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Ectopic retinal ON bipolar cell synapses in the OFF inner plexiform layer: Contacts with dopaminergic amacrine cells and melanopsin ganglion cells
Author(s) -
Dumitrescu Olivia N.,
Pucci Francesco G.,
Wong Kwoon Y.,
Berson David M.
Publication year - 2009
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/cne.22158
Subject(s) - inner plexiform layer , neuroscience , melanopsin , amacrine cell , ribbon synapse , biology , retina , intrinsically photosensitive retinal ganglion cells , giant retinal ganglion cells , microbiology and biotechnology , anatomy , retinal ganglion cell , photopigment , vesicle , genetics , membrane , synaptic vesicle
Abstract A key principle of retinal organization is that distinct ON and OFF channels are relayed by separate populations of bipolar cells to different sublaminae of the inner plexiform layer (IPL). ON bipolar cell axons have been thought to synapse exclusively in the inner IPL (the ON sublamina) onto dendrites of ON‐type amacrine and ganglion cells. However, M1 melanopsin‐expressing ganglion cells and dopaminergic amacrine (DA) cells apparently violate this dogma. Both are driven by ON bipolar cells, but their dendrites stratify in the outermost IPL, within the OFF sublamina. Here, in the mouse retina, we show that some ON cone bipolar cells make ribbon synapses in the outermost OFF sublayer, where they costratify with and contact the dendrites of M1 and DA cells. Whole‐cell recording and dye filling in retinal slices indicate that type 6 ON cone bipolars provide some of this ectopic ON channel input. Imaging studies in dissociated bipolar cells show that these ectopic ribbon synapses are capable of vesicular release. There is thus an accessory ON sublayer in the outer IPL. J. Comp. Neurol. 517:226‐244, 2009. © 2009 Wiley‐Liss, Inc.