Abstract
Solitary rod inner segments were isolated from salamander retinae. Their Ca current was studied with the 'whole-cell, gigaseal' technique (Hamill, Marty, Neher, Sakmann & Sigworth, 1981). The soluble constituents of the cytoplasm exchanged with the solution in the pipette. The external solution could be changed during continuous perfusion. Membrane voltage was controlled with a voltage clamp. After permeant ions other than Ca were replaced with impermeant ions (i.e. tetraethylammonium as a cation, and aspartate or methanesulphonate as an anion), an inward current remained. It activated at approximately -40 mV, reached a maximum at approximately 0 mV, and decreased as the membrane was further depolarized. The size of the current increased when Ba was substituted for external Ca. The current was blocked when Ca was replaced with Co. The voltage at which the current was half-maximum shifted from approximately -22 to -31 mV during the initial 3 min of an experiment. The maximum amplitude of the current continuously declined during the entire course of an experiment. The time course for activation of the Ca current following a step of depolarization could be described by the sum of two exponentials. The time constant of the slower exponential was voltage dependent. Deactivation following repolarization could also be described by the sum of two exponentials. Both time constants for deactivation were independent of voltage (between -30 and 0 mV) and faster than the slower time constant for activation. When the internal Ca concentration was buffered by 10 mM-EGTA, the Ca current did not inactivate during several seconds of maintained depolarization. When the concentration of EGTA was reduced to 0.1 mM, the Ca current declined and the membrane conductance decreased during several seconds of maintained depolarization. This inactivation was incomplete and only occurred after a substantial quantity of Ca entered. Following repolarization the Ca conductance recovered from inactivation. In contrast, the continuous decline observed during the course of an experiment (item 3) was not reversible. The difference suggests that inactivation and the decline are distinct processes.
Full text
PDF


















Selected References
These references are in PubMed. This may not be the complete list of references from this article.
- Ashmore J. F., Falk G. The single-photon signal in rod bipolar cells of the dogfish retina. J Physiol. 1980 Mar;300:151–166. doi: 10.1113/jphysiol.1980.sp013156. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bader C. R., Bertrand D., Schwartz E. A. Voltage-activated and calcium-activated currents studied in solitary rod inner segments from the salamander retina. J Physiol. 1982 Oct;331:253–284. doi: 10.1113/jphysiol.1982.sp014372. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Bader C. R., MacLeish P. R., Schwartz E. A. Responses to light of solitary rod photoreceptors isolated from tiger salamander retina. Proc Natl Acad Sci U S A. 1978 Jul;75(7):3507–3511. doi: 10.1073/pnas.75.7.3507. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Baylor D. A., Lamb T. D., Yau K. W. Responses of retinal rods to single photons. J Physiol. 1979 Mar;288:613–634. [PMC free article] [PubMed] [Google Scholar]
- Brehm P., Eckert R., Tillotson D. Calcium-mediated inactivation of calcium current in Paramecium. J Physiol. 1980 Sep;306:193–203. doi: 10.1113/jphysiol.1980.sp013391. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Byerly L., Hagiwara S. Calcium currents in internally perfused nerve cell bodies of Limnea stagnalis. J Physiol. 1982 Jan;322:503–528. doi: 10.1113/jphysiol.1982.sp014052. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Copenhagen D. R., Owen W. G. Functional characteristics of lateral interactions between rods in the retina of the snapping turtle. J Physiol. 1976 Jul;259(2):251–282. doi: 10.1113/jphysiol.1976.sp011465. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Detwiler P. B., Hodgkin A. L., McNaughton P. A. Temporal and spatial characteristics of the voltage response of rods in the retina of the snapping turtle. J Physiol. 1980 Mar;300:213–250. doi: 10.1113/jphysiol.1980.sp013159. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Doroshenko P. A., Kostyuk P. G., Martynyuk A. E. Intracellular metabolism of adenosine 3',5'-cyclic monophosphate and calcium inward current in perfused neurones of Helix pomatia. Neuroscience. 1982;7(9):2125–2134. doi: 10.1016/0306-4522(82)90124-5. [DOI] [PubMed] [Google Scholar]
- Fain G. L., Gold G. H., Dowling J. E. Receptor coupling in the toad retina. Cold Spring Harb Symp Quant Biol. 1976;40:547–561. doi: 10.1101/sqb.1976.040.01.051. [DOI] [PubMed] [Google Scholar]
- Fedulova S. A., Kostyuk P. G., Veselovsky N. S. Calcium channels in the somatic membrane of the rat dorsal root ganglion neurons, effect of cAMP. Brain Res. 1981 Jun 9;214(1):210–214. doi: 10.1016/0006-8993(81)90457-1. [DOI] [PubMed] [Google Scholar]
- Fenwick E. M., Marty A., Neher E. Sodium and calcium channels in bovine chromaffin cells. J Physiol. 1982 Oct;331:599–635. doi: 10.1113/jphysiol.1982.sp014394. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Fox A. P. Voltage-dependent inactivation of a calcium channel. Proc Natl Acad Sci U S A. 1981 Feb;78(2):953–956. doi: 10.1073/pnas.78.2.953. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Griff E. R., Pinto L. H. Interactions among rods in the isolated retina of Bufo marinus. J Physiol. 1981 May;314:237–254. doi: 10.1113/jphysiol.1981.sp013704. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HODGKIN A. L., HUXLEY A. F., KATZ B. Measurement of current-voltage relations in the membrane of the giant axon of Loligo. J Physiol. 1952 Apr;116(4):424–448. doi: 10.1113/jphysiol.1952.sp004716. [DOI] [PMC free article] [PubMed] [Google Scholar]
- HODGKIN A. L., KATZ B. The effect of sodium ions on the electrical activity of giant axon of the squid. J Physiol. 1949 Mar 1;108(1):37–77. doi: 10.1113/jphysiol.1949.sp004310. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hagiwara S., Byerly L. Calcium channel. Annu Rev Neurosci. 1981;4:69–125. doi: 10.1146/annurev.ne.04.030181.000441. [DOI] [PubMed] [Google Scholar]
- Hagiwara S., Nakajima S. Effects of the intracellular Ca ion concentration upon the excitability of the muscle fiber membrane of a barnacle. J Gen Physiol. 1966 Mar;49(4):807–818. doi: 10.1085/jgp.49.4.807. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hagiwara S., Ohmori H. Studies of single calcium channel currents in rat clonal pituitary cells. J Physiol. 1983 Mar;336:649–661. doi: 10.1113/jphysiol.1983.sp014603. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Hamill O. P., Marty A., Neher E., Sakmann B., Sigworth F. J. Improved patch-clamp techniques for high-resolution current recording from cells and cell-free membrane patches. Pflugers Arch. 1981 Aug;391(2):85–100. doi: 10.1007/BF00656997. [DOI] [PubMed] [Google Scholar]
- Irisawa H., Kokubun S. Modulation by intracellular ATP and cyclic AMP of the slow inward current in isolated single ventricular cells of the guinea-pig. J Physiol. 1983 May;338:321–337. doi: 10.1113/jphysiol.1983.sp014675. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kostyuk P. G., Krishtal O. A. Effects of calcium and calcium-chelating agents on the inward and outward current in the membrane of mollusc neurones. J Physiol. 1977 Sep;270(3):569–580. doi: 10.1113/jphysiol.1977.sp011969. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Kostyuk P. G., Krishtal O. A., Pidoplichko V. I. Calcium inward current and related charge movements in the membrane of snail neurones. J Physiol. 1981 Jan;310:403–421. doi: 10.1113/jphysiol.1981.sp013557. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Leeper H. F., Normann R. A., Copenhagen D. R. Evidence for passive electrotonic interactions in red rods of toad retina. Nature. 1978 Sep 21;275(5677):234–236. doi: 10.1038/275234b0. [DOI] [PubMed] [Google Scholar]
- Miller A. M., Schwartz E. A. Evidence for the identification of synaptic transmitters released by photoreceptors of the toad retina. J Physiol. 1983 Jan;334:325–349. doi: 10.1113/jphysiol.1983.sp014497. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Plant T. D., Standen N. B., Ward T. A. The effects of injection of calcium ions and calcium chelators on calcium channel inactivation in Helix neurones. J Physiol. 1983 Jan;334:189–212. doi: 10.1113/jphysiol.1983.sp014489. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Reuter H., Stevens C. F., Tsien R. W., Yellen G. Properties of single calcium channels in cardiac cell culture. Nature. 1982 Jun 10;297(5866):501–504. doi: 10.1038/297501a0. [DOI] [PubMed] [Google Scholar]
- Schwartz E. A. Electrical properties of the rod syncytium in the retina of the turtle. J Physiol. 1976 May;257(2):379–406. doi: 10.1113/jphysiol.1976.sp011374. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Schwartz E. A. First events in vision: the generation of responses in vertebrate rods. J Cell Biol. 1981 Aug;90(2):271–278. doi: 10.1083/jcb.90.2.271. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Schwartz E. A. Responses of single rods in the retina of the turtle. J Physiol. 1973 Aug;232(3):503–514. doi: 10.1113/jphysiol.1973.sp010283. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Schwartz E. A. Rod-rod interaction in the retina of the turtle. J Physiol. 1975 Apr;246(3):617–638. doi: 10.1113/jphysiol.1975.sp010907. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Takahashi K., Yoshii M. Effects of internal free calcium upon the sodium and calcium channels in the tunicate egg analysed by the internal perfusion technique. J Physiol. 1978 Jun;279:519–549. doi: 10.1113/jphysiol.1978.sp012360. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Tsien R. W. Calcium channels in excitable cell membranes. Annu Rev Physiol. 1983;45:341–358. doi: 10.1146/annurev.ph.45.030183.002013. [DOI] [PubMed] [Google Scholar]