Figure 1. Transient outward rectification and spike broadening in OT neurones.

A, one LD-5 (a) and one LD-21 (b) neurone at resting potential were stimulated by a depolarising current pulse (100 pA, 80–100 ms). In both cases, the first evoked action potential appeared without any delay. In contrast, when the neurones were hyperpolarised near -90 mV, an appropriate depolarising pulse induced a transient outward rectification (⋆) which delayed the occurrence of the first action potential. B, spontaneous bursts of action potentials recorded from a LD-5 (a) and a LD-21 neurone (b). Three action potentials within each burst (indicated by arrows) were superimposed at a higher speed (a and b, lower traces) and clearly show action potential broadening.