Health state utilities associated with weight loss in type 2 diabetes and obesity.

INTRODUCTION: Health state utilities associated with weight change are needed as inputs for cost-utility analyses (CUAs) examining the value of treatments for obesity and type 2 diabetes (T2D). Although some pharmaceutical treatments currently in development are associated with substantial weight loss, little is known about the utility impact of weight decreases greater than 10%. The purpose of this study was to estimate utilities associated with body weight decreases up to 20% based on preferences of individuals with obesity, with and without T2D. METHODS: Health state vignettes were developed to represent respondents' own current weight and weight decreases of 2.5, 5, 10, 15, and 20%. Health state utilities were elicited in time trade-off interviews in two UK locations (Edinburgh and London) with a sample of participants with obesity, with and without T2D. Mean utility increases associated with each amount of weight decrease were calculated. Regression analyses were performed to derive a method for estimating utility change associated with weight decreases. RESULTS: Analyses were conducted with data from 405 individuals with obesity (202 with T2D, 203 without T2D). Utility increases associated with various levels of weight decrease ranged from 0.011 to 0.060 in the subgroup with T2D and 0.015 to 0.077 in the subgroup without T2D. All regression models found that the percentage of weight decrease was a highly significant predictor of change in utility (p < .0001). The relationship between weight change and utility change did not appear to be linear. Equations are recommended for estimating utility change based on the natural logarithm of percentage of weight decrease. DISCUSSION: Results of this study may be used to provide inputs for CUAs examining and comparing the value of treatments that are associated with substantial amounts of weight loss in patients with obesity, with or without T2D.

Assessing patient PREFERence between the dulaglutide pen and the semaglutide pen: A crossover study (PREFER).

AIM: When selecting treatments for type 2 diabetes (T2D), it is important to consider not only efficacy and safety, but also other treatment attributes that have an impact on patient preference. The objective of this study was to examine preference between injection devices used for two weekly GLP-1 receptor agonists. MATERIALS AND METHODS: The PREFER study was an open-label, multicentre, randomized, crossover study assessing patient preference for dulaglutide and semaglutide injection devices among injection-naïve patients receiving oral medication for type 2 diabetes. After being trained to use each device, participants performed all steps of injection preparation and administered mock injections into an injection pad. Time-to-train (TTT) for each device was assessed in a subset. RESULTS: There were 310 evaluable participants (48.4% female; mean age, 60.0 years; 78 participants in the TTT subgroup). More participants preferred the dulaglutide device than the semaglutide device (84.2% vs. 12.3%; P < 0.0001). More participants perceived the dulaglutide device to have greater ease of use (86.8% vs. 6.8%; P < 0.0001). After preparing and using the devices, more participants were willing to use the dulaglutide device (93.5%) than the semaglutide device (45.8%). Training participants to use the dulaglutide device required less time than the semaglutide device (3.38 vs. 8.14 minutes; P < 0.0001). CONCLUSIONS: Participants with type 2 diabetes preferred the dulaglutide injection device to the semaglutide injection device. If patients prefer a device, they may be more willing to use the medication, which could result in better health outcomes. Furthermore, a shorter training time for injection devices may be helpful in busy clinical practice settings.

Location and Cell-Type-Specific Bias of Metabotropic Glutamate Receptor, mGlu5, Negative Allosteric Modulators.

Emerging data indicate that G-protein coupled receptor (GPCR) signaling is determined by not only the agonist and a given receptor but also a variety of cell-type-specific factors that can influence a receptor's response. For example, the metabotropic glutamate receptor, mGlu5, which is implicated in a number of neuropsychiatric disorders such as depression, anxiety, and autism, also signals from inside the cell which leads to sustained Ca2+ mobilization versus rapid transient responses. Because mGlu5 is an important drug target, many negative allosteric modulators (NAMs) have been generated to modulate its activity. Here we show that NAMs such as AFQ056, AZD2066, and RG7090 elicit very different end points when tested in postnatal neuronal cultures expressing endogenous mGlu5 receptors. For example, AFQ056 fails to block intracellular mGlu5-mediated Ca2+ increases whereas RG7090 is very effective. These differences are not due to differential receptor levels, since about the same number of mGlu5 receptors are present on neurons from the cortex, hippocampus, and striatum based on pharmacological, biochemical, and molecular data. Moreover, biotinylation studies reveal that more than 90% of the receptor is intracellular in these neurons. Taken together, these data indicate that the tested NAMs exhibit both location-dependent and cell type specific bias for mGlu5-mediated Ca2+ mobilization which may affect clinical outcomes.

Can CAPTURE be used to identify undiagnosed patients with mild-to-moderate COPD likely to benefit from treatment?

Background: COPD Assessment in Primary Care To Identify Undiagnosed Respiratory Disease and Exacerbation Risk (CAPTURE™) uses five questions and peak expiratory flow (PEF) thresholds (males ≤350 L/min; females ≤250 L/min) to identify patients with a forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC) <0.70 and FEV1 <60% predicted or exacerbation risk requiring further evaluation for COPD. This study tested CAPTURE's ability to identify symptomatic patients with mild-to-moderate COPD (FEV1 60%-80% predicted) who may also benefit from diagnosis and treatment. Methods: Data from the CAPTURE development study were used to test its sensitivity (SN) and specificity (SP) differentiating mild-to-moderate COPD (n=73) from no COPD (n=87). SN and SP for differentiating all COPD cases (mild to severe; n=259) from those without COPD (n=87) were also estimated. The modified Medical Research Council (mMRC) dyspnea scale and COPD Assessment Test (CAT™) were used to evaluate symptoms and health status. Clinical Trial Registration: NCT01880177, https://ClinicalTrials.gov/ct2/show/NCT01880177?term=NCT01880177&rank=1. Results: Mean age (+SD): 61 (+10.5) years; 41% male. COPD: FEV1/FVC=0.60 (+0.1), FEV1% predicted=74% (+12.4). SN and SP for differentiating mild-to-moderate and non-COPD patients (n=160): Questionnaire: 83.6%, 67.8%; PEF (≤450 L/min; ≤350 L/min): 83.6%, 66.7%; CAPTURE (Questionnaire+PEF): 71.2%, 83.9%. COPD patients whose CAPTURE results suggested that diagnostic evaluation was warranted (n=52) were more likely to be symptomatic than patients whose results did not (n=21) (mMRC >2: 37% vs 5%, p<0.01; CAT>10: 86% vs 57%, p<0.01). CAPTURE differentiated COPD from no COPD (n=346): SN: 88.0%, SP: 83.9%. Conclusion: CAPTURE (450/350) may be useful for identifying symptomatic patients with mild-to-moderate airflow obstruction in need of diagnostic evaluation for COPD.

Intracellular GPCRs Play Key Roles in Synaptic Plasticity.

The trillions of synaptic connections within the human brain are shaped by experience and neuronal activity, both of which underlie synaptic plasticity and ultimately learning and memory. G protein-coupled receptors (GPCRs) play key roles in synaptic plasticity by strengthening or weakening synapses and/or shaping dendritic spines. While most studies of synaptic plasticity have focused on cell surface receptors and their downstream signaling partners, emerging data point to a critical new role for the very same receptors to signal from inside the cell. Intracellular receptors have been localized to the nucleus, endoplasmic reticulum, lysosome, and mitochondria. From these intracellular positions, such receptors may couple to different signaling systems, display unique desensitization patterns, and/or show distinct patterns of subcellular distribution. Intracellular GPCRs can be activated at the cell surface, endocytosed, and transported to an intracellular site or simply activated in situ by de novo ligand synthesis, diffusion of permeable ligands, or active transport of non-permeable ligands. Current findings reinforce the notion that intracellular GPCRs play a dynamic role in synaptic plasticity and learning and memory. As new intracellular GPCR roles are defined, the need to selectively tailor agonists and/or antagonists to both intracellular and cell surface receptors may lead to the development of more effective therapeutic tools.

GPCR signalling from within the cell.

Traditionally, signal transduction from GPCRs is thought to emanate from the cell surface where receptor interactions with external stimuli can be transformed into a broad range of cellular responses. However, emergent data show that numerous GPCRs are also associated with various intracellular membranes where they may couple to different signalling systems, display unique desensitization patterns and/or exhibit distinct patterns of subcellular distribution. Although many GPCRs can be activated at the cell surface and subsequently endocytosed and transported to a unique intracellular site, other intracellular GPCRs can be activated in situ either via de novo ligand synthesis, diffusion of permeable ligands or active transport of nonpermeable ligands. Current findings reinforce the notion that intracellular GPCRs play a dynamic role in various biological functions including learning and memory, contractility and angiogenesis. As new intracellular GPCR roles are defined, the need to selectively tailor agonists and/or antagonists to both intracellular and cell surface receptors may lead to the development of more effective therapeutic tools. LINKED ARTICLES: This article is part of a themed section on Molecular Pharmacology of GPCRs. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v175.21/issuetoc.

How Well Does CAPTURE Translate?: An Exploratory Analysis of a COPD Case-Finding Method for Spanish-Speaking Patients.

BACKGROUND: This study tested the properties of a Spanish translation of CAPTURE (COPD Assessment in Primary Care To Identify Undiagnosed Respiratory Disease and Exacerbation Risk) with selective use of peak expiratory flow (PEF). METHODS: This study comprised analyses of data from the Spanish-speaking cohort of the cross-sectional, case-control study used to develop CAPTURE. Translation procedures included forward and backward translation, reconciliation, and cognitive interviewing to assure linguistic and cultural equivalence, yielding CAPTURE-S. Spanish-speaking participants were recruited through one center and designated as case subjects (clinically significant COPD: FEV1 ≤ 60% predicted and/or at risk of COPD exacerbation) or control subjects (no or mild COPD). Subjects completed a questionnaire booklet that included 44 candidate items, the COPD Assessment Test (CAT), and the modified Medical Research Council (mMRC) dyspnea question. PEF and spirometry were also performed. RESULTS: The study included 30 participants (17 case subjects and 13 control subjects). Their mean (± SD) age was 62.6 (11.49) years, and 33% were male. CAPTURE-S scores were significantly correlated with PEF (r = -0.78), the FEV1/FVC ratio (r = -0.74), FEV1 (r = -0.69), FEV1 % predicted (r = -0.69), the CAT score (r = 0.70), and the mMRC dyspnea question (r = 0.59) (P < .0001), with significantly higher scores in case subjects than in control subjects (t = 6.16; P < .0001). PEF significantly correlated with FEV1 (r = 0.89), FEV1 % predicted (r = 0.79), and the FEV1/FVC ratio (r = 0.75) (P < .0001), with significantly lower PEF in case subjects than in control subjects (t = 5.08; P < .0001). CAPTURE-S score + PEF differentiated case subjects and control subjects with a sensitivity of 88.2% and a specificity of 92.3%. CONCLUSIONS: CAPTURE-S with selective use of PEF seems to be useful for identifying Spanish-speaking patients in need of diagnostic evaluation for clinically significant COPD who may benefit from initiation of COPD treatment. TRIAL REGISTRY: ClinicalTrials.gov; No.: NCT01880177; URL: www.clinicaltrials.gov.

Sequences within the C Terminus of the Metabotropic Glutamate Receptor 5 (mGluR5) Are Responsible for Inner Nuclear Membrane Localization.

Traditionally, G-protein-coupled receptors (GPCR) are thought to be located on the cell surface where they transmit extracellular signals to the cytoplasm. However, recent studies indicate that some GPCRs are also localized to various subcellular compartments such as the nucleus where they appear required for various biological functions. For example, the metabotropic glutamate receptor 5 (mGluR5) is concentrated at the inner nuclear membrane (INM) where it mediates Ca2+ changes in the nucleoplasm by coupling with Gq/11 Here, we identified a region within the C-terminal domain (amino acids 852-876) that is necessary and sufficient for INM localization of the receptor. Because these sequences do not correspond to known nuclear localization signal motifs, they represent a new motif for INM trafficking. mGluR5 is also trafficked to the plasma membrane where it undergoes re-cycling/degradation in a separate receptor pool, one that does not interact with the nuclear mGluR5 pool. Finally, our data suggest that once at the INM, mGluR5 is stably retained via interactions with chromatin. Thus, mGluR5 is perfectly positioned to regulate nucleoplasmic Ca2+in situ.

Mechanisms Associated with Activation of Intracellular Metabotropic Glutamate Receptor, mGluR5.

The group 1 metabotropic glutamate receptor, mGluR5, is found on the cell surface as well as on intracellular membranes where it can mediate both overlapping and unique signaling effects. Previously we have shown that glutamate activates intracellular mGluR5 by entry through sodium-dependent transporters and/or cystine glutamate exchangers. Calibrated antibody labelling suggests that the glutamate concentration within neurons is quite high (~10 mM) raising the question as to whether intracellular mGluR5 is maximally activated at all times or whether a different ligand might be responsible for receptor activation. To address this issue, we used cellular, optical and molecular techniques to show that intracellular glutamate is largely sequestered in mitochondria; that the glutamate concentration necessary to activate intracellular mGluR5 is about ten-fold higher than what is necessary to activate cell surface mGluR5; and uncaging caged glutamate within neurons can directly activate the receptor. Thus these studies further the concept that glutamate itself serves as the ligand for intracellular mGluR5.

A New Approach for Identifying Patients with Undiagnosed Chronic Obstructive Pulmonary Disease.

RATIONALE: Chronic obstructive pulmonary disease (COPD) is often unrecognized and untreated. OBJECTIVES: To develop a method for identifying undiagnosed COPD requiring treatment with currently available therapies (FEV1 <60% predicted and/or exacerbation risk). METHODS: We conducted a multisite, cross-sectional, case-control study in U.S. pulmonary and primary care clinics that recruited subjects from primary care settings. Cases were patients with COPD and at least one exacerbation in the past year or FEV1 less than 60% of predicted without exacerbation in the past year. Control subjects were persons with no COPD or with mild COPD (FEV1 ≥60% predicted, no exacerbation in the past year). In random forests analyses, we identified the smallest set of questions plus peak expiratory flow (PEF) with optimal sensitivity (SN) and specificity (SP). MEASUREMENTS AND MAIN RESULTS: PEF and spirometry were recorded in 186 cases and 160 control subjects. The mean (SD) age of the sample population was 62.7 (10.1) years; 55% were female; 86% were white; and 16% had never smoked. The mean FEV1 percent predicted for cases was 42.5% (14.2%); for control subjects, it was 82.5% (15.7%). A five-item questionnaire, CAPTURE (COPD Assessment in Primary Care to Identify Undiagnosed Respiratory Disease and Exacerbation Risk), was used to assess exposure, breathing problems, tiring easily, and acute respiratory illnesses. CAPTURE exhibited an SN of 95.7% and an SP of 44.4% for differentiating cases from all control subjects, and an SN of 95.7% and an SP of 67.8% for differentiating cases from no-COPD control subjects. The PEF (males, <350 L/min; females, <250 L/min) SN and SP were 88.0% and 77.5%, respectively, for differentiating cases from all control subjects, and they were 88.0% and 90.8%, respectively, for distinguishing cases from no-COPD control subjects. The CAPTURE plus PEF exhibited improved SN and SP for all cases versus all control subjects (89.7% and 78.1%, respectively) and for all cases versus no-COPD control subjects (89.7% and 93.1%, respectively). CONCLUSIONS: CAPTURE with PEF can identify patients with COPD who would benefit from currently available therapy and require further diagnostic evaluation. Clinical trial registered with clinicaltrials.gov (NCT01880177).

Insight into Best Variables for COPD Case Identification: A Random Forests Analysis.

RATIONALE: This study is part of a larger, multi-method project to develop a questionnaire for identifying undiagnosed cases of chronic obstructive pulmonary disease (COPD) in primary care settings, with specific interest in the detection of patients with moderate to severe airway obstruction or risk of exacerbation. OBJECTIVES: To examine 3 existing datasets for insight into key features of COPD that could be useful in the identification of undiagnosed COPD. METHODS: Random forests analyses were applied to the following databases: COPD Foundation Peak Flow Study Cohort (N=5761), Burden of Obstructive Lung Disease (BOLD) Kentucky site (N=508), and COPDGene® (N=10,214). Four scenarios were examined to find the best, smallest sets of variables that distinguished cases and controls:(1) moderate to severe COPD (forced expiratory volume in 1 second [FEV1] <50% predicted) versus no COPD; (2) undiagnosed versus diagnosed COPD; (3) COPD with and without exacerbation history; and (4) clinically significant COPD (FEV1<60% predicted or history of acute exacerbation) versus all others. RESULTS: From 4 to 8 variables were able to differentiate cases from controls, with sensitivity ≥73 (range: 73-90) and specificity >68 (range: 68-93). Across scenarios, the best models included age, smoking status or history, symptoms (cough, wheeze, phlegm), general or breathing-related activity limitation, episodes of acute bronchitis, and/or missed work days and non-work activities due to breathing or health. CONCLUSIONS: Results provide insight into variables that should be considered during the development of candidate items for a new questionnaire to identify undiagnosed cases of clinically significant COPD.

Intracellular mGluR5 plays a critical role in neuropathic pain.

Spinal mGluR5 is a key mediator of neuroplasticity underlying persistent pain. Although brain mGluR5 is localized on cell surface and intracellular membranes, neither the presence nor physiological role of spinal intracellular mGluR5 is established. Here we show that in spinal dorsal horn neurons >80% of mGluR5 is intracellular, of which ∼60% is located on nuclear membranes, where activation leads to sustained Ca(2+) responses. Nerve injury inducing nociceptive hypersensitivity also increases the expression of nuclear mGluR5 and receptor-mediated phosphorylated-ERK1/2, Arc/Arg3.1 and c-fos. Spinal blockade of intracellular mGluR5 reduces neuropathic pain behaviours and signalling molecules, whereas blockade of cell-surface mGluR5 has little effect. Decreasing intracellular glutamate via blocking EAAT-3, mimics the effects of intracellular mGluR5 antagonism. These findings show a direct link between an intracellular GPCR and behavioural expression in vivo. Blockade of intracellular mGluR5 represents a new strategy for the development of effective therapies for persistent pain.

Validation of Claims Algorithms for Progression to Metastatic Cancer in Patients with Breast, Non-small Cell Lung, and Colorectal Cancer.

BACKGROUND: Validated algorithms for identifying progression to metastatic cancer could permit the use of administrative claims databases for research in this area. OBJECTIVE: To identify simple algorithms that could accurately detect cancer progression to metastatic breast, non-small cell lung, and colorectal cancer (CRC) using medical and pharmacy claims data. METHODS: Adults with stage I-III breast, non-small cell lung cancer (NSCLC), or CRC in the Geisinger Health System from 2004 to 2011 were selected. Evidence of progression was extracted via manual chart review as the reference standard. In addition to secondary malignancy diagnosis (ICD-9 code for metastases), diagnoses, procedures, and treatments were selected with clinician input as indicators of cancer progression. Random forests models provided variable importance scores. In addition to codes for secondary malignancy, several more complex algorithms were constructed and performance measures calculated. RESULTS: Among those with breast cancer [17/502 (3.4%) progressed], the performance of a secondary malignancy code was suboptimal [sensitivity: 64.7%; specificity: 86.0%; positive predictive value (PPV): 13.9; negative predictive value (NPV): 98.6%]; requiring malignancy at another site or initiation of immunotherapy increased PPV and specificity but decreased sensitivity. For NSCLC [61/236 (25.8%) progressed], codes for secondary malignancy alone (PPV: 47.4%; NPV: 84.8%; sensitivity: 60.7%; specificity: 76.6%) performed similarly or better than more complex algorithms. For CRC [33/276 (12.0%) progressed], secondary malignancy codes had good specificity (92.7%) and NPV (92.3%) but low sensitivity (42.4%) and PPV (43.8%); an algorithm with change in chemotherapy increased sensitivity but decreased other metrics. CONCLUSION: Selected algorithms performed similarly to the presence of a secondary tumor diagnosis code, with low sensitivity/PPV and higher specificity/NPV. Accurate identification of cancer progression likely requires verification through chart review.

The Effects of Guided Imagery on Patients Being Weaned from Mechanical Ventilation.

The study purpose was to assess the effects of guided imagery on sedation levels, sedative and analgesic volume consumption, and physiological responses of patients being weaned from mechanical ventilation. Forty-two patients were selected from two community acute care hospitals. One hospital served as the comparison group and provided routine care (no intervention) while the other hospital provided the guided imagery intervention. The intervention included two sessions, each lasting 60 minutes, offered during morning weaning trials from mechanical ventilation. Measurements were recorded in groups at baseline and 30- and 60-minute intervals and included vital signs and Richmond Agitation-Sedation Scale (RASS) score. Sedative and analgesic medication volume consumption were recorded 24 hours prior to and after the intervention. The guided imagery group had significantly improved RASS scores and reduced sedative and analgesic volume consumption. During the second session, oxygen saturation levels significantly improved compared to the comparison group. Guided imagery group had 4.88 less days requiring mechanical ventilation and 1.4 reduction in hospital length of stay compared to the comparison group. Guided imagery may be complementary and alternative medicine (CAM) intervention to provide during mechanical ventilation weaning trials.

Comprehensive functional characterization of murine infantile Batten disease including Parkinson-like behavior and dopaminergic markers.

Infantile neuronal ceroid lipofuscinosis (INCL, Infantile Batten disease) is a neurodegenerative lysosomal storage disease caused by a deficiency in palmitoyl protein thioesterase-1 (PPT1). The PPT1-deficient mouse (Cln1(-/-)) is a useful phenocopy of human INCL. Cln1(-/-) mice display retinal dysfunction, seizures, motor deficits, and die at ~8 months of age. However, little is known about the cognitive and behavioral functions of Cln1(-/-) mice during disease progression. In the present study, younger (~1-2 months of age) Cln1(-/-) mice showed minor deficits in motor/sensorimotor functions while older (~5-6 months of age) Cln1(-/-) mice exhibited more severe impairments, including decreased locomotor activity, inferior cued water maze performance, decreased running wheel ability, and altered auditory cue conditioning. Unexpectedly, certain cognitive functions such as some learning and memory capabilities seemed intact in older Cln1(-/-) mice. Younger and older Cln1(-/-) mice presented with walking initiation defects, gait abnormalities, and slowed movements, which are analogous to some symptoms reported in INCL and parkinsonism. However, there was no evidence of alterations in dopaminergic markers in Cln1(-/-) mice. Results from this study demonstrate quantifiable changes in behavioral functions during progression of murine INCL and suggest that Parkinson-like motor/sensorimotor deficits in Cln1(-/-) mice are not mediated by dopamine deficiency.

Reassessment of the role of aromatic amino acid hydroxylases and the effect of infection by Toxoplasma gondii on host dopamine.

Toxoplasma gondii infection has been described previously to cause infected mice to lose their fear of cat urine. This behavioral manipulation has been proposed to involve alterations of host dopamine pathways due to parasite-encoded aromatic amino acid hydroxylases. Here, we report successful knockout and complementation of the aromatic amino acid hydroxylase AAH2 gene, with no observable phenotype in parasite growth or differentiation in vitro and in vivo. Additionally, expression levels of the two aromatic amino acid hydroxylases were negligible both in tachyzoites and in bradyzoites. Finally, we were unable to confirm previously described effects of parasite infection on host dopamine either in vitro or in vivo, even when AAH2 was overexpressed using the BAG1 promoter. Together, these data indicate that AAH enzymes in the parasite do not cause global or regional alterations of dopamine in the host brain, although they may affect this pathway locally. Additionally, our findings suggest alternative roles for the AHH enzymes in T. gondii, since AAH1 is essential for growth in nondopaminergic cells.

Functional G protein-coupled receptors on nuclei from brain and primary cultured neurons.

A growing number of G protein-coupled receptors (GPCRs) have been identified on nuclear membranes. In many cases, it is unknown how the intracellular GPCR is activated, how it is trafficked to nuclear membranes, and what long-term signaling consequences follow nuclear receptor activation. Here we describe how to isolate nuclei that are free from plasma membrane and cytoplasmic contamination yet still exhibit physiological properties following receptor activation.

Location-dependent signaling of the group 1 metabotropic glutamate receptor mGlu5.

Although G protein-coupled receptors are primarily known for converting extracellular signals into intracellular responses, some receptors, such as the group 1 metabotropic glutamate receptor, mGlu5, are also localized on intracellular membranes where they can mediate both overlapping and unique signaling effects. Thus, besides "ligand bias," whereby a receptor's signaling modality can shift from G protein dependence to independence, canonical mGlu5 receptor signaling can also be influenced by "location bias" (i.e., the particular membrane and/or cell type from which it signals). Because mGlu5 receptors play important roles in both normal development and in disorders such as Fragile X syndrome, autism, epilepsy, addiction, anxiety, schizophrenia, pain, dyskinesias, and melanoma, a large number of drugs are being developed to allosterically target this receptor. Therefore, it is critical to understand how such drugs might be affecting mGlu5 receptor function on different membranes and in different brain regions. Further elucidation of the site(s) of action of these drugs may determine which signal pathways mediate therapeutic efficacy.

The Parkinsonian mimetic, 6-OHDA, impairs axonal transport in dopaminergic axons.

6-hydroxydopamine (6-OHDA) is one of the most commonly used toxins for modeling degeneration of dopaminergic (DA) neurons in Parkinson's disease. 6-OHDA also causes axonal degeneration, a process that appears to precede the death of DA neurons. To understand the processes involved in 6-OHDA-mediated axonal degeneration, a microdevice designed to isolate axons fluidically from cell bodies was used in conjunction with green fluorescent protein (GFP)-labeled DA neurons. Results showed that 6-OHDA quickly induced mitochondrial transport dysfunction in both DA and non-DA axons. This appeared to be a general effect on transport function since 6-OHDA also disrupted transport of synaptophysin-tagged vesicles. The effects of 6-OHDA on mitochondrial transport were blocked by the addition of the SOD1-mimetic, Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP), as well as the anti-oxidant N-acetyl-cysteine (NAC) suggesting that free radical species played a role in this process. Temporally, microtubule disruption and autophagy occurred after transport dysfunction yet before DA cell death following 6-OHDA treatment. The results from the study suggest that ROS-mediated transport dysfunction occurs early and plays a significant role in inducing axonal degeneration in response to 6-OHDA treatment.

Intracellular mGluR5 can mediate synaptic plasticity in the hippocampus.

Metabotropic glutamate receptor 5 (mGluR5) is widely expressed throughout the CNS and participates in regulating neuronal function and synaptic transmission. Recent work in the striatum led to the groundbreaking discovery that intracellular mGluR5 activation drives unique signaling pathways, including upregulation of ERK1/2, Elk-1 (Jong et al., 2009) and Arc (Kumar et al., 2012). To determine whether mGluR5 signals from intracellular membranes of other cell types, such as excitatory pyramidal neurons in the hippocampus, we used dissociated rat CA1 hippocampal cultures and slice preparations to localize and characterize endogenous receptors. As in the striatum, CA1 neurons exhibited an abundance of mGluR5 both on the cell surface and intracellular membranes, including the endoplasmic reticulum and the nucleus where it colocalized with the sodium-dependent excitatory amino acid transporter, EAAT3. Inhibition of EAAT3 or sodium-free buffer conditions prevented accumulations of radiolabeled agonist. Using a pharmacological approach to isolate different pools of mGluR5, both intracellular and cell surface receptors induced oscillatory Ca(2+) responses in dissociated CA1 neurons; however, only intracellular mGluR5 activation triggered sustained high amplitude Ca(2+) rises in dendrites. Consistent with the notion that mGluR5 can signal from intracellular membranes, uncaging glutamate on a CA1 dendrite led to a local Ca(2+) rise, even in the presence of ionotropic and cell surface metabotropic receptor inhibitors. Finally, activation of intracellular mGluR5 alone mediated both electrically induced and chemically induced long-term depression, but not long-term potentiation, in acute hippocampal slices. These data suggest a physiologically relevant and important role for intracellular mGluR5 in hippocampal synaptic plasticity.