In order to investigate the electrogenesis of defined cell populations, we applied an in vitro system that allows the selective culturing of individual Drosophila CNS precursors under different conditions. CNS midline (ML) precursors prepared from gastrula stage embryos gave rise to progeny cells with neuronal and glial morphology that expressed specific markers. Using whole-cell patch-clamp recordings, a detailed description of ionic currents present in this defined cell population is provided. Most ionic currents of cultured ML neurons were similar to other cultured Drosophila neurons, even though their embryonic origin is different. They displayed at least two voltage-gated potassium currents, a voltage-gated sodium, two voltage-gated calcium currents, and responded to the neurotransmitters ACh and GABA. They showed homogeneity in action potential firing properties, generating only a single spike even upon sustained depolarization. Interestingly, although the expression of the voltage-gated potassium currents appeared to be highly cell autonomous, for all other currents significant changes were observed in the presence of fiber contacts.
Copyright 2000 John Wiley & Sons, Inc.