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  • 1
    Electronic Resource
    Electronic Resource
    GABAergic inhibition shapes frequency tuning and modifies response properties in the auditory midbrain of the leopard frog (1999)
    Springer
    Journal of comparative physiology 185 (1999), S. 479-491 
    Details
    ISSN: 1432-1351
    Keywords: Key words Iontophoresis ; Inferior colliculus ; Amphibian ; Rana pipiens ; Bicuculline ; GABA ; AbbreviationsBIC bicuculline methiodide ; CF characteristic frequency ; DNLL dorsal nucleus of the lateral lemniscus ; eFTC excitatory frequency tuning curve ; GABAγ-amino butyric acid ; IC inferior colliculus ; iFTC inhibitory frequency tuning curve ; PB phasic burst ; PL-1 primary-like 1 ; PL-2 primary-like 2 ; PL-3 primary-like 3 ; PSTH post-stimulus time histogram ; SPL sound pressure level ; SRN superficial reticular nucleus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The functional role of GABAergic inhibition in shaping the frequency tuning of 96 neurons in the torus semicircularis of the leopard frog, Rana pipiens, was studied using microiontophoresis of the GABAA receptor antagonist, bicuculline methiodide. Bicuculline application abolished, or reduced in size, the inhibitory tuning curves of 72 neurons. In each case, there was a concommitant broadening of the excitatory tuning curve such that frequency-intensity combinations that were inhibitory under control conditions, became excitatory during disinhibition with bicuculline methiodide. These effects were observed irrespective of the excitatory tuning curve configuration prior to bicuculline methiodide application. Results indicate an important role for GABA-mediated inhibition in shaping the frequency selectivity of neurons in the torus semicircularis of the leopard frog. Bicuculline application also affected several other response properties of neurons in the leopard frog torus. Disinhibition with bicuculline methiodide increased both the spontaneous firing rate (18 cells) and stimulus-evoked discharge rate (81 cells) of torus neurons, decreased the minimum excitatory threshold for 18 cells, and altered the temporal discharge pattern of 47 neurons. Additional roles for GABAergic inhibition in monaural signal analysis are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003590050409
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  • 2
    Electronic Resource
    Electronic Resource
    Characterization of amino-acid transport in Ricinus communis roots using isolated membrane vesicles (1995)
    Springer
    Planta 196 (1995), S. 166-173 
    Details
    ISSN: 1432-2048
    Keywords: Amino acid transport ; Carrier (amino acids) ; Plasma membrane ; Ricinus (amino acid transport) ; Root (amino acid transport)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The mechanism and specificity of amino-acid transport at the plasma membrane of Ricinus communis L. roots was investigated using membrane vesicles isolated by phase partitioning. The transport of glutamine, isoleucine, glutamic acid and aspartic acid was driven by both a pH gradient and a membrane potential (internally alkaline and negative), created artificially across the plasma membrane. This is consistent with transport via a proton symport. In contrast, the transport of the basic amino acids, lysine and arginine, was driven by a negative internal membrane potential but not by a pH gradient, suggesting that these amino acids may be taken up via a voltage-driven uniport. The energized uptake of all of the amino acids tested showed a saturable phase, consistent with carrier-mediated transport. In addition, the membrane-potential-driven transport of all the amino acids was greater at pH 5.5 than at pH 7.5, which suggests that there could be a direct pH effect on the carrier. Several amino-acid carriers could be resolved, based on competition studies: a carrier with a high affinity for a range of neutral amino acids (apart from asparagine) but with a low affinity for basic and acidic amino acids; a carrier which has a high affinity for a range of neutral amino acids except isoleucine and valine, but with a low affinity for basic and acidic amino acids; and a carrier which has a higher affinity for basic and some neutral amino acids but has a lower affinity for acidic amino acids. The existence of a separate carrier for acidic amino acids is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00193230
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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