Nitrobenzylthioinosine (NBMPR) binding and nucleoside transporter ENT1 mRNA expression after prolonged wakefulness and recovery sleep in the cortex and basal forebrain of rat

We have previously shown that extracellular adenosine levels increase locally in the basal forebrain (BF) during prolonged wakefulness, yet the cellular mechanisms of this local accumulation have remained unknown. The extracellular adenosine levels are strictly regulated by adenosine metabolism and its transport through cell membrane by the nucleoside transporters. As we previously showed that the key adenosine metabolizing enzymes were not affected by prolonged wakefulness, we now focussed on potential changes in the nucleoside transporters. In the present study, we measured the binding of nitrobenzylthioinosine (NBMPR), an ENT1 transporter inhibitor, and the ENT1 transporter mRNA after prolonged wakefulness and recovery sleep. Rats were sleep-deprived for 3 or 6 h using gentle handling. After 6 h one group was allowed to sleep for 2 h. NBMPR binding was determined from BF and cortex by incubating tissue extracts with [3H] NBMPR. The in situ hybridization was carried out on 20 microm cryosections using [35S]dATP-labelled oligonucleotide probe for ENT1 mRNA. The NBMPR binding was significantly decreased in the BF, but not in the cortex, after 6 h sleep deprivation when compared with the time-matched controls, suggesting a decline in adenosine transport. The expression of ENT1 mRNA did not change during prolonged wakefulness or recovery sleep in either cortex or the BF, although circadian variations were measured in both areas. We conclude that the regional decrease in adenosine transport could contribute to the gradual accumulation of extracellular adenosine in the basal forebrain during prolonged wakefulness.

Semantic and syntactic processes during sentence comprehension in patients with schizophrenia: evidence from event-related potentials

Language and thought disorders are core symptoms in schizophrenia. We therefore studied language comprehension processes in patients with schizophrenia and control subjects during a sentence processing paradigm using event-related potentials (ERPs). In the ERP, assignment of syntactic structure to a string of words is reflected by an early left anterior negativity (ELAN) at about 80 ms after stimulus onset. Integration of syntactic and semantic information into a coherent representation is indexed by a positive potential at 600 ms (P600). Amplitudes of the ELAN and the P600 components are higher for grammatically incorrect sentences. Semantic processes are associated with a negative deflection peaking at 400 ms (N400). N400 amplitude is higher in semantically incongruent sentences. Nineteen patients with DSM IV schizophrenia and 19 healthy controls were presented with correct, semantically incorrect (semantic mismatch) and grammatically incorrect sentences (syntactic mismatch). Syntactic mismatch elicited an ELAN component in both subject groups. However, only controls but not patients with schizophrenia exhibited a P600 syntactic mismatch effect. Semantic mismatch was associated with a larger N400 potential which did not differ between groups. These results suggest that patients with schizophrenia are not impaired in syntactic structure assignment as reflected by the ELAN, but show deficits in semantic-syntactic integration processes underlying the P600.

Update on chronic hepatitis C in HIV/HCV-coinfected patients: viral interactions and therapy

With highly active antiretroviral therapy (HAART), HIV-infected patients can now live longer and healthier lives, and other comorbid diseases, such as chronic hepatitis C, have emerged as a significant health concern. Coinfection with the hepatitis C virus (HCV) may limit life expectancy because it can lead to serious liver disease including decompensated liver cirrhosis and hepatocellular carcinoma. HCV-induced fibrosis progresses faster in HIV/HCV-coinfected persons, although HAART may be able to decrease this disease acceleration. Combination therapy for HCV with interferon and ribavirin can achieve a sustained viral response, although at a lower rate than in HCV-monoinfected patients. Combination treatment with pegylated interferon and ribavirin will probably emerge as the next HCV therapy of choice for HIV/HCV-coinfected patients. HCV combination therapy is generally safe, but serious adverse reactions, like lactic acidosis, may occur. Cytopenia may present a problem leading to dose reductions, but the role of growth factors is under study. All HIV/HCV-coinfected patients should be evaluated for therapy against the hepatitis C virus. A sustained viral load will probably lead to regression of liver disease, and even interferon-based treatment without viral clearance may slow down progression of liver disease. HIV/HCV-coinfected patients who have progressed to end-stage liver disease have few therapeutic options other than palliative care, since liver transplants are generally unavailable. The mortality post-transplant may be higher than in HCV-monoinfected patients. We are entering an era where safe and effective HCV therapy is being defined for HIV/HCV-coinfected patients, and all eligible patients should be offered treatment.

Major depressive disorder with anger: a bipolar spectrum disorder?

BACKGROUND

Depression with anger may be more common in bipolar disorders. The aim of the study was to assess whether major depressive disorder (MDD) with anger could be included in the bipolar spectrum, by comparing it to MDD without anger and to bipolar II disorder.

METHODS

Consecutive outpatients (281 bipolar II disorder and 202 MDD) presenting for major depressive episode (MDE) treatment were interviewed with the DSM-IV structured clinical interview. Clinical variables used to support the inclusion of MDD with anger in the bipolar spectrum were age of onset, many MDE recurrences, atypical features of depression, depressive mixed state (an MDE plus some concurrent hypomanic symptoms), and bipolar family history.

RESULTS

Frequency of MDE with anger was 50.5% [61.2% in bipolar II, and 35.6% in MDD (z = 5.5, p = 0.0000, 95% CI 16.8-43.3%)]. Logistic regression of MDE with anger (dependent variable) versus bipolar variables showed that MDE with anger was significantly associated with all bipolar variables, apart from recurrences. MDD with anger, compared with MDD without anger, had significantly lower age of onset, more marked depressive mixed state, a bipolar family history with more cases, but comparable atypical features and Global Assessment of Functioning scores. MDD with anger, compared with bipolar II disorder, had significantly higher age of onset, less atypical features, and a bipolar family history with less cases.

CONCLUSIONS

MDE with anger was common in outpatients (more in bipolar II disorder). MDD with anger may be midway between MDD without anger and bipolar II disorder, and might be included into the bipolar spectrum. However, MDD with anger does not appear to be associated with the often reported negative response to monotherapy with antidepressants.

Molecular Abnormalities of the Glutamate Synapse in the Thalamus in Schizophrenia

Schizophrenia has been associated with dysfunction of glutamatergic neurotransmission. Synaptic glutamate activates pre- and postsynaptic ionotropic NMDA, AMPA, and kainate and metabotropic receptors, is removed from the synapse via five cell surface-expressed transporters, and is packaged for release by three vesicular transporters. In addition, there is a family of intracellular molecules enriched in the postsynaptic density (PSD) that target glutamate receptors to the synaptic membrane, modulate receptor activity, and coordinate glutamate receptor-related signal transduction. Each family of PSD proteins is selective for a given glutamate receptor subtype, the most well characterized being the NMDA receptor binding proteins PSD93, PSD95, NF-L, and SAP102. Besides binding glutamate receptors, many of these proteins also interact with cell surface proteins like cell adhesion molecules, ion channels, cytoskeletal elements, and signal transduction molecules. Given the complexity of the glutamate neurotransmitter system, there are many locations where disruption of normal signaling could occur and give rise to abnormal glutamatergic neurotransmission in schizophrenia. Using multiple cohorts of postmortem tissue, we have examined these synaptic molecules in schizophrenic thalamus. The expression of NR1 and NR2C subunit transcripts is decreased in the thalamus in schizophrenia. Interestingly, three intracellular PSD molecules that link the NMDA receptor to signal transduction pathways are also abnormally expressed. Additionally, several of the cell surface and vesicular transporters are abnormal in the schizophrenic thalamus. While occasional findings of abnormal receptor expression are made, the most dramatic and consistent alterations that we have found in the thalamus in schizophrenia involve the family of intracellular signaling/scaffolding molecules. We propose that schizophrenia has a glutamatergic component that involves alterations in the intracellular machinery that is coupled to glutamate receptors, in addition to abnormalities of the receptors themselves. Our data suggest that schizophrenia is associated with abnormal glutamate receptor-related intracellular signaling in the thalamus, and point to novel targets for innovative drug discovery.

Serotonin reduces the hyperpolarization-activated current (Ih) in ventral tegmental area dopamine neurons: involvement of 5-HT2 receptors and protein kinase C

Dopaminergic neurons of the ventral tegmental area (VTA) have been implicated in the rewarding properties of drugs of abuse and in the etiology of schizophrenia; serotonin modulation of these neurons may play a role in these phenomena. Whole cell patch-in-the-slice recording in rat brain slices was used to investigate modulation of the hyperpolarization-activated cationic current Ih by serotonin in these neurons. Serotonin (50-500 microM) reduced the amplitude of Ih in a concentration-dependent manner; this effect was reversible after prolonged washout of serotonin. This effect was mimicked by the 5-HT2 agonist alpha-methylserotonin (25 microM) and reversed by the 5-HT2 antagonist ketanserin (25 microM). Serotonin reduced the maximal Ih current and conductance (measured at -130 mV) and caused a negative shift in the voltage dependence of Ih activation. The serotonin-induced reduction in Ih amplitude was antagonized by intracellular administration of the nonspecific protein kinase inhibitor H-7 (75 microM) and the selective protein kinase C inhibitor chelerythrine (25 microM). The protein kinase C activator phorbol 12, 13 diacetate (PDA, 2 microM) reduced Ih amplitude; when PDA and serotonin were applied together, the effect on Ih was less than additive. These data support the conclusion that serotonin reduces Ih in dopaminergic VTA neurons by acting at serotonin 5-HT2 receptors, which activate protein kinase C. This reduction of Ih may be physiologically important, as the selective inhibitor of Ih, ZD7288, significantly increased dopamine inhibition of firing rate of dopaminergic VTA neurons, an effect that we previously demonstrated with serotonin.

Treatment of anxiety, tension and restlessness states with Kava special extract WS 1490 in general practice: a randomized placebo-controlled double-blind multicenter trial

The efficacy and tolerability of 150 mg/d Kava special extract WS 1490 were investigated in a randomized, placebo-controlled, double-blind multicenter study in patients suffering from neurotic anxiety (DSM-III-R diagnoses 300.02, 300.22, 300.23, 300.29, or 309.24). 141 adult, male and female out-patients received 3 x 1 capsule of 50 mg/d WS 1490 or placebo for four weeks, followed by two weeks of observation without study-specific treatment. During randomized treatment the total score of the Anxiety Status Inventory (ASI) observer rating scale showed more pronounced decreases in the WS 1490 group than in the placebo group. Although a treatment group comparison of the post-treatment ASI scores was not significant (p > 0.05), an exploratory analysis of variance across the differences between treatment end and baseline, with center as a second factor, showed superiority of the herbal extract over placebo (p < 0.01, two-sided). 73% of the patients treated with WS 1490 exhibited ASI score decreases > 5 points versus baseline, compared to 56% for placebo. Significant advantages for WS 1490 were also evident in a structured well-being self-rating scale (Bf-S) and the Clinical Global Impressions (CGI), while the Erlangen Anxiety, Tension and Aggression Scale (EAAS) and the Brief Test of Personality Structure (KEPS) showed only minor treatment group differences. Although the results show consistent advantages for WS 1490 over placebo in several psychiatric scales and indicate significant improvements in the patients' general well-being, the differences versus placebo were not as large as in previous trials which employed 300 mg/d of the same extract. WS 1490 was well tolerated, with no influence on liver function tests and only one trivial adverse event (tiredness) attributable to the study drug.

Depression with racing thoughts

The aim of this study was to explore the clinical and family history correlates of depression with racing thoughts, an understudied phenomenon. Consecutive outpatients with a major depressive episode (MDE, N=336; unipolar subtype, n=130; bipolar-II subtype, n=206) were interviewed with the Structured Clinical Interview for DSM-IV Axis I Disorders-Clinician Version. Depression with racing thoughts was present in 213 patients (63.3%), a subgroup characterized by significantly more patients with bipolar-II disorder, lower age and lower age of onset, more atypical features, psychomotor agitation, diminished ability to think, suicidal ideation, guilt, leaden paralysis, MDE symptoms, and bipolar-II disorder family history than found in the subgroup without racing thoughts. Logistic regression controlled the diagnosis of bipolar-II disorder (which was associated with most of these variables). Comparisons in the separate bipolar-II and unipolar samples of depression with racing thoughts vs. the variables found significantly different in the total group found that associations with depression with racing thoughts were partly related to bipolar-II and partly related to unipolar diagnoses. Limitations of the study include reliance upon a single interviewer, non-blind cross-sectional assessment and bipolar-II diagnosis based on history. Depression with racing thoughts was very common in depressed outpatients, and was associated with suicidal ideation. Possible differential effects of antidepressants vs. mood stabilizers and antipsychotics are discussed.

Early embryonic death of glutamate carboxypeptidase II (NAALADase) homozygous mutants

Glutamate carboxypeptidase II (EC 3.4.17.21) catalyzes the hydrolysis (Km = 0.2 microM) of the neuropeptide N-acetylaspartylglutamate to yield N-acetylaspartate and glutamate and also serves as a high-affinity folate hydrolase in the gut, cleaving the polyglutamate chain to permit the absorption of folate. N-acetylaspartylglutamate is an agonist at the mGluR3 metabotropic receptor and a source of extracellular glutamate through hydrolysis by glutamate carboxypeptidase II. Given the important role of glutamate in brain development and function, we were interested in the effects of a null mutation of glutamate carboxypeptidase II that would potentiate the effects of N-acetylaspartylglutamate. The PGK-Neomycin cassette was inserted to delete exons 9 and 10, which we previously demonstrated encode for the zinc ligand domain essential for enzyme activity. Successful germline transmission was obtained from chimeras derived from embryonic stem cells with the targeted mutation of glutamate carboxypeptidase II. Homozygous null mutants did not survive beyond embryonic day 8. Folate supplementation of the heterozygous mothers did not rescue the homozygous embryos. Mice heterozygous for the null mutation appeared grossly normal and expressed both mutated and wild-type mRNA but the activity of glutamate carboxypeptidase II is comparable to the wild-type mice. The results indicate that the expression of glutamate carboxypeptidase II is upregulated when one allele is inactivated and that its activity is essential for early embryogenesis.

Unipolar depression with bipolar family history: links with the bipolar spectrum

The aim of the present paper was to find if unipolar major depressive disorder (MDD) with bipolar family history could be included in the bipolar spectrum, by comparing it to unipolar MDD without bipolar family history, and to bipolar II disorder, on typical bipolar variables. A sample of 280 consecutive bipolar II outpatients, and a sample of 135 consecutive unipolar MDD outpatients, presenting for major depressive episode (MDE) treatment, were interviewed with the Structured Clinical Interview for Diagnostic and Statistical Manual of Mental Disorders (4th edn). Hypomanic symptoms during the MDE were systematically assessed. Clinical variables used to validate the inclusion of unipolar MDD with bipolar family history in the bipolar spectrum were young age of onset, many MDE recurrences, atypical features, and depressive mixed state (DMX; an MDE plus >2 concurrent hypomanic symptoms), following many previous studies reporting that these variables were typical features of bipolar disorders. Means were compared by t-test and frequencies by chi2 test (stata 7). Two-tailed P < 0.05 was chosen. Unipolar MDD with bipolar family history was present in 20% of MDD patients. Comparisons among unipolar MDD with bipolar family history (UP+BPFH), unipolar MDD without bipolar family history (UP-BPFH), and bipolar II (BPII), found that UP+BPFH versus UP-BPFH had a significantly lower age, lower age of onset, fewer recurrences, and more DMX; that UP+BPFH versus BPII had no significant differences (apart from recurrences); and that UP-BPFH versus BPII had significantly different age, age of onset, recurrences, atypical features, and DMX. Findings suggest that UP+BPFH shows many bipolar signs, and that it could therefore be included in the bipolar spectrum. Unipolar MDD with bipolar family history had a clinically significant 20.0% frequency in the unipolar MDD sample, supporting the clinical usefulness of this depression subtype. The subtyping of MDD based on bipolar family history could have treatment implications.

An overview of recent findings of the Stanley Foundation Bipolar Network (Part I)

AIM AND METHODS

Selected recent findings of the Stanley Foundation Bipolar Network are briefly reviewed and their clinical implications discussed.

RESULTS

Daily prospective ratings on the NIMH-LCM indicate a high degree of residual depressive morbidity (three times that of hypomania or mania) despite active psychopharmacological treatment with a variety of modalities including mood stabilizers, antidepressants, and benzodiazepines, as well as antipsychotics as necessary. The rates of switching into brief to full hypomania or mania during the use of antidepressants is described, and new data suggesting the potential utility of continuing antidepressants in the small group of patients showing an initial acute and persistent response is noted. Bipolar patients with a history of major environmental adversities in childhood have a more severe course of illness and an increased incidence of suicide attempts compared with those without. Preliminary open data suggest useful antidepressant effects of the atypical antipsychotic quetiapine, while a double-blind randomized controlled study failed to show efficacy of omega-3 fatty acids (6 g of eicosapentaenoic acid compared with placebo for 4 months) in the treatment of either acute depression or rapid cycling. The high prevalence of overweight and increased incidence of antithyroid antibodies in patients with bipolar illness is highlighted.

CONCLUSIONS

Together, these findings suggest a very high degree of comorbidity and treatment resistance in outpatients with bipolar illness treated in academic settings and the need to develop not only new treatment approaches, but also much earlier illness recognition, diagnosis, and intervention in an attempt to reverse or prevent this illness burden.

Thrombocytopenia during valproic acid treatment in young patients with new-onset bipolar disorder

BACKGROUND

To evaluate whether valproic acid (VPA) can cause thrombocytopenia and impaired platelet function in young patients with new-onset bipolar disorder.

METHODS

The authors studied 25 new-onset young bipolar patients. Platelet count, platelet aggregation, platelet release, and bleeding time were evaluated before beginning VPA treatment and at least after 10 months of treatment. The control group consisted of 20 sex-matched and age-matched subjects. Patients were started on VPA at a dose of 250 to 750 mg/d, given in divided doses. Mean dosage of VPA was 1137.5 +/- 241.1 mg/d. Mean VPA total plasma concentration was 61.1 +/- 20 g/mL.

RESULTS

At baseline, no significant differences were observed for platelet count and function between the bipolar group and the control subjects. After 10 months, at the second evaluation, the platelet count was significantly lower in the bipolar patients than in the control subjects: 192.7 +/- 21.4/microL versus 289.8 +/- 23.9/microL; P < 0.0001. An important observation was that platelet counts were negatively correlated with VPA dose (r = -0.47; P = 0.05) and its plasma concentration (r = -0.50; P = 0.05). In the present study, the authors observed impairment in platelet release of ATP and aggregation that correlated with both VPA dosage and plasma levels. Bleeding times were also significantly longer in patients taking VPA compared with control subjects (P < 0.0001).

CONCLUSION

Thrombocytopenia can appear after a few months of therapy and with plasma VPA levels within the therapeutic range.

Potential mechanisms of action of lamotrigine in the treatment of bipolar disorders

Based on the mood-stabilizing properties of carbamazepine and valproate, new anticonvulsants have been explored for use in bipolar disorders. One such agent, lamotrigine, has a novel clinical profile in that it may "stabilize mood from below," as it appears to maximally impact depressive symptoms in bipolar disorders. In this paper, we review the mechanisms of action of lamotrigine in an effort to understand the basis of its distinctive clinical use in the management of bipolar disorders as well as its diverse antiseizure effects. We consider lamotrigine mechanisms, emphasizing commonalities and dissociations among actions of lamotrigine, older mood stabilizers, and other anticonvulsants. Although ion channel effects, especially sodium channel blockade, may importantly contribute to antiseizure effects, such actions may be less central to lamotrigine thymoleptic effects. Antiglutamatergic and neuroprotective actions are important candidate mechanisms for lamotrigine psychotropic effects. Lamotrigine has a variable profile in kindling and contingent tolerance experiments and does not appear to have robust gamma-aminobutyric acid or monoaminergic actions. Lamotrigine intracellular signaling effects warrant investigation. Although lamotrigine mechanisms overlap those of other mood-stabilizing anticonvulsants, important dissociations suggest candidate mechanisms, which could contribute to lamotrigine's distinctive psychotropic profile.

Common pathogenic mechanisms between depression and epilepsy: an experimental perspective

Affective disorders and the epilepsies appear to share partially similar pathogenic mechanisms. Predisposition to both disorders is determined genetically and experientially. A component of the shared predisposition appears to arise from noradrenergic and serotonergic deficits. Shared GABAergic deficits coupled with CRHergic and glutamatergic excesses may trigger and maintain seizures as well as dysfunctional affective episodes, albeit via dissimilar neuronal interplay.

Adjunctive topiramate in bipolar II disorder

We evaluated the efficacy and safety of adjunctive topiramate in bipolar II patients who were either treatment-resistant to or unable to tolerate lithium, carbamazepine or valproate. Nineteen DSM-IV bipolar II patients received increasing doses of open-label topiramate as adjunctive therapy for their hypomanic (n=15) or depressive (n=4) symptoms. Sixteen patients completed the 12-week follow-up. There were highly significant improvements in YMRS, HDRS and CGI-BP-M scores (p=0.0001). Of the fifteen hypomanic patients, eight (53%) were rated as responders to topiramate (50% reduction in YMRS scores), and five (33%) met criteria for remission (YMRS score pound 8). Two of the four patients with a depressive episode at study entry (50%) were rated as responders (50% reduction in HDRS score), and one (25%) achieved remission (HDRS score pound 6). Topiramate was generally well tolerated. One third of the patients experienced weight loss. These preliminary results suggest that adjunctive topiramate may be useful in treating bipolar II disorder.

Caffeine, fatigue, and cognition

Effects of caffeine and fatigue are discussed with special attention to adenosine-dopamine interactions. Effects of caffeine on human cognition are diverse. Behavioural measurements indicate a general improvement in the efficiency of information processing after caffeine, while the EEG data support the general belief that caffeine acts as a stimulant. Studies using ERP measures indicate that caffeine has an effect on attention, which is independent of specific stimulus characteristics. Behavioural effects on response related processes turned out to be mainly related to more peripheral motor processes. Recent insights in adenosine and dopamine physiology and functionality and their relationships with fatigue point to a possible modulation by caffeine of mechanisms involved in the regulation of behavioural energy expenditure.

Oxcarbazepine: clinical experience with hospitalized psychiatric patients

BACKGROUND

Oxcarbazepine (10-keto-carbamazepine) appears to be better tolerated and simpler to use than carbamazepine. It has antimanic effects but, as its potential clinical usefulness and tolerability in broad samples of psychiatric patients remain to be tested, we reviewed both the pharmacology of oxcarbazepine and our early experience with this new agent among psychiatric inpatients.

METHODS

We reviewed medical records of all inpatients given oxcarbazepine in the first 15 months of its use at McLean Hospital. Data analyzed included dosing, presenting illnesses, other medications, clinical changes, and adverse effects.

RESULTS

Oxcarbazepine was given to 56 inpatients (1.3% of admissions; 31 women, 25 men) presenting with depression (n = 23), mania (n = 19), or psychosis (n = 14). The discharge daily dose for the 43 patients (76%) taking oxcarbazepine was 831 mg/day, 34% higher in men than women, and fell by 9 mg/year-of-age. Oxcarbazepine was the only putative mood-stabilizing agent given at discharge in 19 of 43 cases (44%). It was discontinued in 20% of patients for apparent inefficacy, and 4% for adverse effects. Changes in CGI and GAF scores were similarly high across illnesses, and unrelated to days of use of oxcarbazepine or its dose.

CONCLUSIONS

Oxcarbazepine was well tolerated and simpler to use clinically than its precursor carbamazepine. This agent should be studied in controlled trials to test its efficacy in specific types of major psychiatric disorders, and particularly for long-term maintenance treatment in bipolar disorder.

An electrophysiologic study: can semantic context processes be mobilized in patients with thought-disordered schizophrenia?

OBJECTIVE

The aim of this study was to test the hypothesis that reinforcing the structuring of verbal material may bring about an improvement in contextualization processes in patients with formal thought-disordered schizophrenia.

METHOD

A total of 38 schizophrenia patients with formal thought disorders and 24 matched healthy control subjects performed 2 lexical decision tasks, involving 2 levels of contextual structuring (with 16.7% and 33% of related words, respectively). The event-related potentials, N400 and late positive component (LPC), and behavioural variables (reaction times and error percentages) were analyzed.

RESULTS

A context-structuring effect was observed on LPC, but not on N400. In subjects with schizophrenia, the N400 anomalies (that is, increase in amplitude for the related words and reduction of the N400 effect) persisted in both context-structuring conditions. Similarly, a reduction in LPC amplitude for the unrelated word category, as well as a decrease in the LPC effect, was observed in these patients.

CONCLUSIONS

The schizophrenia patients with formal thought disorders did not benefit from the structuring of the context to implement context integration strategies. This deficit appears to be stable. The results are discussed within the framework of a previously published model of language comprehension.

Chronic interferon-alpha potentiates latent inhibition in rats

Several recent reports based on microdialysis have shown that repeated injections of IFN-alpha induce reduced dopamine (DA) activity in the rodent brain, and specifically within the striatum. This mesolimbic DA system is thought to play a central role in controlling latent inhibition (LI), which refers to the phenomenon in which conditioning proceeds more slowly to an irrelevant pre-exposed (PE) stimulus. The purpose of the present experiment was to evaluate whether chronic treatment with IFN-alpha may induce similar effects on LI as other DA-depleting manipulations. Rats were injected daily, for 24 days either with 10(4)IU IFN-alpha or vehicle, while monitoring their locomotor activity in photocell cages. No changes in locomotor activity, either during the acute period after the first injection, or progressively over the chronic period were observed. LI was then evaluated in these rats with a Conditioned Taste Aversion (CTA) paradigm. Half of each group of rats were pre-exposed to the 5% sucrose Conditioned Stimulus (CS) for 30 min on three successive days before the conditioning session in which the 30 min access to the 5% sucrose solution was followed by a 0.15M injection of 127 mg/kg LiCl. Two test sessions, in which rats were given a choice between the 5% sucrose solution and water, were given 48 and 72 h after the conditioning session. The results showed moderate LI in the control group, which was considerably potentiated in the IFN-alpha group despite the absence of any change in locomotor activity. These results are interpreted as providing indirect support for the theory that suggests that LI depends on DA activity in the nucleus accumbens (NAcc).

Effects of adenosine on gabaergic synaptic inputs to identified ventrolateral preoptic neurons

The ventrolateral preoptic nucleus (VLPO) is a key regulator of behavioral state that promotes sleep by directly inhibiting brain regions that maintain wakefulness. Subarachnoid administration of adenosine (AD) or AD agonists promotes sleep and induces expression of Fos protein in VLPO neurons. Therefore, activation of VLPO neurons may contribute to the somnogenic actions of AD. To define the mechanism through which AD activates VLPO neurons, we prepared hypothalamic slices from 9 to 12-day-old rat pups and recorded from 43 neurons in the galaninergic VLPO cluster; nine neurons contained galanin mRNA by post hoc in situ hybridization. Bath application of AD (20 microM) to seven of these neurons had no direct effect but caused a significant decrease in the frequency of spontaneous miniature inhibitory postsynaptic currents in the presence of tetrodotoxin, indicating a presynaptic site of action. We conclude that AD-mediated disinhibition increases the excitability of VLPO neurons thus contributing to the somnogenic properties of AD.

Peeling the onion: NMDA dysfunction as a unifying model in schizophrenia

N-methyl-d-aspartate receptor (NMDAR) dysfunction plays a crucial role in schizophrenia, leading to impairments in cognitive coordination. NMDAR agonists (e.g., glycine) ameliorate negative and cognitive symptoms, consistent with NMDAR models. However, not all types of cognitive coordination use NMDAR. Further, not all aspects of cognitive coordination are impaired in schizophrenia, suggesting the need for specificity in applying the cognitive coordination construct.

High-frequency synchronisation in schizophrenia: Too much or too little?

Phillips & Silverstein's focus on schizophrenia as a failure of “cognitive coordination” is welcome. They note that a simple hypothesis of reduced Gamma synchronisation subserving impaired coordination does not fully account for recent observations. We suggest that schizophrenia reflects a dynamic compensation to a core deficit of coordination, expressed either as hyper- or hyposynchronisation, with neurotransmitter systems and arousal as modulatory mechanisms.

No blind schizophrenics: Are NMDA-receptor dynamics involved?

Numerous searches have failed to identify a single co-occurrence of total blindness and schizophrenia. Evidence that blindness causes loss of certain NMDA-receptor functions is balanced by reports of compensatory gains. Connections between visual and anterior cingulate NMDA-receptor systems may help to explain how blindness could protect against schizophrenia.

Setting domain boundaries for convergence of biological and psychological perspectives on cognitive coordination in schizophrenia

The claim that the disorganized subtype of schizophrenia results from glutamate hypofunction is enhanced by consideration of current subtypology of schizophrenia, symptom definition, interdependence of neurotransmitters, and the nature of the data needed to support the hypothesis. Careful specification clarifies the clinical reality of disorganization as a feature of schizophrenia and increases the utility of the subtype.

Schizophrenia: Putting context in context

Although context-processing deficits may be core features of schizophrenia, context remains a poorly defined concept. To test Phillips & Silverstein's model, we need to operationalize context more precisely. We offer several useful ways of framing context and discuss enhancing or facilitating schizophrenic patients' performance under different contextual situations. Furthermore, creativity may be a byproduct of cognitive uncoordination.

Phenomenology, context, and self-experience in schizophrenia

Impairments in cognitive coordination in schizophrenia are supported by phenomenological data that suggest deficits in the processing of visual context. Although the target article is sympathetic to such a phenomenological perspective, we argue that the relevance of phenomenological data for a wider understanding of consciousness in schizophrenia is not sufficiently addressed by the authors.

Guarding against over-inclusive notions of “context”: Psycholinguistic and electrophysiological studies of specific context functions in schizophrenia

Phillips & Silverstein offer an exciting synthesis of ongoing efforts to link the clinical and cognitive manifestations of schizophrenia with cellular accounts of its pathophysiology. We applaud their efforts but wonder whether the highly inclusive notion of “context” adequately captures some important details regarding schizophrenia and NMDA/glutamate function that are suggested by work on language processing and cognitive electrophysiology.

Mechanisms of disrupted language comprehension in schizophrenia

Mechanisms that contribute to perceptual processing dysfunction in schizophrenia were examined by Phillips & Silverstein, and formulated as involving disruptions in both local and higher-level coordination of signals. We agree that dysfunction in the coordination of cognitive functions (disconnection) is also indicated for many of the linguistic processing deficits documented for schizophrenia. We suggest, however, that it may be necessary to add a timing mechanism to the theoretical account.

Theory of mind in schizophrenia: Damaged module or deficit in cognitive coordination?

Schizophrenics exhibit a deficit in theory of mind (ToM), but an intact theory of biology (ToB). One explanation is that ToM relies on an independent module that is selectively damaged. Phillips & Silverstein's analyses suggest an alternative: ToM requires the type of coordination that is impaired in schizophrenia, whereas ToB is spared because this type of coordination is not involved.

Cognitive coordination and its neurobiological bases: A new continent to explore

The additional arguments and evidence supplied by the commentaries strengthen the hypothesis that underactivity of NMDA receptors produces impaired cognitive coordination in schizophrenia. This encourages the hope that though the distance from molecules to mind is great, it can nevertheless be traversed. We therefore predict that in this decade or the next molecular psychology will be seen to be as fundamental to our understanding of mind as molecular biology is to our understanding of life.

Context rules

It is proposed that cortical activity is normally coordinated across synaptically connected areas and that this coordination supports cognitive coherence relations. This view is consistent with the NMDA- hypoactivity hypothesis of the target article in regarding disorganization symptoms in schizophrenia as arising from disruption of normal interareal coordination. This disruption may produce abnormal contextual effects in the cortex that lead to anomalous cognitive coherence relations.

The ketamine model for schizophrenia

This commentary compares clinical aspects of ketamine with the amphetamine model of schizophrenia. Hallucinations and loss of insight, associated with amphetamine, seem more schizophrenia-like. Flat affect encountered with ketamine is closer to the clinical presentation in schizophrenia. We argue that flat affect is not a sign of schizophrenia, but rather, arisk factorfor chronic schizophrenia.

Cortical connectivity in high-frequency beta-rhythm in schizophrenics with positive and negative symptoms

In chronic schizophrenic patients with both positive and negative symptoms (see Table 1), interhemispheric connections at the high frequency beta2-rhythm are absent during cognitive tasks, in contrast to normal controls, who have many interhemispheric connections at this frequency in the same situation. Connectivity is a fundamental brain feature, evidently greatly promoted by the NMDA system. It is a more reliable measure of brain function than the spectral power of this rhythm.

Gender differences in bipolar disorder

The presentation and course of bipolar disorder differs between women and men. The onset of bipolar disorder tends to occur later in women than men, and women more often have a seasonal pattern of the mood disturbance. Women experience depressive episodes, mixed mania, and rapid cycling more often than men. Bipolar II disorder, which is predominated by depressive episodes, also appears to be more common in women than men. Comorbidity of medical and psychiatric disorders is more common in women than men and adversely affects recovery from bipolar disorder more often in women. Comorbidity, particularly thyroid disease, migraine, obesity, and anxiety disorders occur more frequently in women than men, whereas substance use disorders are more common in men. Although the course and clinical features of bipolar disorder differ between women and men, there is no evidence that gender affects treatment response to mood stabilizers. However, women may be more susceptible to delayed diagnosis and treatment. Treatment of women during pregnancy and lactation is challenging because available mood stabilizers pose potential risks to the developing fetus and infant. Pregnancy neither protects nor exacerbates bipolar disorder, and many women require continuation of medication during the pregnancy. The postpartum period is a time of high risk for onset and recurrence of bipolar disorder in women, and prophylaxis with mood stabilizers might be needed. Individualized risk/benefit assessments of pregnant and postpartum women with bipolar disorder are required to promote the health of the woman and avoid or limit exposure of the fetus or infant to potential adverse effects of medication.

Caffeine and central noradrenaline: effects on mood, cognitive performance, eye movements and cardiovascular function

There have been numerous studies on the effects of caffeine on behaviour and cardiovascular function. It is now important to clarify the mechanisms that underlie such effects, and the main objective of the present study was to investigate whether changes in central noradrenaline underlie some of the behavioural and cardiovascular effects of caffeine. This was examined using a clonidine challenge paradigm. Twenty-four healthy volunteers were assigned to one of four conditions: (i) clonidine/caffeine; (ii) clonidine/placebo; (iii) placebo/caffeine: (iv) placebo/placebo. Baseline measurements of mood, cognitive performance, saccadic eye movements and cardiovascular function were recorded. Subsequently, volunteers were given either clonidine (200 microg) or placebo and consumed coffee containing caffeine (1.5 mg/kg) or placebo. The test battery was then repeated 30 min, 150 min and 270 min later. A second cup of coffee (with the same amount of caffeine as the first) was consumed 120 min after the first cup. The results showed that clonidine reduced alertness, impaired many aspects of performance and slowed saccadic eye movements; caffeine removed many of these impairments. Both clonidine and caffeine influenced blood pressure (clonidine reduced it, caffeine raised it) but the effects appeared to be independent, suggesting that separate mechanisms were involved. In addition, there were some behavioural effects of caffeine that were independent of the clonidine effect (e.g. effects on speed of encoding of new information) and these may reflect other neurotransmitter systems (e.g cholinergic effects). Overall, the results suggest that caffeine counteracts reductions in the turnover of central noradrenaline. This mechanism may underlie the beneficial effects of caffeine seen in low alertness states.

NMDA receptor antagonist effects, cortical glutamatergic function, and schizophrenia: toward a paradigm shift in medication development

There is an urgent need to improve the pharmacotherapy of schizophrenia despite the introduction of important new medications. New treatment insights may come from appreciating the therapeutic implications of model psychoses. In particular, basic and clinical studies have employed the N-methyl-D-aspartate (NMDA) glutamate receptor antagonist, ketamine, as a probe of NMDA receptor contributions to cognition and behavior. These studies illustrate a translational neuroscience approach for probing mechanistic hypotheses related to the neurobiology and treatment of schizophrenia and other disorders. Two particular pathophysiologic themes associated with schizophrenia, the disturbance of cortical connectivity and the disinhibition of glutamatergic activity may be modeled by the administration of NMDA receptor antagonists. The purpose of this review is to consider the possibility that agents that attenuate these two components of NMDA receptor antagonist response may play complementary roles in the treatment of schizophrenia.

NMDA and AMPA receptors contribute to the nicotinic cholinergic excitation of CA1 interneurons in the rat hippocampus

In the hippocampus, glutamatergic inputs to pyramidal neurons and interneurons are modulated by alpha7* and alpha3beta4* nicotinic acetylcholine receptors (nAChRs), respectively, present in glutamatergic neurons. This study examines how nicotinic AMPA, and NMDA receptor nAChR activities are integrated to regulate the excitability of CA1 stratum radiatum (SR) interneurons in rat hippocampal slices. At resting membrane potentials and in the presence of extracellular Mg2+ (1 mM), nicotinic agonists triggered in SR interneurons excitatory postsynaptic currents (EPSCs) that had two components: one mediated by AMPA receptors, and the other by NMDA receptors. As previously shown, nicotinic agonist-triggered EPSCs resulted from glutamate released by activation of alpha3beta4* nAChRs in glutamatergic neurons/fibers synapsing directly onto the neurons under study. The finding that CNQX caused more inhibition of nicotinic agonist-triggered EPSCs than expected from the blockade of postsynaptic AMPA receptors indicated that this nicotinic response also depended on the AMPA receptor activity in the glutamatergic neurons synapsing onto the interneuron under study. Nicotinic agonists always triggered action potentials in CA1 SR interneurons. In most interneurons, these action potentials resulted from activation of somatodendritic AMPA receptors and alpha7* nAChRs. In interneurons expressing somatodendritic alpha4beta2* nAChRs, activation of these receptors caused sufficient membrane depolarization to remove the Mg2+-induced block of somatodendritic NMDA receptors; in these neurons, nicotinic agonist-triggered action potentials were partially dependent on NMDA receptor activation. Removing extracellular Mg2+ or clamping the neuron at positive membrane potentials revealed the existence of a tonic NMDA current in SR interneurons that was unaffected by nAChR activation or inhibition. Thus integration of the activities of nAChRs, NMDA, and AMPA receptors in different compartments of CA1 neurons contributes to the excitability of CA1 SR interneurons.

Interneuron Diversity series: Interneuron research--challenges and strategies

The field of interneuron research has come of age. An influx of new data has shed light on many areas, but has also highlighted major challenges. The articles in this review series will address several of these challenges, including developing a standardized classification scheme, defining how the integrative properties of interneurons shape their functional roles (including the generation of oscillatory activity), and identifying molecular mechanisms of synaptic plasticity. New technologies can help us address these problems in ways not previously possible. To coordinate the vast amount of data being generated, we propose the creation of a world-wide-web Interneuron Database that will facilitate inter-laboratory comparisons and collaborative studies. A well-crafted database has the potential to bring new insight by standardizing and organizing data collected in physiological, anatomical and molecular studies.

Abnormal neural synchrony in schizophrenia

Schizophrenia has been conceptualized as a failure of cognitive integration, and abnormalities in neural circuitry (particularly inhibitory interneurons) have been proposed as a basis for this disorder. We used measures of phase locking and phase coherence in the scalp-recorded electroencephalogram to examine the synchronization of neural circuits in schizophrenia. Compared with matched control subjects, schizophrenia patients demonstrated: (1) absence of the posterior component of the early visual gamma band response to Gestalt stimuli; (2) abnormalities in the topography, latency, and frequency of the anterior component of this response; (3) delayed onset of phase coherence changes; and (4) the pattern of anterior-posterior coherence increases in response to Gestalt stimuli found in controls was replaced by a pattern of interhemispheric coherence decreases in patients. These findings support the hypothesis that schizophrenia is associated with impaired neural circuitry demonstrated as a failure of gamma band synchronization, especially in the 40 Hz range.

Avoiding drug-induced switching in patients with bipolar depression

Antidepressant-induced switching is a major risk during the treatment of bipolar depression. Despite several clinical studies, questions remain regarding both the definition of these mood switches and the most appropriate therapeutic strategy to avoid this adverse effect. This review will first briefly consider the current guidelines for the acute treatment of bipolar depression. We will then review the mechanisms of action of antidepressant and mood stabilisers, and the switches induced by various types of antidepressant treatments, or triggered by antidepressant withdrawal, as well as by atypical antipsychotics. We then will address the risk of mood switch according to the type of mood stabiliser used. The propensity to mood switches in bipolar patients is subject to individual differences. Therefore we will describe both the clinical and biological characteristics of patients prone to mood switches under antidepressant treatment. However, the clinical characteristics of the depressive syndrome may also be a key determinant for mood switches. Various data help identify the most appropriate drug management strategies for avoiding mood switches during the treatment of bipolar depression. Selective serotonin reuptake inhibitors appear to be the drugs of first-choice because of the low associated risk of mood switching. Antidepressants must be associated with a mood stabiliser and the most effective in the prevention of switches seems to be lithium. Whatever the mood stabiliser used, effective plasma levels must be ensured. The optimal duration of antidepressant treatment for bipolar depression is still an open issue - prolonged treatments after recovery may be unnecessary and may facilitate mood elation. Moreover, some mood episodes with mixed symptoms can be worsened by antidepressants pointing to the need for a better delineation of the categories of symptoms requiring antidepressant treatment. Finally, as a result of this review, we suggest some propositions to define drug-induced switches in bipolar patients, and to try to delineate which strategies should be recommended in clinical practice to reduce as far as possible the risk of mood switch during the treatment of bipolar depression.

Which antidepressants flick the switch?

OBJECTIVE

The Black Dog Institute seeks to address issues of relevance to the clinical management of those with a mood disorder. This overview considers the capacity of antidepressant drugs, and particularly the new classes, to induce manic switching in depressed patients.

METHOD

Relevant literature is reviewed.

RESULTS

It is unclear whether antidepressant drugs from any of the classes induce switching in unipolar depressed patients. In bipolar depressed patients, the broad-spectrum tricyclic and monoamine oxidase inhibitor drugs present a clear risk of switching, the selective serotonin re-uptake inhibitors do not appear (at standard doses) to increase the risk, while the capacity of the dual action (serotonergic and noradrenergic) drugs to induce switching remains unestablished but may be slight.

CONCLUSIONS

As switching induced by narrow action antidepressants does not appear to present a substantive causal risk, clinicians can have confidence in prescribing certain anti-depressants for managing bipolar depression, and without any necessity to first prescribe a mood stabilizer to pre-empt switching.

Progressive decrease of left Heschl gyrus and planum temporale gray matter volume in first-episode schizophrenia: a longitudinal magnetic resonance imaging study

BACKGROUND

The Heschl gyrus and planum temporale have crucial roles in auditory perception and language processing. Our previous investigation using magnetic resonance imaging (MRI) indicated smaller gray matter volumes bilaterally in the Heschl gyrus and in left planum temporale in patients with first-episode schizophrenia but not in patients with first-episode affective psychosis. We sought to determine whether there are progressive decreases in anatomically defined MRI gray matter volumes of the Heschl gyrus and planum temporale in patients with first-episode schizophrenia and also in patients with first-episode affective psychosis.

METHODS

At a private psychiatric hospital, we conducted a prospective high spatial resolution MRI study that included initial scans of 28 patients at their first hospitalization (13 with schizophrenia and 15 with affective psychosis, 13 of whom had a manic psychosis) and 22 healthy control subjects. Follow-up scans occurred, on average, 1.5 years after the initial scan.

RESULTS

Patients with first-episode schizophrenia showed significant decreases in gray matter volume over time in the left Heschl gyrus (6.9%) and left planum temporale (7.2%) compared with patients with first-episode affective psychosis or control subjects.

CONCLUSIONS

These findings demonstrate a left-biased progressive volume reduction in the Heschl gyrus and planum temporale gray matter in patients with first-episode schizophrenia in contrast to patients with first-episode affective psychosis and control subjects. Schizophrenia but not affective psychosis seems to be characterized by a postonset progression of neocortical gray matter volume loss in the left superior temporal gyrus and thus may not be developmentally fixed.

Latest maintenance data on lamotrigine in bipolar disorder

Two 18-month, randomised, double-blind trials have compared lamotrigine, lithium, and placebo as maintenance treatment in a total of 1315 recently manic or depressed patients with bipolar I disorder. Individual and combined analyses of these studies showed that both lamotrigine and lithium significantly prolonged the time to intervention for any mood episode compared with placebo. Lamotrigine was primarily effective against depression and lithium was primarily effective against mania. There was no evidence that lamotrigine induced mania/hypomania/mixed states, caused episode acceleration, or destabilised the overall course of illness. Lamotrigine was well tolerated, with a placebo-like adverse-event profile. In summary, lamotrigine is an effective and well-tolerated maintenance treatment for bipolar I disorder, providing a spectrum of efficacy complementary to that of lithium.

Large variability in synaptic N-methyl-D-aspartate receptor density on interneurons and a comparison with pyramidal-cell spines in the rat hippocampus

Pyramidal cells receive input from several types of GABA-releasing interneurons and innervate them reciprocally. Glutamatergic activation of interneurons involves both alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) and N-methyl-D-aspartate (NMDA) type glutamate receptors expressed in type I synapses, mostly on their dendritic shafts. On average, the synaptic AMPA receptor content is several times higher on interneurons than in the spines of pyramidal cells. To compare the NMDA receptor content of synapses, we used a quantitative postembedding immunogold technique on serial electron microscopic sections, and analysed the synapses on interneuron dendrites and pyramidal cell spines in the CA1 area. Because all NMDA receptors contain the obligatory NR1 subunit, receptor localisation was carried out using antibodies recognising all splice variants of the NR1 subunit. Four populations of synapse were examined: i). on spines of pyramidal cells in stratum (str.) radiatum and str. oriens; ii). on parvalbumin-positive interneuronal dendritic shafts in str. radiatum; iii). on randomly found dendritic shafts in str. oriens and iv). on somatostatin-positive interneuronal dendritic shafts and somata in str. oriens. On average, the size of the synapses on spines was about half of those on interneurons. The four populations of synapse significantly differed in labelling for the NR1 subunit. The median density of NR1 subunit labelling was highest on pyramidal cell spines. It was lowest in the synapses on parvalbumin-positive dendrites in str. radiatum, where more than half of these synapses were immunonegative. In str. oriens, synapses on interneurons had a high variability of receptor content; some dendrites were similar to those in str. radiatum, including the proximal synapses of somatostatin-positive cells, whereas others had immunoreactivity for the NR1 subunit similar to or higher than synapses on pyramidal cell spines. These results show that synaptic NMDA receptor density differs between pyramidal cells and interneurons. Some interneurons may have a high NMDA receptor content, whereas others, like some parvalbumin-expressing cells, a particularly low synaptic NMDA receptor content. Consequently, fast glutamatergic activation of interneurons is expected to show cell type-specific time course and state-dependent dynamics.

Regulation of glutamate carboxypeptidase II function in corticolimbic regions of rat brain by phencyclidine, haloperidol, and clozapine

Mounting evidence indicates that hypofunction of NMDA glutamate receptors causes or contributes to the full symptomatology of schizophrenia. N-acetyl-aspartyl-glutamate (NAAG), an endogenous neuropeptide, blocks NMDA receptors and inhibits glutamate release by activating metabotropic mGluR3 receptors. NAAG is catabolized to glutamate and N-acetyl-aspartate by the astrocytic enzyme glutamate carboxypeptidase II (GCP II). Changes in GCP II activity may be critically linked to changes in glutamatergic neurotransmission especially at NMDA receptors. We examined whether GCP II function is altered by treatment with the noncompetitive antagonist and psychotomimetic drug phencyclidine (PCP) and with the neuroleptics haloperidol (HAL) and clozapine (CLOZ), in corticolimbic brain regions of the adult rat. Chronic exposure to PCP produced significant increases in GCP II protein expression and activity in the prefrontal cortex (PFC) and hippocampus (HIPP). This effect may be explained by a compensatory response to persistent blockade of NMDA receptors. In addition, chronic treatment with neuroleptics upregulated GCP II activity, but not protein expression, in the PFC. In contrast, GCP II activity was decreased after acute exposure to HAL or CLOZ and was not changed after acute PCP treatment. These findings provide support for a role of GCP II function in the control of glutamatergic neurotransmission and suggest that some of the therapeutic actions of neuroleptic drugs may be mediated through their effects on GCP II activity. These results demonstrate that psychotomimetic and neuroleptic drugs modulate GCP II function in brain regions that are widely involved in the neuropathology of schizophrenia.

Advances in the pharmacological treatment of bipolar affective disorders

TOPIC

Advances in the psychopharmacologic treatment of bipolar affective disorders (BPAD).

PURPOSE

To increase advanced practice nurses' ability to match prescribing practices with known etiological factors and the neurobiology of this complex set of disorders.

SOURCES

Published literature.

CONCLUSIONS

A wide array of pharmacological agents exist that can be useful to manage BPAD symptoms. APRNs play a critical role in helping patients and their families to use these drugs effectively.