Evaluation of N-type Ca2+ channel currents in cultured rat superior cervical ganglion neurons

Electrophysiological studies of the effects of test compounds on ion channel currents have been useful in the identification of novel therapeutic agents. Here, we examined the use of cultured superior cervical ganglion (SCG) neurons as a model system for the electrophysiological evaluation of N-type Ca2+ channels in vitro. As previously reported, Ca2+ channel currents in acutely dissociated preparations of SCG neurons were mainly N-type, as defined by inhibition of Ca2+ channel current with the specific N-type Ca2+ channel blocker, ω-conopeptides GVIA or MVIIA. However, a cultured preparation that could be used over an extended period of time would be more useful for drug discovery since acutely dissociated preparations require daily dissections. We found that with extended time in culture the amplitudes of Ca2+ channel currents increased with time. While there was a reduction in the percentage of N-type Ca2+ channel component, the majority (70%) of Ca2+ channel currents in long-term cultured SCG neurons remained N-type. A portion of the MVIIA-resistant Ca2+ channel current component was blocked by the ω-conopeptide MVIIC and ω-agatoxin IIIA, but not by ω-agatoxin IVA, a pharmacological profile similar to Q-type Ca2+ channel current. These studies suggest that cultured SCG neurons would be useful for the study of N-type Ca2+ currents even after prolonged time in culture, and may also be used to indicate the selectivity of test compounds for other Ca2+ channel subtypes. Drug Dev. Res. 41:85–90, 1997.