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This Article Full Text Full Text (PDF) Supplemental Figures All Versions of this Article: 101/6/2974    most recent 91001.2008v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Google Scholar Articles by Schlicker, K. Articles by Schmidt, M. PubMed PubMed Citation Articles by Schlicker, K. Articles by Schmidt, M.

GABA_C Receptor-Mediated Inhibition Is Altered But Not Eliminated in the Superior Colliculus of GABA_C 1 Knockout Mice

¹Allgemeine Zoologie and Neurobiologie, Ruhr-Universität Bochum, Bochum, Germany; and ²Department of Ophthalmology and Visual Sciences and Psychological and Brain Sciences, University of Louisville, Louisville, Kentucky

Submitted 5 September 2008; accepted in final form 18 March 2009

GABA_C receptors (GABA_CRs) are widely expressed in the mammalian subcortical visual system, particularly in the retina and superior colliculus (SC). GABA_CRs are composed of specific 1–3 subunits the expression of which varies among visual structures. Thus 1 subunits are most abundant in retina, and their loss eliminates GABA_CR expression and function. In the SC, 2 subunit expression may be equal to or stronger than 1 subunit expression; however, results across studies vary considerably. To more directly assess the expression of GABA_CR subunits, we characterized inhibition in the SC of wild-type (WT) and GABA_C 1 Null mice that lack expression of GABA_C 1 subunits. We used whole cell patch-clamp recordings and evaluated GABA_CR-mediated modulation of electrically evoked post synaptic currents using either agonists or antagonists in WT mice. In GABA_C 1 Null stratum griseum superficiale (SGS) cells, inhibitory postsynaptic currents were shorter in duration and their excitatory postsynaptic currents (EPSCs) were longer, indicating that a slow GABA_CR-mediated inhibitory component was reduced in each case. In contrast to retina, GABA_CR-mediated currents in the SC were altered but not eliminated in GABA_C 1 Null mice. In the majority of SC cells in GABA_C 1 Null mice, GABA_CR activation could still be induced to alter EPSC peak amplitudes in putative interneurons and in many projection neurons. These results, compared with previously published data, indicate a fundamental difference between retina and SC in the control of GABA_CR expression and subunit composition.