Relationships Between Intracellular Calcium and Afterhyperpolarizations in Neocortical Pyramidal Neurons

J Neurophysiol. 2004 Jan;91(1):324-35. doi: 10.1152/jn.00583.2003. Epub 2003 Aug 13.

Abstract

We examined the effects of recent discharge activity on [Ca2+]i in neocortical pyramidal cells. Our data confirm and extend the observation that there is a linear relationship between plateau [Ca2+]i and firing frequency in soma and proximal apical dendrites. The rise in [Ca2+] activates K+ channels underlying the afterhyperpolarization (AHP), which consists of 2 Ca(2+)-dependent components: the medium AHP (mAHP) and the slow AHP (sAHP). The mAHP is blocked by apamin, indicating involvement of SK-type Ca(2+)-dependent K+ channels. The identity of the apamin-insensitive sAHP channel is unknown. We compared the sAHP and the mAHP with regard to: 1) number and frequency of spikes versus AHP amplitude; 2) number and frequency of spikes versus [Ca2+]i; 3) IAHP versus [Ca2+]i. Our data suggest that sAHP channels require an elevation of [Ca2+]i in the cytoplasm, rather than at the membrane, consistent with a role for a cytoplasmic intermediate between Ca2+ and the K+ channels. The mAHP channels appear to respond to a restricted Ca2+ domain.

Publication types

  • Comparative Study
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology
  • Adrenergic beta-Agonists / pharmacology
  • Animals
  • Animals, Newborn
  • Apamin / pharmacology
  • Cadmium / pharmacology
  • Calcium / physiology*
  • Dendrites / drug effects
  • Dendrites / metabolism
  • Dose-Response Relationship, Radiation
  • Electric Impedance
  • Electric Stimulation / methods
  • Extracellular Space / drug effects
  • Extracellular Space / physiology*
  • Fura-2 / metabolism
  • In Vitro Techniques
  • Isoproterenol / pharmacology
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Neocortex / cytology*
  • Patch-Clamp Techniques / methods
  • Pyramidal Cells / cytology
  • Pyramidal Cells / drug effects
  • Pyramidal Cells / physiology*
  • Rats
  • Rats, Sprague-Dawley
  • Time Factors

Substances

  • Adrenergic beta-Agonists
  • Cadmium
  • Apamin
  • Isoproterenol
  • Calcium
  • Fura-2