Figure 12. Synapse-dependent K_Ca2 channel activation.

A–B Recording schematic depicting how responses were presynaptically evoked and recorded postsynaptically in ventral horn neurons in whole-cell patch clamp configuration using either extracellular EIN (A) or paired intracellular RS axon (B) stimulation. Average NMDA receptor EPSCs were recorded in voltage clamp at −60 mV (A, EIN) and −70 mV (B, RS) after removal of extracellular Mg²⁺ in control (black, 5 µM NBQX, 1 µM glycine and 5 µM strychnine), drug (100 nM UCL 1684, dark blue; 5 µM apamin, teal), and washout (grey) conditions. Corresponding subtractions for EIN-evoked responses reveal the underlying K_Ca2 current (A, top traces; light blue for UCL and apamin). Paired NMDA receptor EPSCs (B, top trace) from single RS axon action potentials (B, bottom trace) before (black) and after apamin (teal; 5 µM). Subtraction reveals no underlying K_Ca2 current (top trace, blue). Arrows denote time of single EIN stimulation. Stim = stimulating electrode.