Journal of Neurophysiology, Vol 72, Issue 2 762-777, Copyright © 1994 by APS

ARTICLES

Multiple components of calcium current in acutely dissociated dentate gyrus granule neurons

L. S. Eliot and D. Johnston
Division of Neuroscience, Baylor College of Medicine, Houston, Texas 77030.

1. Specific Ca2+ channel blocker were used to isolate and characterize different components of whole cell Ba2+ current in granule neurons acutely dissociated from guinea pig hippocampal slices. 2. Granule cell Ba2+ current peaked around +5 mV, whether elicited by step or ramp commands, and was completely blocked by 100 microM Cd2+. 3. Saturating doses (> or = 5 microM) of the dihydropyridine antagonist, nimodipine, blocked 39% of the total current, and the inhibition was partially reversible. Nimodipine had a greater effect on current at the end of a depolarizing step, suggesting some voltage dependence of its action. 4. Saturating doses (> or = 3 microM) of omega-conotoxin-GVIA irreversibly blocked 21% of the total current and did not occlude subsequent nimodipine inhibition. 5. High concentrations (> or = 100 nM) of omega-agatoxin-IVA irreversibly blocked another 20% of the total current. The effect of omega-Aga-IVA was quite slow, but saturated after several minutes at 200 nM concentration. A high dose (1 microM) produced rapid effects that were used to quantify the magnitude of block. 6. When applied together, all three blockers inhibited nearly the same amount of total current (77%) as would be expected from the sum of each blocker applied individually (80%), suggesting that the three antagonists blocked different channel types. 7. Quantitatively similar results were obtained for the effect of each blocker alone and in combination on currents elicited by depolarizing ramp commands. Ramp currents blocked by each antagonist (difference ramps) all peaked near the same potential as the initial control ramp, indicating very similar activation properties for the three current components. Difference currents elicited by step commands similarly showed little difference among the three components in their kinetics of inactivation during relatively brief (30 ms) depolarizations. With longer steps, however, the omega-CgTX-GVIA-sensitive component showed some inactivation, whereas the omega-Aga-IVA-sensitive current did not inactivate. 8. The component of current resistant to all three blockers (approximately 23% of total current) was not inhibited by omega-conotoxin-MVIIC, but was half blocked by 50 microM Ni2+. This Ni(2+)-sensitive component showed relatively rapid inactivation and peaked at a somewhat lower potential (-10 mV) than the control current. The resistant current was also inactivated by approximately 50% by holding at -60 compared with -80 mV.(ABSTRACT TRUNCATED AT 400 WORDS)

This article has been cited by other articles:

				W. W. Wu, C. S. Chan, D. J. Surmeier, and J. F. Disterhoft Coupling of L-Type Ca2+ Channels to KV7/KCNQ Channels Creates a Novel, Activity-Dependent, Homeostatic Intrinsic Plasticity J Neurophysiol, October 1, 2008; 100(4): 1897 - 1908. [Abstract] [Full Text] [PDF]

				G. Stocca, C. Schmidt-Hieber, and J. Bischofberger Differential dendritic Ca2+ signalling in young and mature hippocampal granule cells J. Physiol., August 15, 2008; 586(16): 3795 - 3811. [Abstract] [Full Text] [PDF]

				A. E. Metz, T. Jarsky, M. Martina, and N. Spruston R-Type Calcium Channels Contribute to Afterdepolarization and Bursting in Hippocampal CA1 Pyramidal Neurons J. Neurosci., June 15, 2005; 25(24): 5763 - 5773. [Abstract] [Full Text] [PDF]

				D. Sochivko, A. Pereverzev, N. Smyth, C. Gissel, T. Schneider, and H. Beck The CaV2.3 Ca2+ channel subunit contributes to R-Type Ca2+ currents in murine hippocampal and neocortical neurones J. Physiol., August 1, 2002; 542(3): 699 - 710. [Abstract] [Full Text] [PDF]

				S. I. McDonough, L. M. Boland, I. M. Mintz, and B. P. Bean Interactions among Toxins That Inhibit N-type and P-type Calcium Channels J. Gen. Physiol., April 1, 2002; 119(4): 313 - 328. [Abstract] [Full Text] [PDF]

				S. S. Sidach and I. M. Mintz Kurtoxin, A Gating Modifier of Neuronal High- and Low-Threshold Ca Channels J. Neurosci., March 15, 2002; 22(6): 2023 - 2034. [Abstract] [Full Text] [PDF]

				R. C. Foehring, P. G. Mermelstein, W.-J. Song, S. Ulrich, and D. J. Surmeier Unique Properties of R-Type Calcium Currents in Neocortical and Neostriatal Neurons J Neurophysiol, November 1, 2000; 84(5): 2225 - 2236. [Abstract] [Full Text] [PDF]

				S. S. Sidach and I. M. Mintz Low-Affinity Blockade of Neuronal N-Type Ca Channels by the Spider Toxin omega -Agatoxin-IVA J. Neurosci., October 1, 2000; 20(19): 7174 - 7182. [Abstract] [Full Text] [PDF]

				E. M. Blalock, N. M. Porter, and P. W. Landfield Decreased G-Protein-Mediated Regulation and Shift in Calcium Channel Types with Age in Hippocampal Cultures J. Neurosci., October 1, 1999; 19(19): 8674 - 8684. [Abstract] [Full Text] [PDF]

				P. G. Mermelstein, R. C. Foehring, T. Tkatch, W.-J. Song, G. Baranauskas, and D. J. Surmeier Properties of Q-Type Calcium Channels in Neostriatal and Cortical Neurons are Correlated with beta Subunit Expression J. Neurosci., September 1, 1999; 19(17): 7268 - 7277. [Abstract] [Full Text] [PDF]

				H. Beck, R. Steffens, U. Heinemann, and C. E. Elger Ca2+-Dependent Inactivation of High-Threshold Ca2+ Currents in Hippocampal Granule Cells of Patients With Chronic Temporal Lobe Epilepsy J Neurophysiol, August 1, 1999; 82(2): 946 - 954. [Abstract] [Full Text] [PDF]

				J. Magistretti, S. Brevi, and M. de Curtis Biophysical and pharmacological diversity of high-voltage-activated calcium currents in layer II neurones of guinea-pig piriform cortex J. Physiol., August 1, 1999; 518(3): 705 - 720. [Abstract] [Full Text] [PDF]

				T. D. Plant, C. Schirra, E. Katz, O. D. Uchitel, and A. Konnerth Single-Cell RT-PCR and Functional Characterization of Ca2+ Channels in Motoneurons of the Rat Facial Nucleus J. Neurosci., December 1, 1998; 18(23): 9573 - 9584. [Abstract] [Full Text] [PDF]

				U V. Nagerl and I. Mody Calcium-dependent inactivation of high-threshold calcium currents in human dentate gyrus granule cells J. Physiol., May 15, 1998; 509(1): 39 - 45. [Abstract] [Full Text] [PDF]

				D. Churchill and B. A. Macvicar Biophysical and Pharmacological Characterization of Voltage-Dependent Ca2+ Channels in Neurons Isolated From Rat Nucleus Accumbens J Neurophysiol, February 1, 1998; 79(2): 635 - 647. [Abstract] [Full Text] [PDF]

				B. Yu and P. Shinnick-Gallagher Corticotropin-Releasing Factor Increases Dihydropyridine- and Neurotoxin-Resistant Calcium Currents in Neurons of the Central Amygdala J. Pharmacol. Exp. Ther., January 1, 1998; 284(1): 170 - 179. [Abstract] [Full Text]

				Y. Wang, M. J. Rowan, and R. Anwyl LTP Induction Dependent on Activation of Ni2+-Sensitive Voltage-Gated Calcium Channels, but not NMDA Receptors, in the Rat Dentate Gyrus In Vitro J Neurophysiol, November 1, 1997; 78(5): 2574 - 2581. [Abstract] [Full Text] [PDF]

				E. Pan and J. L. Stringer Role of Potassium and Calcium in the Generation of Cellular Bursts in the Dentate Gyrus J Neurophysiol, May 1, 1997; 77(5): 2293 - 2299. [Abstract] [Full Text] [PDF]

				H. Beck, R. Steffens, U. Heinemann, and C. E. Elger Properties of Voltage-Activated Ca2+ Currents in Acutely Isolated Human Hippocampal Granule Cells J Neurophysiol, March 1, 1997; 77(3): 1526 - 1537. [Abstract] [Full Text] [PDF]

				B. Yu and P. Shinnick-Gallagher Dihydropyridine- and Neurotoxin-Sensitive and -Insensitive Calcium Currents in Acutely Dissociated Neurons of the Rat Central Amygdala J Neurophysiol, February 1, 1997; 77(2): 690 - 701. [Abstract] [Full Text] [PDF]

				P. J. Kammermeier and S. W. Jones High-Voltage-Activated Calcium Currents in Neurons Acutely Isolated From the Ventrobasal Nucleus of the Rat Thalamus J Neurophysiol, January 1, 1997; 77(1): 465 - 475. [Abstract] [Full Text] [PDF]

				R. B. Avery and D. Johnston Multiple Channel Types Contribute to the Low-Voltage-Activated Calcium Current in Hippocampal CA3 Pyramidal Neurons J. Neurosci., September 15, 1996; 16(18): 5567 - 5582. [Abstract] [Full Text] [PDF]