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Characterization of the Spontaneous Synaptic Activity of Amacrine Cells in the Mouse Retina

Max-Planck-Institut für Hirnforschung, Neuroanatomische Abteilung, D-60528 Frankfurt am Main, Germany Frech, Moritz J., Jorge Pérez-León, Heinz Wässle, and Kurt H. Backus. Characterization of the Spontaneous Synaptic Activity of Amacrine Cells in the Mouse Retina. J. Neurophysiol. 86: 1632-1643, 200...

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Published in:Journal of neurophysiology 2001-10, Vol.86 (4), p.1632-1643
Main Authors: Frech, Moritz J, Perez-Leon, Jorge, Wassle, Heinz, Backus, Kurt H
Format: Article
Language:English
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Summary:Max-Planck-Institut für Hirnforschung, Neuroanatomische Abteilung, D-60528 Frankfurt am Main, Germany Frech, Moritz J., Jorge Pérez-León, Heinz Wässle, and Kurt H. Backus. Characterization of the Spontaneous Synaptic Activity of Amacrine Cells in the Mouse Retina. J. Neurophysiol. 86: 1632-1643, 2001. Amacrine cells are a heterogeneous class of interneurons that modulate the transfer of the light signals through the retina. In addition to ionotropic glutamate receptors, amacrine cells express two types of inhibitory receptors, GABA A receptors (GABA A Rs) and glycine receptors (GlyRs). To characterize the functional contribution of these different receptors, spontaneous postsynaptic currents (sPSCs) were recorded with the whole cell configuration of the patch-clamp technique in acutely isolated slices of the adult mouse retina. All amacrine cells investigated ( n  = 47) showed spontaneous synaptic activity. In six amacrine cells, spontaneous excitatory postsynaptic currents could be identified by their sensitivity to kynurenic acid. They were characterized by small amplitudes [mean: 13.7 ± 1.5 (SE) pA] and rapid decay kinetics (mean : 1.35 ± 0.16 ms). In contrast, the reversal potential of sPSCs characterized by slow decay kinetics (amplitude-weighted time constant, w , >4 ms) was dependent on the intracellular Cl concentration ( n  = 7), indicating that they were spontaneous inhibitory postsynaptic currents (sIPSCs). In 14 of 34 amacrine cells sIPSCs were blocked by bicuculline (10 µM), indicating that they were mediated by GABA A Rs. Only four amacrine cells showed glycinergic sIPSCs that were inhibited by strychnine (1 µM). In one amacrine cell, sIPSCs mediated by GABA A Rs and GlyRs were found simultaneously. GABAergic sIPSCs could be subdivided into one group best fit by a monoexponential decay function and another biexponentially decaying group. The mean amplitude of GABAergic sIPSCs ( 42.1 ± 5.8 pA) was not significantly different from that of glycinergic sIPSCs ( 28.0 ± 8.5 pA). However, GlyRs (mean T10/90: 2.4 ± 0.08 ms) activated significantly slower than GABA A Rs (mean T10/90: 1.2 ± 0.03 ms). In addition, the decay kinetics of monoexponentially decaying GABA A Rs (mean w : 20.3 ± 0.50), biexponentially decaying GABA A Rs (mean w : 30.7 ± 0.95), and GlyRs (mean w  = 25.3 ± 1.94) were significantly different. These differences in the activation and decay kinetics of sIPSCs indicate that amacrine cells of the mouse retina express at least three ty
ISSN:0022-3077
1522-1598
DOI:10.1152/jn.2001.86.4.1632