CHARACTERIZATION OF 6 VOLTAGE-GATED K-RAT SENSORY NEURONS( CURRENTS IN ADULT)

1. Previously three voltage-gated K+ currents were described in neuron s from mammalian sensory ganglia: two transient and one sustained. Bec ause there is considerable variability in the gating properties of the se three currents, we have investigated the possibility that this vari ability reflects the presence of additional currents in sensory neuron s. 2. Using whole cell patch-clamp techniques, we provide evidence for the existence of six voltage-gated K+ currents in cultured dorsal roo t ganglion (DRG) neurons from the adult rat. The six currents were ide ntified on the basis of distinct biophysical and pharmacological prope rties; three currents are transient (I-Af, I-Aht, and I-As), and three are sustained (I-Ki, I-Kit, and I-Kn). 3. In addition to possessing d istinct biophysical and pharmacological properties, four of the six cu rrents are differentially expressed among subpopulations of DRG neuron s. I-Aht is selectively expressed in small-diameter neurons. I-Ki is e xpressed more frequently in neurons with an action-potential shoulder, and both I-Aht and I-As are selectively coexpressed in neurons that r espond to the algogenic agent capsaicin. I-Af is selectively expressed in large-diameter neurons and is the only current expressed more freq uently in neurons without an action-potential shoulder. 4. It is likel y that much of apparent variability in the properties of the three vol tage-gated K+ currents reported previously in vertebrate sensory neuro ns can be accounted for by the existence of at least three additional voltage-gated K+ currents described in this report.