Journal of Neurophysiology, Vol 68, Issue 1 85-92, Copyright © 1992 by APS

ARTICLES

Characterization of voltage-dependent calcium currents in mouse motoneurons

M. Mynlieff and K. G. Beam
Department of Physiology, Colorado State University, Fort Collins 80523.

1. Calcium channel currents were measured with the whole-cell patch clamp technique in cultured, identified mouse motoneurons. Three components of current were operationally defined on the basis of voltage dependence, kinetics, and pharmacology. 2. Test potentials to -50 mV or greater (10 mM external Ca2+) elicited a low-voltage activated T-type current that was transient (decaying to baseline in less than 200 ms) and had a relatively slow time to peak (20-50 ms). A 1-s prepulse to -45 mV produced approximately half-maximal inactivation of this T current. 3. Two high-voltage activated (HVA) components of current (1 transient and 1 sustained) were activated by test potentials to -20 mV or greater (10 mM external Ca2+). A 1-s prepulse to -35 mV produced approximately half-maximal inactivation of the transient component without affecting the sustained component. 4. When Ba2+ was substituted for Ca2+ as the charge carrier, activation of the HVA components was shifted in the hyperpolarizing direction, and the relative amplitude of the transient HVA component was reduced. 5. Amiloride (1-2 mM) caused a reversible, partial block of the T current without affecting the HVA components. 6. The dihydropyridine agonist isopropyl 4-(2,1,3-benzoxadiazol-4-yl)-1,4-dihydro-2,6-dimethyl-5-nitro-3- pyridine-carboxylate [(+)-SDZ 202-791, 100 nM-1 microM)] shifted the activation of the sustained component of HVA current to more negative potentials and increased its maximal amplitude. Additionally, (+)-SDZ 202-791 caused the appearance of a slowed component of tail current.(ABSTRACT TRUNCATED AT 250 WORDS)

This article has been cited by other articles:

				C. Thaler, W. Li, and P. Brehm Calcium Channel Isoforms Underlying Synaptic Transmission at Embryonic Xenopus Neuromuscular Junctions J. Neurosci., January 15, 2001; 21(2): 412 - 422. [Abstract] [Full Text] [PDF]

				J. C. Rekling, G. D. Funk, D. A. Bayliss, X.-W. Dong, and J. L. Feldman Synaptic Control of Motoneuronal Excitability Physiol Rev, April 1, 2000; 80(2): 767 - 852. [Abstract] [Full Text] [PDF]

				F. P. Elsen and J.-M. Ramirez Calcium Currents of Rhythmic Neurons Recorded in the Isolated Respiratory Network of Neonatal Mice J. Neurosci., December 15, 1998; 18(24): 10652 - 10662. [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]

				R. E. Westenbroek, L. Hoskins, and W. A. Catterall Localization of Ca2+ Channel Subtypes on Rat Spinal Motor Neurons, Interneurons, and Nerve Terminals J. Neurosci., August 15, 1998; 18(16): 6319 - 6330. [Abstract] [Full Text] [PDF]

				K. D. Garcia, L. K. Sprunger, M. H. Meisler, and K. G. Beam The Sodium Channel Scn8a Is the Major Contributor to the Postnatal Developmental Increase of Sodium Current Density in Spinal Motoneurons J. Neurosci., July 15, 1998; 18(14): 5234 - 5239. [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]

				A. E. Manira and N. Bussieres Calcium Channel Subtypes in Lamprey Sensory and Motor Neurons J Neurophysiol, September 1, 1997; 78(3): 1334 - 1340. [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]

				K. D. Garcia and K. G. Beam Reduction of Calcium Currents by Lambert-Eaton Syndrome Sera: Motoneurons Are Preferentially Affected, and L-Type Currents Are Spared J. Neurosci., August 15, 1996; 16(16): 4903 - 4913. [Abstract] [Full Text] [PDF]