The magnitude and significance of Ca2+ domains for release of neurotransmitter.
It is now widely accepted that localized high concentrations of Ca2+ (Ca2+ domains) play a major role in controlling the time course of neurotransmitter release. In the present work we calculate the magnitude and the time course of Ca2+ domains that evolve in the vicinity of a Ca2+ channel and an adjacent release site. In the calculations we consider a accurately dimensioned Ca2+ channel. Moreover, the Ca2+ current is continuously adjusted with regard to the accumulated intracellular Ca2+ and, in addition, endogenous buffers are considered. The calculations, carried out by the software FIDAP, based on finite element method, show that the Ca2+ concentrations achieved near the release sites are significantly lower than claimed by other investigators. Furthermore, we present arguments indicating that the Ca2+ domains, regardless of their magnitude, do not play a role in controlling the time course of release of neurotransmitter.
Department of Neurobiology, Hebrew University, Givat Ram, Jerusalem, Israel.
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D000818:Animals; D002118:Calcium / Q000502:physiology*; D015220:Calcium Channels / Q000502:physiology*; D003198:Computer Simulation; D007700:Kinetics; D008433:Mathematics; D008564:Membrane Potentials; D008959:Models, Neurological; D009411:Nerve Endings / Q000502:physiology*; D018377:Neurotransmitter Agents / Q000502:physiology*; D012984:Software
D015220:Calcium Channels; D018377:Neurotransmitter Agents; D002118:Calcium