Search

Because [GABA.sub.A] receptors containing [alpha]2 subunits are highly represented in areas of the brain, such as nucleus accumbens (NAcc), frontal cortex, and amygdala, regions intimately involved in signaling motivation and reward, we hypothesized that manipulations of this receptor subtype would influence processing of rewards. Voltage-clamp recordings from NAcc medium spiny neurons of mice with [alpha]2 gene deletion showed reduced synaptic [GABA.sub.A] receptor-mediated responses. Behaviorally, the deletion abolished cocaine's ability to potentiate behaviors conditioned to rewards (conditioned reinforcement), and to support behavioral sensitization. In mice with a point mutation in the benzodiazepine binding pocket of [alpha]2-[GABA.sub.A] receptors ([alpha]2H101R), GABAergic neurotransmission in medium spiny neurons was identical to that of WT (i.e., the mutation was silent), but importantly, receptor function was now facilitated by the atypical benzodiazepine Ro 154513 (ethyl 8-amido-5,6-dihydro-5-methyl-6-oxo-4H-imidazo [1,5-a] [1,4] benzodiazepine-3-carboxylate). In [alpha]2H101R, but not WT mice, Ro 15-4513 administered directly into the NAcc-stimulated Iocomotor activity, and when given systemically and repeatedly, induced behavioral sensitization. These data indicate that activation of [alpha]2-[GABA.sub.A] receptors (most likely in NAcc) is both necessary and sufficient for behavioral sensitization. Consistent with a role of these receptors in addiction, we found specific markers and haplotypes of the GABRA2 gene to be associated with human cocaine addiction. GABRA2 | behavioral sensitization | nucleus accumbens | mutant mouse | human genetics doi/10.1073/pnas.0910117107

Renal facilitative urea transporters play a vital role in the urinary concentrating mechanism. UT-A3 is a phloretin-sensitive urea transporter that in the mouse is expressed on the basolateral membrane of renal inner medullary collecting duct (IMCD) cells. In this study, we engineered a Madin-Darby canine kidney (MDCK) I cell line that stably expresses mouse UT-A3 (MDCK-mUT-A3). Immunoblotting using the UT-A-targeted antibody ML446 detected a ~40kDa signal in MDCK-mUT-A3 protein that corresponds to mUT-A3. Using cultured epithelial monolayers, radioactive [sup.14]C-urea flux experiments determined that basolateral urea transport was no different between MDCK-mUT-A3 and control MDCK-FLZ cells under basal conditions [not significant (NS), ANOVA]. However, exposure to arginine vasopressin (AVP) significantly stimulated basolateral urea flux in MDCK-mUT-A3 monolayers (P < 0.05, ANOVA), while it had no effect in control MDCK-FLZ monolayers (NS, ANOVA). The AVP-stimulated basolateral urea transport in MDCK-mUT-A3 was inhibited by 1,3 dimethyl urea (P < 0.05, ANOVA) or phloretin (P < 0.05, ANOVA), both known inhibitors of facilitative urea transporters. MDCK-mUT-A3 basolateral urea flux was also stimulated by increasing intracellular levels of cAMP, via forskolin (P < 0.05, ANOVA), or intracellular calcium, via ATP (P < 0.05, ANOVA). Finally, 1-h preincubation with a specific PKA inhibitor, H89, significantly inhibited the increase in urea transport produced by AVP (P < 0.05, ANOVA). In conclusion, we have produced the first renal cell line to stably express the roUT-A3 urea transporter. Our results indicate that mUT-A3 is acutely regulated by AVP, via a PKA-dependent pathway. These findings have important implications for the regulation of urea transport in the renal IMCD and the urinary concentrating mechanism. arginine vasopressin; urine concentration; protein kinase A; cAMP; intracellular calcium

Introduction: Although early adopters of telehealth have built and sustained telehealth programs over long periods, little research has been conducted differentiating the characteristics of health systems at different stages of maturation. Methods: This study surveyed 165 major teaching hospitals and health systems from fiscal year 2015 through 2018 about the stage and characteristics of their telehealth services. Respondents reported (i) the progression level of their telehealth program, (ii) which of six services they provide, and (iii) greatest barriers and motivators to implementing telehealth, as well as their overall operational and financial characteristics. Results: Telehealth programs at teaching hospitals progressed steadily and adoption of a wide range of telehealth delivery modes expanded. Hospital operational and financial characteristics corresponding to both higher maturation and the adoption of more delivery modes were identified. Reported barriers and motivations were similar across maturation levels. Discussion: With telehealth's broader use and the heterogeneity of delivery modes being utilized, a binary metric of whether or not to implement telehealth does not sufficiently capture key differences in telehealth programs or differentiate implementation scope and scale across health systems. Conclusions: The findings suggest that programs at different levels of maturation are characteristically different from one another. Identifying factors related to mature telehealth programs may help guide policymakers, future telehealth program leaders, and other stakeholders in identifying barriers to continued investment in telehealth. [ABSTRACT FROM AUTHOR]

Complex carbohydrates serve a wide range of biological functions in cells and tissues, and their biosynthesis involves more than 200 distinct glycosyltransferases (GTfs) in human cells. The kinetic properties, cellular expression patterns and subcellular topology of the GTfs direct the glycosylation capacity of a cell. Most GTfs are ER or Golgi resident enzymes, and their specific subcellular localization is believed to be distributed in the secretory pathway according to their sequential role in the glycosylation process, although detailed knowledge for individual enzymes is still highly fragmented. Progress in quantitative transcriptome and proteome analyses has greatly advanced our understanding of the cellular expression of this class of enzymes, but availability of appropriate antibodies for in situ monitoring of expression and subcellular topology have generally been limited. We have previously used catalytically active GTfs produced as recombinant truncated secreted proteins in insect cells for generation of mouse monoclonal antibodies (mAbs) to human enzymes primarily involved in mucin-type O-glycosylation. These mAbs can be used to probe subcellular topology of active GTfs in cells and tissues as well as their presence in body fluids. Here, we present several new mAbs to human GTfs and provide a summary of our entire collection of mAbs, available to the community. Moreover, we present validation of specificity for many of our mAbs using human cell lines with CRISPR/Cas9 or zinc finger nuclease (ZFN) knockout and knockin of relevant GTfs. [ABSTRACT FROM AUTHOR]

In this study we investigated effects of the APOE ε4 allele (which confers an enhanced risk of poorer cognitive ageing, and Alzheimer’s Disease) on sustained attention (vigilance) performance in young adults using the Rapid Visual Information Processing (RVIP) task and event-related fMRI. Previous fMRI work with this task has used block designs: this study is the first to image an extended (6-minute) RVIP task. Participants were 26 carriers of the APOE ε4 allele, and 26 non carriers (aged 18–28). Pupil diameter was measured throughout, as an index of cognitive effort. We compared activity to RVIP task hits to hits on a control task (with similar visual parameters and response requirements but no working memory load): this contrast showed activity in medial frontal, inferior and superior parietal, temporal and visual cortices, consistent with previous work, demonstrating that meaningful neural data can be extracted from the RVIP task over an extended interval and using an event-related design. Behavioural performance was not affected by genotype; however, a genotype by condition (experimental task/control task) interaction on pupil diameter suggested that ε4 carriers deployed more effort to the experimental compared to the control task. fMRI results showed a condition by genotype interaction in the right hippocampal formation: only ε4 carriers showed downregulation of this region to experimental task hits versus control task hits. Experimental task beta values were correlated against hit rate: parietal correlations were seen in ε4 carriers only, frontal correlations in non-carriers only. The data indicate that, in the absence of behavioural differences, young adult ε4 carriers already show a different linkage between functional brain activity and behaviour, as well as aberrant hippocampal recruitment patterns. This may have relevance for genotype differences in cognitive ageing trajectories. [ABSTRACT FROM AUTHOR]

Variations in genes encoding several GABAA receptors have been associated with human drug and alcohol abuse. Among these, a number of human studies have suggested an association between GABRB1, the gene encoding GABAA receptor β1 subunits, with Alcohol dependence (AD), both on its own and comorbid with other substance dependence and psychiatric illnesses. In the present study, we hypothesized that the GABRB1 genetically-associated increased risk for developing alcoholism may be associated with impaired behavioral control and altered sensitivity to reward, as a consequence of altered brain function. Exploiting the IMAGEN database (Schumann et al., 2010), we explored in a human adolescent population whether possession of the minor (T) variant of the single nucleotide polymorphism (SNP) rs2044081 is associated with performance of tasks measuring aspects of impulsivity, and reward sensitivity that are implicated in drug and alcohol abuse. Allelic variation did not associate with altered performance in either a stop-signal task (SST), measuring one aspect of impulsivity, or a monetary incentive delay (MID) task assessing reward anticipation. However, increased functional magnetic resonance imaging (fMRI) blood-oxygen-level dependent (BOLD) response in the right hemisphere inferior frontal gyrus (IFG), left hemisphere caudate/insula and left hemisphere inferior temporal gyrus (ITG) during MID performance was higher in the minor (T) allelic group. In contrast, during SST performance, the BOLD response found in the right hemisphere supramarginal gyrus, right hemisphere lingual and left hemisphere inferior parietal gyrus indicated reduced responses in the minor genotype. We suggest that β1-containing GABAA receptors may play a role in excitability of brain regions important in controlling reward-related behavior, which may contribute to susceptibility to addictive behavior. [ABSTRACT FROM AUTHOR]

Within the nucleus accumbens (NAc), synaptic GABAA receptors (GABAARs) mediate phasic inhibition of medium spiny neurons (MSNs) and influence behavioral responses to cocaine. We demonstrate that both dopamine D1- and D2-receptor-expressing MSNs (D-MSNs) additionally harbor extrasynaptic GABAARs incorporating α4, β, and δ subunits that mediate tonic inhibition, thereby influencing neuronal excitability. Both the selective δ-GABAAR agonist THIP and DS2, a selective positive allosteric modulator, greatly increased the tonic current of all MSNs from wild-type (WT), but not from δ-/- or α4-/- mice. Coupling dopamine and tonic inhibition, the acute activation of D1 receptors (by a selective agonist or indirectly by amphetamine) greatly enhanced tonic inhibition in D1-MSNs but not D2-MSNs. In contrast, prolonged D2 receptor activation modestly reduced the tonic conductance of D2-MSNs. Behaviorally, WT and constitutive α4-/- mice did not differ in their expression of cocaine-conditioned place preference (CPP). Importantly, however, mice with the α4 deletion specific to D1-expressing neurons (α4D1-/-) showed increased CPP. Furthermore, THIP administered systemically or directly into the NAc of WT, but not α4-/- or α4D1-/- mice, blocked cocaine enhancement of CPP. In comparison, α4D2-/- mice exhibited normal CPP, but no cocaine enhancement. In conclusion, dopamine modulation of GABAergic tonic inhibition of D1- and D2-MSNs provides an intrinsic mechanism to differentially affect their excitability in response to psychostimulants and thereby influence their ability to potentiate conditioned reward. Therefore, α4βδ GABAARs may represent a viable target for the development of novel therapeutics to better understand and influence addictive behaviors. [ABSTRACT FROM AUTHOR]

Nicotine has been shown to speed attentional reorienting in cued target detection tasks, and work in young adults suggest that individuals carrying the apolipoprotein E (APOE) e4 allele might show greater sensitivity to the cognitive effects of nicotine. The APOE e4 allele is associated with increased risk of Alzheimer’s disease (AD), and increased sensitivity to nicotine might reflect early cholinergic differences that relate to an enhanced risk of AD. The aim of this study was to investigate effects of nicotine and APOE on attentional reorienting in mid-age participants. APOE e4 (e4+) were compared to non-APOE e4 (e4–) carriers, and functional magnetic resonance imaging (fMRI) data acquired. Neural data showed that nicotine effects, and the network involved in reorienting, was consistent with studies in young adults. Nicotine improved attentional reorienting at the trend level. Although there were no behavioural effects of genotype, genotype effects were present neurally: e4+ showed decreased extrastriate activation, and enhanced effects of nicotine on reorienting in right middle frontal regions. Drug by genotype interactions were present in hippocampal and anterior cingulate regions. These results are consistent with differential sensitivity to nicotine according to APOE status, possibly reflecting abnormal cholinergic function and accelerated cognitive ageing in mid-age e4+. [ABSTRACT FROM PUBLISHER]

Apolipoprotein E is a protein involved in cholesterol and lipid transport. The gene coding for this protein has three different alleles: e2, e3 and e4. The e4 allele is recognised as a significant risk factor for the development of Alzheimer's disease in later life. Paradoxically, behavioural and functional evidence has demonstrated that the e4 allele may confer a cognitive advantage to the carrier in youth. In this article, a range of sophisticated and novel structural imaging techniques were used to identify subtle differences in the brain tissue of groups of young e4 and homozygous e3 carriers that might support this paradox. Using voxel-based morphometry of high-resolution structural MR images, we identified a higher white matter volume ratio in e4 relative to homozygous e3 carriers. Furthermore, diffusion tensor imaging and tract-based spatial statistics studies identified increases in axial diffusivity and mode of anisotropy in carriers of the e4 allele. In addition, quantitative magnetisation transfer data were analysed using tract-based spatial statistics. Evidence of a trend towards an increased transverse relaxation time of the bound proton pool was detected in e4 carriers, indicative of altered white matter composition. These changes were found to correlate with indices of cognitive performance across the two groups, supporting the notion that such subtle differences in white matter integrity may confer neural advantages that contribute to cognitive outcomes and, potentially, to performance differences, such as observed here in a test of verbal fluency and reported previously by other researchers. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

There is evidence to suggest that the APOE ɛ4 allele (which confers an increased risk of developing dementia) might be associated with cognitive advantages earlier in life. Further, nicotine might selectively benefit ɛ4 carriers. We used fMRI to explore performance on a prospective memory (PM) task in young adults (age 18-30) with and without nicotine using a within-subjects design. Participants performed an ongoing task while retaining a PM instruction to respond to specific stimuli embedded in the task. Nicotine effects varied according to APOE status. Reaction times to the PM cue were improved under nicotine in ɛ4 carriers, but not in ɛ3 carriers. In an event-related analysis, extrastriate responses to PM trials were enhanced by nicotine only in ɛ4 carriers. These differences in early visual processing may contribute to the behavioral findings. Activity in medial BA10 (previously implicated in PM) differentiated ɛ4 from ɛ3 carriers. One BA10 subregion showed greater deactivation in ɛ4 carriers during PM trials. Activity in other BA10 subregions was modulated by PM reaction time, pointing to region-specific effects within medial BA10. In addition, activity in right hippocampal formation was only seen in ɛ4 carriers receiving nicotine. These results demonstrate that cognitive enhancement by nicotine can selectively benefit APOE ɛ4 carriers, and point to genotype-specific differences in neural activity during PM. In addition, these results show that the role of medial BA10 in PM likely involves varying contributions from functionally specific subregions. [ABSTRACT FROM AUTHOR]

Human genetic studies have suggested that polymorphisms of the GABRA2 gene encoding the GABAA α2-subunit are associated with ethanol dependence. Variations in this gene also convey sensitivity to the subjective effects of ethanol, indicating a role in mediating ethanol-related behaviours. We therefore investigated the consequences of deleting the α2-subunit on the ataxic and rewarding properties of ethanol in mice. Ataxic and sedative effects of ethanol were explored in GABAA α2-subunit wildtype (WT) and knockout (KO) mice using a Rotarod apparatus, wire hang and the duration of loss of righting reflex. Following training, KO mice showed shorter latencies to fall than WT littermates under ethanol (2 g/kg i.p.) in both Rotarod and wire hang tests. After administration of ethanol (3.5 g/kg i.p.), KO mice took longer to regain the righting reflex than WT mice. To ensure the acute effects are not due to the gabra2 deletion affecting pharmacokinetics, blood ethanol concentrations were measured at 20 minute intervals after acute administration (2 g/kg i.p.), and did not differ between genotypes. To investigate ethanol's rewarding properties, WT and KO mice were trained to lever press to receive increasing concentrations of ethanol on an FR4 schedule of reinforcement. Both WT and KO mice self-administered ethanol at similar rates, with no differences in the numbers of reinforcers earned. These data indicate a protective role for α2- subunits, against the acute sedative and ataxic effects of ethanol. However, no change was observed in ethanol self administration, suggesting the rewarding effects of ethanol remain unchanged. [ABSTRACT FROM AUTHOR]

Background: Down syndrome (DS) individuals suffer mental retardation with further cognitive decline and early onset Alzheimer's disease. Methodology/Principal Findings: To understand how trisomy 21 causes these neurological abnormalities we investigated changes in gene expression networks combined with a systematic cell lineage analysis of adult neurogenesis using the Ts1Cje mouse model of DS. We demonstrated down regulation of a number of key genes involved in proliferation and cell cycle progression including Mcm7, Brca2, Prim1, Cenpo and Aurka in trisomic neurospheres. We found that trisomy did not affect the number of adult neural stem cells but resulted in reduced numbers of neural progenitors and neuroblasts. Analysis of differentiating adult Ts1Cje neural progenitors showed a severe reduction in numbers of neurons produced with a tendency for less elaborate neurites, whilst the numbers of astrocytes was increased. Conclusions/Significance: We have shown that trisomy affects a number of elements of adult neurogenesis likely to result in a progressive pathogenesis and consequently providing the potential for the development of therapies to slow progression of, or even ameliorate the neuronal deficits suffered by DS individuals. [ABSTRACT FROM AUTHOR]

The potential of putative cognitive-enhancing compounds to improve mental processing both in healthy and vulnerable populations is an area of growing interest to scientific and clinical communities. The possible influence of individual genetic differences on efficacy of these compounds has yet to be considered. We sought to investigate the profile of young-adult apolipoprotein E (APOE) ɛ4 carriers across cognitive domains given that possession of this gene variant increases risk of developing dementia in later life. We also explored whether APOE genotype interacts with the cognitive enhancer, nicotine. A total of 1 mg of the cholinergic agonist nicotine was administered through nasal spray to healthy non-smoking young adults (aged 18–30) with either ɛ3/ɛ3 (N=29) or ɛ4 (at least one ɛ4 allele, N=27) genotype. Participants were matched on age, sex, and IQ in a placebo-controlled, double-blind 2 (drug: placebo, nicotine) × 2 (genotype: ɛ3, ɛ4) between subjects design. Here, we show that, paradoxically, possession of the ɛ4 allele confers a cognitive advantage on tasks mediated by the frontal lobe, and that young carriers of the ɛ4 allele show larger cognitive benefit from procholinergic nicotinic stimulation. These results are the first to show that genetic differences influence the efficacy of a cognitive enhancer. [ABSTRACT FROM AUTHOR]

Because GABAA receptors containing α2 subunits are highly represented in areas of the brain, such as nucleus accumbens (NAcc), frontal cortex, and amygdala, regions intimately involved in signaling motivation and reward, we hypothesized that manipulations of this receptor subtype would influence processing of rewards. Voltageclamp recordings from NAcc medium spiny neurons of mice with α2 gene deletion showed reduced synaptic GABAA receptor-mediated responses. Behaviorally, the deletion abolished cocaine's ability to potentiate behaviors conditioned to rewards (conditioned reinforcement), and to support behavioral sensitization. In mice with a point mutation in the benzodiazepine binding pocket of α2-GABAA receptors (α2H101R), GABAergic neurotransmission in medium spiny neurons was identical to that of WT (i.e., the mutation was silent), but importantly, receptor function was now facilitated by the atypical benzodiazepine Ro 15-4513 (ethyl 8-amido-5,6-dihydro-5-methyl6-oxo-4H-imidazo (1,5-a] [1,4] benzodiazepine-3-carboxylate). In α2H101R, but not WT mice, Ro 15-4513 administered directly into the NAcc-stimulated locomotor activity, and when given systemically and repeatedly, induced behavioral sensitization. These data indicate that activation of α2-GABAA receptors (most likely in NAcc) is both necessary and sufficient for behavioral sensitization. Consistent with a role of these receptors in addiction, we found specific markers and haplotypes of the GABRA2 gene to be associated with human cocaine addiction. [ABSTRACT FROM AUTHOR]

Adult hippocampal neurogenesis declines with age in parallel with decreased performance on a variety of hippocampal-dependent tasks. We measured the rate of cellular proliferation in the hippocampus of mice lacking the β2-subunit of the nicotinic acetylcholine receptor (β2−/− mice) at three ages: young adult (3 months old), fully adult (7-10 months old), and aged (22-24 months old). Consistent with previous studies, we observed an age-related decline in hippocampal proliferation in both groups. However, in fully adult β2−/− mice a 43% reduction of granule cell proliferation was detected compared to age-matched controls. This was accompanied by a significant decrease in dentate gyrus area/section and the length of the granule cell layer in β2−/− mice. These alterations were not the result of a change in plasma corticosterone levels or expression of the neurotrophic factor BDNF in the dentate gyrus, two known regulators of hippocampal cell proliferation. Similarly, there was no increase in gliosis, abnormal myelination, or apoptotic cell death in the β2−/− animals, although there was a significant shift in the location of apoptotic cells in the dentate gyrus indicative of a change in neuronal survival. These results suggest that the β2-subunit containing nicotinic acetylcholine receptors play an important role in regulating cell proliferation in the hippocampus and that endogenous acetylcholine may act to oppose the negative effects of normal aging and stress on cellular proliferation. Synapse 54:200-206, 2004. © 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Presents a study which investigated the role of conditional expression in corticothalamic efferents for nicotinic acetylcholine receptors in modulation of passive avoidance behavior. Materials and methods; Results; Discussion and findings.