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Synaptic vesicle dynamics in mouse rod bipolar cells

Published online by Cambridge University Press:  01 July 2008

QUN-FANG WAN
Affiliation:
Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Texas
ALEJANDRO VILA
Affiliation:
Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Texas
ZHEN-YU ZHOU
Affiliation:
Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Texas
RUTH HEIDELBERGER*
Affiliation:
Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, Houston, Texas
*
*Address correspondence and reprint requests to: Ruth Heidelberger, Department of Neurobiology and Anatomy, University of Texas Medical School at Houston, 6431 Fannin Street, MSB 7.046, Houston, TX 77025. E-mail: ruth.heidelberger@uth.tmc.edu

Abstract

To better understand synaptic signaling at the mammalian rod bipolar cell terminal and pave the way for applying genetic approaches to the study of visual information processing in the mammalian retina, synaptic vesicle dynamics and intraterminal calcium were monitored in terminals of acutely isolated mouse rod bipolar cells and the number of ribbon-style active zones quantified. We identified a releasable pool, corresponding to a maximum of ≈35 vesicles/ribbon-style active zone. Following depletion, this pool was refilled with a time constant of ≈7 s. The presence of a smaller, rapidly releasing pool and a small, fast component of refilling was also suggested. Following calcium channel closure, membrane surface area was restored to baseline with a time constant that ranged from 2 to 21 s depending on the magnitude of the preceding Ca2+ transient. In addition, a brief, calcium-dependent delay often preceded the start of onset of membrane recovery. Thus, several aspects of synaptic vesicle dynamics appear to be conserved between rod-dominant bipolar cells of fish and mammalian rod bipolar cells. A major difference is that the number of vesicles available for release is significantly smaller in the mouse rod bipolar cell, both as a function of the total number per neuron and on a per active zone basis.

Information

Type
Research Articles
Copyright
Copyright © Cambridge University Press 2008

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