These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Presynaptic capacitance measurements and Ca2+ uncaging reveal submillisecond exocytosis kinetics and characterize the Ca2+ sensitivity of vesicle pool depletion at a fast CNS synapse.
    Author: Wölfel M, Schneggenburger R.
    Journal: J Neurosci; 2003 Aug 06; 23(18):7059-68. PubMed ID: 12904466.
    Abstract:
    The intracellular Ca2+ sensitivity of synaptic vesicle fusion is an important determinant of transmitter release probability, but it is unknown for most CNS synapses. We combined whole-cell membrane capacitance measurements and Ca2+ uncaging at the large calyx of Held nerve terminals to determine the Ca2+ sensitivity of synaptic vesicle fusion at a glutamatergic CNS synapse, independent of recording EPSCs. Capacitance increases measured 30-50 msec after elevating the intracellular Ca2+ concentration ([Ca2+]i) by Ca2+ uncaging were half-maximal at approximately 5 microm [Ca2+]i. At 10 microm [Ca2+]i, capacitance increases reached maximal values (256 +/- 125 fF; mean +/- SD), indicating the depletion of an average pool of approximately 4000 readily releasable vesicles. Vesicle pool depletion was confirmed in cross-depletion experiments, in which capacitance responses were measured after Ca2+ uncaging, or after combined stimuli of prolonged presynaptic depolarizations and Ca2+ uncaging. To analyze the Ca2+-dependent rates of vesicle pool depletion, the capacitance rise after Ca2+ uncaging was fitted with single- or double-exponential functions. The fast time constants of double-exponential fits, and the time constants of single-exponential fits were 2-3 msec at 10-15 microm [Ca2+]i and reached submillisecond values at 30 microm [Ca2+]i. These results suggest that three to five readily releasable vesicles can fuse within <1 msec at each active zone of a calyx of Held, given that [Ca2+]i rises sufficiently high. Submillisecond kinetics of exocytosis are reached at significantly lower [Ca2+]i than at ribbon-type sensory synapses previously investigated by capacitance measurements.
    [Abstract] [Full Text] [Related] [New Search]