High-voltage-activated Ca2+ currents and the excitability of pyramidal neurons in the hippocampal CA3 subfield in rats depend on corticosterone and time of day

Neurosci Lett. 2001 Jul 6;307(1):53-6. doi: 10.1016/s0304-3940(01)01926-7.

Abstract

This study tested the time-of-day dependence of the intrinsic postsynaptic properties of hippocampal CA3 pyramidal neurons. High-voltage-activated Ca2+ currents and the Ca(2+)- and voltage-dependent afterhyperpolarizations were examined in slices of rat brains obtained at four distinct time periods. Just after onset of the dark phase, the steady-state amplitude of the Ca2+ current (-1.24+/-0.11 nA) was significantly greater (P<0.03) than that of the light phase (-0.84+/-0.06 nA). Over the entire time range, the amplitude of the Ca2+ current correlated with plasma corticosterone levels in a U-shaped function. Furthermore, depolarization-induced excitability during the dark phase exhibited an increased spike after depolarization (3.1+/-0.1 mV) and a slower adaptation of the firing frequency (146+/-18%). These findings point to a dynamic time-of-day dependence of the CA3 neuronal properties and postsynaptic Ca2+ currents.

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology*
  • Animals
  • Cadmium / pharmacology
  • Calcium Channels / drug effects
  • Calcium Channels / metabolism*
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Circadian Rhythm / physiology*
  • Corticosterone / blood*
  • Corticosterone / pharmacology
  • Hippocampus / cytology
  • Hippocampus / drug effects
  • Hippocampus / metabolism*
  • Male
  • Neural Inhibition / drug effects
  • Neural Inhibition / physiology
  • Patch-Clamp Techniques
  • Pyramidal Cells / cytology
  • Pyramidal Cells / drug effects
  • Pyramidal Cells / metabolism*
  • Rats
  • Rats, Wistar

Substances

  • Calcium Channels
  • Cadmium
  • Corticosterone