WILBERT

Wildauer Bücher+E-Medien Recherche-Tool

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Blackwell Publishing Ltd  (2)
Collection
Publisher
Years
  • 1
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: γ-Aminobutyric acid (GABAa) receptor β3 subunits were expressed in Xenopus laevis oocytes and studied using two-electrode voltage clamp. Injected oocytes exhibited an increased resting membrane conductance and more depolarized membrane potentials compared to uninjected control cells. Oocytes expressing β3 subunits were insensitive to GABA and muscimol, but pentobarbitone increased the membrane conductance in a concentration-dependent manner. The membrane current response to pentobarbitone reversed at the Cl−equilibrium potential and at relatively high concentrations (〉500 μM), a rebound CI− current was induced following the removal of pentobarbitone. In transfected human embryonic kidney (HEK) cells, the rebound current amplitude was reduced by desensitizing the β3 receptor with increased durations of ligand application. Both picrotoxin (0.5 nM to 10 μM) and Zn2+ (10 nM to 100 μM) reduced the resting membrane conductance for β3 cDNA-injected oocytes. These oocytes were insensitive to flurazepam (5 μM) and alphaxalone (10 μM), but responded with increased membrane conductance to propofol (10 μM) and pregnanolone (50 nM to 5 μM). The antagonists, bicuculline (10 μM) and strychnine (50 nM to 100 μM), also induced conductance increases in a concentration dependent manner; however, glycine (1 mM) was inactive. It was concluded that β3 subunits form spontaneously opening ion channels that can be up-regulated by some allosteric modulators, principally by pentobarbitone and propofol and, surprisingly, by bicuculline and strychnine, whilst picrotoxin and Zn2+ acted as antagonists. Computer modelling of some kinetic schemes was used to describe the rebound current observed in transfected HEK cells. This indicated that pentobarbitone, after modulation of the conductance, is potentially capable of further binding to the β3 receptor complex ‘driving’ the receptor into one or more desensitized states. This phenomenon may be of some importance for native neuronal GABAA receptors, where pentobarbitone can also evoke rebound current activation.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    ISSN: 1460-9568
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: The interaction of zinc with pre- and postsynaptic GABAB receptors was studied in adult rat hippocampal slices using intracellular recording in CA1 and CA3 pyramidal neurons. Zinc (50 – 300 μM) antagonized baclofen responses with a variable potency, whereas CGP-35348 (100 μM) or barium (300 μM) produced a more substantial and consistent inhibition. Zinc also induced giant GABAA-mediated depolarizing potentials (GDP) in these neurons. After blocking GABAA and excitatory synaptic transmission, monosynaptic hyperpolarizing inhibitory postsynaptic potentials (IPSP) mediated by GABAB receptors (IPSPB) were inhibited by CGP-35348 or barium; however, zinc increased the latency and prolonged the duration of the IPSPB and also induced the appearance of spontaneous giant GABAB-mediated hyperpolarizing potentials (GHP). In some cells, IPSPBs in zinc exhibited a multiphasic appearance. The early component was partially inhibited by 300 μM zinc and was followed by a late GHP. CGP-35348 at 100 μM inhibited the early monosynaptic IPSPB but not the GHP; however, at 300 μM both components were blocked. Paired-pulse inhibition of the IPSPB was used to assess the effect of zinc on presynaptic GABAB receptors. Neither the zinc-chelating agent CP94 (400 μM) nor zinc affected this phenomenon. CGP-35348, barium and polyvalent cations, such as cadmium, copper, cobalt, manganese, iron and aluminium, failed to induce giant potentials in hippocampal neurons. It is concluded that zinc is apparently unique in synchronizing the release of GABA to produce GDPs and GHPs.
    Type of Medium: Electronic Resource
    Location Call Number Limitation Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...