|Multiple calcium signalling pathways in squid giant presynaptic terminals|
Augustine, G.J.; Deitmer, J.; Hans, M.; Swandulla, D.; Zipser, K. (1995). Multiple calcium signalling pathways in squid giant presynaptic terminals, in: Abbott, N.J. et al. (Ed.) Cephalopod neurobiology: neuroscience studies in squid, octopus and cuttlefish. pp. 271-282
In: Abbott, N.J.; Williamson, R.; Maddock, L. (Ed.) (1995). Cephalopod neurobiology: neuroscience studies in squid, octopus and cuttlefish. Oxford University Press: London. ISBN 0-19-854790-0. 542 pp., more
|Authors|| || Top |
- Augustine, G.J.
- Deitmer, J.
- Hans, M.
The fluorescent Ca indicator, fura-2, can be used to measure the changes in presynaptic Ca concentration associated with action potentials. When using either a photomultiplier tube or a video camera to detect fura-2 fluorescence, trains of presynaptic action potentials produce rapid rises in Ca concentration that reach a peak level of a few nM per action potential and that decay very slowly, over hundreds of seconds. However, these measured rises are not those responsible for triggering transmitter release because injection of the Ca buffer, EGTA, blocks these rises in Ca concentration but not transmitter release. EGTA injection blocks synaptic augmentation, a form of synaptic plasticity that increases the amount of release produced by an action potential, suggesting that the measured Ca rises mediate augmentation. Our conclusion is that transmitter release is mediated by a rise in Ca concentration that is too localized to be detected with fura-2 measurements, while augmentation is mediated by a more widespread and detectable Ca signal.