Effects of the Chinese Traditional Prescription Xiaoyaosan Decoction on Chronic Immobilization Stress-induced Changes in Behavior and Brain BDNF, TrkB, and NT-3 in Rats

The Xiaoyaosan (XYS) decoction, a Chinese traditional prescription containing eight commonly used herbs, has been used for treatment of mental disorders such as depression for centuries in China. However, the mechanism underlying its antidepressant activity is poorly understood. In rats with chronic immobilization stress (CIS), we examined the effects of the XYS decoction on tail suspension behavior and the levels of brain-derived neurotrophic factor (BDNF), tyroxine hydroxylase (TrkB), and neurotrophin 3 (NT-3) in the frontal cortex and hippocampus. Rats subjected to CIS exhibited decreases in weight-gain, food intake, and ambulation in the open field test; they also showed an increase in immobility in the tail suspension test. These were all attenuated by the XYS decoction. Biochemically, the XYS decoction also reversed CIS-induced decreases in BDNF and increases in TrkB and NT-3 in the frontal cortex and the hippocampal CA(1) subregion. The behavioral effects of the XYS were correlated to the biochemical actions. These results suggest that the XYS decoction produces an antidepressant-like effect, which appears to be involved by BDNF in the brain.

microRNA expression in the prefrontal cortex of individuals with schizophrenia and schizoaffective disorder

Transcriptional profiling reveals a possible association between schizophrenia and altered miRNA expression

Background

microRNAs (miRNAs) are small, noncoding RNA molecules that are now thought to regulate the expression of many mRNAs. They have been implicated in the etiology of a variety of complex diseases, including Tourette's syndrome, Fragile × syndrome, and several types of cancer.

Results

We hypothesized that schizophrenia might be associated with altered miRNA profiles. To investigate this possibility we compared the expression of 264 human miRNAs from postmortem prefrontal cortex tissue of individuals with schizophrenia (n = 13) or schizoaffective disorder (n = 2) to tissue of 21 psychiatrically unaffected individuals using a custom miRNA microarray. Allowing a 5% false discovery rate, we found that 16 miRNAs were differentially expressed in prefrontal cortex of patient subjects, with 15 expressed at lower levels (fold change 0.63 to 0.89) and 1 at a higher level (fold change 1.77) than in the psychiatrically unaffected comparison subjects. The expression levels of 12 selected miRNAs were also determined by quantitative RT-PCR in our lab. For the eight miRNAs distinguished by being expressed at lower microarray levels in schizophrenia samples versus comparison samples, seven were also expressed at lower levels with quantitative RT-PCR.

Conclusion

This study is the first to find altered miRNA profiles in postmortem prefrontal cortex from schizophrenia patients.

Augmented behavioral response and enhanced synaptosomal calcium transport induced by repeated cocaine administration are decreased by calcium channel blockers

Recent studies suggest that calcium influx via L-type calcium channels is necessary for psychostimulant-induced behavioral sensitization. In addition, chronic amphetamine upregulates subtype Cav1.2-containing L-type calcium channels. In the present studies, we assessed the effect of calcium channel blockers (CCBs) on cocaine-induced behavioral sensitization and determined whether the functional activity of L-type calcium channels is altered after repeated cocaine administration. Rats were administered daily intraperitoneal injections of either flunarizine (40 mg/kg), diltiazem (40 mg/kg) or cocaine (20 mg/kg) and the combination of the CCBs and cocaine for 30 days. Motor activities were monitored on Day 1, and every 6th day during the 30-day treatment period. Daily cocaine administration produced increased locomotor activity. Maximal augmentation of behavioral response to repeated cocaine administration was observed on Day 18. Flunarizine pretreatment abolished the augmented behavioral response to repeated cocaine administration while diltiazem was less effective. Measurement of tissue monoamine levels on Day 18 revealed cocaine-induced increases in DA and 5-HT in the nucleus accumbens. By contrast to behavioral response, diltiazem was more effective in attenuating increases in monoamine levels than flunarizine. Cocaine administration for 18 days produced increases in calcium uptake in synaptosomes prepared from the nucleus accumbens and frontal cortex. Increases in calcium uptake were abolished by flunarizine and diltiazem pretreatment. Taken together, the augmented cocaine-induced behavioral response on Day 18 may be due to increased calcium uptake in the nucleus accumbens leading to increased dopamine (DA) and serotonin (5-HT) release. Flunarizine and diltiazem attenuated the behavioral response by decreasing calcium uptake and decreasing neurochemical release.

Quantitative analysis of glutamatergic and GABAergic neurons expressing 5-HT(2A) receptors in human and monkey prefrontal cortex

5-hydroxytryptamine (5-HT) or serotonin 2A receptors play an important role in modulation of prefrontal cortex (PFC) activity and have been implicated in the physiopathology of psychiatric disorders. There is no quantitative information on the percentage of glutamatergic and GABAergic cells that express 5-HT(2A) receptors in human and monkey PFC. We have used double in situ hybridization to quantify the mRNA co-localization of 5-HT(2A) receptor with the glutamatergic transporter vesicular glutamate transporter 1, and with the GABAergic marker glutamic acid decarboxylase 65/67 and in parvalbumin and calbindin GABAergic cell populations. Our results show that nearly every glutamatergic cell (86-100%) in layers II-V expressed 5-HT(2A) receptor mRNA in both species. This percentage was lower in layer VI (13-31%). In contrast, not all the GABAergic interneurons (13-46%) expressed 5-HT(2A) receptor mRNA. This receptor was expressed in 45-69% of parvalbumin and in 61-87% of calbindin positive cells. These results indicate that, while the majority of glutamatergic neurons can be sensitive to 5-HT action via 5-HT(2A) receptors, this modulation occurs only in a limited population of GABAergic interneurons and provides new neuroanatomical information about the role played by serotonin through 5-HT(2A) receptors in the PFC and on the sites of action for drugs such as antipsychotics and antidepressants used in treatment of psychiatric disorders.

Architectonic distribution of the serotonin transporter within the orbitofrontal cortex of the vervet monkey

To elucidate the organization of the serotoninergic innervation within the orbitofrontal cortex (OFC), serotonin transporter (SERT) density was quantified by autoradiography using [(3)H]cyanoimipramine binding. In six adult vervet monkeys, 15 architectonic areas were delineated according to cytoarchitectonic (Nissl), myeloarchitectonic (Gallyas) and chemoarchitectonic (acetylcholinesterase) criteria to assess SERT distribution at two levels of organization: cortical area and cortical type. For cortical type, the 15 areas were evenly divided into three different categories primarily based upon the degree of granularization of layer IV: agranular, dysgranular, and granular. Within agranular and dysgranular, but not granular cortical types, SERT density was area-specific and progressively decreased in a medial to lateral gradient. Across cortical types, SERT density decreased in a caudal to rostral gradient: agranular>dysgranular>granular. A similar caudal to rostral gradient was seen when serotonin content was measured (using high performance liquid chromatography) in areas representative of each cortical type. Collectively, these results suggest that the serotoninergic innervation is organized according to both cortical type and area, and is thus structured to differentially modulate information processing within the OFC.

Glutamatergic ionotropic blockade within accumbens disrupts working memory and might alter the endocytic machinery in rat accumbens and prefrontal cortex

Effects of blocking N-methyl-D-aspartic acid (NMDA) and non-NMDA glutamatergic receptors on performance in the hole board test was studied in male rats bilaterally cannulated into the nucleus accumbens (Acc). Rats, divided into 5 groups, received either 1 microl injections of saline, (+/-) 2-amino-7-phosphonoheptanoic acid (AP-7) (0.5 or 1 microg) or 2,3-dioxo-6-nitro-1,2,3,4,tetrahydrobenzo-(f)quinoxaline-7-sulphonamide disodium (NBQX, 0.5 or 1 microg) 10 min before testing. An increase by AP-7 was observed in ambulatory movements (0.5 microg; p < 0.05), non-ambulatory movements and number of movements (1 microg; p < 0.05); sniffing and total exploration (1 microg; p < 0.01). When holes were considered in order from the first to the fifth by the number of explorations, the most visited holes (first and second) of the AP-7 group were significantly higher than the corresponding holes of saline group (p < 0.05 for 0.5 microg and p < 0.001 for 1 microg). When the second hole was compared with the first of his group, a difference was only observed in the AP-7 1 microg group (p < 0.001). Increasing differences between the other holes and the first were observed by drug treatment. At molecular level, it was observed that AP-7 induced an increase of the coat protein AP-2 expression in Acc, but not AP-180 neither the synaptic protein synaptophysin. The increase of AP-2 was also observed in the medial prefrontal cortex by the action of AP-7 but not NBQX. We conclude that NMDA glutamatergic blockade might induce an activation of the endocytic machinery into the Acc, leading to stereotypies and perseverations, lacking cortical intentional direction.

Activation of prefrontal cortex by transcranial direct current stimulation reduces appetite for risk during ambiguous decision making

As adult humans, we are continuously faced with decisions in which proper weighing of the risk involved is critical. Excessively risky or overly cautious decision making can both have disastrous real-world consequences. Weighing of risks and benefits toward decision making involves a complex neural network that includes the dorsolateral prefrontal cortex (DLPFC), but its role remains unclear. Repetitive transcranial magnetic stimulation studies have shown that disruption of the DLPFC increases risk-taking behavior. Transcranial direct current stimulation (tDCS) allows upregulation of activity in the DLPFC, and we predicted that it might promote more cautious decision making. Healthy participants received one of the following treatments while they performed the Balloon Analog Risk Task: (1) right anodal/left cathodal DLPFC tDCS, (2) left anodal/right cathodal DLPFC tDCS, or (3) sham tDCS. This experiment revealed that participants receiving either one of the bilateral DLPFC tDCS strategies adopted a risk-averse response style. In a control experiment, we tested whether unilateral DLPFC stimulation (anodal tDCS over the right or left DLPFC with the cathodal electrode over the contralateral supraorbital area) was sufficient to decrease risk-taking behaviors. This experiment showed no difference in decision-making behaviors between the groups of unilateral DLPFC stimulation and sham stimulation. These findings extend the notion that DLPFC activity is critical for adaptive decision making, possibly by suppressing riskier responses. Anodal tDCS over DLPFC by itself did not significantly change risk-taking behaviors; however, when the contralateral DLPFC was modulated with cathodal tCDS, an important decrease in risk taking was observed. Also, the induced cautious decision-making behavior was observed only when activity of both DLPFCs was modulated. The ability to modify risk-taking behavior may be translated into therapeutic interventions for disorders such as drug abuse, overeating, or pathological gambling.

Inhibition of evoked glutamate release by neurosteroid allopregnanolone via inhibition of L-type calcium channels in rat medial prefrontal cortex

Allopregnanolone is one of the most important neurosteroids in the brain. We studied the effect and mechanism of allopregnanolone on spontaneous and evoked glutamate release in the medial prefrontal cortex using electrophysiological and biochemical methods combined with pharmacological approaches. The results showed that allopregnanolone had no effects on the frequency of miniature excitatory postsynaptic current (mEPSCs), but inhibited the depolarizing agent veratridine-evoked increase in the frequency of spontaneous excitatory postsynaptic currents (sEPSCs) and inhibited the first of the two responses evoked by a pair of electrical pulses more effectively than the second, resulting in increased paired-pulse facilitation (PPF) and thus suggesting a presynaptic inhibitory effect on electrical pulse-evoked glutamate release. A similar effect was also obtained for the effect of allopregnanolone on protein kinase A (PKA) activation, an upstream event of presynaptic glutamate release. Interestingly, allopregnanolone had none of these effects in the striatum. In the study of the upstream mechanism of the PKA inhibition by allopregnanolone, we found that allopregnanolone inhibited extracellular calcium influx-evoked PKA activation, but had no effects on intracellular calcium store release-evoked PKA activation; L-type calcium channel antagonists, but not N- and P/Q-type calcium channel antagonist, blocked the effect of allopregnanolone; allopregnanolone inhibited L-type calcium channel agonist-evoked increase in the PKA activity, intrasynaptosomal calcium concentration and frequency of sEPSCs. These results suggest that allopregnanolone inhibits evoked glutamate release via the inhibition of L-type calcium channels in the medial prefrontal cortex, but does not in the striatum.

Chronic antidepressant treatment induces contrasting patterns of synaptophysin and PSA-NCAM expression in different regions of the adult rat telencephalon

Structural modifications occur in the brain of severely depressed patients and they can be reversed by antidepressant treatment. Some of these changes do not occur in the same direction in different regions, such as the medial prefrontal cortex, the hippocampus or the amygdala. Differential structural plasticity also occurs in animal models of depression and it is also prevented by antidepressants. In order to know whether chronic fluoxetine treatment induces differential neuronal structural plasticity in rats, we have analyzed the expression of synaptophysin, a protein considered a marker of synaptic density, and the expression of the polysialylated form of the neural cell adhesion molecule (PSA-NCAM), a molecule involved in neurite and synaptic remodeling. Chronic fluoxetine treatment increases synaptophysin and PSA-NCAM expression in the medial prefrontal cortex and decreases them in the amygdala. The expression of these molecules is also affected in the entorhinal, the visual and the somatosensory cortices.

Testing computational models of dopamine and noradrenaline dysfunction in attention deficit/hyperactivity disorder

We test our neurocomputational model of fronto-striatal dopamine (DA) and noradrenaline (NA) function for understanding cognitive and motivational deficits in attention deficit/hyperactivity disorder (ADHD). Our model predicts that low striatal DA levels in ADHD should lead to deficits in 'Go' learning from positive reinforcement, which should be alleviated by stimulant medications, as observed with DA manipulations in other populations. Indeed, while nonmedicated adult ADHD participants were impaired at both positive (Go) and negative (NoGo) reinforcement learning, only the former deficits were ameliorated by medication. We also found evidence for our model's extension of the same striatal DA mechanisms to working memory, via interactions with prefrontal cortex. In a modified AX-continuous performance task, ADHD participants showed reduced sensitivity to working memory contextual information, despite no global performance deficits, and were more susceptible to the influence of distractor stimuli presented during the delay. These effects were reversed with stimulant medications. Moreover, the tendency for medications to improve Go relative to NoGo reinforcement learning was predictive of their improvement in working memory in distracting conditions, suggestive of common DA mechanisms and supporting a unified account of DA function in ADHD. However, other ADHD effects such as erratic trial-to-trial switching and reaction time variability are not accounted for by model DA mechanisms, and are instead consistent with cortical noradrenergic dysfunction and associated computational models. Accordingly, putative NA deficits were correlated with each other and independent of putative DA-related deficits. Taken together, our results demonstrate the usefulness of computational approaches for understanding cognitive deficits in ADHD.

Neurotoxicological effects of a thrombin-like enzyme isolated from Crotalus durissus terrificus venom (preliminary study)

A thrombin-like enzyme, purified from the venom of Crotalus durissus terrificus by gel filtration and affinity chromatography, showed a single protein band in Sodium dodecyl sulfate-polyacrilamide gel electrophoresis (SDS-PAGE) with a molecular weight of about 33kDa. Clear cellular morphological changes, deep ganglioside level modifications in some brain areas and behavioral alterations in pup rats injected with this protein were detected. Ganglioside composition, one of the chemical markers of brain maturation, was altered specially in the hypothalamus, hippocampus and prefrontal cortex. The most reliable behavioral effects were a delayed, maturation of the righting reflex, posture and motor response after treatment. These effects were consistent with the histological changes revealed in the cerebellum and prefrontal cortex of treated neonate rats, areas related to motor activities.

Carnosine ameliorates morphine-induced conditioned place preference in rats

The histidine-containing dipeptide, carnosine (beta-alanyl-L-histidine), is present in high concentrations in mammalian brain of mammals. There are many theories about its biological functions, such as anti-inflammatory agent, free radical scavenger, and protein glycosylation inhibitor, however, the role of carnosine in morphine addiction is less understood. Therefore, the objectives of this study were to determine the effects of carnosine on the development of morphine-induced conditioned place preference (CPP) and investigate its possible mechanism of action in Sprague-Dawley rats. Intraperitioneal (i.p.) injection of carnosine (200, 500, 1000 mg/kg) significantly inhibited the development of morphine-induced CPP in a dose-dependent manner. Although carnosine had no appreciable effect on the levels of histamine in the ventral tegmental area (VTA), nucleus accumbens (NAc) and prefrontal cortex (PFC), it significantly decreased glutamate level in the VTA, dopamine levels in the NAc and PFC, and DOPAC level in the NAc of morphine-treated rats. These results indicate that carnosine inhibits morphine-induced CPP in rats, and its action may be due to modulation of dopaminergic and glutaminergic activity. The study suggests that carnosine has potential as a new anti-addictive drug.

Dopamine modulation of emotional processing in cortical and subcortical neural circuits: evidence for a final common pathway in schizophrenia?

The neural regulation of emotional perception, learning, and memory is essential for normal behavioral and cognitive functioning. Many of the symptoms displayed by individuals with schizophrenia may arise from fundamental disturbances in the ability to accurately process emotionally salient sensory information. The neurotransmitter dopamine (DA) and its ability to modulate neural regions involved in emotional learning, perception, and memory formation has received considerable research attention as a potential final common pathway to account for the aberrant emotional regulation and psychosis present in the schizophrenic syndrome. Evidence from both human neuroimaging studies and animal-based research using neurodevelopmental, behavioral, and electrophysiological techniques have implicated the mesocorticolimbic DA circuit as a crucial system for the encoding and expression of emotionally salient learning and memory formation. While many theories have examined the cortical-subcortical interactions between prefrontal cortical regions and subcortical DA substrates, many questions remain as to how DA may control emotional perception and learning and how disturbances linked to DA abnormalities may underlie the disturbed emotional processing in schizophrenia. Beyond the mesolimbic DA system, increasing evidence points to the amygdala-prefrontal cortical circuit as an important processor of emotionally salient information and how neurodevelopmental perturbances within this circuitry may lead to dysregulation of DAergic modulation of emotional processing and learning along this cortical-subcortical emotional processing circuit.

Amygdala-prefrontal disconnection in borderline personality disorder

Abnormal fronto-amygdala circuitry has been implicated in impulsive aggression, a core symptom of borderline personality disorder (BPD). We examined relative glucose metabolic rate (rGMR) at rest and after m-CPP (meta-chloropiperazine) with (18)fluorodeoxyglucose (FDG) with positron emission tomography (PET) in 26 impulsive aggressive (IED)-BPD patients and 24 controls. Brain edges/amygdala were visually traced on MRI scans co-registered to PET scans; rGMR was obtained for ventral and dorsal regions of the amygdala and Brodmann areas within the prefrontal cortex (PFC). Correlation coefficients were calculated between rGMR for dorsal/ventral amygdala regions and PFC. Additionally, amygdala volumes and rGMR were examined in BPD and controls. Correlations PFC/amygdala Placebo: Controls showed significant positive correlations between right orbitofrontal (OFC) and ventral, but not dorsal, amygdala. Patients showed only weak correlations between amygdala and the anterior PFC, with no distinction between dorsal and ventral amygdala. Correlations PFC/amygdala: m-CPP response: Controls showed positive correlations between OFC and amygdala regions, whereas patients showed positive correlations between dorsolateral PFC and amygdala. Group differences between interregional correlational matrices were highly significant. Amygdala volume/metabolism: No group differences were found for amygdala volume, or metabolism in the placebo condition or in response to meta-chloropiperazine (m-CPP). We demonstrated a tight coupling of metabolic activity between right OFC and ventral amygdala in healthy subjects with dorsoventral differences in amygdala circuitry, not present in IED-BPD. We demonstrated no significant differences in amygdala volumes or metabolism between BPD patients and controls.

In vivo pharmacological characterization of the structurally novel, potent, selective mGlu2/3 receptor agonist LY404039 in animal models of psychiatric disorders

RATIONALE

Data from both preclinical and clinical studies have provided proof of concept that modulation of limbic and forebrain glutamate, via mGlu2/3 receptor agonists, might provide therapeutic benefits in many psychiatric disorders including schizophrenia and anxiety.

OBJECTIVE

The aim of this study was to assess the efficacy of a structurally novel, potent, selective mGlu2/3 receptor agonist with improved bioavailability (LY404039) in animal models predictive of antipsychotic and anxiolytic efficacy.

MATERIALS AND METHODS

LY404039 was assessed in amphetamine- and phencyclidine-induced hyperlocomotion, conditioned avoidance responding, fear-potentiated startle, marble burying, and rotarod behavioral tests. Monoamine release and turnover were assessed using microdialysis and ex vivo tissue levels.

RESULTS

LY404039 attenuated amphetamine- and phencyclidine-induced hyperlocomotion (3-30 and 10 mg/kg, respectively). LY404039 (3-10 mg/kg) inhibited conditioned avoidance responding. LY404039 also reduced fear-potentiated startle in rats (3-30 microg/kg) and marble burying in mice (3-10 mg/kg), indicating anxiolytic-like effects. Importantly, LY404039 did not produce sedative effects or motor impairment as measured by rotarod performance and lack of escape failures in the conditioned avoidance task (at doses up to 30 and 10 mg/kg, respectively). LY404039 (10 mg/kg) also increased dopamine and serotonin release/turnover in the prefrontal cortex.

CONCLUSIONS

These results demonstrate the broad preclinical efficacy of LY404039 across multiple animal models of antipsychotic and anxiolytic efficacy. Additionally, this compound modulates mesocortical neurotransmission and provides a novel mechanism for the treatment of psychiatric disorders that may be associated with improved efficacy and reduced incidence of undesirable side effects. As glutamatergic dysfunction has been linked to the etiology of schizophrenia, clinical studies with more potent mGlu2/3 agonists, such as LY404039, may be useful to explore the validity of this hypothesis.

Positron Emission Tomography Metabolic Correlates of Apathy in Alzheimer Disease

BACKGROUND

Apathy is the most common neuropsychiatric manifestation in Alzheimer disease (AD). Clinical, single-photon emission computed tomography, magnetic resonance imaging, and pathologic studies of apathy in AD have suggested an association with frontal dysfunction, most supportive of anterior cingulate abnormalities, but without a definitive localization.

OBJECTIVE

To examine the association between apathy and cortical metabolic rate on positron emission tomography in AD.

DESIGN

Forty-one subjects with probable AD underwent [(18)F] fluorodeoxyglucose positron emission tomography imaging and neuropsychiatric and cognitive assessments. Global subscale scores from the Scale for the Assessment of Negative Symptoms in Alzheimer Disease were used to designate the absence or presence of clinically meaningful apathy. Whole-brain voxel-based analyses were performed using statistical parametric mapping (SPM2; Wellcome Department of Imaging Neuroscience, London, England), which yielded significance maps comparing the 2 groups.

RESULTS

Twenty-seven (66%) subjects did not have apathy, whereas 14 (34%) had apathy. Statistical parametric mapping analysis revealed significant reduced activity in the bilateral anterior cingulate region extending inferiorly to the medial orbitofrontal region (P < .001) and the bilateral medial thalamus (P = .04) in subjects with apathy. The results of the statistical parametric mapping analysis remained the same after individually covarying for the effects of global cognitive impairment, depressed mood, and education.

CONCLUSIONS

Apathy in AD is associated with reduced metabolic activity in the bilateral anterior cingulate gyrus and medial orbitofrontal cortex and may be associated with reduced activity in the medial thalamus. These results reinforce the confluence of evidence from other investigational modalities in implicating medial frontal dysfunction and related neuronal circuits in the neurobiology of apathy in AD and other neuropsychiatric diseases.

AC260584 (4-[3-(4-butylpiperidin-1-yl)-propyl]-7-fluoro-4H-benzo[1,4]oxazin-3-one), a selective muscarinic M1 receptor agonist, increases acetylcholine and dopamine release in rat medial prefrontal cortex and hippocampus

Both muscarinic and nicotinic receptors are implicated in cognition. We have previously suggested that stimulation of the muscarinic M1 receptor has a beneficial effect on cognition, based upon evidence that the muscarinic M1 receptor agonist of N-desmethylclozapine, the major metabolite of clozapine, may contribute to the ability of clozapine to improve some domains of cognition in schizophrenia. Present study examined the effectiveness of a new muscarinic M1 receptor agonist, 4-[3-(4-butylpiperidin-1-yl)-propyl]-7-fluoro-4H-benzo[1,4]oxazin-3-one (AC260584), to increase the release of acetylcholine and dopamine in the rat medial prefrontal cortex and hippocampus. Using microdialysis in awake, freely moving rats, AC260584, 3 and 10, but not 1 mg/kg (s.c.), significantly increased dopamine release in the medial prefrontal cortex and hippocampus. However, only the high dose of AC260584, 10 mg/kg (s.c.), significantly increased acetylcholine release in these regions. Moreover, the increases in acetylcholine release produced by AC260584, 10 mg/kg, were attenuated by the muscarinic M1 receptor antagonist telenzepine (3 mg/kg, s.c.) but not by the 5-HT1A receptor antagonist N-[2-(4-2-methoxyphenyl)-1-piperazinyl]-N-(2-pyridyl) cyclohexanecarboxamide (WAY100635, 0.2 mg/kg, s.c.). However, the increase in dopamine release produced by 10 mg/kg AC260584 was blocked by both telenzepine and WAY100635. In addition, pretreatment with the atypical antipsychotic drug risperidone (0.1 mg/kg, s.c.) potentiated AC260584 (1.0 mg/kg, s.c.)-induced acetylcholine and dopamine release in the medial prefrontal cortex. These findings suggest that the muscarinic M1 receptor agonist property of AC260584 contributes to its enhancement of cortical acetylcholine and dopamine efflux. Therefore, AC260584, as well as other muscarinic M1 receptor agonists, may be a valuable target for the development of drugs which can improve the cognitive deficits in schizophrenia and perhaps other neuropsychiatric disorders, as well.

Effects of acute and repeated restraint stress on endocannabinoid content in the amygdala, ventral striatum, and medial prefrontal cortex in mice

Endocannabinoid signaling has been implicated in habituation to repeated stress. The hypothesis that repeated exposures to stress alters endocannabinoid signaling in the limbic circuit was tested by restraining male mice for 30 min/day for 1, 7, or 10 days and measuring brain endocannabinoid content. Amygdalar N-arachidonylethanolamine was decreased after 1, 7, and 10 restraint episodes; 2-arachidonylglycerol was increased after the 10th restraint. A similar pattern occurred in the medial prefrontal cortex (mPFC): N-arachidonylethanolamine was decreased after the 7th and 10th restraints and 2-arachidonylglycerol was increased after the 10th restraint. In the ventral striatum, the pattern reversed: N-arachidonylethanolamine was increased after the 10th restraint and 2-arachidonylglycerol was decreased after the 7th restraint. Palmitoylethanolamide contents changed in parallel with N-arachidonylethanolamine in the amygdala and ventral striatum. A single restraint episode did not affect the activity of fatty acid amide hydrolase (FAAH) in any of the brain regions examined. After the 10th restraint, both V(max) and K(m) for N-arachidonylethanolamine were increased in the mPFC; while only the V(max) was increased in the amygdala. On the other hand, the V(max) of FAAH was decreased in ventral striatum after the 10th restraint. After the 10th restraint, the maximum velocity for 2-oleoylglycerol hydrolysis was increased in mPFC; no other changes in 2-oleoylglycerol hydrolysis occurred. Repeated exposure to restraint produced no changes in CB(1) receptor density in any of the areas examined. These studies are consistent with the hypothesis that stress exposure alters endocannabinoid signaling in the brain and that alterations in endocannabinoid signaling occur during habituation to stress.

Age-related declines in a two-day reference memory task are associated with changes in NMDA receptor subunits in mice

Background

C57BL/6 mice show a relationship during aging between NMDA receptor expression and spatial reference memory performance in a 12-day task. The present study was designed to determine if age-related deficits could be detected with a shorter testing protocol and whether these deficits showed a relationship with NMDA receptors. Mice were trained in a reference memory task for two days in a Morris water maze. Cued testing was performed either after or prior to reference memory testing. Crude synaptosomes were prepared from prefrontal/frontal cortex and hippocampus of the mice that underwent reference memory testing first. NMDA receptor subunit and syntaxin proteins were analyzed with Western blotting.

Results

Young mice showed significant improvement in probe and place learning when reference memory testing was done prior to cued testing. A significant decrease in performance was seen between 3 and 26 months of age with the two-day reference task, regardless of whether cued testing was performed before or after reference memory testing. There was a significant decline in the protein expression of the ε2 and ζ1 subunits of the NMDA receptor and syntaxin in prefrontal/frontal cortex. The subunit changes showed a significant correlation with both place and probe trial performance.

Conclusion

The presence of an age-related decline in performance of the reference memory task regardless of when the cued trials were performed suggests that the deficits were due to factors that were unique to the spatial reference memory task. These results also suggest that declines in specific NMDA receptor subunits in the synaptic pool of prefrontal/frontal brain regions contributed to these age-related problems with performing a spatial reference memory task.

Prefrontal cortex dysfunction and depression in atypical parkinsonian syndromes

Depressive symptoms are common in patients with neurodegenerative disorders. Imaging studies suggest that a disruption of frontal-subcortical pathways may underlie depression associated with basal ganglia disease. This pilot study tested the hypothesis that frontal dysfunction contributes to depression associated with multiple system atrophy (MSA) and progressive supranuclear palsy (PSP). Depressed patients with MSA (n = 11), PSP (n = 9), and age-matched controls (n = 25) underwent measures of cerebral glucose metabolism applying positron emission tomography with (18)F-fluorodeoxyglucose. Regional metabolism in the patient groups was compared to the normal subjects using the voxel-based statistical parametric mapping. Depressive symptom severity (Hamilton Depression Rating) and degree of locomotor disability (Hoehn & Yahr) were assessed in the patient groups. The association between prefrontal metabolism and the occurrence of depressive symptoms and the degree of locomotor disability was investigated. When compared to controls, MSA patients revealed significant metabolic decreases in bilateral frontal, parietal, and cerebellar cortex and in the left putamen. In PSP patients, significant hypometabolism was demonstrated in bilateral frontal cortex, right thalamus, and midbrain. Depression severity but not the patients' functional condition was significantly associated with dorsolateral prefrontal glucose metabolism in both patient groups. The findings of this pilot study support the hypothesis that depressive symptoms in MSA and PSP are associated with prefrontal dysfunction.

Antidepressant effects of high and low frequency repetitive transcranial magnetic stimulation to the dorsolateral prefrontal cortex: a double-blind, randomized, placebo-controlled trial

Repetitive transcranial magnetic stimulation (rTMS) has antidepressant effects in patients with major depressive disorder. The mechanisms of action and optimal stimulation parameters remain unclear. To test the hypothesis that rTMS exerts antidepressant effects either by enhancing left dorsolateral prefrontal cortex (DLPFC) excitability or by decreasing right DLPFC excitability, the authors studied 45 patients with unipolar recurrent major depressive disorder in a double-blind, randomized, parallel group, sham-controlled trial. Patients were randomized to receive 1 Hz or 10 Hz rTMS to the left DLPFC, 1 Hz to the right DLPFC or sham TMS. Left 10 Hz and right 1 Hz rTMS showed similar significant antidepressant effects. Other parameters led to no significant antidepressant effects.

Hypofunctional glutamatergic neurotransmission in the prefrontal cortex is involved in the emotional deficit induced by repeated treatment with phencyclidine in mice: Implications for abnormalities of glutamate release and NMDA–CaMKII signaling

In the present study, we investigated the involvement of prefrontal glutamatergic neurotransmission in the enhancement of immobility (emotional deficit) in a forced swimming test in mice treated with phencyclidine (PCP: 10mg/kg/day for 14 days) repeatedly, which is regarded as an animal model for negative symptoms. A decrease in spontaneous extracellular glutamate release and increase in levels of the glutamate transporter GLAST, were observed in the prefrontal cortex (PFC) of PCP-treated mice, compared to saline-treated mice. NMDA receptor subunit 1 (NR1) and Ca(2+)/calmoduline kinase II (CaMKII) were markedly activated in the PFC of saline-treated mice, but not PCP-treated mice, immediately after the forced swimming test. The facilitation of the function of NMDA receptors by d-cycloserine (30mg/kg i.p.), an NMDA receptor glycine-site partial agonist, reversed the enhancement of immobility in the forced swimming test and impairment of CaMKII activation in the PCP-treated mice. Microinjection of dl-threo-beta-benzyloxyaspartate (10nmol/site/bilaterally), a potent blocker of glutamate transporters, into the PFC of PCP-treated mice also had an attenuating effect. In addition, activation of glial cells and a decrease of neuronal cell size were observed in the PFC of PCP-treated mice. These results suggest that repeated PCP treatment disrupts pre- and post-synaptic glutamatergic neurotransmission and induces morphological changes in the PFC and that such changes cause the emotional deficits exhibited in PCP-treated mice.

Time dependent decreases in central alpha7 nicotinic acetylcholine receptors associated with haloperidol and risperidone treatment in rats

Alpha(7) nicotinic acetylcholine receptor deficits may contribute to cognitive dysfunction in schizophrenia; however, the contribution of antipsychotic drug exposure to these deficits is unknown. In this study, rats were treated orally with haloperidol (2.0 mg/kg/day) or risperidone (2.5 mg/kg/day) for 15 or 90 days. Subsequent immunoassays indicated that both antipsychotics were associated with alpha(7) nicotinic receptor decreases in the basal forebrain and prefrontal cortex when administered for 90 (but not 15) days, a result that was confirmed in autoradiographic experiments. These data suggest that haloperidol and risperidone may be associated with time dependent decreases in an important neurobiological substrate of memory.

Electroconvulsive shock treatment differentially modulates cortical and subcortical endocannabinoid activity

Previous studies indicate that the endocannabinoid system is a potential target for the treatment of depression. To further examine this question we assessed the effects of electroconvulsive shock (ECS) treatment, both a single session and 10 daily sessions, on endocannabinoid content, CB(1) receptor binding parameters and CB(1) receptor-mediated [(35)S]GTPgammaS binding in the prefrontal cortex, hippocampus, hypothalamus and amygdala. A single ECS session resulted in a general reduction in the binding affinity of the CB(1) receptor in all brain regions examined, as well as reductions in N-arachidonylethanolamine (anandamide) content in the prefrontal cortex and the hippocampus, reduced hydrolysis of anandamide by fatty acid amide hydrolase (FAAH) in the prefrontal cortex and an increase in the binding site density of the CB(1) receptor in the amygdala. Following 10 ECS sessions, all these effects subsided except for the reductions in anandamide content in the prefrontal cortex, which increased in magnitude, as well as the reductions in FAAH activity in the prefrontal cortex. Additionally, repeated ECS treatment resulted in a significant reduction in the binding site density of the CB(1) receptor in the prefrontal cortex, but did not alter CB(1) receptor-mediated [(35)S]GTPgammaS binding. Repeated ECS treatment also significantly enhanced the sensitivity of CB(1) receptor-mediated [(35)S]GTPgammaS binding in the amygdala. Collectively, these data demonstrate that ECS treatment results in a down-regulation of cortical and an up-regulation of subcortical endocannabinoid activity, illustrating the possibility that the role of the endocannabinoid system in affective illness may be both complex and regionally specific.

Prenatal alcohol exposure affects frontal-striatal BOLD response during inhibitory control

BACKGROUND

Prenatal alcohol exposure can lead to widespread cognitive impairment and behavioral dysregulation, including deficits in attention and response inhibition. This study characterized the neural substrates underlying the disinhibited behavioral profile of individuals with fetal alcohol spectrum disorders (FASD).

METHODS

Children and adolescents (ages 8-18) with (n=13) and without (n=9) histories of heavy prenatal alcohol exposure underwent functional magnetic resonance imaging while performing a response inhibition (go/no-go) task.

RESULTS

Despite similar task performance (mean response latency, performance accuracy, and signal detection), blood oxygen level-dependent (BOLD) response patterns differed by group. Region-of-interest analyses revealed that during portions of the behavioral task that required response inhibition, alcohol-exposed participants showed greater BOLD response across prefrontal cortical regions (including the left medial and right middle frontal gyri), while they showed less right caudate nucleus activation, compared with control participants.

CONCLUSIONS

These data provide an account of response inhibition-related brain functioning in youth with FASD. Furthermore, results suggest that the frontal-striatal circuitry thought to mediate inhibitory control is sensitive to alcohol teratogenesis.