Adaptation-dependent plasticity of rod bipolar cell axon terminal morphology in the rat retina |
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Authors: | U D Behrens Phillip Kasten Hans-Joachim Wagner |
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Institution: | Anatomisches Institut, ?sterbergstrasse 3, D-72074 Tübingen, Germany Tel.: +49 7071 2973022; Fax +49 7071 294014; e-mail: uwe.behrens@anatu.uni-tuebingen.de, DE
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Abstract: | We chose synaptic terminals of rat rod bipolar cells as a model system to study activity-related changes in the overall morphology
and the fine structure of synaptic sites. Using confocal laser scanning microscopy in conjunction with three-dimensional reconstruction
and electron microscopy, we examined the effect of light and dark adaptation on axon terminals identified by protein kinase
C (PKC) immunoreactivity. Rod bipolar cell axon terminals consisted of 2–3 polymorphic boutons situated close to the ganglion
cell layer and a single ovoid swelling located more distally. Both components of the terminal complex showed adaptation-dependent
differences in the distribution of PKC immunoreactivity and in their morphology. In light-adapted rod bipolar cell axon terminals,
PKC immunoreactivity was homogeneously distributed throughout the cytoplasm, whereas terminals from dark-adapted animals showed
PKC immunoreactivity preferentially localised in the submembrane compartment and a reduced staining of the more central cytoplasm.
In three-dimensional reconstructions of optical sections and at the ultrastructural level, the shape of light-adapted axon
terminals was round and smooth and exhibited more convexly curved synaptic membranes. In contrast, dark-adapted terminals
had irregular contours, numerous dimples and a concave synaptic curvature. No spinules of bipolar cell terminals were observed
in dark-adapted material. These observations are discussed in the context of activity-related morphological plasticity of
central nervous system synapses and of the functions of PKC in the cycle of vesicle fusion and retrieval at the tonically
active ribbon synapses of the rod bipolar axon terminal.
Received: 9 April 1998 / Accepted: 23 June 1998 |
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Keywords: | Retina Synaptic plasticity Rod bipolar cells Adaptation Reconstruction 3D Protein kinase C Rat (Norwegian) |
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