| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX 77030.
1. Calcium current (ICa) activation was studied in denervated extensor digitorum longus muscle fibres of the rat. Denervation was performed by surgically removing 6-8 mm of the sciatic nerve at the sciatic notch. Controls were normal fibres from non-operated rats. Electrical recordings were carried out using the double Vaseline-gap technique. 2. Current-voltage (I-V) curves showed that the ICa amplitude increased during the first 4-6 days after denervation and subsequently decreased during the second week. Between days 4 and 6 after denervation, the peak ICa amplitude (at 0 mV) was -5.9 +/- 0.5 microA/microF (mean +/- S.E.M.) as compared with -4.8 +/- 0.3 microA/microF in normal fibres. Between days 14 and 15 after denervation, the ICa amplitude was -2.9 +/- 0.4 microA/microF. 3. The time constant of ICa activation (tau a) was significantly increased by denervation. At 0 mV, tau a in normal fibres was 44.8 +/- 1.4 ms. Between 4 and 6 days after denervation tau a was 58.1 +/- 4.8 ms, and between 14 and 15 days after denervation, 55.8 +/- 3.8 ms. 4. The time constant of deactivation (tau d) decreased after denervation. At -10 mV, the tau d in normal fibres was 103.4 +/- 14 ms. The value decreased to 74.5 +/- 8.6 and 74.0 +/- 17 ms between days 4 and 6 and days 14 and 15 of denervation respectively. 5. Charge movement (Qon) was reduced progressively without major changes in the steepness (k) and position on the voltage axis of the Qon-Vm relationship. The fitted parameters under control were Qmax = 15.4 nC/microF, mid-point potential Vq1/2 = -25.2 mV and k = 11.9 mV. Between days 14 and 15 of denervation, the values for Qmax, Vq1/2 and k were 6.7 nC/microF, -36.8 mV and 11.3 mV respectively. 6. Calcium permeability (PCa) in normal and denervated fibres at stages during denervation was calculated according to the Hodgkin-Huxley model. At 0 mV PCa was 1.24 x 10(-5) cm/s in normal fibres, and 7.43 x 10(-6) cm/s after 2 weeks of denervation. 7. The m infinity-Vm relationship was shifted to more positive potentials after denervation without significant changes in the steepness factor k. The V1/2 value in normal fibres was -4.4 mV, and 5.8 mV after two weeks of denervation. 8. The ICa sensitivity to nifedipine was not modified in the different groups of denervated fibres studied. With 10 microM-nifedipine, the 1-(ICa in nifedipine/ICa control) relationships were 0.74 +/- 0.03 in normal fibres and 0.76 +/- 0.12, 14 days after denervation.
This article has been cited by other articles:
|
|
 |
|
  R. Jimenez-Moreno, Z.-M. Wang, R. C. Gerring, and O. Delbono Sarcoplasmic Reticulum Ca2+ Release Declines in Muscle Fibers from Aging Mice Biophys. J., April 15, 2008; 94(8): 3178 - 3188. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. A. Anderson, X. Altafaj, Z. Zheng, Z.-M. Wang, O. Delbono, M. Ronjat, S. Treves, and F. Zorzato The junctional SR protein JP-45 affects the functional expression of the voltage-dependent Ca2+ channel Cav1.1 J. Cell Sci., May 15, 2006; 119(10): 2145 - 2155. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. M. Payne, Z. Zheng, M. L. Messi, C. E. Milligan, E. Gonzalez, and O. Delbono Motor neurone targeting of IGF-1 prevents specific force decline in ageing mouse muscle J. Physiol., January 15, 2006; 570(2): 283 - 294. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. M. Payne, Z. Zheng, E. Gonzalez, Z.-M. Wang, M. L. Messi, and O. Delbono External Ca2+-dependent excitation-contraction coupling in a population of ageing mouse skeletal muscle fibres J. Physiol., October 1, 2004; 560(1): 137 - 155. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. L. Messi and O. Delbono Target-Derived Trophic Effect on Skeletal Muscle Innervation in Senescent Mice J. Neurosci., February 15, 2003; 23(4): 1351 - 1359. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Collet, L. Csernoch, and V. Jacquemond Intramembrane Charge Movement and L-Type Calcium Current in Skeletal Muscle Fibers Isolated from Control and mdx Mice Biophys. J., January 1, 2003; 84(1): 251 - 265. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Z. Zheng, Z.-M. Wang, and O. Delbono Insulin-like Growth Factor-1 Increases Skeletal Muscle Dihydropyridine Receptor alpha 1S Transcriptional Activity by Acting on the cAMP-response Element-binding Protein Element of the Promoter Region J. Biol. Chem., December 20, 2002; 277(52): 50535 - 50542. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. A. Morrill, R. H. Brown Jr, and S. C. Cannon Gating of the L-Type Ca Channel in Human Skeletal Myotubes: An Activation Defect Caused by the Hypokalemic Periodic Paralysis Mutation R528H J. Neurosci., December 15, 1998; 18(24): 10320 - 10334. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
O. Delbono, M. Renganathan, and M. L. Messi Regulation of Mouse Skeletal Muscle L-Type Ca2+ Channel by Activation of the Insulin-Like Growth Factor-1 Receptor J. Neurosci., September 15, 1997; 17(18): 6918 - 6928. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Z. Zheng, Z.-M. Wang, and O. Delbono Charge movement and transcription regulation of L-type calcium channel alpha1S in skeletal muscle cells J. Physiol., April 15, 2002; 540(2): 397 - 409. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
