Excitatory synaptic potentials dependent on metabotropic glutamate receptor activation in guinea-pig hippocampal pyramidal cells

J Physiol. 1995 Sep 15;487 ( Pt 3)(Pt 3):663-76. doi: 10.1113/jphysiol.1995.sp020908.

Abstract

1. Intracellular and extracellular recordings of CA1 and CA3 neurones were performed in guinea-pig hippocampal slices to examine synaptic activities dependent on metabotropic glutamate receptors (mGluRs). 2. Long burst activities were elicited by 4-aminopyridine in the presence of ionotropic glutamate receptor and GABAA receptor blockers (6-cyano-7-nitroquinoxaline-2,3-dione and 3-(RS-2-carboxypiperazin-4-yl)-propyl-1-phosphonic acid, and picrotoxin). Long bursts were also elicited by alpha-dendrotoxin. 3. Long bursts consisted of a 5-25 s depolarization with overriding action potentials and occurred rhythmically at intervals ranging from 1 to 20 min. Long bursts were generated in a population of CA3 neurones and the synchronized output elicited long bursts in CA1 cells. Depolarizing potentials underlying long bursts in CA1 cells had a reversal potential of -14.8 +/- 5.1 mV. 4. Long burst-associated depolarizations in CA1 neurones were suppressed by local application of L-(+)-2-amino-3-phosphonopropionic acid (L-AP3) and of the phenylglycine derivatives (+)-alpha-methyl-4-carboxyphenylglycine ((+)-MCPG), S-4-carboxyphenylglycine (S-4CPG) and S-4-carboxy-3-hydroxyphenylglycine (S-4C3HPG). (-)-MCPG or atropine application did not affect the long burst-associated depolarization. 5. Bath perfusion of (+)-MCPG (0.5 mM), S-4CPG (0.5 mM), S-4C3HPG (0.5 mM) or L-AP3 (1 mM) blocked the occurrence of long bursts. 6. The results suggest that the long burst-associated depolarizations are synaptic potentials dependent on mGluR activation. Activation of mGluRs may also be involved in the generation of synchronized long bursts in the CA3 region.

MeSH terms

  • Action Potentials / drug effects
  • Action Potentials / physiology
  • Animals
  • Calcium / physiology
  • Electrophysiology
  • Epilepsy / chemically induced
  • Epilepsy / physiopathology
  • Excitatory Amino Acid Agonists / pharmacology
  • Excitatory Amino Acid Antagonists / pharmacology
  • GABA-A Receptor Agonists
  • GABA-A Receptor Antagonists
  • Glycine Agents / pharmacology
  • Guinea Pigs
  • Hippocampus / cytology
  • Hippocampus / drug effects
  • Hippocampus / physiology*
  • In Vitro Techniques
  • Membrane Potentials / drug effects
  • Membrane Potentials / physiology
  • Pyramidal Cells / drug effects
  • Pyramidal Cells / physiology*
  • Receptors, Metabotropic Glutamate / agonists
  • Receptors, Metabotropic Glutamate / metabolism*
  • Synaptic Membranes / drug effects
  • Synaptic Membranes / physiology*

Substances

  • Excitatory Amino Acid Agonists
  • Excitatory Amino Acid Antagonists
  • GABA-A Receptor Agonists
  • GABA-A Receptor Antagonists
  • Glycine Agents
  • Receptors, Metabotropic Glutamate
  • Calcium