Fig. 1.
An α-dendrotoxin-sensitive current controls cortical axonal excitability. (A) Simultaneous somatic and axonal recording. The intraaxonal injection of current pulses results in only single spikes in both the axon and the soma, followed by a slow ramping depolarization of the axon. (B) After bath application of α-dendrotoxin (100 nM; α-DTX) axonal spike threshold is lower, trains of spikes are initiated with moderate amplitude current pulses, the slow depolarizing ramp of the axonal membrane potential in response to depolarization was blocked, and larger intraaxonal current pulses initiated “spikelets” that were not evident in the somatic recording. (C) The application of α-DTX strongly increased axonal spike duration but not in the soma (first spike to each pulse shown). (D) Expansion of two normal spikes and several “spikelets” (in α-DTX). Axon recorded at 110 μm (P20 rat prefrontal cortex).