Figure 7.
Both 9-cis-RA and atRA lengthened the duration that cells were electrically excitable in culture. Standard intracellular recordings were made from cells treated with 9-cis-RA, atRA, or vehicle control on day 4 of cell culture. A, The RMPs of cells cultured in 9-cis-RA and atRA were not significantly different from each other, although they were significantly more negative than the RMPs of control cells. B, The histogram shows the percentage of cells that were electrically excitable (spontaneous or induced firing) on day 4 of culture. There was no significant difference in the number of cells that fired action potentials between cells cultured in 9-cis-RA or atRA; however, both were significantly different from vehicle controls. C, Representative intracellular electrophysiological recordings from cells cultured in 9-cis-RA (i), atRA (ii), and vehicle control (iii). Following depolarizing current injection, the cells cultured in 9-cis-RA and atRA fired action potentials on day 4. The cell cultured in vehicle control failed to respond to current injection on day 4. Arrowheads indicate the time of current injections. *p < 0.05, **p < 0.01 (compared with control conditions).