Uwe Rudolph

McLean Hospital, Cambridge, Massachusetts, United States

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Publications (161)1061.16 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Background: Surgical interventions like skin incisions trigger withdrawal reflexes which require motor neurones and local circuit interneurones in the spinal ventral horn. This region plays a key role in mediating immobilizing properties of the GABAergic anaesthetic propofol. However, it is unclear how propofol modulates GABA(A) receptors in the spinal ventral horn and whether tonic or phasic inhibition is involved. Methods: Organotypic spinal cord tissue slices were prepared from mice. Whole-cell recordings were performed for quantifying effects of propofol on GABA(A) receptor-mediated phasic transmission and tonic conductance. Results: Propofol increased GABAergic phasic transmission by a prolongation of the decay time constant in a concentration-dependent manner. The amount of the charge transferred per inhibitory post-synaptic current, described by the area under the curve, was significantly augmented by 1 µM propofol (P<0.01). A GABA(A) receptor-mediated tonic current was not induced by 1 µM propofol but at a concentration of 5 µM (P<0.05). Conclusions: Propofol depresses ventral horn interneurones predominantly by phasic rather than by tonic GABA(A) receptor-mediated inhibition. However, the present results suggest that the involvement of a tonic inhibition might contribute to the efficacy of propofol to depress nociceptive reflexes at high concentrations of the anaesthetic.
    BJA British Journal of Anaesthesia 08/2014; · 4.24 Impact Factor
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    ABSTRACT: The enteric nervous system (ENS) provides the intrinsic neural control of the gastrointestinal tract (GIT) and regulates virtually all GI functions. Altered neuronal activity within the ENS underlies various GI disorders with stress being a key contributing factor. Thus, elucidating the expression and function of the neurotransmitter systems, which determine neuronal excitability within the ENS, such as the GABA-GABAA receptor (GABAAR) system, could reveal novel therapeutic targets for such GI disorders. Molecular and functionally diverse GABAARs modulate rapid GABAergic-mediated regulation of neuronal excitability throughout the nervous system. However, the cellular and subcellular GABAAR subunit expression patterns within neurochemically defined cellular circuits of the mouse ENS, together with the functional contribution of GABAAR subtypes to GI contractility remains to be determined. Immunohistochemical analyses revealed that immunoreactivity for the GABAAR gamma (γ) 2 and alphas (α) 1, 2, 3 subunits was located on somatodendritic surfaces of neurochemically distinct myenteric plexus neurons, while being on axonal compartments of submucosal plexus neurons. In contrast, immunoreactivity for the α4-5 subunits was only detected in myenteric plexus neurons. Furthermore, α-γ2 subunit immunoreactivity was located on non-neuronal interstitial cells of Cajal. In organ bath studies, GABAAR subtype-specific ligands had contrasting effects on the force and frequency of spontaneous colonic longitudinal smooth muscle contractions. Finally, enhancement of γ2-GABAAR function with alprazolam reversed the stress-induced increase in the force of spontaneous colonic contractions. The study demonstrates the molecular and functional diversity of the GABAAR system within the mouse colon providing a framework for developing GABAAR-based therapeutics in GI disorders.
    The Journal of neuroscience : the official journal of the Society for Neuroscience. 07/2014; 34(31):10361-10378.
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    ABSTRACT: The dorsal raphe nucleus (DRN) provides the major source of serotonin to the central nervous system (CNS) and modulates diverse neural functions including mood. Furthermore, DRN cellular networks are engaged in the stress-response at the CNS level allowing for adaptive behavioural responses, whilst stress-induced dysregulation of DRN and serotonin release is implicated in psychiatric disorders. Therefore, identifying the molecules regulating DRN activity is fundamental to understand DRN function in health and disease. GABAA receptors (GABAARs) allow for brain region, cell type and subcellular domain-specific GABA-mediated inhibitory currents and are thus key regulators of neuronal activity. Yet, the GABAAR subtypes expressed within the neurochemically diverse cell types of the mouse DRN are poorly described. In this study, immunohistochemistry and confocal microscopy revealed that all serotonergic neurons expressed immunoreactivity for the GABAAR alpha2 and 3 subunits, although the respective signals were co-localised to varying degrees with inhibitory synaptic marker proteins. Only a topographically located sub-population of serotonergic neurons exhibited GABAAR alpha1 subunit immunoreactivity. However, all GABAergic as well as non-GABAergic, non-serotonergic neurons within the DRN expressed GABAAR alpha1 subunit immunoreactivity. Intriguingly, immunoreactivity for the GABAAR gamma2 subunit was enriched on GABAergic rather than serotonergic neurons. Finally, repeated restraint stress increased the expression of the GABAAR alpha3 subunit at the mRNA and protein level. The study demonstrates the identity and location of distinct GABAAR subunits within the cellular networks of the mouse DRN and that stress impacts on the expression levels of particular subunits at the gene and protein level.
    Brain Structure and Function 06/2014; · 7.84 Impact Factor
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    ABSTRACT: Transient receptor potential (TRP) channels are abundant in the brain where they regulate transmission of sensory signals. The expression patterns of different TRPC subunits (TRPC1, 4, and 5) are consistent with their potential role in fear-related behaviors. Accordingly, we found recently that mutant mice lacking a specific TRP channel subunit, TRPC5, exhibited decreased innate fear responses. Both TRPC5 and another member of the same subfamily, TRPC4, form heteromeric complexes with the TRPC1 subunit (TRPC1/5 and TRPC1/4, respectively). As TRP channels with specific subunit compositions may have different functional properties, we hypothesized that fear-related behaviors could be differentially controlled by TRPCs with distinct subunit arrangements. In this study, we focused on the analysis of mutant mice lacking the TRPC4 subunit, which, as we confirmed in experiments on control mice, is expressed in brain areas implicated in the control of fear and anxiety. In behavioral experiments, we found that constitutive ablation of TRPC4 was associated with diminished anxiety levels (innate fear). Furthermore, knockdown of TRPC4 protein in the lateral amygdala via lentiviral-mediated gene delivery of RNAi mimicked the behavioral phenotype of constitutive TRPC4-null (TRPC4(-/-)) mouse. Recordings in brain slices demonstrated that these behavioral modifications could stem from the lack of TRPC4 potentiation in neurons in the lateral nucleus of the amygdala through two Gαq/11 protein-coupled signaling pathways, activated via Group I metabotropic glutamate receptors and cholecystokinin 2 receptors, respectively. Thus, TRPC4 and the structurally and functionally related subunit, TRPC5, may both contribute to the mechanisms underlying regulation of innate fear responses.
    Journal of Neuroscience 03/2014; 34(10):3653-67. · 6.91 Impact Factor
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    ABSTRACT: Despite long-standing concerns regarding the abuse liability of benzodiazepines, the mechanisms underlying properties of benzodiazepines that may be relevant to abuse are still poorly understood. Earlier studies showed that compounds selective for α1-containing GABAA receptors (α1GABAARs) are abused by humans and self-administered by animals, and that these receptors may underlie a preference for benzodiazepines as well as neuroplastic changes observed in the ventral tegmental area following benzodiazepine administration. There is some evidence, however, that even L-838, 417, a compound with antagonistic properties at α1GABAARs and agonistic properties at the other three benzodiazepine-sensitive GABAA receptor subtypes, is self-administered, and that the α2GABAARs may have a role in benzodiazepine-induced reward enhancement. Using a two-bottle choice drinking paradigm to evaluate midazolam preference and an intracranial self-stimulation (ICSS) paradigm to evaluate the impact of midazolam on reward enhancement, we demonstrated that mice carrying a histidine-to- arginine point mutation in the α2 subunit which renders it insensitive to benzodiazepines [α2(H101R) mice] did not prefer midazolam and did not show midazolam-induced reward enhancement in ICSS, in contrast to wild-type controls, suggesting that α2GABAARs are necessary for the reward enhancing effects and preference for oral benzodiazepines. Through a viral-mediated knockdown of α2GABAARs in the nucleus accumbens (NAc), we demonstrated that α2 in the NAc is necessary for the preference for midazolam. Findings imply that α2GABAARs in the NAc are involved in at least some reward-related properties of benzodiazepines, which might partially underlie repeated drug-taking behavior.Neuropsychopharmacology accepted article preview online, 19 February 2014; doi:10.1038/npp.2014.41.
    Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 02/2014; · 8.68 Impact Factor
  • JAMA Psychiatry 11/2013; · 12.01 Impact Factor
  • Uwe Rudolph, Hanns Möhler
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    ABSTRACT: The γ-aminobutyric acid (GABA) system plays a pivotal role in orchestrating the synchronicity of local networks and the functional coupling of different brain regions. Here we review the impact of the GABAA receptor subtypes on cognitive and emotional behavior, paying particular attention to five disease states: cognitive dysfunction and Down syndrome, anxiety disorders, depression, schizophrenia, and autism. Through the bidirectional modulation of tonic inhibition, α5-subunit-containing GABAA receptors permit the bidirectional modulation of cognitive processes, and a partial inverse agonist acting at the α5-subunit-containing GABAA receptor is in a clinical trial in individuals with Down syndrome. With regard to anxiety disorders, the viability of nonsedative anxiolytics based on the modulation of α2- and α3-subunit-containing GABAA receptors has been established in clinical proof-of-concept trials. Regarding the remaining three disease states, the GABA hypothesis of depression offers new options for antidepressant drug development, cognitive symptoms in schizophrenia are attributed to a cortical GABAergic deficit, and dysfunctional GABAergic inhibition is increasingly understood to contribute to the pathophysiology of autism spectrum disorders. Expected final online publication date for the Annual Review of Pharmacology and Toxicology Volume 54 is January 06, 2014. Please see http://www.annualreviews.org/catalog/pubdates.aspx for revised estimates.
    Annual Review of Pharmacology 10/2013; · 21.54 Impact Factor
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    ABSTRACT: Drugs that enhance GABAergic inhibition alleviate inflammatory and neuropathic pain after spinal application. This antihyperalgesia occurs mainly through GABAA receptors (GABAARs) containing α2 subunits (α2-GABAARs). Previous work indicates that potentiation of these receptors in the spinal cord evokes profound antihyperalgesia also after systemic administration, but possible synergistic or antagonistic actions of supraspinal α2-GABAARs on spinal antihyperalgesia have not yet been addressed. Here we generated two lines of GABAAR-mutated mice, which either lack α2-GABAARs specifically from the spinal cord, or, which express only benzodiazepine-insensitive α2-GABAARs at this site. We analyzed the consequences of these mutations for antihyperalgesia evoked by systemic treatment with the novel non-sedative benzodiazepine site agonist HZ166 in neuropathic and inflammatory pain. Wild-type mice and both types of mutated mice had similar baseline nociceptive sensitivities and developed similar hyperalgesia. However, antihyperalgesia by systemic HZ166 was reduced in both mutated mouse lines by about 60% and was virtually indistinguishable from that of global point-mutated mice, in which all α2-GABAARs were benzodiazepine insensitive. The major (α2-dependent) component of GABAAR-mediated antihyperalgesia was therefore exclusively of spinal origin, whereas supraspinal α2-GABAARs had neither synergistic nor antagonistic effects on antihyperalgesia. Our results thus indicate that drugs that specifically target α2-GABAARs exert their antihyperalgesic effect through enhanced spinal nociceptive control. Such drugs may therefore be well-suited for the systemic treatment of different chronic pain conditions.Neuropsychopharmacology advance online publication, 18 September 2013; doi:10.1038/npp.2013.221.
    Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 08/2013; · 8.68 Impact Factor
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    ABSTRACT: Benzodiazepines (BZs) allosterically modulate γ-aminobutyric acid type-A receptors (GABAARs) to increase inhibitory synaptic strength. Diazepam binding inhibitor (DBI) protein is a BZ site ligand expressed endogenously in the brain, but functional evidence for BZ-mimicking positive modulatory actions has been elusive. We demonstrate an endogenous potentiation of GABAergic synaptic transmission and responses to GABA uncaging in the thalamic reticular nucleus (nRT) that is absent in both nm1054 mice, in which the Dbi gene is deleted, and mice in which BZ binding to α3 subunit-containing GABAARs is disrupted. Viral transduction of DBI into nRT is sufficient to rescue the endogenous potentiation of GABAergic transmission in nm1054 mice. Both mutations enhance thalamocortical spike-and-wave discharges characteristic of absence epilepsy. Together, these results indicate that DBI mediates endogenous nucleus-specific BZ-mimicking ("endozepine") roles to modulate nRT function and suppress thalamocortical oscillations. Enhanced DBI signaling might serve as a therapy for epilepsy and other neurological disorders.
    Neuron 05/2013; · 15.77 Impact Factor
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    ABSTRACT: Brain kappa-opioid receptors (KORs) are implicated in states of motivation and emotion. Activation of KORs negatively regulates mesolimbic dopamine (DA) neurons, and KOR agonists produce depressive-like behavioral effects. To further evaluate how KOR function affects behavior, we developed mutant mice in which exon 3 of the KOR gene (Oprk1) was flanked with Cre-lox recombination (loxP) sites. By breeding these mice with lines that express Cre-recombinase (Cre) in early embryogenesis (EIIa-Cre) or only in DA neurons (dopamine transporter [DAT]-Cre), we developed constitutive KOR knockouts (KOR-/-) and conditional knockouts that lack KORs in DA-containing neurons (DAT-KORlox/lox). Autoradiography demonstrated complete ablation of KOR binding in the KOR-/- mutants, and reduced binding in the DAT-KORlox/lox mutants. Quantitative reverse transcription polymerase chain reaction (qPCR) studies confirmed that KOR mRNA is undetectable in the constitutive mutants and reduced in the midbrain DA systems of the conditional mutants. Behavioral characterization demonstrated that these mutant lines do not differ from controls in metrics including hearing, vision, weight, and locomotor activity. Whereas KOR-/- mice appeared normal in the open field and light/dark box tests, DAT-KORlox/lox mice showed reduced anxiety-like behavior, an effect that is broadly consistent with previously reported effects of KOR antagonists. Sensitization to the locomotor-stimulating effects of cocaine appeared normal in KOR-/- mutants, but was exaggerated in DAT-KORlox/lox mutants. Increased sensitivity to cocaine in the DAT-KORlox/lox mutants is consistent with a role for KORs in negative regulation of DA function, whereas the lack of differences in the KOR-/- mutants suggests compensatory adaptations after constitutive receptor ablation. These mouse lines may be useful in future studies of KOR function.Neuropsychopharmacology accepted article preview online, 27 February 2013; doi:10.1038/npp.2013.58.
    Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 02/2013; · 8.68 Impact Factor
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    ABSTRACT: Neocortical neurons mediate the sedative and anticonvulsant properties of benzodiazepines. These agents enhance synaptic inhibition via positive modulation of γ-aminobutyric acid (GABA(A)) receptors harbouring α1-, α2-, α3- or α5-protein subunits. Benzodiazepine-sensitive GABA(A) receptors containing the α5-subunit are abundant in the neocortex, but their impact in controlling neuronal firing patterns is unknown. Here we studied how the discharge rates of cortical neurons are modified by a positive (SH-053-2'F-R-CH3) and a negative (L 655,708) α5-subunit-preferring allosteric modulator in comparison to diazepam, the classical non-selective benzodiazepine. Drug actions were characterized in slice cultures from wild-type and α5(H105R) knock-in mice by performing extracellular multi-unit-recordings. In knock-in mice, receptors containing the α5 subunit are insensitive to benzodiazepines. The non-selective positive allosteric modulator diazepam decreased the discharge rates of neocortical neurons during episodes of ongoing neuronal activity (up states). In contrast to diazepam, the α5-preferring positive modulator SH-053-2'F-R-CH3 accelerated action potential firing during up states. This promoting action was absent in slices from α5(H105R) mice, confirming that it is mediated by the α5-subunit. Consistent with these observations, the negative α5-selective modulator L 655,708 inhibited up state action potential activity in slices from wild-type mice. The opposing actions of diazepam and SH-053-2'F-R-CH3, which both enhance GABA(A) receptor function but differ in subtype-selectivity, uncovers contrasting roles of GABA(A) receptor subtypes in controlling the firing rates of cortical neurons. These findings may have important implications for the design of novel anaesthetic and anticonvulsant benzodiazepines displaying an improved efficacy and fewer side effects.
    European journal of pharmacology 02/2013; · 2.59 Impact Factor
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    ABSTRACT: Postmortem studies have revealed a downregulation of the transcription factor Pax5 in GABAergic neurons in bipolar disorder, a neurodevelopmental disorder, raising the question whether Pax5 in GABAergic neurons has a role in normal brain development. In a genetic approach to study functions of Pax5 in GABAergic neurons, Pax5 was specifically deleted in GABAergic neurons from Pax5 floxed mice using a novel Gad1-Cre transgenic mouse line expressing Cre recombinase in Gad1-positive, i.e. GABAergic neurons. Surprisingly, these mice developed a marked enlargement of the lateral ventricles at approximately seven weeks of age, which was lethal within 1-2 weeks of its appearance. This hydrocephalus phenotype was observed in mice homozygous or heterozygous for the Pax5 conditional knockout, with a gene dosage-dependent penetrance. By QTL (quantitative trait loci) mapping, a 3.5 Mb segment on mouse chromosome 4 flanked by markers D4Mit237 and D4Mit214 containing approximately 92 genes including Pax5 has previously been linked to differences in lateral ventricular size. Our findings are consistent with Pax5 being a relevant gene underlying this QTL phenotype and demonstrate that Pax5 in GABAergic neurons is essential for normal ventricular development.
    genesis 01/2013; · 2.58 Impact Factor
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    ABSTRACT: BACKGROUND:: γ-aminobutyric acidA (GABAA) receptors mediate the actions of several intravenous general anesthetics. However, the contribution of α3-containing GABAA receptors to the action of these drugs is unknown. METHODS:: The authors compared anesthetic endpoints (hypnosis, immobility, hypothermia) in response to various intravenous anesthetics in mice lacking the α3 subunit of the GABAA receptor (α3 knockout) and in wild-type mice. Furthermore, the authors generated and analyzed conditional mutant mice expressing the GABAA receptor α3 subunit exclusively in noradrenergic neurons. RESULTS:: α3 knockout mice displayed decreased hypnotic and hypothermic responses to etomidate and midazolam, but an increased response to pentobarbital. The hypnotic response to ketamine was unaltered, whereas the hypothermic response was increased. In contrast, the hypnotic but not the hypothermic response to medetomidine was increased. The combination of ketamine/xylazine displayed increased hypnotic, immobilizing, and hypothermic effects in α3 knockout mice. Mice expressing the α3 subunit exclusively in noradrenergic neurons were generated to assess whether the lack of α3 subunits on noradrenergic neurons may be responsible for this effect. In these mice, the increases of the hypnotic and immobilizing actions induced by ketamine/xylazine were largely absent, whereas the increase in the hypothermic action was still present. CONCLUSION:: α3-containing GABAA receptors bidirectionally regulate essential anesthetic actions: they mediate anesthetic actions of etomidate and midazolam, known to selectively act at GABAA receptors, and they negatively constrain anesthetic actions of compounds with targets partly or exclusively distinct from GABAA receptors such as medetomidine, ketamine, and pentobarbital. Furthermore, our results indicate that α3-containing GABAA receptors on noradrenergic neurons may contribute to this constraint.
    Anesthesiology 01/2013; · 5.16 Impact Factor
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    ABSTRACT: Benzodiazepines (BZs) are safe drugs for treating anxiety, sleep, and seizure disorders, but their use also results in unwanted effects including memory impairment, abuse, and dependence. The present study aimed to reveal the molecular mechanisms that may contribute to the effects of BZs in the hippocampus (HIP), an area involved in drug-related plasticity, by investigating the regulation of immediate early genes following BZ administration. Previous studies have demonstrated that both brain derived neurotrophic factor (BDNF) and c-Fos contribute to memory- and abuse-related processes that occur within the HIP, and their expression is altered in response to BZ exposure. In the current study, mice received acute or repeated administration of BZs and HIP tissue was analyzed for alterations in BDNF and c-Fos expression. Although no significant changes in BDNF or c-Fos were observed in response to twice-daily intraperitoneal (i.p.) injections of diazepam (10 mg/kg + 5 mg/kg) or zolpidem (ZP; 2.5 mg/kg + 2.5 mg/kg), acute i.p. administration of both triazolam (0.03 mg/kg) and ZP (1.0 mg/kg) decreased BDNF protein levels within the HIP relative to vehicle, without any effect on c-Fos. ZP specifically reduced exon IV-containing BDNF transcripts with a concomitant increase in the association of methyl-CpG binding protein 2 (MeCP2) with BDNF promoter IV, suggesting that MeCP2 activity at this promoter may represent a ZP-specific mechanism for reducing BDNF expression. ZP also increased the association of phosphorylated cAMP response element binding protein (pCREB) with BDNF promoter I. Future work should examine the interaction between ZP and DNA as the cause for altered gene expression in the HIP, given that BZs can enter the nucleus and intercalate into DNA directly.
    PLoS ONE 01/2013; 8(12):e84806. · 3.53 Impact Factor
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    ABSTRACT: GABA type A receptors (GABA(A)-R) are important for ethanol actions and it is of interest to link individual subunits with specific ethanol behaviors. We studied null mutant mice for six different GABA(A)-R subunits (α1, α2, α3, α4, α5 and δ). Only mice lacking the α2 subunit showed reduction of conditioned taste aversion (CTA) to ethanol. These results are in agreement with data from knock-in mice with mutation of the ethanol-sensitive site in the α2-subunit (Blednov et al., 2011) and indicate this aversive property of ethanol is dependent on ethanol action on α2-containing GABA(A)-R. Deletion of the α2-subunit led to faster recovery whereas absence of the α3-subunit slowed recovery from ethanol-induced incoordination (rotarod). Deletion of the other four subunits did not affect this behavior. Similar changes in this behavior for the α2 and α3 null mutants were found for flurazepam motor-incoordination. However, no differences in recovery were found in motor-incoordinating effects of an α1-selective modulator (zolpidem) or an α4-selective agonist (gaboxadol). Therefore, recovery of rotarod incoordination is under control of two GABA(A)-R subunits: α2 and α3. For motor activity, α3 null mice demonstrated higher activation by ethanol (1 g/kg) whereas both α2 and α3 (-/-) knockout mice were less sensitive to ethanol-induced reduction of motor activity (1.5 g/kg). These studies demonstrate that the effects of ethanol at GABAergic synapses containing α2 subunit are important for specific behavioral effects of ethanol which may be relevant to the genetic linkage of the α2 subunit with human alcoholism.
    Neuropharmacology 11/2012; · 4.11 Impact Factor
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    ABSTRACT: Moderate reductions in synaptic γ-aminobutyric acid(A) receptors (GABA(A)Rs) have been associated with an enhanced defensive behavioral reactivity to mild threat, sensitive to diazepam. We here tested whether a deficit in α2 subunit-containing GABAergic synapses is sufficient to cause this anxiety-related phenotype and to prevent its attenuation by the benzodiazepine. Wild type (α2+/+), heterozygous (α2+/-) and homozygous (α2-/-) knock-out littermates were tested in the free-choice exploratory (FCE) and the light/dark choice (LDC) paradigms. α2-/- mice, double mutant α1H101Rα2-/- and α3H126Rα2-/- mice, which combine a lack of α2-GABA(A)Rs with point-mutated diazepam-insensitive either α1H101R or α3H126R-GABA(A)Rs, and double point-mutated α1H101Rα2H101R and α1H101Rα3H126R mice were used to uncover the GABA(A)R subtype(s) mediating the drug effects. Data show that in the FCE, α2-/- mice exhibited more retractions (i.e. risk assessment) and longer latencies to first occurrence into the novel compartment and less transitions and time spent inside it in comparison to α2+/- and α2+/+ mice. In the LDC, α2-/- mice visited and spent less time in the lit box and stayed longer in the tunnel than the other two groups. Minor differences were found between α2+/- and α2+/+ mice in the two paradigms. Diazepam (1.5mg/kg per os) normalized retractions and latencies in the FCE in α2-/- and α3H126Rα2-/- mice, but not in α1H101Rα2-/- mice. The same drug treatment failed to attenuate behavioral aversion in both paradigms in all mutants with impaired α2-GABA(A)R function. These results reveal α2-containing GABA(A)Rs as key molecular determinants in the regulation of anxiety-related responses elicited by exposure to relative novelty and mild threat. In the absence of these receptors, diazepam through activation of α1-GABA(A)Rs remains effective in reducing risk assessment, but not behavioral aversion.
    Pharmacology Biochemistry and Behavior 10/2012; · 2.61 Impact Factor
  • Elif Engin, Jing Liu, Uwe Rudolph
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    ABSTRACT: GABA(A) receptors have important physiological functions, as revealed by pharmacological studies and experiments involving gene-targeted mouse models, and are the target of widely used drugs such as the benzodiazepines. In this review, we are summarizing current knowledge about the function of α2-containing GABA(A) receptors, a receptor subtype representing approximately 15-20% of all GABA(A) receptors. This receptor subtype mediates anxiolytic-like, reward-enhancing, and antihyperalgesic actions of diazepam, and has antidepressant-like properties. Secondary insufficiency of α2-containing GABA(A) receptors has been postulated to play a role in the pathogenesis of schizophrenia, and may be involved in cognitive impairment in other disorders. Moreover, polymorphisms in the GABRA2 gene encoding the GABA(A) receptor α2 subunit have been found to be linked to chronic alcohol dependence and to polydrug abuse. Thus, α2-containing GABA(A) receptors are involved in the regulation and/or modulation of emotional behaviors and of chronic pain, and appear to be a valid target for novel therapeutic approaches for the treatment of anxiety, depression, schizophrenia and chronic pain.
    Pharmacology [?] Therapeutics 08/2012; 136(2):142-52. · 7.79 Impact Factor
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    ABSTRACT: Benzodiazepines such as diazepam are widely prescribed as anxiolytics and sleep aids. Continued use of benzodiazepines, however, can lead to addiction in vulnerable individuals. Here, we investigate the neural mechanisms of the behavioral effects of benzodiazepines using the intracranial self-stimulation (ICSS) test, a procedure with which the reward-enhancing effects of these drugs can be measured. Benzodiazepines bind nonselectively to several different GABA(A) receptor subtypes. To elucidate the α subunit(s) responsible for the reward-enhancing effects of benzodiazepines, we examined mice carrying a histidine-to-arginine point mutation in the α1, α2, or α3 subunit, which renders the targeted subunit nonresponsive to diazepam, other benzodiazepines and zolpidem. In wild-type and α1-point-mutated mice, diazepam caused a dose-dependent reduction in ICSS thresholds (reflecting a reward-enhancing effect) that is comparable to the reduction observed following cocaine administration. This effect was abolished in α2- and α3-point-mutant mice, suggesting that these subunits are necessary for the reward-enhancing action of diazepam. α2 Subunits appear to be particularly important, since diazepam increased ICSS thresholds (reflecting an aversive-like effect) in α2-point-mutant animals. Zolpidem, an α1-preferring benzodiazepine-site agonist, had no reward-enhancing effects in any genotype. Our findings implicate α2 and α3 subunit containing GABA(A) receptors as key mediators of the reward-related effects of benzodiazepines. This finding has important implications for the development of new medications that retain the therapeutic effects of benzodiazepines but lack abuse liability.
    Neuropsychopharmacology: official publication of the American College of Neuropsychopharmacology 07/2012; 37(11):2531-40. · 8.68 Impact Factor
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    ABSTRACT: In mammals, olfactory bulb granule cells (GCs) are generated throughout life in the subventricular zone. GABAergic inputs onto newborn neurons likely regulate their maturation, but the details of this process remain still elusive. Here, we investigated the differentiation, synaptic integration, and survival of adult-born GCs when their afferent GABAergic inputs are challenged by conditional gene targeting. Migrating GC precursors were targeted with Cre-eGFP-expressing lentiviral vectors in mice with a floxed gene encoding the GABA(A) receptor α2-subunit (i.e., Gabra2). Ablation of the α2-subunit did not affect GC survival but dramatically delayed their maturation. We found a reduction in postsynaptic α2-subunit and gephyrin clusters accompanied by a decrease in the frequency and amplitude of GABAergic postsynaptic currents beginning ∼14 d post-injection (dpi). In addition, mutant cells exhibited altered dendritic branching and spine density. Spine loss appeared with mislocation of glutamatergic synapses on dendritic shafts and a reduction of spontaneous glutamatergic postsynaptic currents, underscoring the relevance of afferent GABAergic transmission for a proper synaptic integration of newborn GCs. To test the role of GABAergic signaling during much early stages of GC maturation, we used a genetic strategy to selectively inactivate Gabra2 in precursor cells of the subventricular zone. In these mice, labeling of newborn GCs with eGFP lentiviruses revealed similar morphological alterations as seen on delayed Gabra2 inactivation in migrating neuroblasts, with reduced dendritic branching and spine density at 7 dpi. Collectively, these results emphasize the critical role of GABAergic synaptic signaling for structural maturation of adult-born GCs and formation of glutamatergic synapses.
    Journal of Neuroscience 06/2012; 32(26):9103-15. · 6.91 Impact Factor
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    ABSTRACT: GABAergic inhibition in the amygdala is essential in regulating fear and anxiety. Although fast "phasic" inhibition arising through the activation of postsynaptic GABA(A) receptors (GABA(A)Rs) has been well described in the amygdala, much less is known about extrasynaptic GABA(A)Rs mediating persistent or tonic inhibition and regulating neuronal excitability. Here, we recorded tonic currents in the basolateral (BLA) nucleus and the lateral (LA) nucleus of the amygdala. While all BLA principal cells expressed a robust GABAergic tonic current, only 70% of LA principal cells showed a tonic current. Immunohistochemical stainings revealed that the α3 GABA(A)R subunit is expressed moderately in the LA and strongly throughout the BLA nucleus, where it is located mostly at extrasynaptic sites. In α3 subunit KO mice, tonic currents are significantly reduced in BLA principal cells yet not in LA principal cells. Moreover, the α3 GABA(A)R-selective benzodiazepine site agonist and anxiolytic compound TP003 increases tonic currents and dampens excitability markedly in wild-type BLA principal cells but fails to do so in α3KO BLA cells. Interneurons of the LA and BLA nuclei also express a tonic current, but TP003-induced potentiation is seen in only a small fraction of these cells, suggesting that primarily other GABA(A)R variants underlie tonic inhibition in this cell type. Together, these studies demonstrate that α3 GABA(A)R-mediated tonic inhibition is a central component of the inhibitory force in the amygdala and that tonically activated α3 GABA(A)Rs present an important target for anxiolytic or fear-reducing compounds.
    Journal of Neuroscience 06/2012; 32(25):8611-9. · 6.91 Impact Factor

Publication Stats

7k Citations
1,061.16 Total Impact Points

Institutions

  • 2007–2014
    • McLean Hospital
      • Laboratory of Genetic Neuropharmacology
      Cambridge, Massachusetts, United States
  • 2013
    • Stanford Medicine
      • Department of Neurology and Neurological Sciences
      Stanford, California, United States
  • 2003–2013
    • University of Tuebingen
      • Institute of Pharmacology and Toxicology
      Tübingen, Baden-Württemberg, Germany
  • 1994–2013
    • University of Zurich
      • Institute of Veterinary Pharmakology and Toxicology
      Zürich, ZH, Switzerland
  • 2011
    • Università degli Studi di Torino
      • Dipartimento di Scienze Cliniche e Biologiche
      Torino, Piedmont, Italy
  • 2008–2011
    • Harvard Medical School
      • Department of Psychiatry
      Boston, MA, United States
    • Friedrich-Alexander Universität Erlangen-Nürnberg
      • Department of Experimental and Clinical Pharmacology and Toxicology
      Erlangen, Bavaria, Germany
  • 2010
    • Hertie-Institute for Clinical Brain Research
      Tübingen, Baden-Württemberg, Germany
  • 2006–2009
    • Stanford University
      • Department of Neurology and Neurological Sciences
      Stanford, CA, United States
  • 1997–2002
    • University of California, Los Angeles
      • • Department of Medicine
      • • Department of Anesthesiology
      Los Angeles, CA, United States
  • 1990–1998
    • Baylor College of Medicine
      • Department of Molecular Physiology & Biophysics
      Houston, Texas, United States
  • 1989–1991
    • Freie Universität Berlin
      • Institute of Pharmacology and Toxicology
      Berlin, Land Berlin, Germany