Figure 6. Calcium-dependent mechanisms are not involved in the generation of subthreshold oscillation.

A, subthreshold oscillation is not blocked during superfusion of the brain slice with low Ca²⁺-high Mg²⁺ ACSF, whereas the duration of spike trains is strongly enhanced. B, subthreshold oscillation of the membrane potential is not blocked by addition of 0.5 mM CdCl₂to the ACSF. C, subthreshold oscillation is not blocked by the application of 300 nM apamin together with 3 mM TEA (please note that spike repolarization is delayed). D, subthreshold oscillation is not blocked by 10 nM charybdotoxin. Upper traces represent voltage while lower traces in A-C represent current recordings. The initial hyperpolarized part of the voltage trace in A is out of range. Records are truncated in A, B and D.