These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Functional expression of voltage dependent sodium channels in Xenopus oocytes injected with mRNA from neonatal or adult rat brain.
    Author: Virginio C, Cherubini E.
    Journal: Brain Res Dev Brain Res; 1995 Jul 14; 87(2):153-9. PubMed ID: 7586497.
    Abstract:
    The two electrode voltage clamp technique was used to study voltage-dependent sodium currents (INa) in Xenopus laevis oocytes previously injected with mRNA extracted from adult (A) or neonatal (N, < 5 days old) rat brains. In the presence of niflumic acid (300 microM) to block endogenous Ca(2+)-activated Cl- currents, depolarizing voltage steps from a holding potential of -100 mV to various voltages elicited in both groups of oocytes fast inward sodium currents which peaked at approximately 0 mV and then slowly declined to approximately 75% of the maximum current at +40 mV. At the peak, A INa was significantly larger than N INa (296 +/- 59 nA vs. 147 +/- 32 nA). Inactivation kinetics of N INa was best fit with one exponential component whereas A INa with two exponential components. A significant difference in the voltage dependence of inactivation was found between A INa or N INa. The values of Vh were -53 +/- 0.9 mV or -59.8 +/- 0.7 mV for A INa or N INa respectively. The recovery from inactivation was fitted in both groups with two exponential functions (tau f and tau s) whose values were not significantly different. However the ratio between tau f and tau s was significantly higher for N INa comparing to A INa (5.7 vs. 2.1). TTX reversibly blocked INa. The IC50 value was 58.2 +/- 6.3 nM for A INa and 20.4 +/- 2.2 nM for N INa. These results suggest that different isoforms of TTX-sensitive, voltage-dependent sodium channel subunits are functionally expressed, may be in different proportions in oocytes injected with A or N mRNA.
    [Abstract] [Full Text] [Related] [New Search]