Abnormal anterior cingulate cortical activity during emotional n-back task performance distinguishes bipolar from unipolar depressed females

BACKGROUND

Depression in the context of bipolar disorder (BDd) is often misdiagnosed as unipolar disorder depression (UDd) leading to poor clinical outcomes for many bipolar sufferers. We examined neural circuitry supporting emotion regulation in females with either BDd or UDd as a first stage toward identifying biomarkers that may differentiate BDd from UDd.

METHOD

Fifty-seven females aged 18-45 years participated in this study: 23 with UDd, 18 with bipolar disorder type I depression (BDId) and 16 healthy females. During 3-T functional magnetic resonance imaging (fMRI), the participants performed an emotional face n-back (EFNBACK) task, that is an n-back task with high (2-back) and low (0-back) memory load conditions flanked by two positive, negative or neutral face distracters. This paradigm examines executive control with emotional distracters-emotion regulation.

RESULTS

High memory load with neutral face distracters elicited greater bilateral and left dorsal anterior midcingulate cortex (dAMCC) activity in UDd than in healthy and BDId females respectively, and greater bilateral putamen activity in both depressed groups versus healthy females. High memory load with happy face distracters elicited greater left putamen activity in UDd than in healthy females. Psychotropic medication was associated with greater putamen activity to these contrasts in UDd females.

CONCLUSIONS

During high memory load with neutral face distracters, elevated dAMCC activity in UDd suggests abnormal recruitment of attentional control circuitry to maintain task performance, whereas elevated putamen activity unrelated to psychotropic medication in BDId females may suggest an attentional bias toward ambiguous neutral face distracters. Differential patterns of functional abnormalities in neural circuitry supporting attentional control during emotion regulation, especially in the dAMCC, is a promising neuroimaging measure to distinguish UDd from BDId in females.

Correlation between decreased motor activity and dopaminergic degeneration in the ventrolateral putamen in monkeys receiving repeated MPTP administrations: a positron emission tomography study

Parkinson's disease (PD) patients have remarkably reduced levels of dopaminergic biomarkers in the caudal putamen. However, the relationship between motor impairments and the localization of intrastriatal dopaminergic degeneration in monkey PD models remains unclear. To identify the striatal areas with dopaminergic dysfunction responsible for motor impairments, we measured changes in both general motor activity and in vivo dopaminergic biomarkers in three cynomolgus monkeys that repeatedly received 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), starting in the normal state and continuing until after tremor appearance. Binding of dopamine transporters (DAT) and D(2) receptors were measured by positron emission tomography (PET) using [(11)C]PE2I and [(11)C]raclopride, respectively. Region-of-interest-based regression analysis demonstrated the degree of general motor activity reduction to be explained by striatal DAT binding but not by D(2) receptor binding. Furthermore, voxel-based analysis revealed a significant correlation between reduced general motor activity and decreased DAT binding, specifically in the ventrolateral putamen, which corresponds to the area receiving upper body motor inputs from the primary motor cortex. These results suggest that specific functional deficits in PD models are closely related to the degeneration of dopaminergic terminals in the striatal subregion responsible for these functions and that the level of deficit is dependent on the degree of degeneration.

MDMA (Ecstasy) association with impaired fMRI BOLD thalamic coherence and functional connectivity

BACKGROUND

MDMA exposure is associated with chronic serotonergic dysfunction in preclinical and clinical studies. A recent functional magnetic resonance imaging (fMRI) comparison of past MDMA users to non-MDMA-using controls revealed increased spatial extent and amplitude of activation in the supplementary motor area during motor tasks (Karageorgiou et al., 2009). Blood oxygenation level dependent (BOLD) data from that study were reanalyzed for intraregional coherence and for inter-regional temporal correlations between time series, as functional connectivity.

METHODS

Fourteen MDMA users and ten controls reporting similar non-MDMA abuse performed finger taps during fMRI. Fourteen motor pathway regions plus a pontine raphé region were examined. Coherence was expressed as percent of voxels positively correlated with an intraregional index voxel. Functional connectivity was determined using wavelet correlations.

RESULTS

Intraregional thalamic coherence was significantly diminished at low frequencies in MDMA users compared to controls (p=0.009). Inter-regional functional connectivity was significantly weaker for right thalamo - left caudate (p=0.002), right thalamo - left thalamus (p=0.007), right caudate - right postcentral (p=0.007) and right supplementary motor area - right precentral gyrus (p=0.011) region pairs compared to controls. When stratified by lifetime exposure, significant negative associations were observed between cumulative MDMA use and functional connectivity in seven other region-pairs, while only one region-pair showed a positive association.

CONCLUSIONS

Reported prior MDMA use was associated with deficits in BOLD intraregional coherence and inter-regional functional connectivity, even among functionally robust pathways involving motor regions. This suggests that MDMA use is associated with long-lasting effects on brain neurophysiology beyond the cognitive domain.

Reversible inactivation of the basolateral amygdala, but not the dorsolateral caudate putamen, attenuates consolidation of cocaine-cue associative learning in a reinstatement model of drug-seeking

Previous research has shown that the basolateral amygdala (BLA) mediates stimulus-reward learning, including drug-cue associations, whereas the dorsolateral caudate putamen (dlCPu) primarily mediates stimulus-response (habit) learning. Recent evidence has indicated that the dlCPu may be critical in cocaine-seeking following extended self-administration, but it remains unknown whether the dlCPu plays a role in the early formation of drug-cue associations. The current study used a model of Pavlovian learning to compare the roles of the BLA and dlCPu in the consolidation of cocaine-cue associations that maintain cocaine-seeking during cue-induced reinstatement. Male Sprague-Dawley rats self-administered cocaine (0.2 mg/ 50μL infusion, i.v.) in the absence of cues for 6 days (2 h/day). Immediately following a single 1-h classical conditioning session in which passive cocaine infusions were paired with a light/tone cue, animals received bilateral infusions of the GABA receptor agonists, baclofen/muscimol (1.0/0.1 mm), or vehicle into the BLA or dlCPu. Following additional cocaine self-administration (5 days) and subsequent extinction (no cocaine or cues, 7 days), the ability of the previously cocaine-paired cues to reinstate cocaine-seeking was assessed. Inactivation of the BLA, but not the dlCPu, immediately following the classical conditioning session impaired the consolidation of cocaine-cue associations as seen by decreased cue-induced reinstatement. These results extend previous findings that the BLA mediates the consolidation of learned associations that drive cocaine-seeking during subsequent reinstatement and indicate that the dlCPu does not play a role during initial stimulus-drug associative learning.

Cocaine effects on dopamine and NMDA receptors interactions in the striatum of Fischer rats

Numerous studies have shown that biochemical and behavioral effects of cocaine are mediated by dopamine D1 receptor (D1R) and NMDA R1 receptor (NR1)-mediated transmission. In this study, we investigated the physical interactions between D1R and NR1 in response to acute cocaine administration in a time course of 5-60 min. In the caudate-putamen (CPu) of male Fischer rats, a single cocaine injection (30 mg/kg) reduced D1R-NR1 protein-protein interactions 30 min after treatment. In addition, activation or blockade of the NMDA receptor using NMDA (25mg/kg) or MK-801 (0.25mg/kg), respectively, also reduced the D1R-NR1 physical interactions. Acute cocaine administration did not alter total D1R or NR1 protein levels in our time course of study. These results indicate that D1R-NR1 physical interaction rather than total protein levels may regulate the intracellular signaling after acute cocaine administration.

Dopamine D1 receptor-dependent modifications in the dopamine and cAMP-regulated phosphoprotein of Mr 32 kDa phosphorylation pattern in striatal areas of morphine-sensitized rats

Morphine sensitization is a model of latent, functionally inducible increase in dopamine D(1) receptor-mediated transmission, which may be unmasked by an external stimulus. Morphine-sensitized rats present dopamine D(1) receptor-dependent stereotypies upon morphine challenge and resilience to unavoidable stress-induced behavioral deficits. This tonic increase in dopamine D(1) dopaminergic transmission is counter-adaptive to an enhanced mu-opioid receptor-dependent signaling in striatal areas. Control and sensitized rats show a similar dopamine and cAMP-regulated phosphoprotein of M(r) 32 kDa (DARPP-32) phosphorylation pattern in striatal areas. Acute morphine administration induced an early increase and delayed decrease in phospho-threonine (Thr)34 DARPP-32 levels accompanied by a delayed increase in phospho-Thr75 DARPP-32 levels in the nucleus accumbens and caudate-putamen of sensitized rats, while it had no effects in control animals. The administration of a selective dopamine D(1) receptor antagonist (SCH 23390) before morphine challenge prevented the behavioral and neurochemical modifications in sensitized rats. 6-Methyl-2-(phenylethynyl)-pyridine, a selective metabotropic glutamate receptor 5 (mGluR(5)) antagonist, administered 1 h after morphine challenge, prevented the delayed phosphorylation changes, but it had no effect when administered before challenge. Moreover, the DARPP-32 phosphorylation pattern in the caudate-putamen of sensitized rats after unavoidable stress exposure was studied. The stress-induced neurochemical modifications and their sensitivity to receptor antagonists were similar to those observed after acute morphine administration. In conclusion, these results suggest that in the experimental conditions used an increase in dopamine output in striatal areas is followed by a complex neurochemical pattern, in which the initial stimulation of dopamine D(1) receptors triggers a sequence of signaling events that lead to an mGluR(5)-mediated increase in phospho-Thr75 DARPP-32 levels. Since DARPP-32 phosphorylated in Thr75 inhibits cAMP-dependent protein kinase (PKA) activity, the final result is a decrease in the dopamine D(1) receptor-dependent phosphorylation events.

Cue-elicited drug craving represses ERK activation in mice prefrontal association cortex

Morphine addiction is characterized by compulsive drug-taking behavior and high rates of relapse that reflect reward-controlled learning, consolidation and reconsolidation of drug cues. Extracellular signal-regulated protein kinase (ERK) is one of the cellular molecules that have been highly implicated in the synaptic plasticity processes of learning and memory in cocaine addiction. However, the roles of ERK in the morphine-paired conditioned place preference (CPP) are not clear. In the present study, we found that compared to the morphine-unpaired and saline-paired and saline-unpaired groups, morphine-paired mice showed depressed ERK2 activity in the Frontal Association Cortex (FrA), whereas ERK1 activity was not changed in the same region. In the Accumbens Nucleus (Acb) and Caudate Putamen (CPu) that are associated with cocaine addiction, the activities of ERK1 and ERK2 among four groups showed no difference. These results suggest that the FrA plays an important role in morphine craving and that ERK2 is involved in eliciting the environment-related morphine craving, which is totally different from those induced by morphine itself.

Neurobehavioral protection by single dose l-deprenyl against MPTP-induced parkinsonism in common marmosets

OBJECTIVE

Establishment of preclinical method evaluating behavioral protective actions of drugs for Parkinson's disease was attempted using l-deprenyl (DEP) as a reference drug in 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-treated common marmosets.

MATERIALS AND METHODS

Fifteen marmosets received MPTP at 2 mg/kg, subcutaneously (s.c.) per day for three consecutive days. To these marmosets, intragastric (i.g.) administration of DEP at 10 mg/kg was pretreated 2 h before each MPTP administration in DEP3 group and pretreated only in the first MPTP administration day in DEP1 group. As a control, distilled water (DW) was pretreated before each MPTP administration (n = 5 for each of three groups).

RESULTS

In DW group, decreased daily activity counts and increased dysfunction scores were persistently observed for 3 weeks after MPTP. In DEP groups, the similar changes of both levels to those in DW group were temporally observed after MPTP for several days and then the values recovered to the pre-MPTP levels. The results of autoradiography performed after above behavioral observations indicated that markedly lower bindings of [(11)C]PE2I (ligand for dopamine transporters) were observed at the striatum of DW group marmoset as compared with the striatum of additionally prepared MPTP-free marmoset (n = 5). The bindings in DEP groups were almost the same as in the MPTP-free marmoset brains.

CONCLUSION

The present preclinical methods using continuous recording of activity of marmosets in their living cages and autoradiography using dopamine transporter ligand might be sensitive for detecting protective actions of drugs for Parkinson's disease.

Effects of cocaine and MDMA self-administration on serotonin transporter availability in monkeys

Although serotonin (5-HT) can interact with dopamine (DA) systems to modulate the subjective and reinforcing effects of psychostimulants such as cocaine and 3,4-methyldioxymethamphetamine (MDMA, ecstasy), the long-term effects of exposure to psychostimulants on brain 5-HT systems are not well characterized. The present study assessed 5-HT transporter (SERT) availability using positron emission tomography (PET) in rhesus monkeys with the SERT-specific radioligand [(11)C]3-amino-4-(2-dimethylaminomethyl-phenylsulfanyl)-benzonitrile (DASB). SERT availability was assessed in regions of interest including the caudate nucleus, putamen, anterior cingulate cortex, and cerebellum. [(11)C]DASB distribution volume ratios (DVRs) were calculated using the cerebellum as the reference region. DVRs were calculated in control monkeys and in cocaine or MDMA self-administering monkeys approximately 24 h after the last self-administration (SA) session. SERT availability did not differ between monkeys with a history of MDMA SA and control monkeys in any region examined. In contrast, monkeys with a history of cocaine SA showed significantly higher levels of SERT availability in the caudate nucleus and putamen compared to control subjects. These results suggest that chronic SA of cocaine, but not MDMA, leads to alterations in serotonergic function in brain areas relevant to drug abuse. The higher level of SERT availability in cocaine-experienced monkeys may lead to a reduced inhibitory tone of 5-HT on the DA system, which may explain, in part, differences in the abuse liability between cocaine and MDMA.

Intraputamenal infusion of exogenous neurturin protein restores motor and dopaminergic function in the globus pallidus of MPTP-lesioned rhesus monkeys

The neurorestorative effects of exogenous neurturin (NTN) delivered directly into the putamen via multiport catheters were studied in 10 MPTP-lesioned rhesus monkeys expressing stable parkinsonism. The parkinsonian animals were blindly assigned to receive coded solutions containing either vehicle (n = 5) or NTN (n = 5, 30 microg/day). Both solutions were coinfused with heparin using convection-enhanced delivery for 3 months. The NTN recipients showed a significant and sustained behavioral improvement in their parkinsonian features during the treatment period, an effect not seen in the vehicle-treated animals. At study termination, locomotor activity levels were increased by 50% in the NTN versus vehicle recipients. Also, DOPAC levels were significantly increased by 150% ipsilateral (right) to NTN infusion in the globus pallidus, while HVA levels were elevated bilaterally in the NTN-treated animals by 10% on the left and 67% on the right hemisphere. No significant changes in DA function were seen in the putamen. Volumetric analysis of putamenal NTN labeling showed between-subject variation, with tissue distribution ranging from 214 to 744 mm3, approximately equivalent to 27-93% of area coverage. Our results support the concept that intraparenchymal delivery of NTN protein may be effective for the treatment of PD. More studies are needed to determine strategies that would enhance tissue distribution of exogenous NTN protein, which could contribute to optimize its trophic effects in the parkinsonian brain.

A preliminary study of dopamine transporter binding in bipolar and unipolar depressed patients and healthy controls

OBJECTIVE

We examined striatal dopamine transporter (DAT) binding in bipolar and unipolar depressed patients and compared these values to those obtained from healthy control subjects using the selective DAT radioligand [(99m)Tc]TRODAT-1 and single photon emission computed tomography imaging. We hypothesized that DAT levels might be higher in bipolar versus unipolar patients.

METHODS

[(99m)Tc]TRODAT-1 scans were acquired from 5 bipolar and 10 unipolar patients and from 46 healthy controls. Distribution volume ratio (DVR) of [(99m)Tc]TRODAT-1 binding affinity was calculated for regions of interest in the striatum.

RESULTS

Bipolar patients had greater DVR values compared to controls in the right posterior putamen (p = 0.001) and in the left caudate region (p = 0.007). Bipolar patients had modestly lower DAT binding in all brain regions examined, and a significantly lower DVR in the right caudate region compared to unipolar patients (p = 0.05).

CONCLUSION

These data suggest that striatal DAT density may be increased in bipolar and unipolar depressed patients compared to controls, and that bipolar and unipolar depressed patients may have a different pattern of striatal DAT binding.

Dopamine D(1) and D(3) receptors oppositely regulate NMDA- and cocaine-induced MAPK signaling via NMDA receptor phosphorylation

Development of drug addiction involves complex molecular changes in the CNS. The mitogen-activated protein kinase (MAPK) signaling pathway plays a key role in mediating neuronal activation induced by dopamine, glutamate, and drugs of abuse. We previously showed that dopamine D(1) and D(3) receptors play different roles in regulating cocaine-induced MAPK activation. Although there are functional and physical interactions between dopamine and glutamate receptors, little is known regarding the involvement of D(1) and D(3) receptors in modulating glutamate-induced MAPK activation and underlying mechanisms. In this study, we show that D(1) and D(3) receptors play opposite roles in regulating N-methyl-d-aspartate (NMDA) -induced activation of extracellular signal-regulated kinase (ERK) in the caudate putamen (CPu). D(3) receptors also inhibit NMDA-induced activation of the c-Jun N-terminal kinase and p38 kinase in the CPu. NMDA-induced activation of the NMDA-receptor R1 subunit (NR1), Ca(2+)/calmodulin-dependent protein kinase II and the cAMP-response element binding protein (CREB), and cocaine-induced CREB activation in the CPu are also oppositely regulated by dopamine D(1) and D(3) receptors. Finally, the blockade of NMDA-receptor reduces cocaine-induced ERK activation, and inhibits phosphorylation of NR1, Ca(2+)/calmodulin-dependent protein kinase II, and CREB, while inhibiting ERK activation attenuates cocaine-induced CREB phosphorylation in the CPu. These results suggest that dopamine D(1) and D(3) receptors oppositely regulate NMDA- and cocaine-induced MAPK signaling via phosphorylation of NR1.

High-fat diet exposure increases dopamine D2 receptor and decreases dopamine transporter receptor binding density in the nucleus accumbens and caudate putamen of mice

This experiment examined dopamine D2 receptor and its transporter (DAT) density in mice fed a high-fat or low-fat diet for twenty days as well as fed twenty days of high-fat diet then changed to low-fat diet for one and seven days. Quantitative autoradiography revealed that twenty days of high-fat diet consumption significantly increased D2 receptor and decreased DAT density in the dorsal and ventral parts of the caudal caudate putamen (D2: 32% and 35% respectively, DAT: 33.3% and 28.8% respectively) compared with low-fat diet. High-fat feeding also increased D2 binding in the nucleus accumbens shell (36%). D2 receptor and DAT density remained unchanged following reversal of the diets from high-fat to low-fat diet. The high-fat diet induced increase of D2 receptor and decrease of DAT binding may have occurred due to defensive control over dopaminergic activity in response to a positive energy balance.

Differential effects of aripiprazole on D(2), 5-HT(2), and 5-HT(1A) receptor occupancy in patients with schizophrenia: a triple tracer PET study

OBJECTIVE

Aripiprazole has a unique pharmacological profile that includes partial agonism at D(2) receptors, antagonism at 5-HT(2) receptors, and partial agonism at 5-HT(1A) receptors. The authors conducted a positron emission tomography (PET) study to characterize the simultaneous effects of aripiprazole at the D(2), 5-HT(2), and 5-HT(1A) receptors in patients with schizophrenia or schizoaffective disorder.

METHOD

Twelve patients who had previously received antipsychotic treatment were randomly assigned to receive 10 mg, 15 mg, 20 mg, or 30 mg of aripiprazole. After at least 14 days of treatment, participants underwent high-resolution PET scans using [(11)C]raclopride, [(18)F]setoperone, and [(11)C]WAY100635.

RESULTS

Very high occupancy was observed at striatal D(2) receptors (average putamen, 87%; caudate, 93%; and ventral striatum, 91%), lower occupancy at 5-HT(2) receptors (54%-60%), and even lower occupancy at 5-HT(1A) receptors (16%). D(2) occupancy levels were significantly correlated with plasma drug concentrations, and even the lowest dose (10 mg) led to 85% D(2) occupancy. Extrapyramidal side effects were seen only in two of the four participants with occupancies exceeding 90%.

CONCLUSIONS

Aripiprazole exhibits a unique occupancy profile as compared with other conventional and atypical antipsychotics. The threshold for response appears to be higher than 60%, extrapyramidal side effects appear to be uncommon even at occupancies that exceed the conventional extrapyramidal side effects threshold of 80%, and 5-HT(2) occupancy is lower than D(2) occupancy. Implications for aripiprazole's mechanism of action are discussed.

Effects of chronic alcohol exposure on dopamine uptake in rat nucleus accumbens and caudate putamen

RATIONALE

Existing data strongly suggest that alcohol affects dopamine (DA) neurotransmission in the brain. However, many questions remain about the effects of alcohol on the delicate equilibrium between such neurochemical processes as DA release and uptake. Dysregulation of these processes in the mesolimbic and nigrostriatal systems after chronic alcohol ingestion could be a neuroadaptation contributing to dependence.

OBJECTIVES

In the present study, we have employed an alcohol vapor inhalation model to characterize the effects of chronic alcohol exposure on DA dynamics in rat nucleus accumbens (NAc) and caudate putamen (CP) using fast-scan cyclic voltammetry (FSCV) in brain slices. This method provides a unique view of real-time, spatially resolved changes in DA concentration.

RESULTS

We found that chronic alcohol exposure enhanced DA uptake rates in rat NAc and CP. These changes would have the effect of down-regulating extracellular DA levels, presumably a compensatory effect related to increased DA release by repeated alcohol exposure. The sensitivity of terminal release-regulating DA autoreceptors was not different in alcohol-exposed rats compared with alcohol-naïve animals.

CONCLUSIONS

The DA uptake changes after chronic alcohol exposure documented here using FSCV may be associated with a compensatory response of the DA system aimed at decreasing DA signaling. Alterations in autoreceptor function may require relatively long lasting alcohol exposure.

Six-Month Continuous Intraputamenal Infusion Toxicity Study of Recombinant Methionyl Human Glial Cell Line-Derived Neurotrophic Factor (r-metHuGDNF) in Rhesus Monkeys

Recombinant human glial cell line-derived neurotrophic factor (r-metHuGDNF) is a potent neuronal growth and survival factor that has been considered for clinical use in the treatment of Parkinson's disease (PD). Here we present results of a 6-month toxicology study in rhesus monkeys conducted to support clinical evaluation of chronic intraputamenal infusion of r-metHuGDNF for PD. Monkeys (6-9/sex/group) were treated with 0 (vehicle), 15, 30, or 100 micro g/day r-metHuGDNF by continuous unilateral intraputamenal infusion (150 micro l/day flow rate) for 6 months; a subset of animals (2-3/sex/group) underwent a subsequent 3-month treatment-free recovery period. Notable observations included reduced food consumption and body weight at 100 micro g/day and meningeal thickening underlying the medulla oblongata and/or overlying various spinal cord segments at 30 and 100 micro g/day. In addition, multifocal cerebellar Purkinje cell loss (with associated atrophy of the molecular layer and, in some cases, granule cell loss) was observed in 4 monkeys in the 100-micro g/day group. This cerebellar finding has not been observed in previous nonclinical studies evaluating r-metHuGDNF. The small number of affected animals precludes definitive conclusions regarding the pathogenesis of the cerebellar lesion, but the data support an association with r-metHuGDNF treatment.

Dorsolateral prefrontal cortex N-acetylaspartate/total creatine (NAA/tCr) loss in male recreational cannabis users

BACKGROUND

Cannabinoids present neurotoxic and neuroprotective properties in in vitro studies, inconsistent alterations in human neuroimaging studies, neuropsychological deficits, and an increased risk for psychotic episodes.

METHODS

Proton magnetic resonance spectroscopy ((1)H-MRS), neuropsychological testing, and hair analysis for cannabinoids was performed in 13 male nontreatment-seeking recreational cannabis users and 13 male control subjects.

RESULTS

A significantly diminished N-acetylaspartate/total creatine (NAA/tCr) ratio in the dorsolateral prefrontal cortex (DLPFC) was observed in cannabis users (p = .0003). The NAA/tCr in the putamen/globus pallidum region correlated significantly with cannabidiol (R(2) = .66, p = .004). Results of the Wisconsin Card Sorting test, Trail making Test, and D2 test for attention were influenced by cannabinoids.

CONCLUSIONS

Chronic recreational cannabis use is associated with an indication of diminished neuronal and axonal integrity in the DLPFC in this study. As chronic cannabis use is a risk factor for psychosis, these results are interesting because diminished NAA/tCr ratios in the DLPFC and neuropsychological deficits were also reported in schizophrenia. The strong positive correlation of NAA/tCr and cannabidiol in the putamen/globus pallidum is in line with neuroprotective properties of cannabidiol, which were also observed in in vitro model studies of Parkinson's disease.

Effects of intrastriatal injections of glutamate receptor antagonists on the severity of paroxysmal dystonia in the dtsz mutant

Imbalances of the glutamatergic system are implicated in the pathophysiology of various basal ganglia disorders, but few is known about their role in dystonia, a common neurological syndrome in which involuntary muscle co-contractions lead to twisting movements and abnormal postures. Previous systemic administrations of glutamate receptor antagonists in dtsz hamsters, an animal model of primary paroxysmal dystonia, exerted antidystonic effects and electrophysiological experiments pointed to an enhanced corticostriatal glutamatergic activity. In order to examine the pathophysiological relevance of these findings, we performed striatal microinjections of the alpha-amino-2,3-dihydro-5-methyl-3-oxo-4-isoxazolepropanoic acid (AMPA) receptor antagonist 2,3-dioxo-6-nitro-7-sulfamoylbenzo(f)quinoxaline (NBQX) and the N-methyl-D-aspartate (NMDA) receptor antagonists D(-)-2-amino-5-phosphopentanoic acid (AP-5), (R)-(+)-3-amino-1-hydroxypyrrolidin-2-one (HA-966) and dizocilpine (MK-801). The striatal application of NBQX reduced the severity and increased the latency to onset of dystonia significantly only at a dosage of 0.08 microg per hemisphere, lower (0.03 microg) and higher dosages (0.16 microg and 0.32 microg) failed to exert comparable effects on the severity. None of the striatal injected NMDA receptor antagonists influenced the severity of the dystonic attacks in the mutant hamster. The combined application of NBQX (0.08 microg) with AP-5 (1.0 microg) failed to exert synergistic antidystonic effects, but the beneficial effect on the severity of dystonia of the single application of NBQX was reproduced. Therefore, corticostriatal glutamatergic overactivity mediated by AMPA receptors, but not by NMDA receptors, is possibly important for the manifestation of dystonic attacks in the dtsz hamster mutant.

Long-term Effects of JL 13, a Potential Atypical Antipsychotic, on Ionotropic Glutamate Receptors

Changes in ionotropic glutamate (Glu) N-methyl-d-aspartic acid (NMDA), and 2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propionic acid (AMPA) receptors in rat forebrain regions were autoradiographically quantified after continuous infusion of JL 13 [(5-(4-methylpiperazin-1-yl)-8-chloro-pyrido[2,3-b][1,5]benzoxazepine fumarate] for 28 days using osmotic minipumps, and compared to the effects of representative typical (haloperidol) and atypical (clozapine, olanzapine, and risperidone) antipsychotic drugs from previous studies. Similar to other atypical and not typical antipsychotics, JL 13 decreased labeling of NMDA receptors in medial and lateral caudate-putamen (CPu; by 40%). These findings indicate that down-regulation of NMDA receptors by JL 13 and other atypical antipsychotic agents in CPu may contribute to their low risk of extrapyramidal side effects. In addition, and similar to olanzapine and risperidone, JL 13 increased AMPA receptor binding in CPu (by 42%). Changes in AMPA receptors may contribute to psychopharmacological properties of JL 13 and other atypical agents. Similar to clozapine, JL 13 did not alter levels of NMDA and AMPA receptors in hippocampus and entorhinal cortex. Long-term effects of JL 13 on ionotropic Glu receptors, as well as on other dopamine and serotonin receptors, support the atypical antipsychotic profile of this novel agent.

Quetiapine attenuates the depressive and anxiolytic-like behavioural changes induced by global cerebral ischemia in mice

Recently, we have reported that quetiapine, an atypical antipsychotic drug, prevents memory impairment and hippocampus neurodegeneration induced by global cerebral ischemia (GCI). In the present study, we examined the possible effects of quetiapine on other behavioural deficits, including the depressive and anxiolytic-like behavioural consequences of GCI. Mice were treated with quetiapine (5 or 10mg/kg/day; intraperitoneal (i.p.)) for 14 days. On Day 15, the animals were subjected to GCI. GCI resulted in a decrease of striatal tyrosine hydroxylase (TH) immunostaining and induced depressive and anxiolytic-like behavioural changes. The behavioural changes were indicated by a significant increase in the immobility duration in a tail-suspension test, and an increase in the time spent in the light box in a light/dark box test. Pre-administration of quetiapine significantly alleviated the decreased TH immunostaining and attenuated the depressive and anxiolytic-like behavioural changes induced by GCI. These results enhance our understanding about the mechanisms of quetiapine and suggest a wider perspective for the clinical use of quetiapine.

Changes in Proenkephalin mRNA expression in forebrain areas after amphetamine-induced behavioural sensitization

Acute and repeated psychostimulant administration induces a long-lasting enhanced behavioural response to a subsequent drug challenge, known as behavioural sensitization. This phenomenon involves persistent neurophysiological adaptations, which may lead to drug addiction. Brain dopaminergic pathways have been implicated as the main neurobiological substrates of behavioural sensitization, although other neurotransmitters and neuromodulators may also participate. In order to investigate a possible involvement of opioid systems in amphetamine (AMPH) behavioural sensitization, we studied the AMPH-induced changes in Proenkephalin (Pro-Enk) mRNA expression in forebrain areas in both drug-naïve and AMPH-sensitized rats. Male Sprague-Dawley rats were sensitized to AMPH by means of a single AMPH (1 mg/kg s.c.) injection and the same dose was injected 7 days later to assess the expression of sensitization. Pro-Enk mRNA levels were evaluated by in situ hybridization in coronal brain sections. AMPH injection induced an increase in Pro-Enk mRNA expression in the nucleus accumbens and the medial-posterior caudate-putamen in drug-naïve rats. Challenge with AMPH to rats injected 1 week earlier with AMPH induced motor sensitization and increased and decreased Pro-Enk mRNA expression in the prefrontal cortex and the anterior medial caudate-putamen, respectively. Our results suggest that alterations in cortical and striatal enkephalinergic systems could contribute to the expression of AMPH behavioural sensitization.

Basal ganglia volumes in drug-naive first-episode schizophrenia patients before and after short-term treatment with either a typical or an atypical antipsychotic drug

The present study examined basal ganglia volumes in drug-naive first-episode schizophrenic patients before and after treatment with either a specific typical or atypical antipsychotic compound. Sixteen antipsychotic drug-naive and three minimally medicated first-episode schizophrenic patients and 19 matched controls participated. Patients were randomly assigned to treatment with either low doses of the typical antipsychotic drug, zuclopenthixol, or the atypical compound, risperidone. High-resolution magnetic resonance imaging (MRI) scans were obtained in patients before and after 12 weeks of exposure to medication and in controls at baseline. Caudate nucleus, nucleus accumbens, and putamen volumes were measured. Compared with controls, absolute volumes of interest (VOIs) were smaller in patients at baseline and increased after treatment. However, with controls for age, gender and whole brain or intracranial volume, the only significant difference between patients and controls was a Hemisphere x Group interaction for the caudate nucleus at baseline, with controls having larger left than right caudate nuclei and patients having marginally larger right than left caudate volumes. Within patients, the two medication groups did not differ significantly with respect to volume changes after 3 months of low dose treatment in any of the VOIs. Nevertheless, when medication groups were examined separately, a significant volume increase in the putamen was evidenced in the risperidone group. The altered asymmetry in caudate volume in patients suggests intrinsic basal ganglia pathology in schizophrenia, most likely of neurodevelopmental origin.

Toxic influence of subchronic paraquat administration on dopaminergic neurons in rats

Paraquat is a toxin suggested to contribute to pathogenesis of Parkinson's disease. The aim of the present study was to examine toxic influence of subchronic treatment with this pesticide (5 days, one injection per day, 2-3 days of withdrawal) on dopaminergic, serotonergic, noradrenergic and GABAergic neurons. Paraquat decreased the number of tyrosine hydroxylase-immunoreactive (TH-ir) neurons in the substantia nigra by 22% (measured 3 days after withdrawal). Two days after withdrawal the levels of the dopamine metabolites and dopamine turnover in the caudate-putamen, substantia nigra and prefrontal cortex were reduced by ca. 20-60%, and the binding of [(3)H]GBR 12,935 to dopamine transporter dropped by 25-40% in the caudate-putamen. Three days after paraquat withdrawal, the level of dopamine in the caudate-putamen was significantly increased, and earlier decreases in DOPAC and HVA in the substantia nigra, as well as [(3)H]GBR 12,935 binding in the caudate-putamen were reversed. Moreover, an increase in serotonin turnover in the caudate-putamen and prefrontal cortex, and noradrenaline level in the former structure was observed 2-3 days after paraquat withdrawal. Three days after the last paraquat injection 24-35% decreases in the proenkephalin mRNA levels and 5-7% reduction in glutamic acid decarboxylase (GAD)67 mRNA were found in the caudate-putamen. The present study suggests that subchronic paraquat administration triggers processes characteristic of early stages of dopaminergic neuron degeneration, and activates compensatory mechanisms involving dopaminergic, noradrenergic, serotonergic and GABAergic transmissions.