Local role of Ca2+ in formation of veils in growth cones
Open Access
- 1 July 1988
- journal article
- research article
- Published by Society for Neuroscience in Journal of Neuroscience
- Vol. 8 (7), 2596-2605
- https://doi.org/10.1523/jneurosci.08-07-02596.1988
Abstract
A previous study that used high-resolutoin video (VEC-DIC) microscopy to examine axonal growth cones of Aplysia giant neurons growing in culture had demonstrated that growth occurs by the extension of veils of membrane between filopodia and the subsequent morphological transformation of these veils, in place, into the swollen, organelle-filled central region of the growth cone and then into the cylindrical axon. The possible involvement of Ca2+ in this sequence of events was now examined using VEC-DIC microscopy. Reduction of [Ca2+]o from the normal level of 11 to 1.3 mM or below or the addition of 20 mM Co2+, which blocks Ca2+ channels, caused a large decrease in the area of immature veil (flat and with few organelles) in the growth cone within minutes. Ba2+, 20 mM, which flows well through Ca2+ channels, and 5 .mu.M A23187, a Ca2+ ionophore, caused new immature veil to form in the presence of reduced [Ca2+]o. Maturation of veil into central region was not inhibited by reduced [Ca2+]o. In fact, the disappearance of immature veil was often the result partly, or entirely, of continued veil maturation in the absence of formation of new veil. The next step in maturation, conversion of the central region to cylindrical axon, was also probably not inhibited by reduced [Ca2+]o. Ca2+ was microapplied to large growth cones that had lost their veils by exposure to reduced [Ca2+]o. There was a strong tendency for the first, or only, incidence of veil formation to occur near the micropipette, the rest of the perimeter of the growth cone remaining quiescent. It is concluded that intracellular Ca2+ plays a role in veil formation and that the site of the Ca2+-dependent step is close to the site of veil formation. If this step is exocytosis, veil forms where there is net addition of membrane. Whether a change in [Ca2+]i, rather than some other factor, normally directly triggers veil formation remains uncertain, but, if it does, then the site of formation, which will strongly influence the direction of axon growth, is probably determined by focal changes in [Ca2+]i within the growth cone.This publication has 26 references indexed in Scilit:
- Optical Recording of Calcium Action Potentials from Growth Cones of Cultured Neurons with a Laser MicrobeamScience, 1981
- Lectin labeling of sprouting neurons. II. Relative movement and appearance of glycoconjugates during plasmalemmal expansion.The Journal of cell biology, 1981
- Solubility of amphipathic molecules in biological membranes and lipid bilayers and its implications for membrane structureBiochemistry, 1981
- Incorporation of axonally transported glycoproteins into axolemma during nerve regenerationThe Journal of cell biology, 1981
- Characterization of the turning response of dorsal root neurites toward nerve growth factor.The Journal of cell biology, 1980
- Barium and strontium can substitute for calcium in noradrenaline output induced by excess potassium in the guinea‐pig.The Journal of Physiology, 1980
- Presynaptic membrane potential affects transmitter release in an identified neuron in Aplysia by modulating the Ca 2+ and K + currentsProceedings of the National Academy of Sciences, 1980
- Cell-substratum adhesion of neurite growth cones, and its role in neurite elongationExperimental Cell Research, 1979
- On the role of barium in supporting the asynchronous release of acetylcholine quanta by motor nerve impulses.The Journal of Physiology, 1978
- Initial endocytosis of peroxidase or ferritin by growth cones of cultured nerve cellsJournal of Neurocytology, 1977