Purchase this article with an account.
G. A. Zampighi, C. Schietroma, L. M. Zampighi, N. Brecha; 3D-Structure of Light- and Dark-Adapted Rod Photoreceptors. Invest. Ophthalmol. Vis. Sci. 2010;51(13):1879.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
To identify the changes in the 3D-structure of rod photoreceptor ribbon synapses resulting from the fusion of thousands of synaptic vesicle during dark-adaptation.
Retinas of C57Bl/6J mice that were dark-adapted for 5-15-30-60-180 minutes were prepared for thin sectioning and electron tomography. For each experimental condition, we collected three conical series that were aligned using fiduciary markers and reconstructed using the weighted back projection algorithm. After refinement by projection matching, the resulting 3D-maps were studied by volume rendering and density segmentation methods.
In the dark, ribbon synapses between rod axons and endings of horizontal and bipolar cells underwent rapid but transient changes. These included: a) a mean decrease of 5.1±1.0 µm3 in the axon’s volume, b) an increase of 11.5±1.0 µm2 in the surface area of the area of synaptic contact, and c) an increase in the number of "omega" figures representing fused vesicles (from ~190 to ~1,280 per terminal). In contrast, the "docked" vesicular pool that was comprised of 450-480 hemi-fused vesicles per terminal and occupied 3.1±1.0 µm2 of "active zone" did not change significantly with respect to light-adapted controls. More importantly, this "docked" pool was located along the entire area of synaptic contact between rod photoreceptors and horizontal cells, not just at the ribbon’s base.
Massive synaptic vesicle fusion and glutamate release involves two types of synapses that coexist in the same rod axon terminal; one centered on the ribbon (from base to zenith) for fast and transient release and another along the entire region of contact for slow and sustained release.
This PDF is available to Subscribers Only