The contribution of intracellular calcium stores to mEPSCs recorded in layer II neurones of rat barrel cortex

J Physiol. 2002 Dec 1;545(2):521-35. doi: 10.1113/jphysiol.2002.022103.

Abstract

Loading slices of rat barrel cortex with 50 microM BAPTA-AM while recording from pyramidal cells in layer II induces a marked reduction in both the frequency and amplitudes of mEPSCs. These changes are due to a presynaptic action. Blocking the refilling of Ca(2+) stores with 20 microM cyclopiazonic acid (CPA), a SERCA pump inhibitor, in conjunction with neuronal depolarisation to activate Ca(2+) stores, results in a similar reduction of mEPSCs to that observed with BAPTA-AM, indicating that the source for intracellular Ca(2+) is the endoplasmic reticulum. Block or activation of ryanodine receptors by 20 microM ryanodine or 10 mM caffeine, respectively, shows that a significant proportion of mEPSCs are caused by Ca(2+) release from ryanodine stores. Blocking IP(3) receptors with 14 microM 2-aminoethoxydiphenylborane (2APB) also reduces the frequency and amplitude of mEPSCs, indicating the involvement of IP(3) stores in the generation of mEPSCs. Activation of group I metabotropic receptors with 20 microM (RS)-3,5-dihydroxyphenylglycine (DHPG) results in a significant increase in the frequency of mEPSCs, further supporting the role of IP(3) receptors and indicating a role of group I metabotropic receptors in causing transmitter release. Statistical evidence is presented for Ca(2+)-induced Ca(2+) release (CICR) from ryanodine stores after the spontaneous opening of IP(3) stores.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Caffeine / pharmacology
  • Calcium / physiology*
  • Calcium Channel Agonists / pharmacology
  • Calcium Channel Blockers / pharmacology
  • Calcium-Transporting ATPases / antagonists & inhibitors
  • Calcium-Transporting ATPases / metabolism
  • Central Nervous System Stimulants / pharmacology
  • Chelating Agents / pharmacology
  • Egtazic Acid / analogs & derivatives*
  • Electrophysiology
  • Endoplasmic Reticulum / drug effects
  • Endoplasmic Reticulum / metabolism
  • Excitatory Postsynaptic Potentials / physiology*
  • In Vitro Techniques
  • Inosine Triphosphate / pharmacology
  • Iontophoresis
  • Neurons / physiology*
  • Patch-Clamp Techniques
  • Rats
  • Rats, Wistar
  • Receptors, Presynaptic / drug effects
  • Ryanodine Receptor Calcium Release Channel / drug effects
  • Ryanodine Receptor Calcium Release Channel / metabolism
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Somatosensory Cortex / cytology
  • Somatosensory Cortex / physiology*

Substances

  • Calcium Channel Agonists
  • Calcium Channel Blockers
  • Central Nervous System Stimulants
  • Chelating Agents
  • Receptors, Presynaptic
  • Ryanodine Receptor Calcium Release Channel
  • Inosine Triphosphate
  • Caffeine
  • Egtazic Acid
  • Sarcoplasmic Reticulum Calcium-Transporting ATPases
  • Calcium-Transporting ATPases
  • 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid
  • Calcium