Electrical properties of cultured dorsal root ganglion neurons from normal and trisomy 21 human fetal tissue.

Dorsal root ganglion (DRG) neurons, in 22 degrees C tissue culture containing nerve growth factor, taken from normal and trisomy 21 human fetal tissues, were subjected to current and voltage clamp measurements using a tight-seal whole-cell recording technique. Measurements were made between 1 and 2 weeks in culture, when the electrical properties of both neuron groups were shown to be constant and when mean values for passive electrical parameters did not differ significantly between groups. The duration of the action potential was significantly less in trisomic than in control neurons, and both depolarization and repolarization were accelerated. Tetraethylammonium (5 mM), which partially blocked outward currents, prolonged the rate of repolarization of the action potential in both neuron groups, and abolished the difference in the rate between the groups. Furthermore, the activation rate constants of two model-defined outward potassium currents were significantly higher in trisomic than in control neurons, suggesting that acceleration of repolarization of the action potential in trisomic neurons was due to shorter activation time-constants of outward potassium currents.