Abstract
To maintain neurotransmission in central neurons, several mechanisms are employed to retrieve synaptically exocytosed membrane. The two major modes of synaptic vesicle (SV) retrieval are clathrin-mediated endocytosis and activity-dependent bulk endocytosis (ADBE). ADBE is the dominant SV retrieval mode during intense stimulation, however the precise physiological conditions that trigger this mode are not resolved. To determine these parameters we manipulated rat hippocampal neurons using a wide spectrum of stimuli by varying both the pattern and duration of stimulation. Using live-cell fluorescence imaging and electron microscopy approaches, we established that stimulation frequency, rather than the stimulation load, was critical in the triggering of ADBE. Thus two hundred action potentials, when delivered at high frequency, were sufficient to induce near maximal bulk formation. Furthermore we observed a strong correlation between SV pool size and ability to perform ADBE. We also identified that inhibitory nerve terminals were more likely to utilize ADBE and had a larger SV recycling pool. Thus ADBE in hippocampal synaptic terminals is tightly coupled to stimulation frequency and is more likely to occur in terminals with large SV pools. These results implicate ADBE as a key modulator of both hippocampal neurotransmission and plasticity.
Highlights
In synapses of the central nervous system as well as at the neuromuscular junction (NMJ) a fast mechanism of membrane retrieval following exocytosis of synaptic vesicles (SVs) is necessary for maintenance of neurotransmission
activitydependent bulk endocytosis (ADBE) is the dominant SV retrieval mode during intense stimulation in central nerve terminals [9], little is known regarding the key physiological parameters required for its triggering
To overcome this problem we incubated cultures with an anti-synaptotagmin antibody conjugated to the fluorescent probe cypHer5 prior to dextran loading (Fig. 1A)
Summary
In synapses of the central nervous system as well as at the neuromuscular junction (NMJ) a fast mechanism of membrane retrieval following exocytosis of synaptic vesicles (SVs) is necessary for maintenance of neurotransmission. This is important during intense stimulation, where fused SV membrane must be quickly retrieved to avoid excess plasma membrane growth and to regenerate vesicles for subsequent transmitter release. ADBE is the dominant SV retrieval mode during intense stimulation [9] and compensates for plasma membrane increases that cannot be reversed in the short term by single vesicle endocytosis, due to capacity limitations of the CME machinery [10,11,12,13]. Central nerve terminals possess a variety of SV retrieval strategies that allow them to adapt to a wide spectrum of neuronal activity
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call