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Indoleamine‐accumulating amacrine cells are presynaptic to rod bipolar cells through GABA C receptors
Author(s) -
Fletcher Erica L.,
Wässle Heinz
Publication year - 1999
Publication title -
journal of comparative neurology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.855
H-Index - 209
eISSN - 1096-9861
pISSN - 0021-9967
DOI - 10.1002/(sici)1096-9861(19991011)413:1<155::aid-cne11>3.0.co;2-6
Subject(s) - immunolabeling , biology , amacrine cell , receptor , retina , microbiology and biotechnology , neuroscience , lucifer yellow , gabaa rho receptor , inhibitory postsynaptic potential , gabaa receptor , postsynaptic potential , ionotropic effect , intracellular , glutamate receptor , biochemistry , immunology , gap junction , immunohistochemistry
γ‐Aminobutyric acid (GABA), is a main source of inhibitory modulation of the rod pathway in the mammalian retina. The authors previously showed that rod bipolar cells express at least three types of ionotropic GABA receptors. Here, the authors sought to determine which neurons are the presynaptic partners at these synapses in the rabbit retina. Indoleamine‐accumulating amacrine cells (IACs) were immunolabeled with an antiserum against serotonin (5HT) in vertical sections and wholemounts of rabbit retinae that had been preloaded with 5HT. The tissue was double labeled for the ρ subunits of the GABA C receptor or the α3 subunit of the GABA A receptor. Punctate immunofluorescence was observed for both receptor subunits and was found to coincide with the dendrites and varicosities of IACs. The localization of ρ subunits was examined at the ultrastructural level by using postembedding techniques on slam‐frozen, cryosubstituted tissue. Double labeling at the electron microscopic level revealed that 5HT‐immunoreactive processes were presynaptic to rod bipolar cells through GABA C receptors. Intracellular injection of the two morphologic subclasses of IAC amacrine cells, S1 and S2, with Lucifer yellow followed by immunolabeling for the α3 or ρ subunits revealed that varicosities on the dendrites of both cell types were in register with α3‐ and ρ‐immunoreactive puncta. Taken together, these results suggest that IACs are presynaptic to rod bipolar cells through GABA C receptors and possibly through GABA A receptors. J. Comp. Neurol. 413:155–167, 1999. © 1999 Wiley‐Liss, Inc.