PubMed Health⌕ Search

Biomedical subjects

U Rudolph

Publications and source records attributed to U Rudolph.

At least 19 recordsLinked to original sources
PubMed2003

Diazepam-induced changes on sleep and the EEG spectrum in mice: role of the alpha3-GABA(A) receptor subtype.

Benzodiazepines reduce EEG slow-wave activity in non-REM sleep by potentiating GABAergic neurotransmission at GABAA receptors via a modulatory binding site. However, the mechanisms of action underlying the effects of benzodiazepines on sleep and the sleep EEG are still unknown. Slow waves during sleep are generated by the corticothalamic system and synchronized by the inhibitory GABAergic neurons of the reticular thalamic nucleus. This region contains exclusively alpha3-containing GABAA receptors. We investigated the role of these receptors in the mediation of diazepam effects on the sleep EEG by studying point-mutated mice in which the alpha3-GABAA receptor is diazepam-insensitive [alpha3(H126R)]. Sleep was recorded for 12 h after i.p. injection of 3 mg/kg diazepam or vehicle at light onset in alpha3(H126R) and wild-type controls (n = 13-17 per genotype). The main effect was a marked reduction of slow-wave activity (EEG power density in 0.75-4.00 Hz) in non-REM sleep and a concomitant increase in frequencies above 15.00 Hz in non-REM sleep and waking in both genotypes. Neither effect of diazepam differed significantly between the genotypes. Despite the exclusive expression of alpha3-containing GABAA receptors in the reticular thalamic nucleus, these receptors do not seem to be critical for the mediation of the effects of diazepam on the sleep EEG.

Animals↗
PubMed2002

Trace fear conditioning involves hippocampal alpha5 GABA(A) receptors.

The heterogeneity of gamma-aminobutyric acid type A (GABA(A)) receptors contributes to the diversity of neuronal inhibition in the regulation of information processing. Although most GABA(A) receptors are located synaptically, the small population of alpha5GABA(A) receptors is largely expressed extrasynaptically. To clarify the role of the alpha5GABA(A) receptors in the control of behavior, a histidine-to-arginine point mutation was introduced in position 105 of the murine alpha5 subunit gene, which rendered the alpha5GABA(A) receptors diazepam-insensitive. Apart from an incomplete muscle relaxing effect, neither the sedative, anticonvulsant, nor anxiolytic-like activity of diazepam was impaired in alpha5(H105R) mice. However, in hippocampal pyramidal cells, the point mutation resulted in a selective reduction of alpha5GABA(A) receptors, which altered the drug-independent behavior. In line with the role of the hippocampus in certain forms of associative learning, trace fear conditioning, but not delay conditioning or contextual conditioning, was facilitated in the mutant mice. Trace fear conditioning differs from delay conditioning in that the conditioned and unconditioned stimulus are separated by a time interval. Thus, the largely extrasynaptic alpha5GABA(A) receptors in hippocampal pyramidal cells are implicated as control elements of the temporal association of threat cues in trace fear conditioning.

Animals↗
PubMed2002

Contribution of the alpha1-GABA(A) receptor subtype to the pharmacological actions of benzodiazepine site inverse agonists.

A histidine-to-arginine point-mutation at position 101 in the alpha1-subunit of gamma-aminobutyric acid (GABA)(A) receptors has been shown to switch the in vitro efficacy of Ro 15-4513 from inverse agonism to agonism. In order to assess the consequences of this pharmacological switch in vivo, the motor and proconvulsant effects of Ro 15-4513 were analyzed in knock-in mice containing point-mutated alpha1(H101R)-GABA(A) receptors. Furthermore the influence of the alpha1(H101R) substitution on the efficacy of the beta-carboline inverse agonist DMCM was examined both in vitro and in vivo. Ro 15-4513 (10 mg/kg) increased baseline locomotion and potentiated the convulsant effect of pentylenetetrazole in wild type mice. In alpha1(H101R) mice, Ro 15-4513 decreased locomotion and, at a higher dose (30 mg/kg) it displayed an anticonvulsant action. In vitro, DMCM acted as an inverse agonist at recombinant alpha1beta2gamma2 receptors whereas it potentiated GABA-evoked chloride currents at alpha1(H101R)beta2gamma2 receptors. DMCM was inactive as a convulsant in alpha1(H101R) mice. In keeping with the major contribution of these receptors to the sedative and anticonvulsant properties of benzodiazepine site agonists, the present findings identify the alpha1-GABA(A) receptors as the molecular targets for the allosteric modulation by benzodiazepine site ligands in either direction with regard to the behavioral outputs, sedation/motor stimulation and anticonvulsion/proconvulsion.

Animals↗
PubMed2002

A new benzodiazepine pharmacology.

Classical benzodiazepine drugs are in wide clinical use as anxiolytics, hypnotics, anticonvulsants, and muscle relaxants. They act by enhancing the gamma-aminobutyric acid(A) (GABA(A)) receptor function in the central nervous system. The pharmacological relevance of the multitude of structurally diverse GABA(A) receptor subtypes has only recently been identified. Based on an in vivo point mutation strategy, alpha(1)-GABA(A) receptors were found to mediate sedation, anterograde amnesia, and part of the seizure protection, whereas alpha(2)-GABA(A) receptors, but not alpha(3)-receptors, mediate anxiolysis. Rational drug targeting to specific receptor subtypes has now become possible. Only restricted neuronal networks will be modulated by the new subtype-selective drugs. Promising new anxiolytics have already been developed. A new pharmacology of the benzodiazepine site is on the horizon.

Animals↗
PubMed2002

Regression of Peyer's patches in G alpha i2 deficient mice prior to colitis is associated with reduced expression of Bcl-2 and increased apoptosis.

BACKGROUND: G protein deficient (G alpha i2-/-) mice spontaneously develop an inflammatory bowel disease (IBD) closely resembling ulcerative colitis. Previous studies have demonstrated that gut T cells are hyperreactive to the endogenous microflora in most IBD models. AIMS: The aim of this study was to analyse Peyer's patches (PP), the inductive sites for gut mucosal immune responses. SUBJECTS AND METHODS: G alpha i2-/- mice, an animal model for IBD, were analysed using immunological methods with regard to phenotype and function. RESULTS: We found significantly decreased numbers of PP in G alpha i2-/- mice. Even before the onset of colitis, G alpha i2 deficient animals exhibited diminished size of PP, as judged by histology. This involution of PP was associated with strongly increased levels of apoptotic lymphocytes, associated with decreased levels of antiapoptotic intracellular protein Bcl-2. PP T lymphocytes showed highly elevated production of interferon gamma in response to the enteric flora compared with PP T cells from wild-type mice, which produced predominantly interleukin 10. CONCLUSIONS: Thus even before the onset of colitis, the PP in G alpha i2 deficient mice is a Th1 dominated milieu associated with downregulated levels of Bcl-2, resulting in increased apoptosis of lymphocytes leading to regression of PP. We speculate that this Th1 dominated microenvironment in the inductive site for mucosal immune responses contributes to the development of colitis in G alpha i2 deficient mice.

Animals↗
PubMed2001

Diazepam-induced changes in sleep: role of the alpha 1 GABA(A) receptor subtype.

Ligands acting at the benzodiazepine (BZ) site of gamma-aminobutyric acid type A (GABA(A)) receptors currently are the most widely used hypnotics. BZs such as diazepam (Dz) potentiate GABA(A) receptor activation. To determine the GABA(A) receptor subtypes that mediate the hypnotic action of Dz wild-type mice and mice that harbor Dz-insensitive alpha1 GABA(A) receptors [alpha1 (H101R) mice] were compared. Sleep latency and the amount of sleep after Dz treatment were not affected by the point mutation. An initial reduction of rapid eye movement (REM) sleep also occurred equally in both genotypes. Furthermore, the Dz-induced changes in the sleep and waking electroencephalogram (EEG) spectra, the increase in power density above 21 Hz in non-REM sleep and waking, and the suppression of slow-wave activity (SWA; EEG power in the 0.75- to 4.0-Hz band) in non-REM sleep were present in both genotypes. Surprisingly, these effects were even more pronounced in alpha1(H101R) mice and sleep continuity was enhanced by Dz only in the mutants. Interestingly, Dz did not affect the initial surge of SWA at the transitions to sleep, indicating that the SWA-generating mechanisms are not impaired by the BZ. We conclude that the REM sleep inhibiting action of Dz and its effect on the EEG spectra in sleep and waking are mediated by GABA(A) receptors other than alpha1, i.e., alpha2, alpha3, or alpha5 GABA(A) receptors. Because alpha1 GABA(A) receptors mediate the sedative action of Dz, our results provide evidence that the hypnotic effect of Dz and its EEG "fingerprint" can be dissociated from its sedative action.

Animals↗
PubMed2001

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 GABA(A) receptor which is different from the GABA binding site, thus increasing the chloride current. Benzodiazepines like diazepam bind to GABA(A) receptors containing the alpha subunits alpha 1, alpha 2, alpha 3, or alpha 5, most likely in alphabetagamma combinations.

Animals↗
PubMed2001

GABA(A) receptor subtypes: dissecting their pharmacological functions.

The enhancement of GABA-mediated synaptic transmission underlies the pharmacotherapy of various neurological and psychiatric disorders. GABA(A) receptors are pluripotent drug targets that display an extraordinary structural heterogeneity: they are assembled from a repertoire of at least 18 subunits (alpha1-6, beta1-3, gamma1-3, delta, epsilon, theta, rho1-3). However, differentiating defined GABA(A) receptor subtypes on the basis of function has had to await recent progress in the genetic dissection of receptor subtypes in vivo. Evidence that the various actions of allosteric modulators of GABA(A) receptors, in particular the benzodiazepines, can be attributed to specific GABA(A) receptor subtypes will be discussed. Such discoveries could open up new avenues for drug development.

Animals↗
PubMed2001

GABA(A)-receptor subtypes: a new pharmacology.

The GABA(A) receptor is a pluripotent drug target mediating anxiolytic, sedative, anticonvulsant, muscle relaxant and amnesic activity. These drug actions have now been attributed to defined receptor subtypes. Thus, precise guidelines are available for the development of novel drugs with more selective action and less side effects than those currently in clinical use.

Amnesia↗
PubMed2001

Antibody response to dietary and autoantigens in G alpha i2-deficient mice.

BACKGROUND: Mice with a targeted mutation in the G protein subunit G alpha i2 gene develop a colonic mucosal inflammation, with a highly activated B-cell response. We wanted to investigate whether this increased B-cell activity was directed against dietary antigens and/or various self tissues. METHODS: The level of antibodies specific for dietary (gliadin, soya and fish meal) antigens was measured by ELISA. Reactivity against self antigens was measured by immunohistochemistry on cryo-sectioned mouse and rat tissue. Sera and intestinal lavages were analysed from G alpha i2-/- mice before and after development of colitis and in age-matched wild type litter mates. RESULTS: Titres of antibodies against dietary antigens were significantly enhanced both in serum and in large intestinal lavages from G alpha i2-/- mice with ongoing colitis but not prior to disease, as compared to wild type mice. The autoreactivity to self tissues was significantly increased in G alpha i2-/- mice both before and after development of colitis as compared to litter mate control animals. Self tissue reactivity was directed not only against epithelial cells of the colon, small intestine and gastric glands, but also against smooth muscle cells, hepatocytes, bile duct cells, renal tubule and collecting tubule cells of the kidney. In analogy to human ulcerative colitis, autoantibodies against epithelial cells, bile duct epithelium and neutrophil granulocytes were found. CONCLUSIONS: Earlier increase in levels of autoantibodies (before onset of colitis) than of food antibodies (after onset of colitis) suggests the latter response to be a secondary phenomenon to e.g. a destroyed barrier function.

Animals↗
PubMed2001

Molecular targets for the myorelaxant action of diazepam.

Diazepam is used clinically for its myorelaxant, anxiolytic, sedative, and anticonvulsant properties. Although the anxiolytic action is mediated by alpha2 gamma-aminobutyric acid A (GABA(A)) receptors, the sedative action and in part the anticonvulsant action are mediated by alpha1 GABA(A) receptors. To identify the GABA(A) receptor subtypes mediating the action of diazepam on muscle tone, we have assessed the myorelaxant properties of diazepam in alpha2(H101R) and alpha3(H126R) knock-in mice harboring diazepam-insensitive alpha2 or alpha3 GABA(A) receptors, respectively. Whereas in alpha2(H101R) mice the myorelaxant action of diazepam was almost completely abolished at doses up to 10 mg/kg, the same dose induced myorelaxation in both wild-type and alpha3(H126R) mice. It was only at a very high dose (30 mg/kg diazepam) that alpha2(H101R) mice showed partial myorelaxation and alpha3(H126R) mice were partially protected from myorelaxation compared with wild-type mice. Thus, the myorelaxant activity of diazepam seems to be mediated primarily by alpha2 GABA(A) receptors and at high concentrations also by alpha3 GABA(A) receptors.

Animals↗
PubMed2000

Molecular and neuronal substrate for the selective attenuation of anxiety.

Benzodiazepine tranquilizers are used in the treatment of anxiety disorders. To identify the molecular and neuronal target mediating the anxiolytic action of benzodiazepines, we generated and analyzed two mouse lines in which the alpha2 or alpha3 GABAA (gamma-aminobutyric acid type A) receptors, respectively, were rendered insensitive to diazepam by a knock-in point mutation. The anxiolytic action of diazepam was absent in mice with the alpha2(H101R) point mutation but present in mice with the alpha3(H126R) point mutation. These findings indicate that the anxiolytic effect of benzodiazepine drugs is mediated by alpha2 GABAA receptors, which are largely expressed in the limbic system, but not by alpha3 GABAA receptors, which predominate in the reticular activating system.

Animals↗
PubMed2000

Mechanism of action of the hypnotic zolpidem in vivo.

Zolpidem is a widely used hypnotic agent acting at the GABA(A) receptor benzodiazepine site. On recombinant receptors, zolpidem displays a high affinity to alpha 1-GABA(A) receptors, an intermediate affinity to alpha(2)- and alpha(3)-GABA(A) receptors and fails to bind to alpha(5)-GABA(A) receptors. However, it is not known which receptor subtype is essential for mediating the sedative-hypnotic action in vivo. Studying alpha1(H101R) mice, which possess zolpidem-insensitive alpha(1)-GABA(A) receptors, we show that the sedative action of zolpidem is exclusively mediated by alpha(1)-GABA(A) receptors. Similarly, the activity of zolpidem against pentylenetetrazole-induced tonic convulsions is also completely mediated by alpha(1)-GABA(A) receptors. These results establish that the sedative-hypnotic and anticonvulsant activities of zolpidem are due to its action on alpha(1)-GABA(A) receptors and not on alpha(2)- or alpha(3)-GABA(A) receptors.

Animals↗
PubMed2000

Immune activation in the intestinal mucosa before the onset of colitis in Galphai2-deficient mice.

G-protein subunit Galphai2-deficient mice spontaneously develop an inflammatory bowel disease that clinically and histopathologically resembles ulcerative colitis in humans. The aim of this study was to determine whether immunological changes precede the development of colitis in Galphai2-deficient mice. Therefore, Galphai2-deficient mice with no clinical or histopathological signs of colitis were compared with Galphai2-deficient mice with established colitis and wild-type animals, concerning immunological parameters. Healthy Galphai2-deficient mice displayed an increased frequency of CD4+ T cells and a decreased frequency of CD19+ B lymphocytes in the intestinal mucosa compared with control mice. The CD4+ population was characterized by a memory phenotype, i.e. increased expression of CD44 and decreased expression of CD45RB and CD62L, as well as increased expression of the mucosal homing receptors integrins alpha4beta7 and alphaEbeta7. Production of pro-inflammatory cytokines, interleukin (IL)-1beta and interferon (IFN)-gamma, were increased in Galphai2-deficient mice before clinical signs of disease were evident. In addition, total immunoglobulin (Ig)G and IgA levels in large intestinal secretions were increased significantly compared with wild-type mice, and antibodies specific for the normal intestinal flora in large intestinal secretions were present in Galphai2-deficient mice several weeks before the onset of colitis. In contrast, antibodies against tropomyosin, a putative autoantigen in human ulcerative colitis, were not found in Galphai2-deficient mice before the onset of colitis, although they were present in animals with established disease. In conclusion, activation of the intestinal immune system precedes histopathological and clinical signs of inflammation in Galphai2-deficient mice, suggesting that immune abnormalities play an important role in the induction of colitis.

Animals↗
PubMed2000

[What is your profession? Evaluative approach and normal word choice for occupational descriptions in German].

Terms of occupation are often used in psychological research to refer to stimulus persons. The first comprehensive study for the German language is presented, in which 95 German commonly used terms of occupation are evaluated concerning a number of variables discussed in the literature, specifically perceptions of sympathy, prestige, typicality, positivity, negativity and ambivalence. As a consequence, it will be possible to balance terms of occupation in future research.

Adult↗
PubMed1999

Benzodiazepine actions mediated by specific gamma-aminobutyric acid(A) receptor subtypes.

GABA(A) (gamma-aminobutyric acid(A)) receptors are molecular substrates for the regulation of vigilance, anxiety, muscle tension, epileptogenic activity and memory functions, which is evident from the spectrum of actions elicited by clinically effective drugs acting at their modulatory benzodiazepine-binding site. Here we show, by introducing a histidine-to-arginine point mutation at position 101 of the murine alpha1-subunit gene, that alpha1-type GABA(A) receptors, which are mainly expressed in cortical areas and thalamus, are rendered insensitive to allosteric modulation by benzodiazepine-site ligands, whilst regulation by the physiological neurotransmitter gamma-aminobutyric acid is preserved. alpha1(H101R) mice failed to show the sedative, amnesic and partly the anticonvulsant action of diazepam. In contrast, the anxiolytic-like, myorelaxant, motor-impairing and ethanol-potentiating effects were fully retained, and are attributed to the nonmutated GABA(A) receptors found in the limbic system (alpha2, alpha5), in monoaminergic neurons (alpha3) and in motoneurons (alpha2, alpha5). Thus, benzodiazepine-induced behavioural responses are mediated by specific GABA(A) receptor subtypes in distinct neuronal circuits, which is of interest for drug design.

Animals↗
PubMed1999

Genetically modified animals in pharmacological research: future trends.

The recognition of molecular control elements which govern cell and organ function is essential for the development of novel drug therapies and for an understanding of drug actions. Thus, a major interest is focused on methodologies which permit the identification of novel control elements. This is of particular relevance for the identification of drug targets, the distinction of target isoforms, the differentiation of signalling pathways, the generation of disease models and toxicological testing. In this review, we discuss different classes of genetically modified animals and their potential to elucidate biological processes relevant for pharmacological research including functional genomics. Techniques which permit the time- and tissue-specific inducible regulation of gene expression present an important methodological advance.

Animals↗