Cooperative Ca2+ removal from presynaptic terminals of the spiny lobster neuromuscular junction

Stimulation-induced changes in presynaptic free calcium concentration ([Ca2+]i) were examined by fluorescent imaging at the spiny lobster excitor motor nerve terminals. The Ca2+ removal process in the terminal was analyzed based on a single compartment model, under the assumption that the Ca2+ remov...

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Bibliographic Details
Published in:Biophysical journal 1999-04, Vol.76 (4), p.1819-1834
Main Authors: Ohnuma, K, Kazawa, T, Ogawa, S, Suzuki, N, Miwa, A, Kijima, H
Format: Article
Language:English
Subjects:
Animals
Astacoidea - metabolism
Biophysical Phenomena
Biophysics
Calcium
Calcium - metabolism
Crustaceans
Electric Stimulation
Fluorescent Dyes
In Vitro Techniques
Ion Transport
Kinetics
Models, Neurological
Muscular system
Nephropidae - metabolism
Neurology
Neuromuscular Junction - metabolism
Physics
Presynaptic Terminals - metabolism
Spectrometry, Fluorescence
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Summary:Stimulation-induced changes in presynaptic free calcium concentration ([Ca2+]i) were examined by fluorescent imaging at the spiny lobster excitor motor nerve terminals. The Ca2+ removal process in the terminal was analyzed based on a single compartment model, under the assumption that the Ca2+ removal rate from the terminal cytoplasm is proportional to nth power of [Ca2+]i. During 100 nerve stimuli at 10-100 Hz, [Ca2+]i reached a plateau that increased in a less-than-linear way with stimulation frequency, and the power index, n, was about 2. In the decay time course after stimulation, n changed with the number of stimuli from about 1.4 after 10 stimuli to about 2 after 100 stimuli. With the change of n from 1.4 to 2, the rate became larger at high [Ca2+]i (>1.5 microM), but was smaller at low [Ca2+]i (
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(99)77342-X