Identification of Molecular Substrate for the Attenuation of Anxiety: A Step Toward the Development of Better Anti-Anxiety Drugs

Anxiety disorders affect some 19 million people in the U.S. alone, costing $46.6 billion, or one third of the nation’s total mental health bill in 1990. Benzodiazepine tranquilizers like the prototypic diazepam are among the most widely used anti-anxiety agents. In addition to their anxiolytic action, they also induce sedation and may impair motor coordination, both of which are undesired side effects when they are used as anxiolytics. Not surprisingly, road traffic accidents may be increased for patients on classical benzodiazepines. In addition, these drugs carry the risk of dependence liability. Benzodiazepines augment the action of the inhibitory neurotransmitter g-aminobutyric acid (GABA) at contact points between two nerve cells called synapses, points at which information is transmitted from one nerve cell to the next. Synaptically released GABA binds to postsynaptic GABAA receptors, thus causing an influx of negatively charged chloride ions into the postsynaptic neuron. This leads to a hyperpolarization and thus functional inhibition of the postsynaptic cell. Benzodiazepines bind to a site on the GABAA receptor which is different from the GABA binding site, thus increasing the chloride current. Benzodiazepines like diazepam bind to GABAA receptors containing the α subunits α1, α2, α3, or α5, most likely in abgabg combinations

Einkommensentwicklung bei Betriebswechsel und Betriebsverbleib im Vergleich : empirische Ergebnisse aus der Beschäftigtenstichprobe des IAB für die Gruppe der Arbeiter

"In der Arbeit wird untersucht, wie sich das Einkommen von stabil in einem Betrieb beschäftigten männlichen Arbeitern im Vergleich zum Einkommen von jenen entwickelt, die wechseln. Datenbasis der Untersuchung ist die Beschäftigtenstichprobe des IAB. Die Analyse erfolgt anhand einer Darstellung und mit multivariaten statistischen Methoden. Aufgrund theoretischer Überlegungen wird in der Gruppe der Wechsler zwischen Fällen mit Arbeitslosigkeit und solchen mit direkten Übergang unterschieden, Betriebswechsel ohne Arbeitslosigkeit erfolgen vermutlich überwiegend auf Initiative des betreffenden Arbeiters. Der Zusammenhang von Einkommensentwicklung und Betriebsverbleib oder Betriebswechsel mit und ohne Arbeitslosigkeit wird vor dem Hintergrund von Arbeitsmarkttheorien diskutiert. Effizienzlohn-, Segmentations-, Humankapital-, Allokations- und Suchansätze werden benutzt. Die empirischen Ergebnissse zeigen, daß (vermutlich freiwillige) Wechsel ohne Unterbrechungszeiten im Durchschnitt mit einem Lohnanstieg verbunden sind, der höher als bei jenen Arbeitern ausfällt, die im selben Betrieb verbleiben. Die Einkommenszuwächse von Arbeitern, deren Betriebswechsel Folge einer Kündigung von seiten des Arbeitgebers ist, fallen hingegen durchschnittlich aus. Es finden sich nur schwach ausgeprägte Hinweise, daß Entlohnung gemäß Betriebsseniorität auf dem untersuchten Teilarbeitsmarkt der Bundesrepublik eine Rolle spielt." (Autorenreferat)zwischenbetriebliche Mobilität - Auswirkungen, Lohnhöhe, Arbeiter

The heterogeneity in GABAA receptor-mediated IPSC kinetics reflects heterogeneity of subunit composition among inhibitory and excitatory interneurons in spinal lamina II

GABAergic inhibition displays rich functional diversity throughout the CNS, which arises from variations in the nature of inputs, subunit composition, subcellular localization of receptors and synapse geometry, or reuptake mechanisms. In the spinal dorsal horn (SDH), GABAA and glycine receptors play a major role in the control of excitability and accuracy of nociceptive processing. Identifying which components shape the properties of the inhibitory synapses in different cell types is necessary to understand how nociceptive information is integrated. To address this, we used transgenic mice where inhibitory interneurons express GAD65-EGFP. We found that GABAA, but not glycine receptor-mediated evoked IPSCs displayed slower kinetics in EGFP+ vs. EGFP− interneurons. GABAA miniature IPSC decay kinetics showed a large variability in both populations, however the distribution of decays differed between EGFP+ and EGFP− interneurons. The range of mIPSC decay kinetics observed was replicated in experiments using rapid application of GABA on outside-out patches taken from SDH neurons in slices. Furthermore, GABAA decay kinetics were not affected by uptake blockers and were not different in mice lacking δ or α5 subunits, indicating that intrinsic channel properties likely underlie the heterogeneity. To identify whether other α subunits shape the various kinetic properties observed we took advantage of knock-in mice carrying point mutations in either the α1, α2, or α3 subunits rendering Ro 15-4513 a selective agonist at the benzodiazepine modulatory site. We found that α1 and α2 subunit underlie the fast decaying component of IPSCs while the slow component is determined by the α3 subunit. The differential distribution of GABAA subunits at inhibitory synapses thus sculpts the heterogeneity of the SDH inhibitory circuitry. This diversity of inhibitory elements can be harnessed to selectively modulate different components of the spinal nociceptive circuitry for therapeutic interventions

Mutational analysis of molecular requirements for the actions of general anaesthetics at the γ-aminobutyric acid(A )receptor subtype, α1β2γ2

BACKGROUND: Amino acids in the β subunit contribute to the action of general anaesthetics on GABA(A )receptors. We have now characterized the phenotypic effect of two β subunit mutations in the most abundant GABA(A )receptor subtype, α1β2γ2. RESULTS: The β2(N265M) mutation in M2 decreased the modulatory actions of propofol, etomidate and enflurane, but not of alphaxalone, while the direct actions of propofol, etomidate and alphaxalone were impaired. The β2(M286W) mutation in M3 decreased the modulatory actions of propofol, etomidate and enflurane, but not of alphaxalone, whereas the direct action of propofol and etomidate, but not of alphaxalone, was impaired. CONCLUSIONS: We found that the actions of general anaesthetics at α1β2(N265M)γ2 and α1β2(M286W)γ2 GABA(A )receptors are similar to those previously observed at α2β3(N265M)γ2 and α2β3(M286W)γ2 GABA(A )recpetors, respectively, with the notable exceptions that the direct action of propofol was decreased in α1β2(M286W)γ2 receptors but indistinguishable form wild type in α2β3(M286W)γ2 receptors and that the direct action of alphaxalone was decreased in α1β2(N265M)γ2 but not α2β3(N265M)γ2 receptors and indistinguishable form wild type in α1β2(M286W)γ2 receptors but increased in α2β3(M286W)γ2 receptors. Thus, selected phenotypic consequences of these two mutations are GABA(A )receptor subtype-specific

Pharmacology of recombinant γ-aminobutyric acidA receptors rendered diazepam-insensitive by point-mutated α-subunits

AbstractAmino acids in the α- and γ-subunits contribute to the benzodiazepine binding site of GABAA-receptors. We show that the mutation of a conserved histidine residue in the N-terminal extracellular segment (α1H101R, α2H101R, α3H126R, and α5H105R) results not only in diazepam-insensitivity of the respective αxβ2,3γ2-receptors but also in an increased potentiation of the GABA-induced currents by the partial agonist bretazenil. Furthermore, Ro 15-4513, an inverse agonist at wild-type receptors, acts as an agonist at all mutant receptors. This conserved molecular switch can be exploited to identify the pharmacological significance of specific GABAA-receptor subtypes in vivo

GABAA_A Receptors Containing the α\alpha2 Subunit Are Critical for Direction-Selective Inhibition in the Retina

Far from being a simple sensor, the retina actively participates in processing visual signals. One of the best understood aspects of this processing is the detection of motion direction. Direction-selective (DS) retinal circuits include several subtypes of ganglion cells (GCs) and inhibitory interneurons, such as starburst amacrine cells (SACs). Recent studies demonstrated a surprising complexity in the arrangement of synapses in the DS circuit, i.e. between SACs and DS ganglion cells. Thus, to fully understand retinal DS mechanisms, detailed knowledge of all synaptic elements involved, particularly the nature and localization of neurotransmitter receptors, is needed. Since inhibition from SACs onto DSGCs is crucial for generating retinal direction selectivity, we investigate here the nature of the GABA receptors mediating this interaction. We found that in the inner plexiform layer (IPL) of mouse and rabbit retina, GABA$_A$ receptor subunit $\alpha$2 (GABA$_A$R $\alpha$2) aggregated in synaptic clusters along two bands overlapping the dendritic plexuses of both ON and OFF SACs. On distal dendrites of individually labeled SACs in rabbit, GABA$_A$R $\alpha$2 was aligned with the majority of varicosities, the cell's output structures, and found postsynaptically on DSGC dendrites, both in the ON and OFF portion of the IPL. In GABA$_A$R $\alpha$2 knock-out (KO) mice, light responses of retinal GCs recorded with two-photon calcium imaging revealed a significant impairment of DS responses compared to their wild-type littermates. We observed a dramatic drop in the proportion of cells exhibiting DS phenotype in both the ON and ON-OFF populations, which strongly supports our anatomical findings that $\alpha$2-containing GABA$_A$Rs are critical for mediating retinal DS inhibition. Our study reveals for the first time, to the best of our knowledge, the precise functional localization of a specific receptor subunit in the retinal DS circuit

Neurosteroids Mediate Neuroprotection in an In Vitro Model of Hypoxic/Hypoglycaemic Excitotoxicity via δ-GABAA_{A} Receptors without Affecting Synaptic Plasticity

Neurosteroids and benzodiazepines are modulators of the GABA$_{A}$ receptors, thereby causing anxiolysis. Furthermore, benzodiazepines such as midazolam are known to cause adverse side-effects on cognition upon administration. We previously found that midazolam at nanomolar concentrations (10 nM) blocked long-term potentiation (LTP). Here, we aim to study the effect of neurosteroids and their synthesis using XBD173, which is a synthetic compound that promotes neurosteroidogenesis by binding to the translocator protein 18 kDa (TSPO), since they might provide anxiolytic activity with a favourable side-effect profile. By means of electrophysiological measurements and the use of mice with targeted genetic mutations, we revealed that XBD173, a selective ligand of the translocator protein 18 kDa (TSPO), induced neurosteroidogenesis. In addition, the exogenous application of potentially synthesised neurosteroids (THDOC and allopregnanolone) did not depress hippocampal CA1-LTP, the cellular correlate of learning and memory. This phenomenon was observed at the same concentrations that neurosteroids conferred neuroprotection in a model of ischaemia-induced hippocampal excitotoxicity. In conclusion, our results indicate that TSPO ligands are promising candidates for post-ischaemic recovery exerting neuroprotection, in contrast to midazolam, without detrimental effects on synaptic plasticity