Figure 1.

The effects of l-cys on the excitability of T-current-containing and T-current-deficient rat C-type nociceptors. A–D, Traces are from a single, acutely dissociated, l-cys-sensitive rat DRG neuron. E–G, Traces from another, acutely dissociated, l-cys-insensitive rat DRG neuron. A, AP elicited by a 1 ms, 2 nA current injection at the RMP of the cell. B, The cell was manually hyperpolarized to −90 mV and progressively greater current injections (Δ100 pA) delivered every 10 s to determine the threshold for AP firing. Threshold was 1.9 nA in control (left) and 1.7 nA in the presence of l-cys (right). C, Continuous segment of an experiment showing that l-cys increases the probability (percentage) to fire APs in response to trains of subthreshold stimuli (stimuli were 1 ms, 1.7 nA delivered every 10 s). D, I–V traces recorded in Ca²⁺ current-isolating external solution after current-clamp recording. Note the presence of both T-type (rapidly inactivating; gray lines) and HVA (slowly inactivating; black lines) currents. E, AP elicited by a 1 ms, 2.5 nA current injection at the RMP of the cell. F, Threshold was unaffected by the application of l-cys. G, I–V traces; note the presence of only HVA currents.