Transcriptional activators and repressors for the neuron-specific expression of a metabotropic glutamate receptor

Metabotropic glutamate receptor 1 (mGlu1) has a discrete distribution in the central nervous system restricted to neurons. Its expression undergoes important changes during development and in response to physiological and pathological modifications. Here, we have determined the structure of the mGlu1 gene and demonstrated that mGlu1 transcription takes places at alternative first exons. Moreover, we have identified active promoter regions upstream from the two most expressed first exons by means of luciferase reporter gene assays performed in primary cerebellar granule neurons. Targeted mutations of active elements constituting the core promoter and electrophoretic mobility shift assays demonstrated that the factors thyroid transcription factor-1 and CCAAT/enhancer-binding proteins β act synergistically to promote mGlu1 transcription. We have also elucidated the molecular bases for the neuron-specific expression of mGlu1 identifying a neural restrictive silencing element and a regulatory factor for X box element, which suppressed mGlu1 expression in nonneuronal cells. These results reveal the molecular bases for cell- and context-specific expression of an important glutamate receptor critically involved in synaptogenesis, neuronal differentiation, synaptic transmission, and plasticity. © 2007 by The American Society for Biochemistry and Molecular Biology, Inc

Human-robot coexistence and interaction in open industrial cells

Recent research results on human\u2013robot interaction and collaborative robotics are leaving behind the traditional paradigm of robots living in a separated space inside safety cages, allowing humans and robot to work together for completing an increasing number of complex industrial tasks. In this context, safety of the human operator is a main concern. In this paper, we present a framework for ensuring human safety in a robotic cell that allows human\u2013robot coexistence and dependable interaction. The framework is based on a layered control architecture that exploits an effective algorithm for online monitoring of relative human\u2013robot distance using depth sensors. This method allows to modify in real time the robot behavior depending on the user position, without limiting the operative robot workspace in a too conservative way. In order to guarantee redundancy and diversity at the safety level, additional certified laser scanners monitor human\u2013robot proximity in the cell and safe communication protocols and logical units are used for the smooth integration with an industrial software for safe low-level robot control. The implemented concept includes a smart human-machine interface to support in-process collaborative activities and for a contactless interaction with gesture recognition of operator commands. Coexistence and interaction are illustrated and tested in an industrial cell, in which a robot moves a tool that measures the quality of a polished metallic part while the operator performs a close evaluation of the same workpiece

Functional expression of the GABA A receptor α2 and α3 subunits at synapses between intercalated medial paracapsular neurons of mouse amygdala

In the amygdala, GABAergic neurons in the intercalated medial paracapsular cluster (Imp) have been suggested to play a key role in fear learning and extinction. These neurons project to the central (CE) amygdaloid nucleus and to other areas within and outside the amygdala. In addition, they give rise to local collaterals that innervate other neurons in the Imp. Several drugs, including benzodiazepines (BZ), are allosteric modulators of GABA A receptors. BZ has both anxiolytic and sedative actions, which are mediated through GABA A receptors containing α2/α3 and α1 subunits, respectively. To establish whether α1 or α2/α3 subunits are expressed at Imp cell synapses, we used paired recordings of anatomically identified Imp neurons and high resolution immunocytochemistry in the mouse. We observed that a selective α3 subunit agonist, TP003 (100 nM), significantly increased the decay time constant of the unitary IPSCs. A similar effect was also induced by zolpidem (10 μM) or by diazepam (1 μM). In contrast, lower doses of zolpidem (0.1-1 μM) did not significantly alter the kinetics of the unitary IPSCs. Accordingly, immunocytochemical experiments established that the α2 and α3, but not the α1 subunits of the GABA A receptors, were present at Imp cell synapses of the mouse amygdala. These results define, for the first time, some of the functional GABA A receptor subunits expressed at synapses of Imp cells. The data also provide an additional rationale to prompt the search of GABA A receptor α3 selective ligands as improved anxiolytic drugs. © 2012 Geracitano, Fischer, Kasugai, Ferraguti and Capogna

Control of Theta Oscillatory Activity Underlying Fear Expression by mGlu5 Receptors

Metabotropic glutamate 5 receptors (mGlu5) are thought to play an important role in mediating emotional information processing. In particular, negative allosteric modulators (NAMs) of mGlu5 have received a lot of attention as potential novel treatments for several neuropsychiatric diseases, including anxiety-related disorders. The aim of this study was to assess the influence of pre- and post-training mGlu5 inactivation in cued fear conditioned mice on neuronal oscillatory activity during fear retrieval. For this study we used the recently developed mGlu5 NAM Alloswicth-1 administered systemically. Injection of Alloswicth-1 before, but not after, fear conditioning resulted in a significant decrease in freezing upon fear retrieval. Mice injected with Alloswicth-1 pre-training were also implanted with recording microelectrodes into both the medial prefrontal cortex (mPFC) and ventral hippocampus (vHPC). The recordings revealed a reduction in theta rhythmic activity (4–12 Hz) in both the mPFC and vHPC during fear retrieval. These results indicate that inhibition of mGlu5 signaling alters local oscillatory activity in principal components of the fear brain network underlying a reduced response to a predicted threat

Individual contribution of metabotropic glutamate receptor (mGlu) 2 and 3 to c-Fos expression pattern evoked by mGlu2/3 antagonism

Objectives and materials and methods: The aims of the present study were (1) to determine the neuronal activation pattern elicited by the group II mGlu antagonist LY341495 and (2) to evaluate the contribution of each group II mGlu subtype by using wild-type (WT) and knockout (KO) mice lacking either mGlu2 or mGlu3. c-Fos expression was used as a marker of neuronal activation. Results and discussion: In WT mice, LY341495 induced widespread c-Fos expression in 68 out of 92 brain areas, including limbic areas such as the amygdala, septum, prefrontal cortex, and hippocampus. LY341495-induced c-Fos response was markedly decreased in the medial part of the central amygdala (CeM) and lateral septum (LS) in mGlu3-KO mice, as well as in the lateral parabrachial nucleus (LPB) in both KO strains. In the majority of investigated areas, LY341495-induced c-Fos expression was similar in KO and WT mice. Analysis of the cellular and subcellular distribution of mGlu2 and mGlu3 revealed a prevailing presence of mGlu3-immunoreactivity in the CeM in glial processes and in postsynapstic neuronal elements, whereas only rare presynaptic axon terminals were found immunoreactive for mGlu2. Conclusion: In conclusion, our data indicate that group II mGlu blockade increases neuronal activation in a variety of brain areas, including many stress- and anxiety-related areas. The activation of two key brain areas, the CeM and LS, is mediated via mGlu3, while activation in the LPB involves both subtypes. Moreover, in the majority of investigated areas, LY341495-mediated neuronal activation appears to require a complex cross talk between group II mGlu subtypes or the action of LY341495 on additional receptors. © 2008 The Author(s)

Kv4.2 potassium channels segregate to extrasynaptic domains and influence intrasynaptic NMDA receptor NR2B subunit expression

Neurons of the intercalated cell clusters (ITCs) represent an important relay site for information flow within amygdala nuclei. These neurons receive mainly glutamatergic inputs from the basolateral amygdala at their dendritic domains and provide feed-forward inhibition to the central nucleus. Voltage-gated potassium channels type-4.2 (Kv4.2) are main players in dendritic signal processing and integration providing a key component of the A currents. In this study, the subcellular localization and distribution of the Kv4.2 was studied in ITC neurons by means of light- and electron microscopy, and compared to other types of central principal neurons. Several ultrastructural immunolocalization techniques were applied including pre-embedding techniques and, most importantly, SDS-digested freeze-fracture replica labeling. We found Kv4.2 densely expressed in somato-dendritic domains of ITC neurons where they show a differential distribution pattern as revealed by nearest neighbor analysis. Comparing ITC neurons with hippocampal pyramidal and cerebellar granule cells, a cell type- and domain-dependent organization in Kv4.2 distribution was observed. Kv4.2 subunits were localized to extrasynaptic sites where they were found to influence intrasynaptic NMDA receptor subunit expression. In samples of Kv4.2 knockout mice, the frequency of NR1-positive synapses containing the NR2B subunit was significantly increased. This indicates a strong, yet indirect effect of Kv4.2 on the synaptic content of NMDA receptor subtypes, and a likely role in synaptic plasticity at ITC neurons. © 2012 The Author(s)

Fear Memory Retrieval Is Associated With a Reduction in AMPA Receptor Density at Thalamic to Amygdala Intercalated Cell Synapses

The amygdala plays a crucial role in attaching emotional significance to environmental cues. Its intercalated cell masses (ITC) are tight clusters of GABAergic neurons, which are distributed around the basolateral amygdala complex. Distinct ITC clusters are involved in the acquisition and extinction of conditioned fear responses. Previously, we have shown that fear memory retrieval reduces the AMPA/NMDA ratio at thalamic afferents to ITC neurons within the dorsal medio-paracapsular cluster. Here, we investigate the molecular mechanisms underlying the fear-mediated reduction in the AMPA/NMDA ratio at these synapses and, in particular, whether specific changes in the synaptic density of AMPA receptors underlie the observed change. To this aim, we used a detergent-digested freeze-fracture replica immunolabeling technique (FRIL) approach that enables to visualize the spatial distribution of intrasynaptic AMPA receptors at high resolution. AMPA receptors were detected using an antibody raised against an epitope common to all AMPA subunits. To visualize thalamic inputs, we virally transduced the posterior thalamic complex with Channelrhodopsin 2-YFP, which is anterogradely transported along axons. Using face-matched replica, we confirmed that the postsynaptic elements were ITC neurons due to their prominent expression of μ-opioid receptors. With this approach, we show that, following auditory fear conditioning in mice, the formation and retrieval of fear memory is linked to a significant reduction in the density of AMPA receptors, particularly at spine synapses formed by inputs of the posterior intralaminar thalamic and medial geniculate nuclei onto identified ITC neurons. Our study is one of the few that has directly linked the regulation of AMPA receptor trafficking to memory processes in identified neuronal networks, by showing that fear-memory induced reduction in AMPA/NMDA ratio at thalamic-ITC synapses is associated with a reduced postsynaptic AMPA receptor density

An appraisal of the influence of the metabotropic glutamate 5 (mglu5) receptor on sociability and anxiety

Amongst the many neurotransmitter systems causally linked to the expression of social behavior, glutamate appears to play a pivotal role. In particular, metabotropic glutamate 5 (mGlu5) receptors have received much attention as its altered function has been reported in several mouse models of autism spectrum disorders and mental retardation. Inhibition of the activity of mGlu5 receptors by means of genetic or pharmacological manipulations improved social deficits in some of these animal models. However, in normal wild-type (WT) mice, pharmacological blockade of mGlu5 receptors yielded inconsistent results. The aim of our study was to investigate the actual contribution of decreased or absent mGlu5 receptor function in sociability and anxiety-like behavior as well as to explore the impact of mGlu5 receptor ablation on the pattern of brain activation upon social exposure. Here we show that Grm5-/- mice display higher social preference indexes compared to age-matched WT mice in the three-chambered social task. However, this effect was accompanied by a decreased exploratory activity during the test and increased anxiety-like behavior. Contrary to mGlu5 receptor ablation, the mGlu5 receptor negative allosteric modulator 3-((2-methyl-1,4-thiazolyl)ethynyl)pyridine (MTEP) induced anxiolytic effects without affecting social preference in WT mice. By mapping c-Fos expression in 21 different brain regions known to be involved in social interaction, we detected a specific activation of the prefrontal cortex and dorsolateral septum in Grm5-/- mice following social interaction. C-Fos expression correlation-based network and graph theoretical analyses further suggested dysfunctional connectivity and disruption of the functional brain network generated during social interaction in Grm5-/- mice. The lack of mGlu5 receptors resulted in profound rearrangements of the functional impact of prefrontal and hippocampal regions in the social interaction network. In conclusion, this work reveals a complex contribution of mGlu5 receptors in sociability and anxiety and points to the importance of these receptors in regulating brain functional connectivity during social interaction

Cell-Type-Specific Recruitment of Amygdala Interneurons to Hippocampal Theta Rhythm and Noxious Stimuli In Vivo

Neuronal synchrony in the basolateral amygdala (BLA) is critical for emotional behavior. Coordinated theta-frequency oscillations between the BLA and the hippocampus and precisely timed integration of salient sensory stimuli in the BLA are involved in fear conditioning. We characterized GABAergic interneuron types of the BLA and determined their contribution to shaping these network activities. Using in vivo recordings in rats combined with the anatomical identification of neurons, we found that the firing of BLA interneurons associated with network activities was cell type specific. The firing of calbindin-positive interneurons targeting dendrites was precisely theta-modulated, but other cell types were heterogeneously modulated, including parvalbumin-positive basket cells. Salient sensory stimuli selectively triggered axo-axonic cells firing and inhibited firing of a disctinct projecting interneuron type. Thus, GABA is released onto BLA principal neurons in a time-, domain-, and sensory-specific manner. These specific synaptic actions likely cooperate to promote amygdalo-hippocampal synchrony involved in emotional memory formation

Loss of mglur5 in d1 receptor-expressing neurons improves stress coping

The metabotropic glutamate receptor type 5 (mGluR5) has been proposed to play a crucial role in the selection and regulation of cognitive, affective, and emotional behaviors. However, the mechanisms by which these receptors mediate these effects remain largely unexplored. Here, we studied the role of mGluR5 located in D1 receptor-expressing (D1) neurons in the manifestation of different behavioral expressions. Mice with conditional knockout (cKO) of mGluR5 in D1 neurons (mGluR5D1 cKO) and littermate controls displayed similar phenotypical profiles in relation to memory expression, anxiety, and social behaviors. However, mGluR5D1 cKO mice presented different coping mechanisms in response to acute escapable or inescapable stress. mGluR5D1 cKO mice adopted an enhanced active stress coping strategy upon exposure to escapable stress in the two-way active avoidance (TWA) task and a greater passive strategy upon exposure to inescapable stress in the forced swim test (FST). In summary, this work provides evidence for a functional integration of the dopaminergic and glutamatergic system to mediate control over internal states upon stress exposure and directly implicates D1 neurons and mGluR5 as crucial mediators of behavioral stress responses