Pre- and postsynaptic K+ and Ca2+ fluxes in area CA1 of the rat hippocampus in vitro: effects of Ni2+, TEA and 4-AP.
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.
Jones
R S
RS
Department of Neurophysiology, Max-Planck-Institute for Psychiatry, Planegg-Martinsried, Federal Republic of Germany.
Heinemann
U
U
D015761:4-Aminopyridine; D000631:Aminopyridines / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D003470:Culture Media; D006624:Hippocampus / Q000378:metabolism*; D066298:In Vitro Techniques; D009532:Nickel / Q000494:pharmacology; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D013569:Synapses / Q000502:physiology*; D019789:Tetraethylammonium; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D000631:Aminopyridines; D003470:Culture Media; D013757:Tetraethylammonium Compounds; D019789:Tetraethylammonium; D009532:Nickel; D015761:4-Aminopyridine; D011188:Potassium; D002118:Calcium