanic drugs have opposite effects.

Clozapine, but not haloperidol, enhances glial D-serine and L-glutamate release in rat frontal cortex and primary cultured astrocytes

BACKGROUND AND PURPOSE

Deficient transmission at the glutamate NMDA receptor is considered a key component of the pathophysiology of schizophrenia. However, the effects of antipsychotic drugs on the release of the endogenous NMDA receptor partial agonist, D-serine, remain to be clarified.

EXPERIMENTAL APPROACH

We determined the interaction between antipsychotic drugs (clozapine and haloperidol) and transmission-modulating toxins (tetanus toxin, fluorocitrate, tetrodotoxin) on the release of L-glutamate and D-serine in the medial prefrontal cortex (mPFC) of freely moving rats, using microdialysis, and primary cultures of astrocytes using extreme high-pressure liquid chromatography.

KEY RESULTS

Release of L-glutamate and D-serine in the mPFC and in cultured astrocytes was inhibited by tetanus toxin (a synaptobrevin inhibitor) and fluorocitrate (a glial toxin), whereas tetrodotoxin (a voltage-sensitive Na(+) blocker) inhibited depolarization-induced L-glutamate release in the mPFC without affecting that of D-serine. Clozapine (1 and 5 mg·kg(-1)), but not haloperidol (0.5 and 1 mg·kg(-1)), dose-dependently increased L-glutamate and D-serine release from both astrocytes and mPFC. Clozapine-induced release of L-glutamate and D-serine was also reduced by tetanus toxin and fluorocitrate. Tetrodotoxin reduced clozapine-induced mPFC L-glutamate release but not that of D-serine. Clozapine-induced L-glutamate release preceded clozapine-induced D-serine release. MK-801 (a NMDA receptor antagonist) inhibited the delayed clozapine-induced L-glutamate release without affecting that of D-serine.

CONCLUSIONS AND IMPLICATIONS

Clozapine predominantly activated glial exocytosis of D-serine, and this clozapine-induced D-serine release subsequently enhances neuronal L-glutamate release via NMDA receptor activation. The enhanced D-serine associated glial transmission seems a novel mechanism of action of clozapine but not haloperidol.

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'.

Drug therapy in patients with Parkinson's disease

Parkinson`s disease (PD) is a progressive, disabling neurodegenerative disorder with onset of motor and non-motor features. Both reduce quality of life of PD patients and cause caregiver burden. This review aims to provide a survey of possible therapeutic options for treatment of motor and non motor symptoms of PD and to discuss their relation to each other. MAO-B-Inhibitors, NMDA antagonists, dopamine agonists and levodopa with its various application modes mainly improve the dopamine associated motor symptoms in PD. This armentarium of PD drugs only partially influences the onset and occurrence of non motor symptoms. These PD features predominantly result from non dopaminergic neurodegeneration. Autonomic features, such as seborrhea, hyperhidrosis, orthostatic syndrome, salivation, bladder dysfunction, gastrointestinal disturbances, and neuropsychiatric symptoms, such as depression, sleep disorders, psychosis, cognitive dysfunction with impaired execution and impulse control may appear. Drug therapy of these non motor symptoms complicates long-term PD drug therapy due to possible occurrence of drug interactions, - side effects, and altered pharmacokinetic behaviour of applied compounds. Dopamine substituting compounds themselves may contribute to onset of these non motor symptoms. This complicates the differentiation from the disease process itself and influences therapeutic options, which are often limited because of additional morbidity with necessary concomitant drug therapy.

Effect of lamotrigine and carbamazepine on corticotropin-releasing factor-associated serotonergic transmission in rat dorsal raphe nucleus

Corticotropin-releasing factor (CRF) and serotonin are important transmitters of the pathophysiology of mood disorder. To clarify the mechanisms of action of lamotrigine (LTG) and carbamazepine (CBZ), we determined their effects on serotonin release associated with CRF in rat dorsal raphe nucleus (DRN) and median prefrontal cortex (mPFC) using dual-probe microdialysis. Neither perfusion with CRF1 nor CRF2 antagonists into DRN-affected serotonin release in DRN and mPFC. Perfusion of 10 μM CRF into DRN increased serotonin release in both regions, whereas 0.1 μM CRF decreased and had no effect on serotonin release in DRN and mPFC, respectively. Pre-perfusion with CRF1 antagonist into DRN inhibited 0.1 μM CRF-induced serotonin reduction, whereas pre-perfusion with CRF2 antagonist in DRN inhibited 10 μM CRF-induced serotonin elevation, without affecting 0.1 μM CRF-induced serotonin reduction. LTG perfusion concentration dependently decreased serotonin releases in DRN and mPFC. Therapeutic and supratherapeutic concentrations of CBZ increased and decreased serotonin releases in both regions, respectively. Pre-perfusion with sub-therapeutic concentration LTG inhibited CRF1-induced serotonin reduction without affecting CRF2-induced serotonin release, whereas pre-perfusion with therapeutic concentration of LTG inhibited both CRF1- and CRF2-actions. In contrast, both therapeutic and supratherapeutic concentrations of CBZ inhibited CRF2-induced serotonin release without affecting CRF1-induced serotonin reduction. Neither LTG nor CBZ affected the CRF-induced cAMP production in cells over-expressing CRF1 and CRF2 receptors. This study demonstrated that inhibition of CRF2-receptor-mediated serotonergic transmission is a mechanism shared by LTG and CBZ, two clinically related compounds, whereas LTG but not CBZ inhibits CRF1-receptor-mediated serotonergic transmission. Therefore, these mechanisms may contribute to the clinical actions of these agents.

Novel δ1-receptor agonist KNT-127 increases the release of dopamine and L-glutamate in the striatum, nucleus accumbens and median pre-frontal cortex

The effects of systemic δ1-agonist on neurotransmission remains obscure, since no selective δ1-agonist exists that can penetrate the blood-brain barrier. Recently, we succeeded in synthesizing a putative δ1-receptor agonist, KNT-127, which has been demonstrated the effectiveness of systemic administration against anxiety and depressive-like behavior. To clarify the functional selectivity of KNT-127 and neurotransmission regulating system of δ1-receptor, the present study investigated the interaction between KNT-127 and δ-receptor antagonists on the release of dopamine, L-glutamate and GABA in nucleus accumbens (NAc), striatum and median pre-frontal cortex (mPFC) using multi-probe microdialysis. Intraperitoneal administration of KNT-127 increased the release of dopamine and L-glutamate in three regions, but decreased and increased GABA releases in respective NAc and mPFC without affecting that in striatum. The effects of KNT-127 in the three regions were abrogated by δ1-antagonist but not by δ2-antagonist. MK801 inhibited KNT-127-induced dopamine release in striatum and NAc, but enhanced that in mPFC, inhibited KNT-127-induced mPFC GABA release without affecting KNT-127-induced GABA reduction in NAc. Muscimol enhanced KNT-127-induced dopamine release in mPFC. Sulpiride inhibited KNT-127-induced reduction of GABA release in NAc. The results indicated that KNT-127 is a selective δ1-agonist, and suggested that δ1-receptor directly activates the release of dopamine and L-glutamate in the striatum, NAc and mPFC, but not that of GABA in the three regions. δ1-receptor indirectly inhibited GABA release in NAc via activated dopaminergic transmission, while δ1-receptor indirectly enhanced GABA release in mPFC via activated glutamatergic transmission.