Priming of intracellular calcium stores in rat CA1 pyramidal neurons

J Physiol. 2007 Oct 1;584(Pt 1):75-87. doi: 10.1113/jphysiol.2007.137661. Epub 2007 Aug 9.

Abstract

Repetitive synaptic stimulation evokes large amplitude Ca(2+) release waves from internal stores in many kinds of pyramidal neurons. The waves result from mGluR mobilization of IP(3) leading to Ca(2+)-induced Ca(2+) release. In most experiments in slices, regenerative Ca(2+) release can be evoked for only a few trials. We examined the conditions required for consistent release from the internal stores in hippocampal CA1 pyramidal neurons. We found that priming with action potentials evoked at 0.5-1 Hz for intervals as short as 15 s were sufficient to fill the stores, while sustained subthreshold depolarization or subthreshold synaptic stimulation lasting from 15 s to 2 min was less effective. A single episode of priming was effective for about 2-3 min. Ca(2+) waves could also be evoked by uncaging IP(3) with a UV flash in the dendrites. Priming was necessary to evoke these waves repetitively; 7-10 spikes in 15 s were again effective for this protocol, indicating that priming acts to refill the stores and not at a site upstream to the production of IP(3). These results suggest that normal spiking activity of pyramidal neurons in vivo should be sufficient to maintain their internal stores in a primed state ready to release Ca(2+) in response to an appropriate physiological stimulus. This may be a novel form of synaptic plasticity where a cell's capacity to release Ca(2+) is modulated by its average firing frequency.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Action Potentials / physiology*
  • Animals
  • Calcium / metabolism*
  • In Vitro Techniques
  • Inositol 1,4,5-Trisphosphate
  • Intracellular Fluid / metabolism*
  • Pyramidal Cells / metabolism*
  • Rats
  • Synaptic Transmission / physiology*
  • Time Factors

Substances

  • Inositol 1,4,5-Trisphosphate
  • Calcium