New aspects of dopaminergic interplexiform cell organization in the goldfish retina.
Dopaminergic interplexiform cells (DA-IPCs) in the goldfish retina have been reexamined by light and electron microscopic immunocytochemistry with antisera against dopamine (DA) or tyrosine hydroxylase (TH). Successful immunostaining with a specific anti-DA antiserum offers further direct support for DA-IPCs. Anti-DA immunocytochemistry in combination with [3H]-DA autoradiography shows 92% colocalization of the two markers, indicating that [3H]-DA autoradiography is a reliable technique for identification of DA-IPCs. Incubations with anti-TH antiserum show that immunoreactive DA-IPCs have a homogeneous distribution, with an average frequency of 71 +/- 8 cells/mm2 in retinas of 14-15 cm long goldfish. Their arrangement is distinctly nonrandom. Electron microscopy of TH-immunoreactive cell processes confirms that horizontal cell axons synapse onto DA-IPCs and adds the following junctional arrangements to the circuit diagram of the DA-IPC: 1) adjacent serial synapses between DA-IPCs, external horizontal cells, and putative glycinergic interplexiform cells, 2) junctional appositions between DA-IPCs and photoreceptor cells, 3) junctional appositions between neighbouring DA-IPCs, and 4) the "gap junctional complex," typically consisting of a DA-IPC process juxtaposed with a gap junction between horizontal cell axons. The gap junction is flanked by clusters of small, round vesicles and groups of electron-dense structures resembling intermediate filaments. These morphological results support the functional involvement of DA-IPCs in adaptive retinomotor movements and in horizontal cell gap junction modulation and/or dynamics. They also suggest particular interaction between the dopaminergic and the glycinergic IPC system in the outer plexiform layer of goldfish retina.
Van Haesendonck
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Eye Research Laboratory, Katholieke Universiteit te Leuven, Belgium.
Marc
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Missotten
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D000818:Animals; D000918:Antibody Specificity; D001345:Autoradiography; D001369:Axons / Q000648:ultrastructure; D004298:Dopamine / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D006054:Goldfish / Q000502:physiology*; D007150:Immunohistochemistry; D007382:Intermediate Filaments / Q000648:ultrastructure; D008854:Microscopy, Electron; D010786:Photoreceptor Cells / Q000648:ultrastructure; D012160:Retina / Q000166:cytology* / Q000502:physiology; D013569:Synapses / Q000502:physiology / Q000648:ultrastructure; D014446:Tyrosine 3-Monooxygenase / Q000276:immunology / Q000378:metabolism
D014446:Tyrosine 3-Monooxygenase; D004298:Dopamine