Coordinated multivesicular release at a mammalian ribbon synapse.
Traditional models of synaptic transmission hold that release sites within an active zone operate independently. Although the release of multiple vesicles (multivesicular release; MVR) from single active zones occurs at some central synapses, MVR is not thought to require coordination among release sites. Ribbon synapses seem to be optimized to release many vesicles over an extended period, but the dynamics of MVR at ribbon synapses is unknown. We examined MVR at a ribbon synapse in a retinal slice preparation using paired recordings from presynaptic rod bipolar and postsynaptic AII amacrine cells. When evoked release was highly desynchronized, discrete postsynaptic events were larger than quantal miniature excitatory postsynaptic currents (mEPSCs) but had the same time course. The amplitude of these multiquantal mEPSCs, which seem to arise from the essentially simultaneous release of multiple vesicles, was reduced by lowering release probability. The release synchrony reflected in these multivesicular events suggests that release within an active zone is coordinated during MVR.
Singer
Joshua H
JH
Synaptic Physiology Unit, NIH/NINDS, 36 Convent Drive, MSC-4066, Building 36 Room 2C-09, Bethesda, Maryland 20892, USA. singerj@ninds.nih.gov
Lassová
Luisa
L
Vardi
Noga
N
Diamond
Jeffrey S
JS
D000818:Animals; D022162:Cytoplasmic Vesicles / Q000187:drug effects / Q000502:physiology*; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials; D005089:Exocytosis / Q000502:physiology*; D007150:Immunohistochemistry; D009010:Monte Carlo Method; D009924:Organ Culture Techniques; D018408:Patch-Clamp Techniques; D051381:Rats; D012160:Retina / Q000187:drug effects / Q000502:physiology*; D013569:Synapses / Q000187:drug effects / Q000502:physiology*; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology
D018691:Excitatory Amino Acid Antagonists