Controlling Ca2+-activated K+ channels with models of Ca2+ buffering in Purkinje cells

Cerebellum. 2012 Sep;11(3):681-93. doi: 10.1007/s12311-010-0224-3.

Abstract

Intracellular Ca(2+) concentrations play a crucial role in the physiological interaction between Ca(2+) channels and Ca(2+)-activated K(+) channels. The commonly used model, a Ca(2+) pool with a short relaxation time, fails to simulate interactions occurring at multiple time scales. On the other hand, detailed computational models including various Ca(2+) buffers and pumps can result in large computational cost due to radial diffusion in large compartments, which may be undesirable when simulating morphologically detailed Purkinje cell models. We present a method using a compensating mechanism to replace radial diffusion and compared the dynamics of different Ca(2+) buffering models during generation of a dendritic Ca(2+) spike in a single compartment model of a PC dendritic segment with Ca(2+) channels of P- and T-type and Ca(2+)-activated K(+) channels of BK- and SK-type. The Ca(2+) dynamics models used are (1) a single Ca(2+) pool; (2) two Ca(2+) pools, respectively, for the fast and slow transients; (3) detailed Ca(2+) dynamics with buffers, pump, and diffusion; and (4) detailed Ca(2+) dynamics with buffers, pump, and diffusion compensation. Our results show that detailed Ca(2+) dynamics models have significantly better control over Ca(2+)-activated K(+) channels and lead to physiologically more realistic simulations of Ca(2+) spikes and bursting. Furthermore, the compensating mechanism largely eliminates the effect of removing diffusion from the model on Ca(2+) dynamics over multiple time scales.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Algorithms
  • Buffers
  • Calcium / metabolism
  • Calcium / physiology*
  • Calcium Channels, P-Type / physiology
  • Calcium Channels, T-Type / physiology
  • Calcium Signaling / physiology*
  • Computer Simulation
  • Dendrites / physiology
  • Diffusion
  • Humans
  • Large-Conductance Calcium-Activated Potassium Channels / physiology
  • Models, Neurological
  • Potassium Channels, Calcium-Activated / physiology*
  • Purkinje Cells / physiology*
  • Small-Conductance Calcium-Activated Potassium Channels / physiology

Substances

  • Buffers
  • Calcium Channels, P-Type
  • Calcium Channels, T-Type
  • Large-Conductance Calcium-Activated Potassium Channels
  • Potassium Channels, Calcium-Activated
  • Small-Conductance Calcium-Activated Potassium Channels
  • Calcium