Figure 3.

In adult sensory neurons, direct activation of PKC by application of the phorbol ester PDAc produces a significant increase in action potential duration consistent with a resultant modulation of I_KV (A and D). By the end of late stage 12, at a time when 5HT is not able to produce the adult complement of spike broadening, PDAc produces significant broadening that is identical in magnitude to that observed in mature neurons (B and D). These data suggest that the inability of 5HT to modulate repolarizing currents such as I_KV is because of an inability of 5HT to activate PKC. At the beginning of late stage 12, even direct activation of PKC is unable to produce significant spike broadening (C and D), demonstrating that PKC is not able to modulate the ion channel protein(s) responsible for repolarization at this earlier developmental stage.