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Jorge Pérez-León, Moritz J. Frech, Jörn E. Schröder, Frauke Fischer, Matthias Kneussel, Heinz Wässle, Kurt H. Backus; Spontaneous Synaptic Activity in an Organotypic Culture of the Mouse Retina. Invest. Ophthalmol. Vis. Sci. 2003;44(3):1376-1387. doi: 10.1167/iovs.02-0702.
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purpose. Many strains of mutant mice die at birth, when the retina is still very immature. The retinas of such mice can be studied in organotypic cultures. After a preceding anatomic study of the synaptic development, the electrical activity of the synaptic circuits within such cultures was studied in wild-type and gephyrin-deficient mice.
methods. Organotypic cultures of newborn mouse retinas were grown for 14 days in vitro. Spontaneous postsynaptic currents (sPSCs) of amacrine cells were measured by using the whole-cell configuration of the patch-clamp technique. GABAergic and glycinergic currents that were isolated with specific antagonists, and retinas from wild-type (geph +/+) and gephyrin-deficient (geph −/−) mice were compared.
results. Rapidly decaying sPSCs that were blocked by kynurenic acid were mediated by ionotropic glutamate receptors, whereas sPSCs with significantly higher peak amplitudes and slow-decay kinetics were identified as spontaneous inhibitory postsynaptic currents (sIPSCs) mediated by γ-aminobutyric acid type A receptors (GABAARs) and glycine receptors (GlyRs). In gephyrin-deficient (geph −/−) cultures, we found no sIPSCs mediated by GlyRs. sIPSCs mediated by GABAARs expressed in amacrine cells of geph −/− retinas decayed significantly faster than GABAergic sIPSCs recorded in amacrine cells of geph +/+ retinas.
conclusions. The different decay kinetics of GABAARs expressed in amacrine cells of geph +/+ and of geph −/− retinas suggests that these cells express at least two types of GABAAR subtypes. In amacrine cells of geph −/− mice, a specific GABAAR subtype that may contain the α2 subunit, is impaired by the absence of gephyrin, whereas other GABAARs appear to function normally.
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