Electrophysiological properties of cultured dorsal root ganglion and spinal cord neurons of normal and trisomy 16 fetal mice.

Dorsal root ganglion (DRG) and spinal cord neurons from normal and trisomy 16 fetal mice, an animal model for human trisomy 21 (Down syndrome), were maintained in primary culture and their electrical membrane properties were compared with intracellular recording techniques. After 3-4 weeks in culture, trisomic DRG neurons had a higher mean resting potential (+10%), a higher specific membrane resistance (+50%) and higher excitability (+17%), a shorter action potential (-22%), higher maximal rates of depolarization (+39%) and of two phases of repolarization (+20% and +10%) and a lower duration (-42%) of the afterhyperpolarization, than did control DRG neurons (P less than 0.05). The duration of the action potential was 2X greater than in control neurons, when external calcium was elevated from 1.2 to 10 mM. Differences in the electrical parameters like those observed in DRG neurons also were found in cultured spinal cord neurons. These results indicate that trisomy 16 in fetal mice alters passive and active electrical membrane properties in DRG and spinal cord neurons, and suggest that some differences are related to differences in calcium currents.