Abstract
Prior electrical activity in the indirect flight muscles of Drosophila facilitates membrane excitability. The mechanism of facilitation involves the inactivation of an early, fast, transient outward current by prior membrane depolarization. In the facilitated state the Ca-dependent spike-like response has a decreased current and voltage threshold. The facilitated state persists for 1.5 s after a membrane-active response. A single nerve-driven spike is sufficient to facilitate membrane excitability.