The effect of intracellular tetraethylammonium ions on the reversal potential of monosynaptic EPSPs and excitatory amino acids in cultured spinal cord neurones.

Using the whole cell patch clamp recording technique, the reversal potential of currents generated by the application of excitatory amino acids and by stimulation of excitatory synapses has been examined in cultured spinal cord neurones, with the partial substitution of intracellular K+ by TEA+. A previous report (Clements et al. 1986) showed that intracellular injection of TEA into the soma of spinal motoneurones in the cat shifted the reversal of the 1a EPSC to more positive potentials, but the reason for this shift was not clear. The results reported here show that the observed change in the reversal potential for both excitatory amino acid agonists and the excitatory synaptic current, was not due to a change in the relative permeability of the channels to potassium or sodium, but could be explained by a change in driving force for the permeant intracellular ions (K+ and/or Cs+) on their substitution with the impermeant TEA+ ion.