Voltage-independent inhibition of Ca(V)2.2 channels is delimited to a specific region of the membrane potential in rat SCG neurons

Acta Biochim Biophys Sin (Shanghai). 2012 Jun;44(6):544-9. doi: 10.1093/abbs/gms025. Epub 2012 Apr 23.

Abstract

Neurotransmitters and hormones regulate Ca(V)2.2 channels through a voltage-independent pathway which is not well understood. It has been suggested that this voltage-independent inhibition is constant at all membrane voltages. However, changes in the percent of voltage-independent inhibition of Ca(V)2.2 have not been tested within a physiological voltage range. Here, we used a double-pulse protocol to isolate the voltage-independent inhibition of Ca(V)2.2 channels induced by noradrenaline in rat superior cervical ganglion neurons. To assess changes in the percent of the voltage-independent inhibition, the activation voltage of the channels was tested between -40 and +40 mV. We found that the percent of voltage-independent inhibition induced by noradrenaline changed with the activation voltage used. In addition, voltage-independent inhibition induced by oxo-M, a muscarinic agonist, exhibited the same dependence on activation voltage, which supports that this pattern is not exclusive for adrenergic activation. Our results suggested that voltage-independent inhibition of Ca(V)2.2 channels depends on the activation voltage of the channel in a physiological voltage range. This may have relevant implications in the understanding of the mechanism involved in voltage-independent inhibition.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Calcium Channels, N-Type / drug effects*
  • Cells, Cultured
  • Male
  • Membrane Potentials / drug effects*
  • Muscarinic Agonists / pharmacology
  • Norepinephrine / pharmacology
  • Oxotremorine / analogs & derivatives
  • Oxotremorine / pharmacology
  • Rats
  • Rats, Wistar
  • Superior Cervical Ganglion / physiology*

Substances

  • Cacna1b protein, rat
  • Calcium Channels, N-Type
  • Muscarinic Agonists
  • Oxotremorine
  • oxotremorine M
  • Norepinephrine