Pre- and postsynaptic K+ and Ca2+ fluxes in area CA1 of the rat hippocampus in vitro: effects of Ni2+, TEA and 4-AP

Exp Brain Res. 1987;68(1):205-9. doi: 10.1007/BF00255246.

Abstract

Pre- and postsynaptic fluxes of Ca2+ and K+ were determined concurrently in CA1 of the hippocampus in vitro under conditions where synaptic transmission was blocked. The Ca2+ entry blocker, Ni2+, abolished both pre- and postsynaptic Ca2+-influx and reduced presynaptic K+-efflux by about 20%. Postsynaptic K+-efflux was reduced nearly by 60%. 4-aminopyridine (4-AP) strongly enhanced presynaptic Ca2+-influx but only marginally increased Ca2+-entry into the postsynaptic neurones. At the same time, total K+-efflux from presynaptic sites was increased by about 30% but was unaltered postsynaptically. Finally, tetraethylammonium (TEA) enhanced both pre- and postsynaptic Ca2+-influx. Postsynaptic influx was more profoundly affected than presynaptic. Neither pre- nor postsynaptic efflux of K+ was altered by TEA. The results indicate a complex balance between inward Ca2+ and outward K+ currents in CA1 and that this balance may differ pre- and postsynaptically.

MeSH terms

  • 4-Aminopyridine
  • Aminopyridines / pharmacology
  • Animals
  • Calcium / metabolism*
  • Calcium / pharmacology
  • Culture Media
  • Hippocampus / metabolism*
  • In Vitro Techniques
  • Nickel / pharmacology
  • Osmolar Concentration
  • Potassium / metabolism*
  • Rats
  • Synapses / physiology*
  • Tetraethylammonium
  • Tetraethylammonium Compounds / pharmacology

Substances

  • Aminopyridines
  • Culture Media
  • Tetraethylammonium Compounds
  • Tetraethylammonium
  • Nickel
  • 4-Aminopyridine
  • Potassium
  • Calcium