TTX-sensitive action potentials and excitability of adult rat sensory neurons cultured in serum- and exogenous nerve growth factor-free medium.

The excitability of adult rat dorsal root ganglion (DRG) neurons cultured in the absence of serum and exogenously added nerve growth factor (NGF) was studied. Current-clamp recordings revealed the presence of tetrodotoxin (TTX)-sensitive action potentials. Voltage-clamp recordings demonstrated the presence of both inward and outward currents. The inward Na+ current had a maximal amplitude near -10 mV and was completely blocked by TTX. A sustained Ca2+ inward current and a slowly activating outward K+ current were also observed. TTX-sensitive and TTX-resistant action potentials have been observed in previous studies in DRG neurons cultured in the presence of serum. By contrast, in the study reported here, only TTX-sensitive action potentials and Na+ currents were found in the neurons cultured in the absence of serum and nerve growth factor.