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. 1978 Mar;75(3):1587–1590. doi: 10.1073/pnas.75.3.1587

Opposing effects of calcium and barium in vertebrate rod photoreceptors

Kenneth T Brown 1, Dale G Flaming 1
PMCID: PMC411519  PMID: 418416

Abstract

Intracellular recording in outer segments of red rods of the toad retina showed that increasing Ca2+ concentration in the perfusate mimicked certain aspects of light adaptation. Light sensitivity was reduced, the amplitude of light responses was reduced, the time course of light responses was altered by shortening the delay to the peak and increasing the decay rate, and the resting membrane potential was generally increased. These results provide further support for the hypothesis that Ca2+ acts as an internal transmitter that is subject to light-induced release from the rod saccules. The addition of Ba2+ to the perfusate mimicked dark adaptation by having effects opposite to all those described for Ca2+. The Ba2+ effects were specific, Mg2+ and Sr2+ being ineffective in similar or greater concentration. Also, Ba 2+ gave clear effects at concentrations as low as 0.1 mM. It is proposed that Ba2+ enters the cell and reduces the uptake of Ca2+ into the rod saccules, because the various effects of Ba2+ upon light responses all seem explicable from this hypothesis. Ba2+ also reduced the resting membrane potential, probably by reducing the membrane conductance for K+. The demonstrated effects of Ba2+ indicate an important role for Ba2+ in analyzing the ionic aspects of transduction in vertebrate photoreceptors. They also suggest a critical physiological role for Ba2+ in controlling both the resting properties and light-induced responses of vertebrate rods, because barium has been reported to be concentrated in outer and inner segments of cat photoreceptors.

Keywords: visual transduction, ionic control of vertebrate rods, adaptation in vertebrate rods

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Selected References

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  1. Bellhorn M. B., Lewis R. K. Localization of ions in retina by secondary ion mass spectrometry. Exp Eye Res. 1976 May;22(5):505–518. doi: 10.1016/0014-4835(76)90188-3. [DOI] [PubMed] [Google Scholar]
  2. Brown J. E., Pinto L. H. Ionic mechanism for the photoreceptor potential of the retina of Bufo marinus. J Physiol. 1974 Feb;236(3):575–591. doi: 10.1113/jphysiol.1974.sp010453. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Brown K. T., Flaming D. G. Instrumentation and technique for beveling fine micropipette electrodes. Brain Res. 1975 Mar 14;86(1):172–180. doi: 10.1016/0006-8993(75)90652-6. [DOI] [PubMed] [Google Scholar]
  4. Hagins W. A., Yoshikami S. Proceedings: A role for Ca2+ in excitation of retinal rods and cones. Exp Eye Res. 1974 Mar;18(3):299–305. doi: 10.1016/0014-4835(74)90157-2. [DOI] [PubMed] [Google Scholar]
  5. Hagiwara S., Fukuda J., Eaton D. C. Membrane currents carried by Ca, Sr, and Ba in barnacle muscle fiber during voltage clamp. J Gen Physiol. 1974 May;63(5):564–578. doi: 10.1085/jgp.63.5.564. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Katz B., Miledi R. A study of synaptic transmission in the absence of nerve impulses. J Physiol. 1967 Sep;192(2):407–436. doi: 10.1113/jphysiol.1967.sp008307. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Korenbrot J. I., Cone R. A. Dark ionic flux and the effects of light in isolated rod outer segments. J Gen Physiol. 1972 Jul;60(1):20–45. doi: 10.1085/jgp.60.1.20. [DOI] [PMC free article] [PubMed] [Google Scholar]
  8. Normann R. A., Pochobradský J. Oscillations in rod and horizontal cell membrane potential: evidence for feed-back to rods in the vertebrate retina. J Physiol. 1976 Sep;261(1):15–29. doi: 10.1113/jphysiol.1976.sp011546. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Normann R. A., Werblin F. S. Control of retinal sensitivity. I. Light and dark adaptation of vertebrate rods and cones. J Gen Physiol. 1974 Jan;63(1):37–61. doi: 10.1085/jgp.63.1.37. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Schroeder H. A., Tipton I. H., Nason A. P. Trace metals in man: strontium and barium. J Chronic Dis. 1972 Sep;25(9):491–517. doi: 10.1016/0021-9681(72)90150-6. [DOI] [PubMed] [Google Scholar]
  11. Sperelakis N., Schneider M. F., Harris E. J. Decreased K+ conductance produced by Ba++ in frog sartorius fibers. J Gen Physiol. 1967 Jul;50(6):1565–1583. doi: 10.1085/jgp.50.6.1565. [DOI] [PMC free article] [PubMed] [Google Scholar]
  12. Szuts E. Z., Cone R. A. Calcium content of frog rod outer segments and discs. Biochim Biophys Acta. 1977 Jul 14;468(2):194–208. doi: 10.1016/0005-2736(77)90114-6. [DOI] [PubMed] [Google Scholar]
  13. WERMAN R., GRUNDFEST H. Graded and all-or-none electrogenesis in arthropod muscle. II. The effects of alkali-earth and onium ions on lobster muscle fibers. J Gen Physiol. 1961 May;44:997–1027. doi: 10.1085/jgp.44.5.997. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. WERMAN R., McCANN F. V., GRUNDFEST H. Graded and all-or-none electrogenesis in arthropod muscle. I. The effects of alkali-earth cations on the neuromuscular system of Romalea microptera. J Gen Physiol. 1961 May;44:979–995. doi: 10.1085/jgp.44.5.979. [DOI] [PMC free article] [PubMed] [Google Scholar]
  15. Zengel J. E., Magleby K. L. Transmitter release during repetitive stimulation: selective changes produced by Sr2+ and Ba2+. Science. 1977 Jul 1;197(4298):67–69. doi: 10.1126/science.17160. [DOI] [PubMed] [Google Scholar]
  16. Zuckerman R. Ionic analysis of photoreceptor membrane currents. J Physiol. 1973 Dec;235(2):333–354. doi: 10.1113/jphysiol.1973.sp010390. [DOI] [PMC free article] [PubMed] [Google Scholar]

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