The GTPase dynamin I is required for synaptic vesicle (SV) endocytosis, Our observation that dynamin binds to the SV protein synaptophysin in a Ca2+-dependent fashion suggested the possibility that a dynamin/synaptoph...
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The GTPase dynamin I is required for synaptic vesicle (SV) endocytosis, Our observation that dynamin binds to the SV protein synaptophysin in a Ca2+-dependent fashion suggested the possibility that a dynamin/synaptophysin complex functions in SV recycling, In this paper we show that disruption of the dynamin/synaptophysin interaction by peptide injection into the squid giant synapse preterminal results in a decrease in transmitter release during high-frequency stimulation, indicating an inhibition of SV recycling, Electron microscopy of these synapses reveals a depletion of SVs. demonstrating a block of vesicle retrieval after fusion, In addition, we observed an increase in clathrin-coated vesicles, indicating that the peptide does not block clathrin-dependent endocytosis, We conclude that the dynamin/synaptophysin complex functions in a clathrin-independent mechanism of SV endocytosis that is required for efficient synaptic transmission.
One of the most numerous neurons in the cochlear nucleus is the type I stellate cell. Previous attempts to understand the structural basis for its signal coding assumed that integration of synaptic potentials arising ...
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One of the most numerous neurons in the cochlear nucleus is the type I stellate cell. Previous attempts to understand the structural basis for its signal coding assumed that integration of synaptic potentials arising from axodendritic synapses should account for the generation of its response properties. However, the present study documents the importance of excitatory and inhibitory types of synapses on the soma and axon. Retrograde transport of cholera toxin B subunit, injected in the inferior colliculus of chinchillas, was used to label exclusively type I stellate cells in the anteroventral cochlear nucleus. The relative distribution of terminal types by vesicle morphology was pleomorphic > large spherical > flattened > smaller spherical. The somatic perimeter covered by endings ranged from almost none to nearly half. More flattened-vesicle terminals contacted somata in the high-frequency than in the low-frequency region. Eight of twenty axons received endings that contained large spherical vesicles and made asymmetric junctions;half of these extensively apposed the initial segment, forming a collar of presumed excitatory input. Thus, type I stellate cells are a heterogeneous group. Inhibitory synapses probably compose the majority of terminals. Some cells receive mostly inhibitory synapses near the presumed site of the spike generator, but others also have a prominent excitatory input. These findings call for a new look at the mechanisms for signal coding in stellate cells in the auditory system in particular and raise issues concerning the stochastic nature of information processing in sensory systems in general.
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