The mammalian rod synaptic ribbon is essential for Cav channel facilitation and ultrafast synaptic vesicle fusion

eLife

Chad Paul Grabner¹  Tobias Moser² 

[1] Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany;Synaptic Nanophysiology Group, Max Planck Institute of Biophysical Chemistry, Göttingen, Germany;Collaborative Research Center 1286 'Quantitative Synaptology', University of Göttingen, Göttingen, Germany;Institute for Auditory Neuroscience and InnerEarLab, University Medical Center Göttingen, Göttingen, Germany;Synaptic Nanophysiology Group, Max Planck Institute of Biophysical Chemistry, Göttingen, Germany;Collaborative Research Center 1286 'Quantitative Synaptology', University of Göttingen, Göttingen, Germany;Multiscale Bioimaging Cluster of Excellence (MBExC), University of Göttingen, Göttingen, Germany;

关键词: synaptic ribbon;    rod photoreceptor;    exocytosis;    synaptic transmission;    calcium channels;    active zone;    Mouse;   

DOI  :  10.7554/eLife.63844

来源: eLife Sciences Publications, Ltd

【 摘 要 】

Rod photoreceptors (PRs) use ribbon synapses to transmit visual information. To signal ‘no light detected’ they release glutamate continually to activate post-synaptic receptors. When light is detected glutamate release pauses. How a rod’s individual ribbon enables this process was studied here by recording evoked changes in whole-cell membrane capacitance from wild-type and ribbonless (Ribeye-ko) mice. Wild-type rods filled with high (10 mM) or low (0.5 mM) concentrations of the Ca2+-buffer EGTA created a readily releasable pool (RRP) of 87 synaptic vesicles (SVs) that emptied as a single kinetic phase with a τ<0.4 ms. The lower concentration of EGTA accelerated Cav channel opening and facilitated release kinetics. In contrast, ribbonless rods created a much smaller RRP of 22 SVs, and they lacked Cav channel facilitation; however, Ca2+ channel-release coupling remained tight. These release deficits caused a sharp attenuation of rod-driven scotopic light responses. We conclude that the synaptic ribbon facilitates Ca2+-influx and establishes a large RRP of SVs.

【 授权许可】

CC BY