Availability of dopamine transporters in heroin-dependent subjects: A 18F-FECNT PET imaging study

This study was to reconfirm the reduced dopamine transporter (DAT) availability in heroin-dependent subjects and validate the use of 2β-carbomethoxy-3β-(4-chlorophenyl)-8-(2-fluoroethyl)-nortropane (¹⁸F-FECNT) as a PET radiotracer to assess the changes of striatal DAT in drug addicted subjects. Herein, we assessed DAT standardized uptake values (SUV) of ¹⁸F-FECNT in the striatum and cerebellum of 20 heroin-dependent subjects and 10 healthy controls and analyzed the correlation between DAT availability and heroin withdrawal symptom scores and anxiety/depression rating scales in heroin-dependent subjects, as well as the relationship between the withdrawal symptoms scores and age. The striatal DAT availability in heroin-dependent subjects was significantly lower (by ~15.7-17.6%) than that in healthy controls. Age was positively related to heroin withdrawal symptom scores. The withdrawal symptom scores in older patients (Age: 49.5±2.5) were significantly higher (by ~20%) than those in younger patients (Age: 30.9±4.8). These results confirm that chronic heroin use induces striatal DAT reduction, suggesting that ¹⁸F-FECNT could be used as an alternative PET imaging radioligand for in vivo imaging of DAT in drug addicted subjects. Moreover, older patients might suffer more severe withdrawal symptoms than younger patients, suggesting that older patients with heroin withdrawal could be given more medication.

Brain neurotransmitters in an animal model with postpartum depressive-like behavior

Post-Partum Depression (PPD) occurs in 15% of pregnancies and its patho-physiology is not known. We studied female BALB/c ("depressive") and C57BL/6 (control) mice as a model for PPD and assessed their behavior and correlates with brain neurotransmitters (NTs) - norepinephrine, dopamine, serotonin and intermediates, during the pre-pregnancy (PREP), pregnancy (PREG) and post-partum (PP) periods. Depressive-like behavior was evaluated by the Open Field (OFT), Tail Suspension (TST) and Forced Swim (FST) tests. Neurotransmitters (NTs) were determined in the striatum (care-giving), hippocampus (cognitive function) and hypothalamus (maternal care & eating behavior). In the BALB/c mice, while their performance in all behavioral tests was significantly reduced during pregnancy and P-P indicative of the development of depressive-like responses, no changes were observed in the C57BL/6 mice. Changes in NTs in BALB/C were as follows: PREP, all NTs in the three brain areas were decreased, although an increase in dopamine release was observed in the hippocampus. PREG: No changes were observed in the NTs except for a decrease in 5-HT in the striatum. P-P: striatum, low 5-HT, NE and dopamine; Hippocampus: low 5-HT, NE and high Dopamine; hypothalamus: all NTs increased, especially NE. Following pregnancy and delivery, the BALB/c mice developed depressive-like behavior associated with a significant decrease in 5-HT, dopamine and NE in the striatum and 5-HT and NE in the hippocampus. Dopamine increased in the latter together with a significant increase in all NTs in the hypothalamus. These findings suggest that the development of PPD may be associated with NT changes. Normalization of these alterations may have a role in the treatment of PPD.

Corticotropin-releasing hormone and dopamine release in healthy individuals

Corticotropin-releasing hormone (CRH) is a key component of the neuroendocrine response to stress. In animal models, CRH has been shown to modulate dopamine release, and this interaction is believed to contribute to stress-induced relapse in neuropsychiatric disorders. Here we investigated whether CRH administration induces dopamine release in humans, using positron emission tomography (PET). Eight healthy volunteers (5 female, 22-48 years old) completed two PET scans with the dopamine D_2/3 receptor radioligand [¹¹C]-(+)-PHNO: once after saline injection, and once after injection of corticorelin (synthetic human CRH). We also assessed subjective reports and measured plasma levels of endocrine hormones (adrenocorticotropic hormone and cortisol). Relative to saline, corticorelin administration decreased binding of the D_2/3 PET probe [¹¹C]-(+)-PHNO, suggesting dopamine release. Endocrine stress markers were also elevated, in line with activation of the hypothalamic-pituitary-adrenal axis, but we detected no changes in subjective ratings. Preliminary results from this proof-of-concept study suggests that CRH challenge in combination with [¹¹C]-(+)-PHNO PET may serve as an assay of dopamine release, presenting a potential platform for evaluating CRH/dopamine interactions in neuropsychiatric disorders and CRH antagonists as potential treatment avenues.

Manganese and the Insulin-IGF Signaling Network in Huntington's Disease and Other Neurodegenerative Disorders

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease resulting in motor impairment and death in patients. Recently, several studies have demonstrated insulin or insulin-like growth factor (IGF) treatment in models of HD, resulting in potent amelioration of HD phenotypes via modulation of the PI3K/AKT/mTOR pathways. Administration of IGF and insulin can rescue microtubule transport, metabolic function, and autophagy defects, resulting in clearance of Huntingtin (HTT) aggregates, restoration of mitochondrial function, amelioration of motor abnormalities, and enhanced survival. Manganese (Mn) is an essential metal to all biological systems but, in excess, can be toxic. Interestingly, several studies have revealed the insulin-mimetic effects of Mn-demonstrating Mn can activate several of the same metabolic kinases and increase peripheral and neuronal insulin and IGF-1 levels in rodent models. Separate studies have shown mouse and human striatal neuroprogenitor cell (NPC) models exhibit a deficit in cellular Mn uptake, indicative of a Mn deficiency. Furthermore, evidence from the literature reveals a striking overlap between cellular consequences of Mn deficiency (i.e., impaired function of Mn-dependent enzymes) and known HD endophenotypes including excitotoxicity, increased reactive oxygen species (ROS) accumulation, and decreased mitochondrial function. Here we review published evidence supporting a hypothesis that (1) the potent effect of IGF or insulin treatment on HD models, (2) the insulin-mimetic effects of Mn, and (3) the newly discovered Mn-dependent perturbations in HD may all be functionally related. Together, this review will present the intriguing possibility that intricate regulatory cross-talk exists between Mn biology and/or toxicology and the insulin/IGF signaling pathways which may be deeply connected to HD pathology and, perhaps, other neurodegenerative diseases (NDDs) and other neuropathological conditions.

Loss of Pink1 modulates synaptic mitochondrial bioenergetics in the rat striatum prior to motor symptoms: concomitant complex I respiratory defects and increased complex II-mediated respiration

PURPOSE

Mutations in PTEN-induced putative kinase 1 (Pink1), a mitochondrial serine/threonine kinase, cause a recessive inherited form of Parkinson's disease (PD). Pink1 deletion in rats results in a progressive PD-like phenotype, characterized by significant motor deficits starting at 4 months of age. Despite the evidence of mitochondrial dysfunction, the pathogenic mechanism underlying disease due to Pink1-deficiency remains obscure.

EXPERIMENTAL DESIGN

Striatal synaptic mitochondria from 3-month-old Pink1-deficient rats were characterized using bioenergetic and mass spectroscopy (MS)-based proteomic analyses.

RESULTS

Striatal synaptic mitochondria from Pink1-deficient rats exhibit decreased complex I-driven respiration and increased complex II-mediated respiration compared with wild-type rats. MS-based proteomics revealed 69 of the 811 quantified mitochondrial proteins were differentially expressed between Pink1-deficient rats and controls. Down-regulation of several electron carrier proteins, which shuttle electrons to reduce ubiquinone at complex III, in the Pink1-knockouts suggests disruption of the linkage between fatty acid, amino acid, and choline metabolism and the mitochondrial respiratory system.

CONCLUSIONS AND CLINICAL RELEVANCE

These results suggest that complex II activity is increased to compensate for loss of electron transfer mechanisms due to reduced complex I activity and loss of electron carriers within striatal nerve terminals early during disease progression. This may contribute to the pathogenesis of PD.

Salience attribution and its relationship to cannabis-induced psychotic symptoms

BACKGROUND

Cannabis is a widely used drug associated with increased risk for psychosis. The dopamine hypothesis of psychosis postulates that altered salience processing leads to psychosis. We therefore tested the hypothesis that cannabis users exhibit aberrant salience and explored the relationship between aberrant salience and dopamine synthesis capacity.

METHOD

We tested 17 cannabis users and 17 age- and sex-matched non-user controls using the Salience Attribution Test, a probabilistic reward-learning task. Within users, cannabis-induced psychotic symptoms were measured with the Psychotomimetic States Inventory. Dopamine synthesis capacity, indexed as the influx rate constant K i cer , was measured in 10 users and six controls with 3,4-dihydroxy-6-[18F]fluoro-l-phenylalanine positron emission tomography.

RESULTS

There was no significant difference in aberrant salience between the groups [F 1,32 = 1.12, p = 0.30 (implicit); F 1,32 = 1.09, p = 0.30 (explicit)]. Within users there was a significant positive relationship between cannabis-induced psychotic symptom severity and explicit aberrant salience scores (r = 0.61, p = 0.04) and there was a significant association between cannabis dependency/abuse status and high implicit aberrant salience scores (F 1,15 = 5.8, p = 0.03). Within controls, implicit aberrant salience was inversely correlated with whole striatal dopamine synthesis capacity (r = -0.91, p = 0.01), whereas this relationship was non-significant within users (difference between correlations: Z = -2.05, p = 0.04).

CONCLUSIONS

Aberrant salience is positively associated with cannabis-induced psychotic symptom severity, but is not seen in cannabis users overall. This is consistent with the hypothesis that the link between cannabis use and psychosis involves alterations in salience processing. Longitudinal studies are needed to determine whether these cognitive abnormalities are pre-existing or caused by long-term cannabis use.

ASIC1a Deficient Mice Show Unaltered Neurodegeneration in the Subacute MPTP Model of Parkinson Disease

Inflammation contributes to the death of dopaminergic neurons in Parkinson disease and can be accompanied by acidification of extracellular pH, which may activate acid-sensing ion channels (ASIC). Accordingly, amiloride, a non-selective inhibitor of ASIC, was protective in an acute 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) mouse model of Parkinson disease. To complement these findings we determined MPTP toxicity in mice deficient for ASIC1a, the most common ASIC isoform in neurons. MPTP was applied i.p. in doses of 30 mg per kg on five consecutive days. We determined the number of dopaminergic neurons in the substantia nigra, assayed by stereological counting 14 days after the last MPTP injection, the number of Nissl positive neurons in the substantia nigra, and the concentration of catecholamines in the striatum. There was no difference between ASIC1a-deficient mice and wildtype controls. We are therefore not able to confirm that ASIC1a are involved in MPTP toxicity. The difference might relate to the subacute MPTP model we used, which more closely resembles the pathogenesis of Parkinson disease, or to further targets of amiloride.

GABAρ selective antagonist TPMPA partially inhibits GABA-mediated currents recorded from neurones and astrocytes in mouse striatum

The neostriatum plays a central role in motor coordination where nerve cells operate neuronal inhibition through GABAergic transmission. The neostriatum expresses a wide range of GABA-A subunits, including GABAρ1 and ρ2 which are restricted to a fraction of GABAergic interneurons and astrocytes. Spontaneous postsynaptic currents (sPSCs) evoked by 4-aminopyridine (4-AP) were recorded from neurones of the dorsal neostriatum, and their frequency was reduced > 50% by the selective GABAρ antagonist (1,2,5,6-Tetrahydropyridine-4-yl) methylphosphinic acid (TPMPA). Additionally, we recorded GABA evoked currents from astrocytes in vitro and in situ. Astrocytes in vitro showed modulation by pentobarbital and desensitization upon consecutive applications of GABA. However, modulation by pentobarbital was absent and no significant desensitization was detected from astrocytes in situ. Moreover, TPMPA-sensitive GABA-currents that were insensitive to bicuculline were also recorded from astrocytes in situ, consistent with our previous study where GABAρ expression was demonstrated. Finally, we assessed the mRNA expression of GABAρ3, through different stages of postnatal development; double immunofluorescence disclosed GABAρ3 expression in calretinin-positive interneurons as well as in astrocytes (>70%). These results add new information about the participation of GABAρ subunits in neostriatal interneurons and astrocytes.

Increased susceptibility of G-protein coupled receptor 6 deficient mice to MPTP neurotoxicity

The G-protein coupled receptor 6 (GPR6) is a constitutive active orphan GPCR which is predominantly expressed in striatopallidal neurons. GPR6 deficiency in mice may alter the susceptibility of the nigrostriatal dopaminergic system relevant for Parkinson's disease (PD). Here, we investigated the effect of GPR6 deficiency in mice on neurotoxicity induced by the dopaminergic neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine). GPR6^-/-- and control mice were treated with MPTP (4×12.5mg/kg, i.p., 2h intervals) and analyzed after seven days. Striatal dopamine (DA), 3,4-dihydroxyphenylacetic acid (DOPAC) and 4-hydroxy-3-methoxyphenylacetic acid (HVA) concentrations were measured by HPLC. The number of tyrosine hydroxylase (TH)-positive neurons in the substantia nigra pars compacta (SNpc) was analyzed by immunohistochemistry. In a separate group of mice, MPP⁺ (500μM for 20min) was administered via an intrastriatal microdialysis probe to measure the MPP⁺-induced DA release. MPTP produced a significant reduction in striatal DA, DOPAC, HVA and an increase in dopamine turnover in control and GPR6^-/--mice. The MPTP-induced DA and HVA depletion was significantly more pronounced in GPR6^-/--mice. Consistently, the MPTP-induced reduction of TH-positive neurons in the SPpc was significantly higher in GPR6^-/--mice. Furthermore, the MPP⁺-induced dopamine release was significantly higher in GPR6^-/--mice. In conclusion, we showed that MPTP induces an enhanced dopaminergic neurodegeneration in GPR6^-/--mice indicated by alterations at the striatal and nigral level. We propose that GPR6 signaling is involved in the cascade of neurodegenerative events of the parkinsonian neurotoxin MPTP and suggest that pharmacological modulation of GPR6 might represent an entry point to further investigate GPR6 in PD.

Contingent and non-contingent recreational-like exposure to ethanol alters BDNF expression and signaling in the cortico-accumbal network differently

RATIONALE

Although brain-derived neurotrophic factor (BDNF) is part of a homeostatic pathway involved in the development of alcohol dependence, it is not clear whether this is also true after recreational ethanol consumption.

OBJECTIVES

We examined BDNF expression and signaling in the cortico-striatal network immediately and 24 h after either a single intravenous (i.v.) ethanol operant self-administration session or the last of 14 sessions.

METHODS

To compare contingent and non-contingent ethanol exposure, we incorporated the "yoked control-operant paradigm" in which rats actively taking ethanol (S-Et) were paired with two yoked controls receiving passive infusions of ethanol (Y-Et) or saline.

RESULTS

A single ethanol exposure transiently reduced BDNF mRNA levels in the medial prefrontal cortex (mPFC) of Y-Et. Immediately after the last of 14 sessions, mRNA and mature BDNF protein levels (mBDNF) were reduced in the mPFC in both S-Et and Y-Et while mBDNF expression was raised in the nucleus accumbens (NAc), suggesting enhanced anterograde transport from the mPFC. Conversely, 24 h later mBDNF expression and signaling were raised in the mPFC and NAc of S-Et rats but reduced in the NAc of Y-Et rats, with concomitant reduction of downstream signaling pathways.

CONCLUSIONS

Our findings indicate that recreational-like i.v. doses of ethanol promote early changes in neurotrophin expression, depending on the length and modality of administration, the brain region investigated, and the presence of the drug. A rapid intervention targeting the BDNF system might be useful to prevent escalation to alcohol abuse.

Striatal Dopamine Depletion Patterns and Early Non-Motor Burden in Parkinsons Disease

Background

The mechanism underlying non-motor symptoms in Parkinson’s disease has not yet been elucidated. In this study, we hypothesized that Parkinson patients with more non-motor symptoms have a different pattern of striatal dopamine depletion, particularly in areas other than the sensorimotor striatum, compared to those with fewer non-motor symptoms.

Methods

We conducted a prospective survey of the degree of non-motor symptoms (using the Korean version of the Non-Motor Symptoms Scale; K-NMSS) in 151 patients with early-stage Parkinson’s disease who had undergone a dopamine transporter PET scan as an initial diagnostic procedure. We classified the patients into two groups; high non-motor patients (HNM-PD; K-NMSS score ≥ 41) and low non-motor patients (LNM-PD).

Results

Patients in the HNM-PD group (n = 71) were older, had longer symptom duration, exhibited more severe motor deficits, and had been prescribed higher levodopa-equivalent doses at follow-up than those in the LNM-PD group. However, dopamine transporter binding to the striatal sub-regions and inter-sub-regional binding ratios were comparable between the two groups. A general linear model showed that the HNM-PD group had significantly more severe motor deficits than the LNM-PD group after controlling for age, gender, symptom duration, and dopamine transporter binding to the sensorimotor striatum.

Conclusions

This study demonstrated that the pattern of striatal dopamine depletion does not contribute to early non-motor burden in Parkinson’s disease. Our results suggest that LNM-PD patients may have a more benign course of motor symptom progression than HNM-PD patients.

Regulation of striatal astrocytic receptor for advanced glycation end-products variants in an early stage of experimental Parkinson's disease

Convincing evidence indicates that advanced glycation end-products and danger-associated protein S100B play a role in Parkinson's disease (PD). These agents operate through the receptor for advanced glycation end-products (RAGE), which displays distinct isoforms playing protective/deleterious effects. However, the nature of RAGE variants has been overlooked in PD studies. Hence, we attempted to characterize RAGE regulation in early stages of PD striatal pathology. A neurotoxin-based rodent model of PD was used in this study, through administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) to C57BL/6 mice. Animals were killed 6 h post-MPTP to assess S100B/RAGE contents (RT-qPCR, ELISA) and RAGE isoform density (WB) and cellular distribution (immunohistochemistry). Dopaminergic and gliotic status were also mapped (HPLC-ED, WB, immunohistochemistry). At this preliminary stage of MPTP-induced PD in mice, RAGE inhibitory isoforms were increased whereas full-length RAGE was not affected. This putative cytoprotective RAGE phenotype paired an inflammatory and pro-oxidant setting fueling DAergic denervation. Increased RAGE inhibitory variants occur in astrocytes showing higher S100B density but no overt signs of hypertrophy or NF-κB activation, a canonical effector of RAGE. These findings expand our understanding of the toxic effect of MPTP on striatum and offer first in vivo evidence of RAGE being a responder in early stages of astrogliosis dynamics, supporting a protective rather tissue-destructive phenotype of RAGE in the initial phase of PD degeneration. These data lay the groundwork for future studies on the relevance of astrocytic RAGE in DAergic neuroprotection strategies. We report increased antagonistic RAGE variants paralleling S100B up-regulation in early stages of MPTP-induced astrogliosis dynamics . We propose that selective RAGE regulation reflects a self-protective mechanism to maintain low levels of RAGE ligands , preventing long-term inflammation and oxidative stress arising from sustained ligands/flRAGE activation . Understanding loss of RAGE protective response to stress may provide new therapeutic options to halt or slow down dopaminergic axonopathy and, ultimately, neuronal death .

Highlights from the 2016 Schizophrenia International Research Society Conference, April 2-6, 2016

The 2016 Schizophrenia International Research Society (SIRS) Conference, held in Florence, Italy, attracted approximately 1,800 attendees from over 54 countries to the stately Firenze Fiera Conference Center from April 2-6, 2016. Providing plenary sessions, special sessions, symposia, workshops, oral presentations and poster presentations, this 5th Biennial SIRS Conference focused on "Deconstructing Schizophrenia towards Targeted Treatment." In conjunction with the Schizophrenia Research Forum, a Web project of the Brain and Behavior Research Foundation, and with our thanks to the SIRS organizers and staff, we bring you the following selected highlights.

Association between cerebral cannabinoid 1 receptor availability and body mass index in patients with food intake disorders and healthy subjects: a [(18)F]MK-9470 PET study

Although of great public health relevance, the mechanisms underlying disordered eating behavior and body weight regulation remain insufficiently understood. Compelling preclinical evidence corroborates a critical role of the endocannabinoid system (ECS) in the central regulation of appetite and food intake. However, in vivo human evidence on ECS functioning in brain circuits involved in food intake regulation as well as its relationship with body weight is lacking, both in health and disease. Here, we measured cannabinoid 1 receptor (CB1R) availability using positron emission tomography (PET) with [(18)F]MK-9470 in 54 patients with food intake disorders (FID) covering a wide body mass index (BMI) range (anorexia nervosa, bulimia nervosa, functional dyspepsia with weight loss and obesity; BMI range=12.5-40.6 kg/m(2)) and 26 age-, gender- and average BMI-matched healthy subjects (BMI range=18.5-26.6 kg/m(2)). The association between regional CB1R availability and BMI was assessed within predefined homeostatic and reward-related regions of interest using voxel-based linear regression analyses. CB1R availability was inversely associated with BMI in homeostatic brain regions such as the hypothalamus and brainstem areas in both patients with FID and healthy subjects. However, in FID patients, CB1R availability was also negatively correlated with BMI throughout the mesolimbic reward system (midbrain, striatum, insula, amygdala and orbitofrontal cortex), which constitutes the key circuit implicated in processing appetitive motivation and hedonic value of perceived food rewards. Our results indicate that the cerebral homeostatic CB1R system is inextricably linked to BMI, with additional involvement of reward areas under conditions of disordered body weight.

Report: Protective effects of rice bran oil in haloperidol-induced tardive dyskinesia and serotonergic responses in rats

Effect of administration of Rice bran oil (RBO) was evaluated on haloperidol elicited tardive dyskinesia in rats. Albino Wistar rats treated with haloperidol in drinking water at a dose of 0.2mg/kg/day and RBO by oral tubes at a dose of 0.4 mL/day for 5 weeks. Motor coordination, VCMs and 8-hydroxy-2-(di-n-propylamino) tetraline)[8-OH-DPAT] _syndrome were monitored. Striatal serotonin (5-hydroxytryptamine; 5-HT) and 5-hydroxyindolacetic acid (5-HIAA) levels were determined by high performance liquid chromatography (HPLC-EC). Rats treated with haloperidol orally at a dose of for a period of 5 weeks developed VCMs, which increased progressively as the treatment continued for 5 weeks. Motor coordination impairment started after the 1st week and was maximally impaired after 3 weeks and gradually returned to the 1st week value. Co-administration of RBO prevented haloperidol_induced VCMs as well impairment of motor coordination. The intensity of 8-OH-DPAT_induced syndrome and decreased 5-HT metabolism were greater in water + haloperidol treated animals than RBO + haloperidol treated animals. The present study suggested that involvement of free radical in the development of TD and point to RBO as a possible therapeutic option to treat this hyperkinetic motor disorder.

Structural and molecular myelination deficits occur prior to neuronal loss in the YAC128 and BACHD models of Huntington disease

White matter (WM) atrophy is a significant feature of Huntington disease (HD), although its aetiology and early pathological manifestations remain poorly defined. In this study, we aimed to characterize WM-related features in the transgenic YAC128 and BACHD models of HD. Using diffusion tensor magnetic resonance imaging (DT-MRI), we demonstrate that microstructural WM abnormalities occur from an early age in YAC128 mice. Similarly, electron microscopy analysis of myelinated fibres of the corpus callosum indicated that myelin sheaths are thinner in YAC128 mice as early as 1.5 months of age, well before any neuronal loss can be detected. Transcript levels of myelin-related genes in striatal and cortical tissues were significantly lower in YAC128 mice from 2 weeks of age, and these findings were replicated in differentiated primary oligodendrocytes from YAC128 mice, suggesting a possible mechanistic explanation for the observed structural deficits. Concordant with these observations, we demonstrate reduced expression of myelin-related genes at 3 months of age and WM microstructural abnormalities using DT-MRI at 12 months of age in the BACHD rats. These findings indicate that WM deficits in HD are an early phenotype associated with cell-intrinsic effects of mutant huntingtin on myelin-related transcripts in oligodendrocytes, and raise the possibility that WM abnormalities may be an early contributing factor to the pathogenesis of HD.

Bacopa monnieri (Brahmi) Prevents Cognitive Deficit by Maintaining CA2/3 VGLUT1 Density of Sub-Chronic Phencyclidine Rat Model of Schizophrenia in Normal Level

BACKGROUND

Decreased vesicular glutamate transporter type 1 (VGLUT1) has been reported in the brains of both postmortem and animal models of schizophrenia. It indicates the deficit of glutamatergic function which is implicated in the cognitive deficit in schizophrenia. Our previous study investigated that Brahmi can recover the cognitive deficit in schizophrenia by upregulating cerebral VGLUT1 density. However, the neuroprotective effects of Brahmi have not been studied yet.

OBJECTIVE

To study the effects of Brahmi on the prevention of cognitive deficit and cerebral VGLUT1 density in sub-chronic phencyclidine (PCP) rat model of schizophrenia.

MATERIAL AND METHOD

Rats were assigned to three groups; Group-A: Control, Group-B: PCP administration and Group- C: Brahmi + PCP. Cognitive ability was represented by the Discrimination ratio (DR) calculated from novel object recognition test. VGLUT1 optical density was measured in prefrontal cortex, striatum, cornu ammonis fields 1 (CA1) and 2/3 (CA2/3) and dentate gyrus (DG) of the hippocampus using immunohistochemistry.

RESULTS

DR in PCP group was significantly decreased compared with control. This occurred alongside significantly reduced VGLUT1 in prefrontal cortex and CA2/3. Brahmi + PCP group showed a significant increase in DR score compared with PCP alone; however, it was still lower than control. This occurred alongside significant increase in VGLUT1 in CA2/3.

CONCLUSION

Cognitive deficit observed in PCP-administered rats was mediated by VGLUT1 reduction in prefrontal cortex and CA2/3. Interestingly, Brahmi could prevent this cognitive deficit by maintaining VGLUT1 density in CA2/3 in normal level.

Dopamine efflux in response to ultraviolet radiation in addicted sunbed users

Compulsive tanning despite awareness of ultraviolet radiation (UVR) carcinogenicity may represent an "addictive" behavior. Many addictive disorders are associated with alterations in dopamine (D2/D3) receptor binding and dopamine reactivity in the brain's reward pathway. To determine if compulsive tanners exhibited neurobiologic responses similar to other addictive disorders, this study assessed basal striatal D2/D3 binding and UVR-induced striatal dopamine efflux in ten addicted and ten infrequent tanners. In a double-blind crossover trial, UVR or sham UVR was administered in separate sessions during brain imaging with single photon emission computerized tomography (SPECT). Basal D2/D3 receptor density and UVR-induced dopamine efflux in the caudate were assessed using (123)I-iodobenzamide ((123)I-IBZM) binding potential non-displaceable (BPnd). Basal BPnd did not significantly differ between addicted and infrequent tanners. Whereas neither UVR nor sham UVR induced significant changes in bilateral caudate BPnd in either group, post-hoc analyses revealed left caudate BPnd significantly decreased (reflecting increased dopamine efflux) in the addicted tanners - but not the infrequent tanners - during the UVR session only. Bilateral ∆BPnd correlated with tanning severity only in the addicted tanners. These preliminary findings are consistent with a stronger neural rewarding response to UVR in addicted tanners, supporting a cutaneous-neural connection driving excessive sunbed use.

Potential Transfer of Polyglutamine and CAG-Repeat RNA in Extracellular Vesicles in Huntington's Disease: Background and Evaluation in Cell Culture

In Huntington's disease (HD) the imperfect expanded CAG repeat in the first exon of the HTT gene leads to the generation of a polyglutamine (polyQ) protein, which has some neuronal toxicity, potentially mollified by formation of aggregates. Accumulated research, reviewed here, implicates both the polyQ protein and the expanded repeat RNA in causing toxicity leading to neurodegeneration in HD. Different theories have emerged as to how the neurodegeneration spreads throughout the brain, with one possibility being the transport of toxic protein and RNA in extracellular vesicles (EVs). Most cell types in the brain release EVs and these have been shown to contain neurodegenerative proteins in the case of prion protein and amyloid-beta peptide. In this study, we used a model culture system with an overexpression of HTT-exon 1 polyQ-GFP constructs in human 293T cells and found that the EVs did incorporate both the polyQ-GFP protein and expanded repeat RNA. Striatal mouse neural cells were able to take up these EVs with a consequent increase in the green fluorescent protein (GFP) and polyQ-GFP RNAs, but with no evidence of uptake of polyQ-GFP protein or any apparent toxicity, at least over a relatively short period of exposure. A differentiated striatal cell line expressing endogenous levels of Hdh mRNA containing the expanded repeat incorporated more of this mRNA into EVs as compared to similar cells expressing this mRNA with a normal repeat length. These findings support the potential of EVs to deliver toxic expanded trinucleotide repeat RNAs from one cell to another, but further work will be needed to evaluate potential EV and cell-type specificity of transfer and effects of long-term exposure. It seems likely that expanded HD-associated repeat RNA may appear in biofluids and may have use as biomarkers of disease state and response to therapy.

Prolonged Induction of miR-212/132 and REST Expression in Rat Striatum Following Cocaine Self-Administration

Chronic exposure to cocaine in vivo induces long-term synaptic plasticity associated with the brain’s circuitry that underlies development of repetitive and automatic behaviors called habits. In fact, prolonged drug consumption results in aberrant expression of protein-coding genes and small regulatory RNAs, including miRNAs that are involved in synaptic plasticity and neuroadaptations. However, the mechanisms mediating cocaine use disorder are still not fully understood. The present study is designed to examine the expression of miR-124, miR-132, miR-134, and miR-212, as well as the levels of the Ago2, Pum2, and REST mRNAs and proteins implicated in their regulation. We applied rat cocaine self-administration (SA) and extinction training procedures with a yoked triad to assess the changes in the levels of four miRNAs and three protein-coding genes and corresponding proteins in the dorsal striatum. We demonstrated that elevated expression of mature miR-212 and miR-132 is long-lasting and persists in the drug-free period (till 10-day abstinence). Moreover, mRNA and protein of REST, a regulator of neuronal transcription, was raised selectively in cocaine self-administering rats and Ago2 transcript decreased after cocaine treatment. Unexpectedly, the expression level of Ago2 and Pum2 proteins changed only in the active cocaine-receiving animals. These results point out the important aspects of long-lasting alterations in microRNAs, genes, and protein expressions involved in the control of synaptic plasticity associated with reward and motivation learning related to cocaine addiction.

Memory enhancement by Tamoxifen on amyloidosis mouse model

Tamoxifen (TMX) is a selective estrogen receptor modulator (SERM) used in the treatment of breast cancer. Earlier studies show its neuroprotection via regulating apoptosis, microglial functions, and synaptic plasticity. TMX also showed memory enhancement in ovariectomized mice, and protection from amyloid induced damage in hippocampal cell line. These reports encouraged us to explore the role of TMX in relevance to Alzheimer's disease (AD). We report here, the effect of TMX treatment a) on memory, and b) levels of neurotransmitters (acetylcholine (ACh) and dopamine (DA)) in breeding-retired-female mice injected with beta amyloid1-42 (Aβ1-42). Mice were treated with TMX (10mg/kg, i.p.) for 15 days. In Morris water maze test, the TMX treated mice escape latency decreased during training trials. They also spent longer time in the platform quadrant on probe trial, compared to controls. In Passive avoidance test, TMX treated mice avoided stepping on the shock chamber. This suggests that TMX protects memory from Aβ induced toxicity. In frontal cortex, ACh was moderately increased, with TMX treatment. In striatum, dopamine was significantly increased, 3,4-dihydroxyphenylacetic acid (DOPAC) level and DOPAC/DA ratio was decreased post TMX treatment. Therefore, TMX enhances spatial and contextual memory by reducing dopamine metabolism and increasing ACh level in Aβ1-42 injected-breeding-retired-female mice.

IGF-1 protects dopamine neurons against oxidative stress: association with changes in phosphokinases

Insulin-like growth factor-1 (IGF-1) is an endogenous peptide transported across the blood brain barrier that is protective in several brain injury models, including an acute animal model of Parkinson's disease (PD). Motor deficits in PD are due largely to the progressive loss of nigrostriatal dopaminergic neurons. Thus, we examined the neuroprotective potential of IGF-1 in a progressive model of dopamine deficiency in which 6-hydroxydopamine (6-OHDA) is infused into the striatum. Rats received intrastriatal IGF-1 (5 or 50 µg) 6 h prior to infusion of 4 µg 6-OHDA into the same site and were euthanized 1 or 4 weeks later. Both concentrations of IGF-1 protected tyrosine hydroxylase (TH) immunoreactive terminals in striatum at 4 weeks but not at 1 week, indicating that IGF-induced restoration of the dopaminergic phenotype occurred over several weeks. TH-immunoreactive cell loss was only attenuated with 50 µg IGF-1. We then examined the effect of striatal IGF-1 on the Ras/ERK1/2 and PI3K/Akt pathways to ascertain whether their activation correlated with IGF-1-induced protection. Striatal and nigral levels of phospho-ERK1/2 were maximal 6 h after IGF-1 infusion and, with the exception of an increase in nigral pERK2 at 48 h, returned to basal levels by 7 days. Phospho-Akt (Ser473) was elevated 6-24 h post-IGF-1 infusion in both striatum and substantia nigra concomitant with inhibition of pro-death GSK-3β, a downstream target of Akt. These results suggest that IGF-1 can protect the nigrostriatal pathway in a progressive PD model and that this protection is preceded by activation of key pro-survival signaling cascades.

Comparison of Human Primary with Human iPS Cell-Derived Dopaminergic Neuron Grafts in the Rat Model for Parkinson's Disease

Neuronal degeneration within the substantia nigra and the loss of the dopaminergic nigro-striatal pathway are the major hallmarks of Parkinson's disease (PD). Grafts of foetal ventral mesencephalic (VM) dopaminergic (DA) neurons into the striatum have been shown to be able to restore striatal dopamine levels and to improve overall PD symptoms. However, human foetus-derived cell grafts are not feasible for clinical application. Autologous induced pluripotent stem cell (iPS cell)-derived DA neurons are emerging as an unprecedented alternative. In this review, we summarize and compare the efficacy of human iPS cell-derived DA neuron grafts to restore normal behaviour in a rat model for PD with that of human foetal primary DA neurons. The differences we observed in the efficacy to restore normal function between the 2 types of DA neuron grafts could be ascribed to intrinsic properties of the iPS cell-derived DA neurons that critically affected survival and proper neurite extension in the striatum after implantation.

Effect of cocaine on striatal dopamine clearance in a rat model of developmental stress and attention-deficit/hyperactivity disorder

Attention-deficit/hyperactivity disorder (ADHD) and developmental stress are considered risk factors for the development of drug abuse. Though the physiological mechanisms underlying this risk are not yet clear, ADHD, developmental stress and drug abuse are known to share underlying disturbances in dopaminergic neurotransmission. Thus, we hypothesized that clearance of cocaine-induced elevations in striatal dopamine would be prolonged in a rat model of ADHD and that this would be further increased by exposure to developmental stress. In the current study, male spontaneously hypertensive rats (SHRs), a well-validated model of ADHD, and control Wistar-Kyoto (WKY) rats were exposed to either standard rearing (nMS) or a maternal separation (MS) paradigm involving removal of the pups from the dam for 180 min/day over 13 days. This produced a 2 × 2 factorial design (SHR/WKY × nMS/MS) with 5-6 rats/group. Striatal clearance of exogenously applied dopamine was measured via in vivo chronoamperometry, and the difference in dopamine uptake parameters before and after cocaine administration was compared between experimental groups. Cocaine, a potent dopamine transporter inhibitor, reliably increased the clearance time of dopamine though no difference in this parameter was found between SHR and WKY strains. However, developmental stress elevated the cocaine-induced increase in time to clear 50% of exogenously applied dopamine (T50) in SHR but had no effect in WKY rats. These findings suggest that a strain × environment interaction prolongs elevated levels of dopamine thereby potentially increasing the rewarding properties of this drug in SHR.

Methylation QTLs in the developing brain and their enrichment in schizophrenia risk loci

We characterized DNA methylation quantitative trait loci (mQTLs) in a large collection (n = 166) of human fetal brain samples spanning 56-166 d post-conception, identifying >16,000 fetal brain mQTLs. Fetal brain mQTLs were primarily cis-acting, enriched in regulatory chromatin domains and transcription factor binding sites, and showed substantial overlap with genetic variants that were also associated with gene expression in the brain. Using tissue from three distinct regions of the adult brain (prefrontal cortex, striatum and cerebellum), we found that most fetal brain mQTLs were developmentally stable, although a subset was characterized by fetal-specific effects. Fetal brain mQTLs were enriched amongst risk loci identified in a recent large-scale genome-wide association study (GWAS) of schizophrenia, a severe psychiatric disorder with a hypothesized neurodevelopmental component. Finally, we found that mQTLs can be used to refine GWAS loci through the identification of discrete sites of variable fetal brain methylation associated with schizophrenia risk variants.