Abstract
Bursting pacemaker neurons of the snail Helix pomatia were voltage-clamped and Ca currents in response to depolarizing steps were recorded. Simultaneously, changes in intracellular Ca concentrations were measured using the fluorescent dye fura-2 and a highly sensitive digital camera. Ca influx through voltage-gated channels induced a spatially non-uniform increase in intracellular Ca. The Ca signals decayed with a time constant of about 5 s. By increasing the concentration of the indicator dye, its Ca-buffering capacity was enhanced and Ca transients in response to depolarization were diminished. Thereby, the endogenous Ca buffer capacity could be determined and was calculated to be about 480 buffered ions for every free Ca ion. The buffer capacity did not vary significantly with the amount of Ca influx within the range tested, suggesting that the buffer is not saturated at Ca concentrations of up to 1μM.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Ahmed Z, Connor JA (1988) Calcium regulation by and buffer capacity of molluscan neurons during calcium transients. Cell Calcium 9: 57–69
Baudier J (1988) S100 proteins: structure and calcium binding properties. In: Gerday C, Gilles R, Bolis L (eds) Calcium and calcium binding proteins. Springer, Berlin Heidelberg New York, pp 102–113
Belan P, Kostyuk P, Snitsarev V, Tepikin A (1993). Calcium clamp in isolated neurones of the snail Helix pomatia. J Physiol (Lond) 462: 47–58
Born M, Wolf E (1970) Principles of optics. Pergamon Press, Oxford
Chad JE, Eckert RO (1984) Calcium domains associated with individual channels can account for anomalous voltage relations of Ca-dependent responses. Biophys J 45: 993–999
Connor JA, Kater SB, Cohan C, Fink L (1990) Ca2+ dynamics in neuronal growth cones: regulation and changing patterns of Ca2+entry. Cell Calcium 11: 233–239
Cox JA, Comte M, Mamar-Bachi A, Milos M, Schaer J-J (1988) Cation binding to calmodulin and relation to function. In: Gerday C, Gilles R, Bolis L (eds) Calcium and calcium binding proteins. Springer, Berlin Heidelberg New York, pp 141–162
Fogelson AL, Zucker RS (1985). Presynaptic calcium diffusion from various arrays of single channels. Biophys J 48: 1003–1017
Grynkiewicz G, Poenie M, Tsien RY (1985) A new generation of fluorescent calcium indicators with greatly improved fluorescence properties. J Biol Chem 260: 3440–3450
Gutnick MJ, Lux HD, Swandulla D, Zucker H (1989). Voltage-dependent and calcium-dependent inactivation of calcium channel current in identified snail neurones. J Physiol (Lond) 412: 197–220
Hofmeier G, Lux HD (1981) The time courses of intracellular calcium and related electrical effects after injection of CaCl2 into neurons of the snail Helix pomatia. Pflügers Arch 391: 242–251
Johnson BD, Byerly L (1993) Photo-released intracellular Ca2+ rapidly blocks Ba2+ current in Lymnaea neurons. J Physiol (Lond) 462: 321–347
Kerkut GA, Lambert JDC, Gayton RJ, Loker JE, Walker RJ (1975) Map** of nerve cells in the subesophageal ganglia of Helix aspersa. Comp Biochem Physiol 50: 1–25
Lux HD, K Nagy (1981) Single channel Ca currents in Helix pomatia neurons. Pflügers Arch 391: 252–254
Neher E, Augustine GJ (1992) Calcium gradients and buffers in bovine chromaffin cells. J Physiol (Lond) 450: 273–301
Müller TH, Swandulla D, Lux HD (1989) Activation of three types of membrane currents by various divalent cations in identified molluscan pacemaker neurons. J Gen Physiol 94: 997–1014
Partridge LD, D Swandulla (1987) Single Ca-activated cation channels in bursting neurons of Helix. Pflügers Arch 410: 627–631
Sala F, Hernandez-Cruz A (1990) Calcium diffusion modeling in a spherical neuron. Relevance of buffering properties. Biophys J 57: 313–324
Simon SM, Llinas RR (1985) Compartmentalization of the submembrane calcium activity during calcium influx and its significance in transmitter release. Biophys J 48: 485–498
Smith SJ, Zucker RS (1980) Aequorin response facilitation and intracellular calcium accumulation in molluscan neurones. J Physiol (Lond) 48: 485–498
Swandulla D, HD Lux (1985) Activation of a nonspecific cation conductance by intracellular Ca elevation in bursting pacemaker neurons of Helix pomatia. J Neurophysiol 54: 1430–1443
Tillotson D, Gorman ALF (1980) Non-uniform Ca2+ buffer distribution in a nerve cell body. Nature (Lond) 286: 816–817
Tillotson D, Gorman ALF (1983) Localization of neuronal Ca2+ buffering near plasma membrane studied with different divalent cations. Cell Mol Neurobiol 3: 297–310
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Müller, T.H., Partridge, L.D. & Swandulla, D. Calcium buffering in bursting Helix pacemaker neurons. Pflugers Arch. 425, 499–505 (1993). https://doi.org/10.1007/BF00374877
Received:
Revised:
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00374877