Ionic currents in cultured dorsal root ganglion cells from adult guinea pigs.
Ionic currents in cultured dorsal root ganglion (DRG) neurons from adult guinea pigs were analyzed by voltage-clamp techniques. The Na+ inward current had a reversal potential at +33 mV, and revealed activation and inactivation kinetics similar to those of squid giant axons. A typical value for the maximum Na+ conductance was 178 mS/cm2 and the peak current was 2.5 mA/cm2. The delayed K+ outward current showed a fast and a slow phase of inactivation and was sensitive to tetraethylammonium (TEA; approximately 130 mM) and 4-aminopyridine (approximately 2 mM). The maximum K+ conductance was 26 +/- 9 (mean +/- SD) mS/cm2. The slow Ca2+ inward current was identified in Na+-free, TEA-containing solution. Its peak value was increased by 1.7-fold when [Ca2+]o was increased from 5 to 10 mM. The current was blocked by Co2+ but not by tetrodotoxin. Sr2+ and Ba2+ could substitute in carrying this current. The maximum peak of the Ca2+ current was 0.22 +/- 0.14 mA/cm2. At potentials positive to 0 mV, the Ca2+ current was often followed by a slowly developing outward current, which was also sensitive to Co2+, suggesting a Ca2+-activated outward current. It is concluded that the action potential of the adult guinea pig DRG neuron is mediated by Ca2+ as well as by Na+ and K+ currents. The current densities of these ionic channels are considered to be different from embryonic neurons and from nodes of Ranvier.
D000367:Age Factors; D000818:Animals; D002118:Calcium / Q000502:physiology*; D002478:Cells, Cultured; D005727:Ganglia, Spinal / Q000502:physiology*; D006168:Guinea Pigs; D007700:Kinetics; D011188:Potassium / Q000502:physiology*; D012964:Sodium / Q000502:physiology*
D012964:Sodium; D011188:Potassium; D002118:Calcium