Journal of Neuroscience, Vol 6, 2915-2920, Copyright © 1986 by Society for Neuroscience
Intracellular fluoride alters the kinetic properties of calcium currents facilitating the investigation of synaptic events in hippocampal neurons
AR Kay, R Miles and RK Wong
We have attempted to suppress voltage-dependent conductances in hippocampal
neurons by introducing various intracellular agents. Voltage-clamp studies
were carried out using acutely dissociated hippocampal neurons from adult
guinea pigs. Synaptic events were examined using intracellular recordings
in the slice preparation. Sodium conductance was suppressed when the
quaternary lidocaine derivative QX 314 was introduced intracellularly.
Potassium conductances were blocked by intracellular cesium or Tris. We
also found that the anion fluoride could affect calcium conductance by an
intracellular action. When anions other than fluoride were used for
intracellular recordings, the voltage-dependent calcium current inactivated
slowly and showed persistent activation at membrane potentials between -40
and -10 mV. In contrast, when fluoride was present intracellularly, the
inactivation kinetics of the calcium current were accelerated and the
persistent component of the current was largely suppressed. Intracellular
recordings in the hippocampal slice showed that when electrodes contained
cesium, QX 314, and fluoride, the spiking and nonlinear responses of the
neuronal membrane to depolarization were blocked. In these conditions the
time course and voltage-dependence of EPSPs could be examined in detail
without complications due to voltage-dependent currents of the postsynaptic
cell.