ABSTRACT
Recent studies have revealed great functional and structural heterogeneity in the ribbon-type synapses at the basolateral pole of the isopotential inner hair cell (IHC). This feature is believed to be critical for audition over a wide dynamic range, but whether the spatial gradient of ribbon morphology is fine-tuned in each IHC and how the mitochondrial network is organized to meet local energy demands of synaptic transmission remain unclear. By means of three-dimensional electron microscopy and artificial intelligence-based algorithms, we demonstrated the cell-wide structural quantification of ribbons and mitochondria in mature mid-cochlear IHCs of mice. We found that adjacent IHCs in staggered pairs differ substantially in cell body shape and ribbon morphology gradient as well as mitochondrial organization. Moreover, our analysis argues for a location-specific arrangement of correlated ribbon and mitochondrial function at the basolateral IHC pole.
Subject(s)
Animals , Mice , Artificial Intelligence , Cochlea/metabolism , Hair Cells, Auditory, Inner , Mitochondria , Synapses/metabolismABSTRACT
Objective To investigate the number changes of the ribbon synapses(RS) in the inner hair cell of C57BL/6J mice with age .Methods The cochlear basilar membrane was obtained from C57BL/6J mice in 2 ,6 ,10 , 12 months old .RIBEYE on the presynaptic membrane and AMPA receptor on the postsynaptic membrane were double labeled by immunofluorescence histochemical technique .The stained sections were observed under a confocal laser-scanning microscope .Then the number of RS of the basilar membrane was calculated by three dimensional reconstruction images using 3DS max software .Results The numbers of RS reduced gradually from the cochlear a‐pex to base in the same developing stages .The numbers of RS in apex and middle turn of cochlea were gradually re‐duced with the age increasing .The number of RS in basilar turn reduced first and increased slowly then .Conclusion The decreases of the number of RS maybe the main pathological change at the early stage of presbycusis .In addi‐tion ,there may be a kind of compensatory mechanism by increaseing the number of RS to delay the hearing deficits .
ABSTRACT
Some retinal neurons, including intrinsically photosensitive retinal ganglion cells have their dendrites stratified in sublamina a of the inner plexiform (IPL), the OFF sublayer, but paradoxically show light-driven ON electrophysiological responses. In order to understand the mechanism on this paradoxical response, by using immunoelectron microscopy with a specific antibody against calbindin, we examined the synaptic connections of the calbindin-immunoreactive ON cone bipolar cell of the rabbit retina, which is thought to make the ribbon synapse in sublamina a of the IPL. The ribbon synapses in sublamina a by calbindin-immunoreactive ON cone bipolar cells were mainly found at the border between the inner nuclear layer and the IPL. Interestingly, the output targets at these ribbon synapses turned out as monads, and multiple synaptic ribbons were engaged in each synapse. These findings were different from those at the conventional ribbon synapse formed by calbindin-immunoreactive ON cone bipolar axon terminals. Thus, these findings may be the characteristics of the calbindin-immunoreactive ON cone bipolar ribbon synapse in sublamina a and can be used to classify the synapse in the retinal circuit research.