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. 1988 Nov;405:397–419. doi: 10.1113/jphysiol.1988.sp017339

Characterization of membrane currents in dissociated adult rat pineal cells.

L G Aguayo 1, F F Weight 1
PMCID: PMC1190982  PMID: 2855641

Abstract

1. Membrane currents, particularly the outward components, were studied in pineal cells acutely dissociated from adult rats using the whole-cell variant of the patch-clamp technique. 2. In current clamp, outward constant current elicited a transient graded depolarizing response. A sustained membrane rectification developed within 20 ms; this phenomenon was reduced in cells internally dialysed with 120 mM-CsCl. 3. Study of the membrane current revealed the existence of a transient and a delayed outward current. These currents were virtually eliminated when the cell was internally dialysed with CsCl. 4. The delayed outward current, isolated from a holding potential of -50 mV, activated at potentials near -20 mV, reached a steady-state current amplitude within 60 ms and had little or no decay during steps up to 400 ms in duration. This component was reduced by 80% or more with the addition of 5 mM-TEA. 5. From -100 mV, the transient outward current reached a peak within 15 ms and decayed with a single-exponential time course. The mean decay time constant was 66 +/- 10 ms (at -33 mV) and it showed little voltage sensitivity. This current, which activated at potentials positive to -60 mV and displayed half-inactivation at -76 +/- 8 mV, was reduced by 50% with the addition of 5 mM-4-AP (4-amino-pyridine). 6. In the presence of external Ca2+, the current-voltage relationship for the delayed current did not display a region of negative-slope conductance (N-shape). Increasing the intracellular ionized Ca2+ concentration by varying the Ca-EGTA buffer ratio did not alter the dependence of the current on the membrane potential. 7. Block of outward currents with internal Cs+ revealed a small (less than 90 pA) inward Ca2+ current when the external Ca2+ concentration was increased to 10 mM. From a holding potential of -50 mV, it had a threshold at -30 mV and peaked at +5 mV. Evidence for an inward Na+ current was not obtained. 8. We conclude that acutely dissociated pineal cells display two distinct K+ currents: (i) a slowly activating, sustained current similar to the delayed rectifier (IK); and (ii) a transient A-current (IA). At normal Ca2+ concentrations, no macroscopic Ca2+-activated outward current was observed.

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Selected References

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  1. Armstrong C. M., Lopez-Barneo J. External calcium ions are required for potassium channel gating in squid neurons. Science. 1987 May 8;236(4802):712–714. doi: 10.1126/science.2437654. [DOI] [PubMed] [Google Scholar]
  2. Armstrong C. M., Matteson D. R. The role of calcium ions in the closing of K channels. J Gen Physiol. 1986 May;87(5):817–832. doi: 10.1085/jgp.87.5.817. [DOI] [PMC free article] [PubMed] [Google Scholar]
  3. Bader C. R., Bertrand D., Dupin E. Voltage-dependent potassium currents in developing neurones from quail mesencephalic neural crest. J Physiol. 1985 Sep;366:129–151. doi: 10.1113/jphysiol.1985.sp015789. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Barish M. E. Differentiation of voltage-gated potassium current and modulation of excitability in cultured amphibian spinal neurones. J Physiol. 1986 Jun;375:229–250. doi: 10.1113/jphysiol.1986.sp016114. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. Belluzzi O., Sacchi O., Wanke E. A fast transient outward current in the rat sympathetic neurone studied under voltage-clamp conditions. J Physiol. 1985 Jan;358:91–108. doi: 10.1113/jphysiol.1985.sp015542. [DOI] [PMC free article] [PubMed] [Google Scholar]
  6. Belluzzi O., Sacchi O., Wanke E. Identification of delayed potassium and calcium currents in the rat sympathetic neurone under voltage clamp. J Physiol. 1985 Jan;358:109–129. doi: 10.1113/jphysiol.1985.sp015543. [DOI] [PMC free article] [PubMed] [Google Scholar]
  7. Bossu J. L., Feltz A., Thomann J. M. Depolarization elicits two distinct calcium currents in vertebrate sensory neurones. Pflugers Arch. 1985 Apr;403(4):360–368. doi: 10.1007/BF00589247. [DOI] [PubMed] [Google Scholar]
  8. Connor J. A., Stevens C. F. Prediction of repetitive firing behaviour from voltage clamp data on an isolated neurone soma. J Physiol. 1971 Feb;213(1):31–53. doi: 10.1113/jphysiol.1971.sp009366. [DOI] [PMC free article] [PubMed] [Google Scholar]
  9. Connor J. A., Stevens C. F. Voltage clamp studies of a transient outward membrane current in gastropod neural somata. J Physiol. 1971 Feb;213(1):21–30. doi: 10.1113/jphysiol.1971.sp009365. [DOI] [PMC free article] [PubMed] [Google Scholar]
  10. Dubinsky J. M., Oxford G. S. Ionic currents in two strains of rat anterior pituitary tumor cells. J Gen Physiol. 1984 Mar;83(3):309–339. doi: 10.1085/jgp.83.3.309. [DOI] [PMC free article] [PubMed] [Google Scholar]
  11. Ebels I., Balemans M. G. Physiological aspects of pineal functions in mammals. Physiol Rev. 1986 Jul;66(3):581–605. doi: 10.1152/physrev.1986.66.3.581. [DOI] [PubMed] [Google Scholar]
  12. 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]
  13. Fernandez J. M., Fox A. P., Krasne S. Membrane patches and whole-cell membranes: a comparison of electrical properties in rat clonal pituitary (GH3) cells. J Physiol. 1984 Nov;356:565–585. doi: 10.1113/jphysiol.1984.sp015483. [DOI] [PMC free article] [PubMed] [Google Scholar]
  14. Freschi J. E., Parfitt A. G. Intracellular recordings from pineal cells in tissue culture: membrane properties and response to norepinephrine. Brain Res. 1986 Mar 19;368(2):366–370. doi: 10.1016/0006-8993(86)90583-4. [DOI] [PubMed] [Google Scholar]
  15. Gallacher D. V., Morris A. P. A patch-clamp study of potassium currents in resting and acetylcholine-stimulated mouse submandibular acinar cells. J Physiol. 1986 Apr;373:379–395. doi: 10.1113/jphysiol.1986.sp016054. [DOI] [PMC free article] [PubMed] [Google Scholar]
  16. Galvan M., Sedlmeir C. Outward currents in voltage-clamped rat sympathetic neurones. J Physiol. 1984 Nov;356:115–133. doi: 10.1113/jphysiol.1984.sp015456. [DOI] [PMC free article] [PubMed] [Google Scholar]
  17. 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]
  18. Ikeda S. R., Schofield G. G. Tetrodotoxin-resistant sodium current of rat nodose neurones: monovalent cation selectivity and divalent cation block. J Physiol. 1987 Aug;389:255–270. doi: 10.1113/jphysiol.1987.sp016656. [DOI] [PMC free article] [PubMed] [Google Scholar]
  19. Israel J. M., Kirk C., Vincent J. D. Electrophysiological responses to dopamine of rat hypophysial cells in lactotroph-enriched primary cultures. J Physiol. 1987 Sep;390:1–22. doi: 10.1113/jphysiol.1987.sp016682. [DOI] [PMC free article] [PubMed] [Google Scholar]
  20. Latorre R., Coronado R., Vergara C. K+ channels gated by voltage and ions. Annu Rev Physiol. 1984;46:485–495. doi: 10.1146/annurev.ph.46.030184.002413. [DOI] [PubMed] [Google Scholar]
  21. Lingle C. J., Sombati S., Freeman M. E. Membrane currents in identified lactotrophs of rat anterior pituitary. J Neurosci. 1986 Oct;6(10):2995–3005. doi: 10.1523/JNEUROSCI.06-10-02995.1986. [DOI] [PMC free article] [PubMed] [Google Scholar]
  22. MacDermott A. B., Weight F. F. Action potential repolarization may involve a transient, Ca2+-sensitive outward current in a vertebrate neurone. Nature. 1982 Nov 11;300(5888):185–188. doi: 10.1038/300185a0. [DOI] [PubMed] [Google Scholar]
  23. Marty A. Ca-dependent K channels with large unitary conductance in chromaffin cell membranes. Nature. 1981 Jun 11;291(5815):497–500. doi: 10.1038/291497a0. [DOI] [PubMed] [Google Scholar]
  24. Marty A., Neher E. Potassium channels in cultured bovine adrenal chromaffin cells. J Physiol. 1985 Oct;367:117–141. doi: 10.1113/jphysiol.1985.sp015817. [DOI] [PMC free article] [PubMed] [Google Scholar]
  25. Matteson D. R., Armstrong C. M. Properties of two types of calcium channels in clonal pituitary cells. J Gen Physiol. 1986 Jan;87(1):161–182. doi: 10.1085/jgp.87.1.161. [DOI] [PMC free article] [PubMed] [Google Scholar]
  26. Mayer M. L., Sugiyama K. A modulatory action of divalent cations on transient outward current in cultured rat sensory neurones. J Physiol. 1988 Feb;396:417–433. doi: 10.1113/jphysiol.1988.sp016970. [DOI] [PMC free article] [PubMed] [Google Scholar]
  27. Parfitt A., Weller J. L., Klein D. C., Sakai K. K., Marks B. H. Blockade by ouabain or elevated potassium ion concentration of the adrenergic and adenosine cyclic 3',5'-monophosphate-induced stimulation of pineal serotonin N-acetyltransferase activity. Mol Pharmacol. 1975 May;11(3):241–255. [PubMed] [Google Scholar]
  28. Reuss S., Vollrath L. Electrophysiological properties of rat pinealocytes: evidence for circadian and ultradian rhythms. Exp Brain Res. 1984;55(3):455–461. doi: 10.1007/BF00235276. [DOI] [PubMed] [Google Scholar]
  29. Ritchie A. K. Two distinct calcium-activated potassium currents in a rat anterior pituitary cell line. J Physiol. 1987 Apr;385:591–609. doi: 10.1113/jphysiol.1987.sp016509. [DOI] [PMC free article] [PubMed] [Google Scholar]
  30. Sakai K. K., Marks B. H. Adrenergic effects on pineal cell membrane potential. Life Sci I. 1972 Mar 15;11(6):285–291. doi: 10.1016/0024-3205(72)90231-7. [DOI] [PubMed] [Google Scholar]
  31. Sugden L. A., Sugden D., Klein D. C. Alpha 1-adrenoceptor activation elevates cytosolic calcium in rat pinealocytes by increasing net influx. J Biol Chem. 1987 Jan 15;262(2):741–745. [PubMed] [Google Scholar]
  32. Zbicz K. L., Weight F. F. Transient voltage and calcium-dependent outward currents in hippocampal CA3 pyramidal neurons. J Neurophysiol. 1985 Apr;53(4):1038–1058. doi: 10.1152/jn.1985.53.4.1038. [DOI] [PubMed] [Google Scholar]

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