Figure 5.

Comparison of two outward K⁺ currents evoked by intracellular Ca²⁺ injection. Recordings were made in a single acutely isolated adult rabbit nodose neuron. A slow outward current (I_K-slow) was activated by a 5-nA, 1-s iontophoretic Ca²⁺ injection at a holding potential of −50 mV. A second outward current (I_K-medium) was activated at −20 mV (5 nA, 0.5 sec). I_K-medium activates and decays completely before I_K-slow reaches peak amplitude. I_K-medium was blocked by 10 mM tetraethylammonium; I_K-slow was blocked by 100 nM prostaglandin D₂. The iontophoretic pipette was filled with a 0.2 M CaCl₂ solution. Voltage-clamp currents were recorded with a second intracellular pipette. The discontinuous (switched) current injection mode of an Axoclamp II amplifier was used for both currentand voltage-clamp applications. The larger calibration value is for I_K-medium. Population data is shown in Table 2.