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Morphological analysis of the hyperpolarization‐activated cyclic nucleotide‐gated cation channel 1 (HCN1) immunoreactive bipolar cells in the rabbit retina
Author(s) -
Kim InBeom,
Lee EunJin,
Kang TaeHoon,
Chung JinWoong,
Chun MyungHoon
Publication year - 2003
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.10957
Subject(s) - retina , inner plexiform layer , hyperpolarization (physics) , amacrine cell , biology , neuroscience , axon , outer plexiform layer , biophysics , population , postsynaptic potential , microbiology and biotechnology , chemistry , biochemistry , receptor , organic chemistry , nuclear magnetic resonance spectroscopy , demography , sociology
Hyperpolarization‐activated cation currents ( I h ) have been identified in neurons in the central nervous system, including the retina. There is growing evidence that these currents, mediated by the hyperpolarization‐activated cyclic nucleotide‐gated cation channel (HCN), may play important roles in visual processing in the retina. This study was conducted to identify and characterize HCN1‐immunoreactive (IR) bipolar cells by immunocytochemistry, quantitative analysis, and electron microscopy. The HCN1‐IR bipolar cells were a subtype of OFF‐type cone bipolar cells and comprised 10% of the total number of cone bipolar cells. The axons of the HCN1‐IR cone bipolar cells ramified narrowly in the border of strata 1 and 2 of the inner plexiform layer (IPL). These cells formed a regular distribution, with a density of 1,825 cells/mm 2 at a position 1 mm ventral to the visual streak, falling to 650 cells/mm 2 in the ventral periphery. Double‐labeling experiments demonstrated that their axons stratified narrowly within and slightly proximal to the OFF‐starburst amacrine cell processes. In the IPL, they were presynaptic to amacrine cell processes. The most frequent postsynaptic dyads formed of HCN1‐IR bipolar cell axon terminals are pairs composed of both amacrine cell processes. These results suggest that these HCN1‐IR cone bipolar cells might be the same as the DAPI‐Ba1 bipolar population, and might therefore be involved in a direction‐selective mechanism, providing inputs to the OFF‐starburst amacrine cells and/or the OFF‐plexus of the ON–OFF ganglion cells. J. Comp. Neurol. 467:389–402, 2003. © 2003 Wiley‐Liss, Inc.